Group Publications
Group Publications
Year
- Publications in 2012
- Publications in 2011
- Publications in 2010
- Publications in 2009
- Publications in 2008
- Publications in 2007
- Publications in 2006
- Publications in 2005
- Publications in 2004
- Publications in 2003
- Publications in 2002
- Publications in 2001
- Publications in 2000
- Publications in 1999
- Publications in 1998
- Publications in 1997
- Publications in 1996
- Publications in 1995
- Publications in 1994
- Publications in 1993
2012
Rigby, M., A. J. Manning, and R. G. Prinn, The value of high-frequency, high-precision methane isotopologue measurements for source and sink estimation, J. Geophys. Res., 117 D12312, doi:10.1029/2011JD017384, 2012
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Abstract
Ivy, D. J., Arnold, T., Harth, C. M., Steele, L. P., Mühle, J., Rigby, M., Salameh, P. K., Leist, M., Krummel, P. B., Fraser, P. J., Weiss, R. F., and Prinn, R. G.:,Atmospheric histories and growth trends of C4F10, C5F12, C6F14, C7F16 and C8F18, Atmos. Chem. Phys., 12, 4313-4325, doi:10.5194/acp-12-4313-2012, 2012
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Abstract
Ganshin, A., Oda, T., Saito, M., Maksyutov, S., Valsala, V., Andres, R. J., Fisher, R. E., Lowry, D., Lukyanov, A., Matsueda, H., Nisbet, E. G., Rigby, M., Sawa, Y., Toumi, R., Tsuboi, K., Varlagin, A., and Zhuravlev, R.:, A global coupled Eulerian-Lagrangian model and 1 × 1 km CO2 surface flux dataset for high-resolution atmospheric CO2 transport simulations, Geosci. Model Dev., 5 231-243, doi:10.5194/gmd-5-231-2012, 2012
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Abstract
Ivy, D. J., Rigby, M., Baasandorj, M., Burkholder, J. B., and Prinn, R. G., Global emission estimates and radiative impact of C4F10, C5F12, C6F14, C7F16 and C8F18, Atmos. Chem. Phys., 12, 7635-7645, doi:10.5194/acp-12-7635-2012, 2012
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2011
Manning A, S. O'Doherty, A. R. Jones, P. G. Simmonds, and R. G. Derwent, Mace Head CH4 and the NAME model, J. Geophys. Res., 116 D0230, doi:10.1029/2010JD014763, 2011
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Abstract
Yver C, I. Pison, A. Fortems-Cheiney, M. Schmidt, P. Bousquet, M. Ramonet, A. Jordan, A. Søvde, A. Engel, R. Fisher, D. Lowry, E. Nisbet, I. Levin, S. Hammer, J. Necki, J. Bartyzel, S. Reimann, M. K. Vollmer, M. Steinbacher, T. Aalto, M. Maione, I. Arduini, S. O'Doherty, A. Grant, W. Sturges, C. R. Lunder, V. Privalov, and N. Paramonova, A new estimation of the recent tropospheric molecular hydrogen budget using atmospheric observations and variational inversion, Atmos. Chem. Phys., 11, 3375-3392, 2011
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Abstract
Corazza M, P. Bergamaschi, A. T. Vermeulen, T. Aalto, L. Haszpra, F. Meinhardt, S. O'Doherty, R. Thompson, J. Moncrieff, E. Popa, M. Steinbacher, A. Jordan, E. Dlugokencky, C. Brühl, M. Krol, and F. Dentener, Inverse modelling of European N2O emissions: Assimilating observations from different networks, Atmos. Chem. Phys., 11, 2381-2398, 2011
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Abstract
Grant A, E. Yates, P.G. Simmonds, R.G. Derwent, A.J. Manning, D. Young, D.E. Shallcross, S. O’Doherty, A five year record of high-frequency in-situ measurements of hydrocarbons at Mace Head, Ireland, Atmos. Meas. Tech., 4, 955-964, 2011
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Abstract
Jones C.E, S. J. Andrews, L. J. Carpenter, C. Hogan, F. E. Hopkins, J. C. Laube, A. D. Robinson, T. G. Spain, S. D. Archer, N. R. P. Harris, P. D. Nightingale, S. J. O’Doherty, D. E. Oram, J. A. Pyle, J. H. Butler, and B. D. Hall, Results from the first national UK inter-laboratory calibration for very short-lived halocarbons, Atmos. Meas. Tech. Discuss., 4, 865-874, 2011
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Abstract
Nevison, C.D, E. Dlugokencky, G. Dutton, J.W. Elkins, P. Fraser, B. Hall, P.B. Krummel, R.L. Langenfelds, S. O’Doherty, R.G. Prinn, L.P. Steele, R.F. Weiss, Exploring causes of interannual variability in the seasonal cycles of tropospheric nitrous oxide, Atmos. Chem. Phys., 11, 3713-3730, 2011
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Abstract
Giostra, U, F. Furlani, J. Arduini, D. Cava, A.J. Manning, S. O’Doherty and M. Maione, The determination of a “European” atmospheric background mixing ratio for anthropogenic greenhouse gases: a comparison of two independent methods, in preparation 2011
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Abstract
Derwent, R.G, W.J. Collins, P.G. Simmonds, S. O'Doherty, and G.A. Sturrock, Observations and model studies of CH3CCl3, CH2Cl2, CHCl3, CH3Br and CHCl:CCl2 at Mace Head, Ireland and other AGAGE baseline stations, in preparation 2011
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Abstract
Keller, C.A, D. Brunner, S. Henne, M.K. Vollmer, S. O'Doherty, S. Reimann, Evidence for under-reported Western European emissions of the potent greenhouse gas HFC-23, submitted to JRL 2011
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2010
Lee J.D, G. McFiggans, J. D. Allan, A. R. Baker, S. M. Ball, A. K. Benton, L. J. Carpenter, R. Commane, B. D. Finley, M. Evans, E. Fuentes, K. Furneaux, A. Goddard, N. Good, J. F. Hamilton, D. E. Heard, H. Herrmann, A. Hollingsworth, J. R. Hopkins, T. Ingham, M. Irwin, C. E. Jones, R. L. Jones, W. C. Keene, M. J. Lawler, S. Lehmann, A. C. Lewis, M. S. Long, A. Mahajan, J. Methven, S. J. Moller, K. Müller, T. Müller, N. Niedermeier, S. O'Doherty, H. Oetjen, J. M. C. Plane, A. A. P. Pszenny, K. A. Read, A. Saiz-Lopez, E. S. Saltzman, R. Sander, R. von Glasow, L. Whalley, A. Wiedensohler, and D. Young, Reactive Halogens in the Marine Boundary Layer (RHaMBLe): the tropical North Atlantic experiments, Atmos. Chem. Phys., 10, 1031-1055, 2010 .
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Abstract
Grant A, C. S. Witham, P. G. Simmonds, A. J. Manning, and S. O'Doherty, A 15 year record of high-frequency, in situ measurements of hydrogen at Mace Head, Ireland, Atmos. Chem. Phys., 10, 1203-1214, 2010 .
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Abstract
Grant A, K. F. Stanley, S. J. Henshaw, D.E. Shallcross and S. O'Doherty, High-frequency urban measurements of hydrogen and carbon monoxide, Atmos. Chem. Phys., 10, 4715-4724, 2010 .
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Abstract
Stohl A, Kim J, Li S, S. O'Doherty, Salameh P.K, Saito T, Vollmer M.K, Wan D, Yao B, Yokouchi Y and Zhou L.Z, Hydrochlorofluorocarbon and hydrofluorocarbons emissions in East Asia determined by inverse modelling, Atmos. Chem. Phys., 10, 3545- 3560, 2010 .
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Abstract
Mühle J, A. L. Ganesan, B. R. Miller, P. K. Salameh, C. M. Harth, B. R. Greally, M. Rigby, L. W. Porter, L. P. Steele, C. M. Trudinger, P. B. Krummel, S. O'Doherty, P. J. Fraser, P. G. Simmonds, R. G. Prinn, and R. F. Weiss, Perfluorocarbons in the global atmosphere: tetrafluoromethane, hexafluoroethane, and octafluoropropane, Atmos. Chem. Phys. 10, 5145-5164, 2010 .
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Abstract
Yates E, R.G. Derwent, P. G. Simmonds, B.R. Greally, S. O'Doherty, D. E. Shallcross., The seasonal cycles and photochemistry of C2 - C5 alkanes at Mace Head,. Atmospheric Environment, 44, 2705-2713, 2010 .
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Abstract
Xiao X, R. G. Prinn, P. J. Fraser, P. G. Simmonds, R. F. Weiss, S. O'Doherty, B.R. Miller, P. Salameh, C. Harth, L. W. Porter, P. B. Krummel, J.Muhle, D. Cunnold, R.Wang, S. A. Montzka, J. W. Elkins, G. S. Dutton, T. M. Thompson, J. H. Butler, B. D. Hall, S. Reimann, M. K. Vollmer, F. Stordal, C. Lunder, M. Maione, and Y. Yokouchi, Optimal Estimation of the Surface Fluxes of Methyl Chloride using a 3-D Global Chemical Transport Model, Atmos. Chem. Phys., 10, 5515-5530, 2010 .
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Abstract
Miller B.R, M. Rigby, L. J. M. Kuijpers, P. B. Krummel, L. P. Steele, M. Leist, P. J. Fraser, A. McCulloch, C. Harth, P. Salameh, J. Mühle, R. F. Weiss, R. G. Prinn, R. H. J. Wang, S. O'Doherty, B. Greally, and P. G. Simmonds, CHF3 (HFC-23) emission trend response to CHClF2 (HCFC-22) production and recent CHF3 emission abatement measures, Atmos. Chem. Phys., 10, 7875-7890, 2010 .
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Abstract
Xiao X, R. G. Prinn, R. F. Weiss, P. G. Simmonds, P. J. Fraser, S. O'Doherty, B. R. Miller, P. K. Salameh, C. M. Harth, P. B. Krummel, A. Golombek, L. W. Porter, J. W. Elkins, G. S. Dutton, B. D. Hall, S. A. Montzka, R. H. J. Wang and D. M. Cunnold, Three Dimensional Inverse Modeling of Regional Industrial Emissions and Global Oceanic Uptake of Carbon Tetrachloride, Atmos. Chem. Phys., 10, 10,421-10,434 2010 .
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Abstract
Rigby M, J. Mühle, B. Miller, R. Prinn, P. Fraser, P. Krummel, P. Steele, N. Derek, R. Weiss, P. Salameh, C. Harth, S. O'Doherty, P. Simmonds, M. Vollmer, S. Reimann, J. Kim, R. Wang, E. Dlugokencky, and G. Dutton, History of atmospheric SF6 mole fractions and emissions from 1973 to 2008, Atmos. Chem. Phys., 10, 10,305-10,320, 2010 .
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Abstract
Tripathi O, S. G. Jennings, C. D. O'Dowd, L. Coleman, S. Leinert, E. Moran, S.J. O'Doherty, T.G. Spain, Statistical Analysis of Eight Surface Ozone Measurement Series for various sites in Ireland, J. Geophys. Res., 115, D19302, doi:10.1029/2010JD014040, 2010 .
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Abstract
Manning A, S. O'Doherty, A. R. Jones, P. G. Simmonds, and R. G. Derwent, Mace Head CH4 and the NAME model, J. Geophys. Res., doi:10.1029/2010JD014763, 2010 .
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Abstract
Corazza M, P. Bergamaschi, A. T. Vermeulen, T. Aalto, L. Haszpra, F. Meinhardt, S. O'Doherty, R. Thompson, J. Moncrieff, E. Popa, M. Steinbacher, A. Jordan, E. Dlugokencky, C. Brühl, M. Krol, and F. Dentener, Inverse modelling of European N2O emissions: Assimilating observations from different networks, Atmos. Chem. Phys. Discuss., 10, 26,319-26,359, 2010 .
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Abstract
C. Yver, I. Pison, A. Fortems-Cheiney, M. Schmidt, P. Bousquet, M. Ramonet, A. Jordan, A. Søvde, A. Engel, R. Fisher, D. Lowry, E. Nisbet, I. Levin, S. Hammer, J. Necki, J. Bartyzel, S. Reimann, M. K. Vollmer, M. Steinbacher, T. Aalto, M. Maione, I. Arduini, S. O'Doherty, A. Grant, W. Sturges, C. R. Lunder, V. Privalov, and N. Paramonova, A new estimation of the recent tropospheric molecular hydrogen budget using atmospheric observations and variational inversion, Atmos. Chem. Phys. Discuss., 10, 28,963-29,005 2010 .
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2009
Utembe, S. R., Watson, L. A., Shallcross, D. E, Jenkin, M. E., A Common Representative Intermediates (CRI) mechanism for VOC degradation. Part 3., Atmos. Environ., 43 12 1982-1990, 2009 .
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Abstract
A Photochem. Trajectory Model (PTM), contg. the Master Chem. Mechanism version 3.1 (MCM v3.1) coupled with an optimized representation of gas-aerosol absorptive partitioning of 365 oxygenated product species, has been used to simulate mass concns. of secondary org. aerosol (SOA) for the conditions of the TORCH-2003 campaign in the south-east UK in late July and August 2003. A comprehensive ref. dataset of 50 case study arrival events (and 4750 assocd. hourly air mass history events) has been compiled, which considers the base case conditions and scenarios in which emissions of anthropogenic pollution have been reduced by factors of up to 100. The relative contributions of SOA derived from anthropogenic and biogenic precursors are presented for the range of conditions, and the compn. of these simulated components is discussed in terms of av. mol. formulas, at. ratios (H/C, O/C and N/C) and org. aerosol mass to org. carbon mass ratios (OM/OC), which are compared to reported measurements. The MCM v3.1 dataset has been used as a ref. benchmark for development and optimization of a reduced (14 species) SOA module for use with version 2 the Common Representative Intermediates mechanism (CRI v2), described in the first of two preceding companion papers [Jenkin, M.E., Watson, L.A., Utembe, S.R., Shallcross, D.E., 2008a. A Common Representative Intermediates (CRI) mechanism for VOC degrdn. Part 1
Stohl A, P. Seibert, J. Arduini, S. Eckhardt, P. Fraser, B. R. Greally, M. Maione, S. O'Doherty, R. G. Prinn, S. Reimann, T. Saito, N. Schmidbauer, P. G. Simmonds, M. K. Vollmer, R. F. Weiss, and Y. Yokouchi, A new analytical inversion method for determining regional and global emissions of greenhouse gases: sensitivity studies and application to halocarbons, Atmos. Chem. Phys., 9, 1597-1620, 2009 .
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Abstract
Brooks I.M, R. C. Upstill-Goddard, Margaret J. Yelland, Steve Archer, Eric d'Asaro, Philip Balitsky, Rachael Beale, Cory Beatty, Byron Blomquist, A. Anthony Bloom, Barbara J. Brooks, John Cluderay, David Coles, John Dacey, Michael DeGrandpre, Jo Dixon, William Drennan, Joseph Gabriele, Laura Goldson, Nick Hardman-Mountford, Martin K. Hill, Matt Horn, Ping-Chang Hsueh, Barry Huebert, Gerrit de Leeuw, Timothy G. Leighton, Malcolm Liddicoat, Justin J. N. Lingard, Craig McNeil, James B. McQuaid, Ben I. Moat, Gerald Moore, Craig Neill, Philip D. Nightingale, Sarah J. Norris, Simon O'Doherty, Robin W. Pascal, Mike Rebozo, Erik Sahlee, Matt Salter, Ute Schuster, Ingunn Skjelvan, Hans Slagter, Michael H. Smith, Paul D. Smith, Meric Srokosz, John A. Stephens, Peter K. Taylor, Maciek Telszewski, Roisin Walsh, Brian Ward, David K. Woolf, Dickon Young, Henk Zemmelink, Physical Exchanges at the Air-Sea Interface UK-SOLAS Field Measurements, Bulletin of the American meteorological Society, 90, 5, 629-644, 2009 .
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Abstract
Brooks I.M, R. C. Upstill-Goddard, Margaret J. Yelland, Steve Archer, Eric d'Asaro, Philip Balitsky, Rachael Beale, Cory Beatty, Byron Blomquist, A. Anthony Bloom, Barbara J. Brooks, John Cluderay, David Coles, John Dacey, Michael DeGrandpre, Jo Dixon, William Drennan, Joseph Gabriele, Laura Goldson, Nick Hardman-Mountford, Martin K. Hill, Matt Horn, Ping-Chang Hsueh, Barry Huebert, Gerrit de Leeuw, Timothy G. Leighton, Malcolm Liddicoat, Justin J. N. Lingard, Craig McNeil, James B. McQuaid, Ben I. Moat, Gerald Moore, Craig Neill, Philip D. Nightingale, Sarah J. Norris, Simon O'Doherty, Robin W. Pascal, Mike Rebozo, Erik Sahlee, Matt Salter, Ute Schuster, Ingunn Skjelvan, Hans Slagter, Michael H. Smith, Paul D. Smith, Meric Srokosz, John A. Stephens, Peter K. Taylor, Maciek Telszewski, Roisin Walsh, Brian Ward, David K. Woolf, Dickon Young, Henk Zemmelink, UK-SOLAS field measurements of air-sea exchange, Instrumentation., Bulletin of the American meteorological Society, 95, 5, ES9-ES16, 2009 .
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Abstract
Derwent R.G., P.G. Simmonds, A.J. Manning, S. O'Doherty, G. Spain, Methane emissions from peat bogs in the vicinity of the Mace Head Research Station over a 12-year period, Atmospheric Environment, 43, 2328-2335, 2009 .
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Abstract
Mühle, J., J. Huang, R. Weiss, R. Prinn, B. Miller, P. Salameh, C. Harth, P. Fraser, L. Porter, B. Greally, S. O'Doherty and P. Simmonds, Sulfuryl fluoride in the global atmosphere, J. Geophys. Res., 114, 2009 .
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Patra P.K, Masayuki Takigawa, Kentaro Ishijima, Byoung-Choel Choi, Derek Cunnold, Edward J. Dlugokencky, Paul Fraser, Angel J. Gomez-Pelaez, Tae-Young Goo, Jeong-Sik Kim, Paul Krummel, Ray Langenfelds, Frank Meinhardt, Hitoshi Mukai, Simon O'Doherty, Ronald G. Prinn, Peter Simmonds, Paul Steele, Yasunori Tohjima, Kazuhiro Tsuboi, Karin Uhse, Ray Weiss, Doug Worthy And Takakiyo Nakazawa, Growth rate, seasonal, synoptic and diurnal variations in lower atmospheric methane, J. Meteorol. Society of Japan, 87, 4, 635-663, 2009 .
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Abstract
S. O'Doherty, Cunnold, D.M Miller, B.R., Mühle, J. McCulloch, A. Simmonds, P.G. Manning, A.J. Reimann, S. Vollmer, M.K. Greally, B.R. Prinn, R.G. Fraser, P.J. Steele, L.P. Krummel P.B., Dunse, B.L. Porter, L.W. Lunder, C.R. Schmidbauer, N. Hermansen, O. Salameh, P.K. Harth, C.M. Wang R.H.J. and Weiss R.F., Global and regional emissions of HFC-125 (CHF2CF3) from in situ and air archive atmospheric observations at AGAGE and SOGE observatories, J. Geophys. Res., 114, D23304, 2009 .
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2008
Watson, L. A., Shallcross, D. E, Utembe, S. R., Jenkin, M. E., A Common Representative Intermediates (CRI) mechanism for VOC degradation. Part 2., Atmos. Environ., 42 31,7196-72042008
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Abstract
The Common Representative Intermediates mechanism version 2 (CRI v2) is a reduced mechanism of intermediate complexity, traceable to the Master Chem. Mechanism version 3.1 (MCM v3.1), which couples with a detailed speciation of 112 emitted anthropogenic non-methane volatile org. compds. (VOCs). Systematic lumping techniques for the emitted anthropogenic VOC species have been used to reduce CRI v2, creating a series of five reduced variants, the performances of which have been evaluated against that of CRI v2 for a range of ambient conditions. For the initial redn. phases, minor emitted VOCs accounting for increasing proportions of the VOC mass emissions total, up to 20%, were redistributed into appropriate surrogates, and the redundant species and their assocd. chem. were removed from the chem. mechanism. The surrogates were selected to maintain the chem. class of the redistributed VOCs within a no. of VOC sub-categories, and aimed to preserve the ozone-forming ability of each category using the photochem. ozone creation potential (POCP) index as a criterion. This yielded three reduced mechanisms (CRI v2-R1, CRI v2-R2 and CRI v2-R3) and allowed resp. redns. of up to 25% and 32% in the nos. of reactions and species, with no significant degrdn. in the overall performance of the mechanisms or in the relative contributions of the VOC sub-categories to ozone formation. More severe levels of redn. were also imposed, to limit the no. of representative VOCs in each sub-catergory, with the choice of species taking account of their abundance in the detailed speciation, and the simplicity of the assocd. degrdn. mechanism. The POCP index was once again used as a guide to help optimize the overall ozone-forming ability of the VOC speciation. This yielded two further mechanisms (CRI v2-R4 and CRI v2-R5) with redns. of up to 53% and 55% in the nos. of reactions and species relative to CRI v2. These mechanisms display a degree of compromise in the ozone-forming ability of the VOC sub-categories, but retain a good level of overall performance. The most reduced variant (CRI v2-R5) uses 19 non-methane VOCs to represent the anthropogenic speciation, and is considered appropriate as a traceable ref. mechanism for use in global chem.-transport models.
Jenkin, M. E., Watson, L. A., Utembe, S. R., Shallcross, D. E, A Common Representative Intermediates (CRI) mechanism for VOC degradation. Part 1., Atmos. Environ., 42 31 7185-7195 , 2008
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Abstract
A reduced mechanism describing ozone formation from the tropospheric degrdn. of methane and 115 emitted non-methane hydrocarbons and oxygenated volatile org. compds. has been developed, using the Master Chem. Mechanism version 3.1 (MCM v3.1) as a ref. benchmark. The Common Representative Intermediates mechanism version 2 (CRI v2) has been built up on a compd.-by-compd. basis, with the performance of its chem. optimized for each compd. in turn by comparison with that of MCM v3.1, using a series of five-day box model simulations. The resultant mechanism contains 1183 reactions of 434 chem. species, i.e., ca. 10% of the no. of reactions and species to degrade the same set of VOCs in MCM v3.1. Similarly to CRI v1 (Jenkin et al., 2002a), a key assumption in the CRI v2 construction methodol. is that the potential for ozone formation from a given volatile org. compd. (VOC) is related to the no. of reactive (i.e., C-C and C-H) bonds it contains. This index allows a series of generic intermediates to be defined, with each being used as a "common representative" for a large set of species possessing the same index, as formed in detailed mechanisms such as the MCM. The performance of CRI v2 is shown to compare well with that of MCM v3.1 for a wide range of ambient conditions, which consider variations in VOC/NOx emissions ratio over ranges of 32 and 400 for anthropogenic and biogenic VOCs, resp., in box model simulations, and in simulations of the TORCH 2003 campaign in the southern UK using a photochem. trajectory model, which considers notable ranges in the relative and abs. emissions of NOx and VOCs, and in the relative contributions of anthropogenic and biogenic species to the VOC total. CRI v2 is a reduced mechanism of intermediate complexity, which is traceable to MCM v3.1, and which provides the basis for further systematic redn. Two companion papers consider further redn. of CRI v2 through emissions lumping and development and assessment of an assocd. SOA module.
Jenkin, M. E., Utembe, S. R., Derwent, R. G., Modelling the impact of elevated primary NO2 and HONO emissions on regional scale oxidant formation in the UK., Atmos. Environ., 42 2 323-336 , 2008
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Abstract
Recent increases in the fractional contribution of NO2 to NOx emissions from the road transport sector in Europe are well documented in the literature. A photochem. trajectory model has been used to simulate the impact of increasing the NO2 fraction on the chem. evolution of air masses arriving at the TORCH field campaign site in the southern UK during late July and August 2003, a period which included a widespread photochem. pollution episode assocd. with a heat-wave. The impact of partial emissions of NOx in the form of nitrous acid (HONO) has also been considered. The model incorporates emissions of NOx, CO, SO2, methane and a detailed speciation of non-methane volatile org. compds. (VOC), coupled with a comprehensive description of the chem. of secondary pollutant formation. An increase in the fractional contribution of NO2 to NOx emissions from 0% to 30% (vol./vol.) results in a 2.49 ppb increase in the simulated campaign mean mixing ratio of oxidant (defined as the sum of O3 and NO2). This is almost exclusively in the form of O3, and represents a ca. 7% increase in the simulated campaign mean O3 mixing ratio. Consideration of 156 events, at 6-hourly resoln. throughout the campaign period, indicates that oxidant increments during the heat-wave period are generally simulated to be greater than those for the remainder of the campaign, with a max. increment of ca. 12 ppb. The increases in oxidant mixing ratios are shown to derive from both the direct effect of increased NO2 input, and indirectly from the enhanced regional-scale chem. processing that this promotes. An illustrative increase in the fractional contribution of HONO to NOx emissions from 0% to 5% (vol./vol.) results in increases in the simulated campaign mean mixing ratios of O3 and oxidant of 1.51 and 1.15 ppb, resp., with the smaller increment for oxidant reflecting a decrease in the NO2 mixing ratio resulting from a notably enhanced NOx oxidn. rate. The oxidant increments during the heat-wave period are once again simulated to be greater than those for the remainder of the campaign, with a max. increment of ca. 11 ppb, which results exclusively from the enhanced regional-scale chem. processing that the HONO emissions promote. The impact of increased fractional NO2 and HONO emissions on the rate of oxidn. of NOx to nitrate is also illustrated and discussed.
Mead, M. I., Khan, M. A. H., Bull, I. D., White, I. R., Nickless, G., Shallcross, D. E, Stable carbon isotope analysis of selected halocarbons at parts per trillion concentration in an urban location., Environ. Chem., 5 5 340-346, , 2008
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Abstract
delta 13C values of a suite of halocarbons have been detd. in an urban background site in Bristol, UK. A novel mobile preconcn. system, based on the use of multi-adsorbent sample tubes, has been developed for trapping relatively large-vol. air samples in potentially remote areas. An Adsorption Desorption System-Gas Chromatog.-Electron Capture Detector was used to measure the mixing ratios of the selected halocarbon species, while a Gas Chromatog.-Combustion-Isotope Ratio Mass Spectrometer was used to det. delta 13C values. For the species with strong local sources, the variation of isotope ratios has been obsd. over the exptl. period. Some of the results reported in the present study differ from previously reported values and resons for this are discussed. The reporting of different delta 13C values for selected halocarbons from different areas in the present study suggests that delta 13C values may be used to det. the relative magnitudes of anthropogenic and biogenic sources.
Wang, K.-Y., Shallcross, D. E, Pyle, J. A., Modelling the spring ozone maximum and the interhemispheric asymmetry in the remote marine boundary layer 1. Comparison with surface and ozonesonde measurements., arXiv.org, e-Print Arch., Phys., 5 5 1-31, arXiv, , 2008
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Abstract
Here we report a modeling study of the spring ozone max. and its interhemispheric asymmetry in the remote marine boundary layer (MBL). The modelled results are examd. at the surface and on a series of time-height cross sections at several locations spread over the Atlantic, the Indian, and the Pacific Oceans. Comparison of model with surface measurements at remote MBL stations indicate a close agreement. The most striking feature of the hemispheric spring ozone max. in the MBL can be most easily identified at the NH sites of Westman Island, Bermuda, and Mauna Loa, and at the SH site of Samoa. Modelled ozone vertical distributions in the troposphere are compared with ozone profiles. For the Atlantic and the Indian sites, the model generally produces a hemispheric spring ozone max. close to those of the measurements. The model also produces a spring ozone max. in the northeastern and tropical north Pacific close to those measurements, and at sites in the NH high latitudes. The good agreement between model and measurements indicate that the model can reproduce the proposed mechanisms responsible for producing the spring ozone max. in these regions of the MBL, lending confidence in the use of the model to investigate MBL ozone chem. The spring ozone max. in the tropical central south Pacific and eastern equatorial Pacific are less well reproduced by the model, indicating that both the transport of O3 precursors from biomass burning emissions taking place in southeastern Asia, Australia, Oceania, southern Africa, and South America are not well represented in the model in these regions. Overall, the model produces a better simulation at sites where the stratosphere and biomass burning emissions are the major contributors.
Wang, Kuo-Ying, Shallcross, Dudley E., Modelling atmospheric chemistry and long-range transport of emerging Asian pollutants., arXiv.org, e-Print Arch., Phys., 5 5 1-30, arXiv , 2008
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Abstract
Modeling is a very important tool for scientific processes, requiring long-term dedication, desire, and continuous reflection. In this work, we discuss several aspects of modeling, and the reasons for doing it. We discuss two major modeling systems that have been built by us over the last 10 years. It is a long and arduous process but the reward of understanding can be enormous, as demonstrated in the examples shown in this work. We found that long-range transport of emerging Asian pollutants can be interpreted using a Lagrangian framework for wind anal. More detailed processes still need to be modeled but an accurate representation of the wind structure is the most important thing above all others. Our long-term chem. integrations reveal the capability of the IMS model in simulating tropospheric chem. on a climate scale. These long-term integrations also show ways for further model development. Modeling is a quant. process, and the understanding can be sustained only when theories are vigorously tested in the models and compared with high quality measurements. We should also not over look the importance of data visualization techniques. Humans feel more con dent when they see things. Hence, modeling is an incredible journey, combining data collection, theor. formulation, detailed computer coding and harnessing computer power. The best is yet to come.
Carbajo, Paula Gorrotxategi, Smith, Shona C., Holloway, Anne-Louise, Smith, Carina A., Pope, Francis D., Shallcross, Dudley E., Orr-Ewing, Andrew J., Ultraviolet Photolysis of HCHO., J. Phys. Chem. A, 112 48 12437-12448, 2008
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Abstract
Abs. quantum yields for the radical (H + HCO) channel of HCHO photolysis, FHCO, have been measured for the tropospherically relevant range of wavelengths (l) between 300 and 330 nm. The HCO photoproduct was directly detected by using a custom-built, combined ultra-violet (UV) absorption and cavity ring down (CRD) detection spectrometer. This instrument was previously employed for high-resoln. (spectral resoln. .apprx.0.0035 nm) measurements of absorption cross-sections of HCHO, sHCHO(l), and relative HCO quantum yields. Abs. FHCO values were measured at seven wavelengths, l = 303.70, 305.13, 308.87, 314.31, 320.67, 325.59, and 329.51 nm, using an independent calibration technique based on the simultaneous UV photolysis of HCHO and Cl2. These FHCO measurements display greater variability as a function of wavelength than the current NASA-JPL recommendations for FHCO. The abs. FHCO(l) detns. and previously measured sHCHO(l) were used to scale an extensive set of relative HCO yield measurements. The outcome of this procedure is a full suite of data for the product of the abs. radical quantum yield and HCHO absorption cross-section, FHCO(l)sHCHO(l), at wavelengths from 302.6 to 331.0 nm with a wavelength resoln. of 0.005 nm. This product of photochem. parameters is combined with high-resoln. solar photon flux data to calc. the integrated photolysis rate of HCHO to the radical (H + HCO) channel, J(HCO). Comparison with the latest NASA-JPL recommendations, reported at 1 nm wavelength resoln., suggests an increased J(HCO) of 25% at 0 Deg solar zenith angle (SZA) increasing to 33% at high SZA (80 Deg). The differences in the calcd. photolysis rate compared with the current HCHO data arise, in part, from the higher wavelength resoln. of the current data set and highlight the importance of using high-resoln. spectroscopic techniques to achieve a complete and accurate picture of HCHO photodissocn. processes. All exptl. FHCO(l)sHCHO(l) data are available for the wavelength range 302.6-331.0 nm (at 294 and 245 K and under 200 Torr of N2 bath gas) as Supporting Information with wavelength resolns. of 0.005, 0.1, and 1.0 nm. Equivalent data sets of FH2+CO(l)sHCHO(l) for the mol. (H2 + CO) photofragmentation channel, produced using the measured FHCO(l) sHCHO(t) values, are also provided at 0.1 and 1.0 nm resoln.
Jones, A. E., Wolff, E. W., Salmon, R. A., Bauguitte, S. J.-B., Roscoe, H. K., Anderson, P. S., Ames, D., Clemitshaw, K. C., Fleming, Z. L., Bloss, W. J., Heard, D. E., Lee, J. D., Read, K. A., Hamer, P., Shallcross, D. E, Jackson, A. V., Walker, S. L., Lewis, A. C., Mills, G. P., Plane, J. M. C., Saiz-Lopez, A., Sturges, W. T., Worton, D. R., Chemistry of the Antarctic Boundary Layer and the Interface with Snow., Atmos. Chem. Phys., 8 14 3789-3803, 2008
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Abstract
CHABLIS (Chem. of the Antarctic Boundary Layer and the Interface with Snow) was a collaborative UK research project aimed at probing the detailed chem. of the Antarctic boundary layer and the exchange of trace gases at the snow surface. The center-piece to CHABLIS was the measurement campaign, conducted at the British Antarctic Survey station, Halley, in coastal Antarctica, from Jan. 2004 through to Feb. 2005. The campaign measurements covered an extremely wide range of species allowing investigations to be carried out within the broad context of boundary layer chem. Here we present an overview of the CHABLIS campaign. We provide details of the measurement location and introduce the Clean Air Sector Lab. (CASLab) where the majority of the instruments were housed. We describe the meteorol. conditions experienced during the campaign and present supporting chem. data, both of which provide a context within which to view the campaign results. Finally we provide a brief summary of highlights from the measurement campaign. Unexpectedly high halogen concns. profoundly affect the chem. of many species at Halley throughout the sunlit months, with a secondary role played by emissions from the snowpack. This overarching role for halogens in coastal Antarctic boundary layer chem. was completely unanticipated, and the results have led to a step-change in our thinking and understanding.
Hamer, P. D., Shallcross, D. E, Yabushita, A., Kawasaki, M., Modelling the impact of possible snowpack emissions of O(3P) and NO2 on photochemistry in the South Pole boundary layer., Environ. Chem., 5 4 268-273 , 2008
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Abstract
Environmental context. The study of surface photochem. ozone prodn. on the Antarctic continent has direct relevance to climate change and general air quality and is scientifically noteworthy given the otherwise pristine nature of this environmental region. The identification of possible direct ozone emissions from snow surfaces and their contribution to the already active photochem. pollution present there represents a unique phys. phenomenon. This process could have wider global significance for other snow-covered regions and therefore for global climate change. Abstr. O(3P) emissions due to photolysis of nitrate were recently identified from ice surfaces doped with nitric acid. O(3P) atoms react directly with mol. oxygen to yield ozone. Therefore, these results may have direct bearing on photochem. activity monitored at the South Pole, a site already noted for elevated summertime surface ozone concns. NO2 is also produced via the photolysis of nitrate and the firn air contains elevated levels of NO2, which will lead to direct emission of NO2. A photochem. box model was used to probe what effect O(3P) and NO2 emissions have on ozone concns. within the South Pole boundary layer. The results suggest that these emissions could account for a portion of the obsd. ozone prodn. at the South Pole and may explain the obsd. upward fluxes of ozone identified there.
Taatjes, Craig A., Meloni, Giovanni, Selby, Talitha M., Trevitt, Adam J., Osborn, David L., Percival, Carl J., Shallcross, Dudley E., Direct Observation of the Gas-Phase Criegee Intermediate (CH2OO)., J. Am. Chem. Soc., 130 36 11883-11885 , 2008
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Abstract
Carbonyl oxide species play a key role in tropospheric oxidn. of org. mols. and in low-temp. combustion processes. In the late 1940s, Criegee first postulated the participation of carbonyl oxides, now often called "Criegee intermediates," in ozonolysis of alkenes. However, despite decades of effort, no gas phase Criegee intermediate has before been obsd. As a result, knowledge of gas phase carbonyl oxide reactions has heretofore been inferred by indirect means, with derived rate coeffs. spanning orders of magnitude. We have directly detected the primary Criegee intermediate, formaldehyde oxide (CH2OO), in the chlorine-initiated gas-phase oxidn. of DMSO (DMSO). This work not only establishes that the Criegee intermediate is formed in DMSO oxidn. also but opens the possibility for explicit kinetics studies on this crit. atm. species.
Mead, M. I., Khan, M. A. H., White, I. R., Nickless, G., Shallcross, D. E, Methyl halide emission estimates from domestic biomass burning in Africa., Atmos. Environ., 42 21 5241-5250 , 2008
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Abstract
Inventories of Me halide emissions from domestic burning of biomass in Africa, from 1950 to the present day and projected to 2030, have been constructed. By combining emission factors from Andreae and Merlet [2001. Emission of trace gases and aerosols from biomass burning. Global Biogeochem. Cycles 15, 955-966], the biomass burning ests. from Yevich and Logan [2003. An assessment of biofuel use and burning of agricultural waste in the developing world. Global Biogeochem. Cycles 17(4), 1095, ] and the population data from the UN population division, the emission of Me halides from domestic biomass usage in Africa has been estd. Data from this study suggest that Me halide emissions from domestic biomass burning have increased by a factor of 4-5 from 1950 to 2005 and based on the expected population growth could double over the next 25 years. This estd. change has a non-negligible impact on the atm. budgets of Me halides.
Patra, Aditya, Colvile, Roy, Arnold, Samantha, Bowen, Emma,
Shallcross, Dudley, Martin, Damien, Price, Catheryn, Tate, James, ApSimon, Helen, Robins, Alan.,
On street observations of particulate matter movement and dispersion due to traffic on an urban road., Atmos. Environ., 42 17 3911-3926 , 2008
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Abstract
Empirical models for particulate matter emissions from paved road surfaces have been criticized for their lack of realism and accuracy. To support the development of a less empirical model, a study was conducted in a busy street at the DAPPLE site in Central London to understand the processes and to identify important parameters that influence emission from paved roads. Ordinary road gritting salt was applied to the road and the particulate matter entering the air at near-road surface level was monitored using optical particle counters. The grit acted as a tracer. The grit moved rapidly along the road in the direction of traffic flow. Build-up of material at the kerb indicated material being thrown across the road by the traffic. Coarser particles were resuspended faster than the finer ones. A clear decay profile was seen in the case of particles >2 micro m, particles <2 micro m did not show any decay pattern during the expt. duration. Grinding of material appears to control the reservoir of fine particles on the road surface. The amt. of material resuspended by traffic is .apprx.30% less than those removed along the road and a factor of 6 higher than the amt. removed across the road. Resuspension accounts for 40% of the total material removed from a road segment and 70% of the material removed together along and across the road. On av. a single vehicle pass removes 0.08% of material present on a road segment at that instant. The calcn. scheme is obtained from a short-duration study and therefore further studies of long duration involving varying road geometry and different traffic and meteorol. condition need to be carried out before applying parameter ests. presented.
McGillen, Max R., Carey, Trevor J., Archibald, Alex T., Wenger, John C., Shallcross, Dudley E., Percival, Carl J., Structure-activity relationship (SAR) for the gas-phase ozonolysis of aliphatic alkenes and dialkenes., Phys. Chem. Chem. Phys., 10 13 1757-1768 , 2008
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Abstract
The configuration of alkyl substituents about carbon-carbon unsatd. bonds exerts a controlling influence on the rate of the ozonolysis reaction. Alkyl substituents can increase (via the inductive effect) and decrease (via the steric effect) the activity of unsatd. bonds, and an accurate description of this information ought to correlate with the ozonolysis rate coeff. A strong linear relationship is obsd. (R2 = 0.94), providing the basis of our SAR method. SAR ests. were tested against literature measurements of ozonolysis rate coeffs. for 48 aliph. alkenes and dialkenes, and were found to be accurate to within a factor of 2.3 of the measured value for the entire dataset. This represents a significant improvement over methods reported in the literature, where quoted predictions are at best accurate to within a factor of 6.5. Rates of gas-phase ozonolysis of alkenes and dialkenes can now be predicted with unprecedented accuracy using a simple SAR. The SAR was then validated against new exptl. data. Abs. rate coeffs. for the gas-phase reaction of ozone with a series of alkenes were detd. in a simulation chamber at 295 +- 2 K and atm. pressure by monitoring the loss of ozone in the presence of excess alkene. The rate coeffs. (in units of 1 * 10-18 cm3 mol.-1 s-1) are
Mead, M. I., Khan, M. A. H., Nickless, G., Greally, B. R., Tainton, D., Pitman, T., Shallcross, D. E, Leaf cutter ants., Environ. Chem., 5 1 5-10 , 2008
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Abstract
Environmental context. With large redns. in anthropogenic emissions of many ozone-depleting gases in response to the Montreal Protocol, gases with biogenic sources have become relatively more important in recent years. The global budgets of the biogenic halocarbons are unbalanced with known sinks outweighing sources, suggesting that addnl. natural sources are required to balance the budgets. In the present study, an investigation has been carried out to det. the importance of leaf cutter ants as a missing source of the biogenic halocarbons, which will reduce the discrepancy of the global budget of the halocarbons. Abstr. Leaf cutter ant colonies are shown to be a potentially significant new source of biogenic halocarbons. Fungus cultivated by these ant species may emit CH3Br, CH3I, CH3Cl, CH2Cl2 and CHCl3 in significant quantities, contributing to their resp. global atm. budgets. The study suggests that the mixing ratios of CH3Br, CH3I, CH3Cl, CH2Cl2 and CHCl3 in the ant colony under test were significantly higher than background levels, by on av. a factor of 1.55.0. Sampling was carried out during three stages of ant colony development (new, moderately active and highly active) and it was found that levels of these halocarbons were elevated during the active phases of the ant colony life cycle. A very rough est. of the possible emission of CH3Br, CH3I, CH3Cl, CH2Cl2 and CHCl3 from ant colonies globally are 0.50, 0.02, 0.80, 0.15 and 0.22 Gg year-1.
Mead, M. Iqbal, White, Iain R., Nickless, Graham, Wang, Kuo-Ying, Shallcross, Dudley E., An estimation of the global emission of methyl bromide from rapeseed (Brassica napus) from 1961 to 2003., Atmos. Environ., 42 2 337-345 , 2008
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Abstract
Gan et al. have reported that plants of the family Brassicaceae take up bromide from soils and subsequently release Me bromide (CH3Br) to the atm. deriving a significant emission from this source of ~7 Gg(109 g) yr-1. In this study, a yearly global emission rate for CH3Br from one such species, rapeseed, was detd. from 1961 to 2003 using data on crop harvest index and growth rate in conjunction with global prodn. data. This study suggests that CH3Br emissions from rapeseed have increased 10-fold from 1961 to 2003 and by a factor of 3-4 since 1980. It also suggests that the geog. distribution of emissions has also changed substantially in the last 40 yr. The annual emission of CH3Br from mustard and cabbage is also estd., while relative levels emitted from these species are less significant, as these crops are continually exploited for new applications CH3Br emissions are set to increase.
Miller, Benjamin R., Weiss, Ray F., Salameh, Peter K., Tanhua, Toste, Greally, Brian R., Muehle, Jens, Simmonds, Peter G., Medusa., Anal. Chem. (Washington, DC, U. S.), 80 5 1536-1545 , 2008
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Abstract
Significant changes occurred in anthropogenic emissions of compds. related to the Kyoto and Montreal Protocols within the last 20 years, atm. abundance responded dramatically for many compds. There are also several related natural compds. with under-detd. source or sink budgets. A new instrument, Medusa, was developed to make high frequency in-situ measurements required to det. the atm. lifetimes and emissions of these compds. This automated system measures a range of halocarbons, hydrocarbons, and S compds. involved in O3 depletion and/or climate forcing, from very volatile perfluorocarbons (e.g., CF4 and CF3CF3) and hydrofluorocarbons (e.g., CH3CF3) to higher b.p. solvents (e.g., CH3CCl3 and CCl2
Rigby M, R. G. Prinn, P. J. Fraser, P. G. Simmonds, R. L. Langenfelds, J. Huang, D. M. Cunnold, L. P. Steele, P. B. Krummel, R. F. Weiss, S. O'Doherty, P. K. Salameh, H. J. Wang, C. M. Harth, J. Mühle, and L. W. Porter, Renewed growth of atmospheric methane, Geophys. Res. Lett., 35, doi:10.1029/2008GL036037, 2008 .
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Abstract
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2007
Archibald, A. T., Khan, M. A. H., Watson, L. A., Clemitshaw, K. C., Utembe, S. R., Jenkin, M. E., Shallcross, D. E, Long-term atmospheric measurements of C1-C5 alkyl nitrates in the Pearl River Delta region of southeast China. Comment., Atmos. Environ., 41 34 7369-7370 , 2007
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Abstract
Recent increases in the fractional contribution of NO2 to NOx emissions from the road transport sector in Europe are well documented in the literature. A photochem. trajectory model has been used to simulate the impact of increasing the NO2 fraction on the chem. evolution of air masses arriving at the TORCH field campaign site in the southern UK during late July and August 2003, a period which included a widespread photochem. pollution episode assocd. with a heat-wave. The impact of partial emissions of NOx in the form of nitrous acid (HONO) has also been considered. The model incorporates emissions of NOx, CO, SO2, methane and a detailed speciation of non-methane volatile org. compds. (VOC), coupled with a comprehensive description of the chem. of secondary pollutant formation. An increase in the fractional contribution of NO2 to NOx emissions from 0% to 30% (vol./vol.) results in a 2.49 ppb increase in the simulated campaign mean mixing ratio of oxidant (defined as the sum of O3 and NO2). This is almost exclusively in the form of O3, and represents a ca. 7% increase in the simulated campaign mean O3 mixing ratio. Consideration of 156 events, at 6-hourly resoln. throughout the campaign period, indicates that oxidant increments during the heat-wave period are generally simulated to be greater than those for the remainder of the campaign, with a max. increment of ca. 12 ppb. The increases in oxidant mixing ratios are shown to derive from both the direct effect of increased NO2 input, and indirectly from the enhanced regional-scale chem. processing that this promotes. An illustrative increase in the fractional contribution of HONO to NOx emissions from 0% to 5% (vol./vol.) results in increases in the simulated campaign mean mixing ratios of O3 and oxidant of 1.51 and 1.15 ppb, resp., with the smaller increment for oxidant reflecting a decrease in the NO2 mixing ratio resulting from a notably enhanced NOx oxidn. rate. The oxidant increments during the heat-wave period are once again simulated to be greater than those for the remainder of the campaign, with a max. increment of ca. 11 ppb, which results exclusively from the enhanced regional-scale chem. processing that the HONO emissions promote. The impact of increased fractional NO2 and HONO emissions on the rate of oxidn. of NOx to nitrate is also illustrated and discussed.
Archibald, Alex T., McGillen, Max R., Taatjes, Craig A., Percival, Carl J., Shallcross, Dudley E., Atmospheric transformation of enols., Geophys. Res. Lett., 34 21 L21801/1-L21801/4 , 2007
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Abstract
Following the recent discovery that enols are important intermediates in combustion chem., the possible impact of these species on atm. chem. is investigated. A novel mechanism is proposed by which the reactions of enols contribute significantly towards atm. carboxylic acid concns. in the gas-phase. Inclusion of ethenol in the Common Representative Intermediates CRI mechanism was found to increase predicted secondary prodn. of formic acid considerably (.apprx.40 pptv in the first 6 h in a base case scenario, with typical increases of [HCOOH] ranging from 20-60 pptv over a period of 96 h) whereas its effect on other important trace species (i.e. O3, NOx, HOx and HCHO) was negligible. Carboxylic acid concns. are at present underestimated by major atm. chem. models, and these results indicate that the atm. transformation of enols may be an important missing secondary source term for carboxylic acids in the urban troposphere.
Raventos-Duran, M. Teresa, McGillen, Max, Percival, Carl J., Hamer, Paul D., Shallcross, Dudley E., Kinetics of the CH3O2 + HO2 reaction., Int. J. Chem. Kinet., 39 10 571-579 , 2007
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Abstract
A temp. and pressure kinetic study for the CH3O2 + HO2 reaction was performed using the turbulent flow technique with a chem. ionization mass spectrometry detection system. An Arrhenius expression was obtained for the overall rate coeff. of CH3O2 + HO2 reaction
McGillen, M. R., Percival, C. J., Pieterse, G., Watson, L. A., Shallcross, D. E, Predicting arene rate coefficients with respect to hydroxyl and other free radicals in the gas-phaseAtmos. Chem. Phys., 7 13 3559-3569 , 2007
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Abstract
The reactivity of arom. compds. is of great relevance to pure and applied chem. disciplines, yet existing methods for estg. gas-phase rate coeffs. for their reactions with free radicals lack accuracy and universality. Here a novel approach is taken, whereby strong relationships between rate coeffs. of arom. hydrocarbons and a Randic-type topol. index are investigated, optimized and developed into a method which requires no specialist software or computing power. Measured gas-phase rate coeffs. for the reaction of arom. hydrocarbons with OH radicals were correlated with a calcd. Randic-type index, and optimized by including a term for side chain length. Although this method is exclusively for use with hydrocarbons, it is more diverse than any single existing methodol. since it incorporates alkenylbenzenes into correlations, and can be extended towards other radical species such as O(3P) (and tentatively NO3, H and Cl). A comparison (with species common to both techniques) is made between the topol. approach advocated here and a popular approach based on electrophilic substituent consts., where it compares favorably. A modeling study was carried out to assess the impact of using estd. rate coeffs. as opposed to measured data in an atm. model. The difference in model output was negligible for a range of NOx concns., which implies that this method has utility in complex chem. models. Strong relationships (e.g. for OH, R2 = 0.96) between seemingly diverse compds. including benzene, multisubstituted benzenes with satd., unsatd., aliph. and cyclic substitutions and the nonbenzenoid arom., azulene suggests that the Randic-type index presented here represents a new and effective way of describing arom. reactivity, based on a quant. structure-activity relationship (QSAR).
Yabushita, Akihiro, Kawanaka, Noboru, Kawasaki, Masahiro, Hamer, Paul D., Shallcross, Dudley E., Release of Oxygen Atoms and Nitric Oxide Molecules from the Ultraviolet Photodissociation of Nitrate Adsorbed on Water Ice Films at 100 K., J. Phys. Chem. A, 111 35 8629-8634 , 2007
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Abstract
Prodn. of O(3PJ, J = 2, 1, 0) atoms from the 295-320 nm photodissocn. of NO3- adsorbed on water polycryst. ice films at 100 K was directly confirmed using the resonance-enhanced multiphoton ionization technique. Detection of the O atom signals required an induction period after deposition of HNO3 onto the ice film held at 130 K due to the slow ionization rate of HNO3 to H+ and NO3- with a rate const. of k = (5.3 +- 0.2) * 10-3 s-1. Translational energy distributions of the O atoms were represented by a combination of two Maxwell-Boltzmann energy distributions with translational temps. of 2000 and 100 K. Direct detection of NO from the secondary photodissocn. process was also successful. On the atm. implications, the influence of the direct release of the oxygen atoms into the air from NO3- adsorbed on the natural snowpack was included in an atm. model calcn. on the mixing ratios of ozone and nitric oxide at the South Pole, and the results compared favorably with the field data.
Teresa Raventos-Duran, M., Percival, Carl J., McGillen, Max R., Hamer, Paul D., Shallcross, Dudley E., Kinetics and branching ratio studies of the reaction of C2H5O2 + HO2 using chemical ionization mass spectrometry., Phys. Chem. Chem. Phys., 9 31 4338-4348 , 2007
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Abstract
The overall rate coeff. for the reaction of C2H5O2 with HO2 was detd. using a turbulent flow chem. ionization mass spectrometer (TF-CIMS) system over the pressure range of 75 to 200 Torr and temps. between 195 and 298 K. The temp. dependence of the overall rate coeff. for the reaction between C2H5O2 and HO2 was fitted using the following Arrhenius expression
McGillen, Max R., Percival, Carl J., Shallcross, Dudley E., Harvey, Jeremy N., Is hydrogen abstraction an important pathway in the reaction of alkenes with the OH radical?, Phys. Chem. Chem. Phys., 9 31 4349-4356 , 2007
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Abstract
In this paper, we report the first temp. dependent kinetic measurements of the reaction of C>=5 1-alkenes with OH radicals and also report the first room temp. measurements for 1-alkenes between C8-11. The rate coeffs. at room temp. and between 75 and 100 Torr for the reaction of OH with 1-pentene, 1-octene, 1-nonene, 1-decene and 1-undecene are (2.74 +- 0.38) * 10-11, (3.62 +- 0.68) * 10-11, (4.20 +- 0.41) * 10-11, (7.00 +- 0.96) * 10-11 and (12.44 +- 1.62) * 10-11 cm3 mol.-1 s-1, resp., at 298 K. No pressure dependence is obsd., suggesting that these reactions are at their high pressure limit. Inspection of the variation of rate coeff. with temp. over the temp. range 262-300 K shows a weak neg. temp. dependence, suggesting that adduct formation is taking place, however, a curved Arrhenius plot is clearly seen for 1-decene and theor. anal. suggests that abstraction by OH is a non-negligible channel. An estn. of products formed from OH oxidn. suggests that abstraction will lead to products that have a lower photochem. ozone creation potential than those formed via addn.
Enami, Shinichi, Yamanaka, Takashi, Nakayama, Tomoki, Hashimoto, Satoshi, Kawasaki, Masahiro, Shallcross, Dudley E., Nakano, Yukio, Ishiwata, Takashi., A Gas-Phase Kinetic Study of the Reaction between Bromine Monoxide and Methylperoxy Radicals at Atmospheric Temperatures., J. Phys. Chem. A, 111 17 3342-3348 , 2007
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Abstract
The rate const. of the reaction of BrO with CH3O2 was detd. to be k1 = (6.2 +- 2.5) * 10-12 cm3 mol.-1 s-1 at 298 K and 100-200 Torr of O2 diluent. Quoted uncertainty was two std. deviations. No significant pressure dependence of the rate consts. was obsd. at 100-200 Torr total pressure of N2 or O2 diluents. Temp. dependence of the rate consts. was further investigated over the range 233-333 K, and an Arrhenius type expression was obtained for k1 = 4.6 * 10-13 exp[(798 +- 76)/T] cm3 mol.-1 s-1. The product branching ratios were evaluated and the atm. implications were discussed.
Shallcross, Dudley E., Harrison, Timothy G., Lectures., Chem. Educ. Res. Pract., 8 1 73-79 , 2007
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Abstract
An extensive survey of undergraduate Chem. lectures from years 1-4 during 2004-2005 has been undertaken. They were categorized according to the method used for delivery, where category 1 used only electronic media to deliver courses, category 2 used a mixt. of electronic and non-electronic and category 3 used non-electronic only. Anal. of student questionnaires, coupled with interviews with a selection of students and lecturers from each category, revealed that the impact of the method of lecture delivery is very slight indeed. Non-electronic methods were preferred, but the differences were not significant. The main problems identified with electronic presentations were
Stemmler, Konrad, Folini, Doris, Ubl, Sandy, Vollmer, Martin K., Reimann, Stefan, O'Doherty, Simon, Greally, Brian R., Simmonds, Peter G., Manning, Alistair J., European Emissions of HFC-365mfc, a Chlorine-Free Substitute for the Foam Blowing Agents HCFC-141b and CFC-11., Environ. Sci. Technol., 41 4 1145-1151 , 2007
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Abstract
HFC-365mfc (1,1,1,3,3-pentafluorobutane) is an industrial chem. used for polyurethane foam blowing. From early 2003, HFC-365mfc has been com. produced as a substitute for HCFC-141b, whose use in Europe was banned in Jan. 2004. The first atm. detection of HFC-365mfc and a 2-yr record at the high Alpine station, Jungfraujoch, Switzerland, and the Atlantic coast station, Mace Head, Ireland, are reported. Jungfraujoch measurements were used to est. central European emissions of HFC-365mfc, HCFC-141b, and CFC-11. For HFC-365mfc, it was estd. that central European emissions (Germany, France, Italy, Switzerland, The Netherlands, Belgium, Luxembourg) in 2003 and 2004 were 400-500 tons/yr. These emissions were .apprx.1/3 lower on a per capita basis than that estd. at Mace Head measurements for the entirety of Europe. Estd. HCFC-141b emissions for central Europe were higher (7.2-3.5 ktonnes/yr) with a decreasing trend for 2000 to 2004, residual CFC-11 emissions were estd. at 2.4-4.7 ktonnes/yr for the same period. The Po Valley (northern Italy) appears to be a main source region for HFC-365mfc and for former blowing agents, HCFC-141b and CFC-11. In 2004, HFC-365mfc emissions increased from a wider region of Europe, attributed to an increased penetration of HFC-365mfc in the European market.
Derwent, R. G., Simmonds, P. G., Greally, B. R., O'Doherty, S., McCulloch, A., Manning, A., Reimann, S., Folini, D., Vollmer, M. K., The phase-in and phase-out of European emissions of HCFC-141b and HCFC-142b under the Montreal Protocol., Atmos. Environ., 41 4 757-767 , 2007
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Abstract
The mixing ratios of HCFC-141b (1,1-dichlorofluoroethane) and HCFC-142b (1-chloro-1,1-difluoroethane) have been rising steadily in baseline air at Mace Head, Ireland over the 10-yr period from 1994 to 2004. These HCFCs are widely used replacements for the chlorofluorocarbons phased out under the Montreal Protocol and its subsequent amendments. Anal. of the HCFC content of regionally-polluted air arriving at Mace Head from the European continent shows that European emissions reached a peak during 2000-2001 and have declined subsequently, following the phase-out in their usage. European emissions of HCFC-141b have been further constrained by observations at the High-Alpine Jungfraujoch site. The redns. are consistent with the phase-out of HCFC prodn. and use from the year 2001 onwards mandated by European regulations designed to exceed the requirements of the Montreal Protocol.
O'Doherty, S. and Carpenter, L. J., Volatile halogenated compounds' in Koppman R. (ed), Volatile Organic Compounds in the Atmosphere, Blackwell Ltd, London, 2007 .
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Abstract
Stemmler, K., D. Folini, S. Ubl, M.K. Vollmer, S. Reimann, S. O'Doherty, B.R. Greally, P.G. Simmonds and A.J. Manning, European emissions of HFC-365mfc, a Chlorine free substitute for the foam blowing agents HCFC-141b and CFC-11, Environmental Science & Technology, 41, 1145-1151, 2007 .
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Abstract
Greally, B.R., P.G. Simmonds, S. O'Doherty, A. McCulloch, B.R. Miller, P.K. Salameh, J. Mühle, T. Tanhua, C. Harth, R.F. Weiss, P.J. Fraser, P.B. Krummel, B.L. Dunse, L.W. Porter and R.G. Prinn, Improved continuous in situ measurements of C1-C3 PFCs, HFCs, HCFCs, CFCs and SF6 in Europe and Australia, Environmental Sciences, 41, 4, 1145-1151, 2007 .
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Abstract
X. Xiao, R. G. Prinn, P. G. Simmonds, L. P. Steele, P. C. Novelli, J. Huang, R. L. Langenfelds, S. O'Doherty, P. B. Krummel, P. J. Fraser, L. W. Porter, R. F. Weiss, P. Salameh, and R. H. J. Wang, Optimal estimation of the soil uptake rate of molecular hydrogen from the Advanced Global Atmospheric Gases Experiment and other measurements, J. Geophys. Res., 112, D07303, 2007 .
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Abstract
Greally G.R, A.J. Manning, S. Reimann, A. McCulloch, J. Huang, B.L. Dunse, P.G. Simmonds, R.G. Prinn, P.J. Fraser, D.M. Cunnold, S. O'Doherty, L.W. Porter, G.A. Sturrock, K. Stemmler, M.K. Vollmer, C.R. Lunder, N. Schmidbauer, O. Hermansen, J. Arduini, P.K. Salameh, P.B. Krummel, R.H.J. Wang, D. Folini, R.F. Weiss, M. Maione, G. Nickless, F. Stordal and R.G. Derwent, Observation of 1,1-difluoroethane (HFC-152a) at AGAGE and SOGE monitoring stations 1994-2004 and derived Global and regional emission estimates, J. Geophys. Res., 112, D6, D06308, 2007 .
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Abstract
Derwent R.G, P.G. Simmonds, B.R. Greally, S. O'Doherty, A. McCulloch, A. Manning, S. Reimann, D. Folini ,M.K. Vollmer, The phase-in and phase-out of European emissions of HCFC-141b and HCFC-142b under the Montreal Protocol: Evidence from observations at Mace Head, Ireland from 1994-2004, Atmospheric Environment, 41, 4, 757-767, 2007 .
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Abstract
Legreid, G., S. Reimann, M. Steinbacher, J. Staehelin, D. Young, and K. Stemmler, Measurements of OVOCs and NMHCs in a swiss highway tunnel for estimation of road transport emissions, Environmental Science & Technology, 41(20), 7060-7066, 2007
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Abstract
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2006
Johnson, D., Utembe, S. R., Jenkin, M. E., Simulating the detailed chemical composition of secondary organic aerosol formed on a regional scale during the TORCH 2003 campaign in the southern UK., Atmos. Chem. Phys., 6 2 419-431 , 2006
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Abstract
Following a companion study (Johnson, et al., 2006), a photochem. trajectory model (PTM) simulated the chem. compn. of org. aerosols for selected events during the 2003 TORCH (Tropospheric Org. Chem. Expt.) field campaign. The PTM incorporated speciated emissions of 124 non-methane anthropogenic volatile org. compds. (VOC) and 3 representative biogenic VOC, a highly-detailed representation of the atm. degrdn. of these VOC, emissions of primary org. aerosols (POA), and formation of secondary org. aerosol (SOA). SOA formation was represented by the transfer of semi- and non-volatile oxidn. products from the gas-phase to a condensed org. aerosol-phase, according to estd. thermodn. equil. phase-partitioning characteristics for .apprx.2000 reaction products. After significantly scaling all phase-partitioning coeffs. and assuming a persistent background org. aerosol (both required to match obsd. org. aerosol loads), a detailed chem. compn. of simulated SOA was examd. in terms of intermediate oxygenated species in the Master Chem. Mechanism, version 3.1 (MCM v3.1). For various case studies considered, 90% of simulated SOA mass comprised from .apprx.70 to 100 multi-functional oxygenated species derived, in varying amts., from the photooxidn. of anthropogenic and biogenic VOC. The anthropogenic contribution was dominated by arom. hydrocarbons, the biogenic contribution by alpha - and beta -pinene (which also constituted surrogates for other emitted monoterpene species). Sensitivity in the simulated SOA mass to changes in anthropogenic and biogenic VOC emission rates was also assessed for 11 case study events, results were compared to detailed chem. compn. data. The role of accretion chem. in SOA formation and its implications for results of this investigation, is discussed.
Johnson, D., Utembe, S. R., Jenkin, M. E., Derwent, R. G., Hayman, G. D., Alfarra, M. R., Coe, H., McFiggans, G., Simulating regional scale secondary organic aerosol formation during the TORCH 2003 campaign in the southern UK., Atmos. Chem. Phys., 6 2 403-418 , 2006
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Abstract
A photochem. trajectory model simulated the chem. evolution of air masses arriving at the TORCH (tropospheric org. chem. expt.) field campaign site in southern UK in late July and Aug. 2003, a period which included a widespread, prolonged photochem. pollution episode. This model incorporated speciated emissions of 124 non-methane anthropogenic volatile org. compds. (VOC) and 3 representative biogenic VOC, coupled with a comprehensive description of the chem. of their degrdn. A representation of gas/aerosol absorptive partitioning of .apprx.2000 oxygenated org. species generated in the Master Chem. Mechanism (MCM v3.1) was implemented, allowing modeling of the contribution to org. aerosols (OA) made by semi- and non-volatile products of VOC oxidn., primary org. aerosol (POA) and elemental C (EC) emissions are also represented. Modeled total OA mass concns. in 9 case study events (optimized by comparison with obsd. hourly-mean mass loadings derived from aerosol mass spectrometry measurements) implied that OA can be ascribed to 3 general sources
Utembe, S. R., Hansford, G. M., Sanderson, M. G., Freshwater, R. A., Pratt, K. F. E., Williams, D. E., Cox, R. A., Jones, R. L., An ozone monitoring instrument based on the tungsten trioxide (WO3) semiconductor., Sens. Actuators, B, B114 1 507-512
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Abstract
Novel sensors based on W trioxide (WO3) semiconductors hold much promise as a cheaper alternative for ozone monitoring. The sensitivity of the metal oxide to ozone is owed to the presence of surface O vacancies. The filling of O vacancies by the decompg. ozone traps free charge carriers with consequent measurable increase in resistance. A Langmuir-type model simulating the fundamental surface reactions was found to reproduce the measured sensor response. Using a temp.-cycling technique in which the temp. of the sensor is alternated between 600 and 530 Deg representing scrubbing and measurement resistances, resp., ozone measurements were obtained from several urban sites. Results from eight sensors show that the sensors have adequate sensitivity and response time with measurements comparable to ozone measured by UV absorption spectrometer (root-mean-square of variances up to 7 ppbv). Problems of apparent changes in sensor sensitivity in field measurements were explained by inadequate burn-in' period prior to calibration and field deployment. The sensors should be run in ambient conditions for about a week before calibration.
McGillen, Max R., Crosier, Jonny, Percival, Carl J., Sanchez-Reyna, Gabriela, Shallcross, Dudley E., Can topological indices be used to predict gas-phase rate coefficients of importance to tropospheric chemistry? Reactions of alkenes with OH, NO3 and O3., Chemosphere, 65 11 2035-2044
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Abstract
Rate coeffs. for the gas-phase reactions of unsatd. hydrocarbons with OH, NO3, and O3 are of vital importance to atm. modeling. Many of these rate coeffs. are unknown, possibly resulting from the variety of these compds. and the inherent expense of deriving these data exptl., and a reliable method for their prediction would therefore be of value to such models. This study presents a method for estg. rate coeffs. for C2-10 olefins. Measured rate coeffs. for the reaction of unsatd. hydrocarbons with OH and NO3 radicals and O3 are correlated with the Randic topol. descriptor and an established correlation parameter, i.e. ionization potentials calcd. using the frontier MO (FMO) approach. Although the ionization potential method produces better correlations in general, OH correlations of aliph. species, subdivided into groups of varying total no. of primary (1 Deg), secondary (2 Deg) and tertiary (3 Deg) carbon atoms (.sum.x Degx) produced several new trends with the Randic index that were not present in the ionization potential correlations. Strong correlation was obsd. with a Randic-type index optimized to include a term for side chain length (.sum.x Degx). The presence of strong relationships, made predictable by mol. constitution, makes topol. descriptors a useful and accessible tool for estg. rate coeffs. for the reactions of OH with aliph. species. This study indicates that alkene reactivity is affected strongly by constitution and that abstraction as well as addn. may be important for some classes of compd.
Shallcross, Dudley E., Dirty air., Educ. Chem., 43 5 131-135 , 2006
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Abstract
A review on sources of widespread primary (SO2, NOx, CO, volatile org. compds., particulate matter) and secondary (O3, secondary aerosols) air pollutants and their impacts on human health and plants.
Shallcross, Dudley E., Vaughan, Stewart, Trease, David R., Canosa-Mas, Carlos E., Ghosh, Mariana V., Dyke, John M., Wayne, Richard P., Kinetics of the reaction between OH radicals and monochlorodimethylsulphide (CH3SCH2Cl)., Atmos. Environ., 40 36 6899-6904 , 2006
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Abstract
The gas-phase rate coeff. for the reaction between OH radicals and CH3SCH2Cl (MCDMS) was detd. to be 2.5 * 10-12 cm3 mol-1 s-1 using the discharge-flow kinetic technique. An est. of ~10-10 cm3 mol-1 s-1 was obtained for the rate coeff. for reaction of Cl with MCDMS. It would appear that the reaction with OH is not the main loss process for CH3SCH2Cl in the marine boundary layer. The possible implications for the MBL of halogen-promoted oxidn. of dimethylsulfide are considered.
Vaughan, Stewart, Canosa-Mas, Carlos E., Pfrang, Christian, Shallcross, Dudley E., Watson, Laura, Wayne, Richard P., Kinetic studies of reactions of the nitrate radical (NO3) with peroxy radicals (RO2)., Phys. Chem. Chem. Phys., 8 32 3749-3760 , 2006
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Abstract
A discharge-flow system, coupled to cavity-enhanced absorption spectroscopy (CEAS) detection systems for NO3 at l = 662 nm and NO2 at l = 404 nm, was used to investigate the kinetics of the reactions of NO3 with eight peroxy radicals at P .apprx. 5 Torr and T .apprx. 295 K. Values of the rate consts. obtained were (k/10-12 cm3 mol.-1 s-1)
Warwick, N. J., Pyle, J. A., Shallcross, D. E, Global Modelling of the Atmospheric Methyl Bromide Budget., J. Atmos. Chem., 54 2 133-159 , 2006
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Abstract
A global three-dimensional chem. transport model has been used to identify and evaluate possible candidates for the missing surface source required to balance the atm. budget of Me bromide. Both natural and anthropogenic emissions of Me bromide are colored in the model, thus allowing the global CH3Br distribution to be broken-down into its source components. These colored CH3Br tracers are then combined in various ways to create one base-line emission scenario and five further plausible scenarios. The addnl. emission scenarios are specifically designed to test whether the geog. distribution and seasonal cycles of addnl. vegetation and/or increased biomass burning emissions are consistent with atm. observations of Me bromide mixing ratios. Due to an imbalance in our current understanding of the Me bromide budget, simulated CH3Br mixing ratios from the base-line emission scenario are significantly lower than atm. measurements. Both the inclusion of a vegetation source in the tropics and a double strength biomass burning source substantially improve the agreement between model simulations and atm. measurements compared with the base-line emission scenario. While measurement data provides useful information on global fluxes and regional CH3Br seasonal cycles, small differences between the simulated seasonal cycles of different emission scenarios makes it difficult to distinguish between the relative likelihoods of model scenarios contg. a tropical vegetation source or an increased biomass burning source. Further measurements performed in continental mid-to-high northern latitudes, central-southern Africa and South America would be of particular benefit in future attempts to constrain the location and magnitude of the natural terrestrial sources of Me bromide.
Percival, Carl, Harrison, Tim, Shallcross, Dudley., Catching the cheats., Chem. Rev. (Deddington, U. K.), 15 4 24-27 , 2006
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Abstract
A review. Increasingly sensitive tests for drug testing of athletes, such as immunoassays, thin-layer chromatog., GC-MS, the use of molecularly imprinted polymers, and quartz crystal microbalance are described, including a new type of sensor.
Dyke, J. M., Ghosh, M. V., Goubet, M., Lee, E. P. F., Levita, G., Miqueu, K., Shallcross, D. E, A study of the atmospherically relevant reaction between molecular chlorine and dimethylsulfide (DMS)., Chem. Phys., 324 1 85-95 , 2006
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Abstract
In a study using UPS (PES) of the atmospherically relevant reaction bands assocd. with a reaction intermediate have been obsd. These have been assigned to ionization of the covalently bound mol. (CH3)2SCl2 on the basis of the intensity of the obsd. bands as a function of reaction time, MO calcns. of vertical ionization energies and evidence from IR spectroscopy. A method has also been developed, with the flow-tube/PE spectrometer combination used, to measure photoionization cross-sections of the reagents and products at the photon energy utilized and this has allowed the photoionization cross-section of the intermediate to be estd. This work augments an earlier study in which the rate const. of the reaction between CH3SCH3 (DMS) and Cl2 has been measured at room temp.
McGillen, Max R., Percival, Carl J., Raventos-Duran, Teresa, Sanchez-Reyna, Gabriela, Shallcross, Dudley E., Can topological indices be used to predict gas-phase rate coefficients of importance to tropospheric chemistry? Free radical abstraction reactions of alkanes., Atmos. Environ., 40 14 2488-2500 , 2006
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Abstract
As tropospheric chem. models become ever more complex, reliable rate coeff. data for gas-phase hydrogen abstraction reactions involving trace hydrocarbons becomes increasingly necessary. There are hundreds of nonmethane hydrocarbons (NMHCs) of potential importance to tropospheric chem., many of which were not subjected to exptl. inquiry. This study-the 1st of its kind to study hydrocarbons ranging from C2 to C10 using topol. indexes-aims to provide a reliable and accessible method of estg. rate coeffs. for these species. Rate coeffs. of free radical abstraction reactions of NMHCs were correlated with the Randic and Balaban topol. indexes for radical moieties OH, Cl and NO3. These correlations were compared with those of an established frontier orbital approach based on calcd. ionization potentials (IPs). The Randic index was found to correlate better than IP for each of the radicals studied, and correlated particularly effectively for the Cl radical. The Balaban index did not correlate for branched alkanes except for NO3. Where only unbranched alkanes were considered, the Balaban index proved most reliable, demonstrating a clear linear relation. Topol. indexes present an accurate and diverse method for estg. free radical abstraction rate coeffs. that does not require the computing power, specialist software packages, or complex mathematics inherent in ab initio calcns. A further advantage of using topol. indexes is that they are calcd. in an unambiguous manner. More reliable tools for estg. rate coeffs. have direct implications for improving models, and may also provide a direction for future lab. work, either by highlighting particularly reactive species or identifying potentially spurious rate coeff. data.
Harrison, Timothy, Shallcross, Dudley, Henshaw, Stephen., Detecting CO2., Chem. Rev. (Deddington, U. K.) , 15 3 27-30 , 2006
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Abstract
CO2 is the primary greenhouse gas in the atm. and is generated by the combustion of fossil fuels. The atm. concns. of CO2 are increasing at an unprecedented rate, contributing to global warming. To quantify CO2 levels in the atm., scientists use a detector based on IR spectroscopy. The CO2 detector contains an IR lamp that emits radiation over a wide range of wavelengths. A photocell measures the intensity of the radiation that reaches it, while a second ref. cell dets. the radiation intensity when no CO2 is present. The amt. of light absorbed by each CO2 mol. is a const. at a particular wavelength, and is known as the absorption coeff. Together with the length of the cell and the amt. of light absorbed, the concn. of CO2 in the sample can be calcd. using the Beer-Lambert law. In the detector, the concn. is detd. using an onboard microprocessor. The efficiency of the detector can be improved by fitting an air pump to draw samples of air inside. This detector can measure CO2 concns. in the range 0-2000 ppm (ppm). Levels of atm. CO2 are typically in the region of 350 ppm and so fall well within these limits. Such detectors are useful in continually monitoring air quality in cities and along busy roads.
Bacak, Asan, Bardwell, Max W., Raventos-Duran, M. Teresa, Percival, Carl J., Hamer, Paul D., Shallcross, Dudley E., Kinetics of the CH3O2 + NO2 reaction., Chem. Phys. Lett., 419 1-3 125-129 , 2006
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Abstract
The rate coeff. for the reaction CH3O2 + NO2 has been measured using a turbulent flow technique with high pressure chem. ionization mass spectrometry for the detection of reactants. The rate const. was measured between 75 and 600 Torr and at 298 and 223 K. This work represents the first exptl. evaluation of this rate coeff. at temps. below 253 K.
Simmonds, P. G., Manning, A. J., Cunnold, D. M., McCulloch, A., O'Doherty, S., Derwent, R. G., Krummel, P. B., Fraser, P. J., Dunse, B., Porter, L. W., Wang, R. H. J., Greally, B. R., Miller, B. R., Salameh, P., Weiss, R. F., Prinn, R. G., Global trends, seasonal cycles, and European emissions of dichloromethane, trichloroethene, and tetrachloroethene from the AGAGE observations at Mace Head, Ireland, and Cape Grim, Tasmania., J. Geophys. Res., [Atmos.], 111 D18 D18304/1-D18304/19 , 2006
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Abstract
In situ observations (every 4 h) of dichloromethane (CH2Cl2) from Apr. 1995 to Dec. 2004 and trichloroethene (C2HCl3) and tetrachloroethene (C2Cl4) from Sept. 2000 to Dec. 2004 are reported for the Advanced Global Atm. Gases Expt. (AGAGE) station at Mace Head, Ireland. At a second AGAGE station at Cape Grim, Tasmania, CH2Cl2 and C2Cl4 data collection commenced in 1998 and 2000, resp. C2HCl3 is below the limit of detection at Cape Grim except during pollution episodes. At Mace Head CH2Cl2 shows a downward trend from 1995 to 2004 of 0.7 +- 0.2 ppt yr-1 (ppt
Greally, Brian R., Nickless, Graham, Simmonds, Peter G., Retention behavior of volatile C1-C3 fluoroalkanes upon selected preconcentration adsorbents., J. Chromatogr., A, 1133 1-2 49-57 , 2006
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Abstract
The retention behavior of several gaseous fluorinated greenhouse gases on C-based adsorbents is presented. Retention, calcd. on the basis of compd. breakthrough vol. (BTV), is dependent on the mol. compn. of the adsorbate, with compds. possessing Cl or polarizable hydrogens being better retained than those possessing higher F content. Of the adsorbents tested the C mol. sieves (CMSs) of highest surface area show greater retention than those with lower area. Retention of fluorocarbons is generally higher on activated charcoals but this adsorbent type can cause irreversible retention, possible degrdn. and is more difficult to use practically due to its heterogeneous compn. These breakthrough vol. results can be used to det. the best combination and quantities of each adsorbent that can be used within a preconcn. device with a view to developing an anal. system for the detn. of fluorocarbon gases in low concn. air samples.
Derwent R.G, P.G. Simmonds, S. O'Doherty, D. S. Stevenson, F. Dentener, J. Cofala, R. Mechler, M. Amann, External influences on Europe's air quality: baseline methane, carbon monoxide and ozone from 1990 to 2030 at Mace Head, Ireland, Atmospheric Environment, 40, 5, 844-855, 2006 .
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Abstract
Derwent Richard, Peter Simmonds, Simon O'Doherty, Alistair Manning, William Collins, David Stevenson, Global environmental impacts of the hydrogen economy, Int. J. Nuclear Hydrogen Production and Applications, 1, 1, 57-67, 2006 .
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Abstract
Simmonds P.G, A. J. Manning, D. M. Cunnold, A. McCulloch, S. O'Doherty, R.G. Derwent, P. B. Krummel, P.J. Fraser, B. Dunse, L.W. Porter, R.H.J. Wang, B. R. Greally1, B.R. Miller, P. Salameh, R.F. Weiss, and R.G. Prinn, Global trends, seasonal cycles and European emissions of dichloromethane, trichloroethene and tetrachloroethene from the AGAGE observations at Mace Head, Ireland and Cape Grim, Tasmania., J. Geophys. Res., 111, D18304, doi: 10.1029/2006JD007082, 2006 .
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Abstract
Heard DE, Read KA, Methven J, Al-Haider S, Bloss WJ, Johnson GP, Pilling MJ, Seakins PW, Smith SC, Sommariva R, Stanton JC, Still TJ, Ingham T, Brooks B, De Leeuw G, Jackson AV, McQuaid JB, Morgan R, Smith MH, Carpenter LJ, Carslaw N, Hamilton J, Hopkins JR, Lee JD, Lewis AC, Purvis RM, Wevill DJ, Brough N, Green T, Mills G, Penkett SA, Plane JMC, Saiz-Lopez A, Worton D, Monks PS, Fleming Z, Rickard AR, Alfarra MR, Allan JD, Bower K, Coe H, Cubison M, Flynn M, McFiggans G, Gallagher M, Norton EG, O'Dowd CD, Shillito J, Topping D, Vaughan G, Williams P, Bitter M, Ball SM, Jones RL, Povey IM, S. O'Doherty, Simmonds PG, Allen A, Kinnersley RP, Beddows DCS, Dall'Osto M, Harrison RM, Donovan RJ, Heal MR, Jennings SG, Noone C, Spain G, The North Atlantic Marine Boundary Layer Experiment (NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002, Atmospheric Chemistry and Physics, 6, 2241-2272, 2006 .
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Abstract
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2005
Utembe, Steven R., Jenkin, Michael E., Derwent, Richard G., Lewis, Alastair C., Hopkins, James R., Hamilton, Jacqueline F., Modelling the ambient distribution of organic compounds during the August 2003 ozone episode in the southern UK., Faraday Discuss., 130 Atmospheric Chemistry 311-326 , 2005
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Abstract
A photochem. trajectory model contg. speciated emissions of 124 non-methane volatile org. compds. (VOC), and a comprehensive description of the chem. of VOC degrdn., was used to simulate the chem. evolution of boundary layer air masses arriving at a field campaign site in the southern UK during a widespread and prolonged photochem. pollution event in August 2003. The simulated concns. and distributions of org. compds. at the arrival location are compared with observations of a series of hydrocarbons and carbonyl compds., which were measured using GC-FID and multidimensional GC methods. The comparison of the simulated and obsd. distributions of 34 emitted hydrocarbons provides some support for the magnitude and applied emissions speciation of anthropogenic hydrocarbons, but is indicative of an under representation of the input of biogenic hydrocarbons, particularly at elevated temps. Simulations of the detailed distribution of ca. 1250 carbonyl compds., formed primarily from the degrdn. of the 124 emitted VOC, focus on 61 aldehydes, ketones, dicarbonyls, hydroxycarbonyls, and arom. aldehydes which collectively account for ca. 90% of the simulated total molar concn. of carbonyls. The simulated distributions indicate that the photolysis of formaldehyde and alpha -dicarbonyls make major contributions to free radical prodn. for the arrival conditions of 5 case study trajectories. The simulated concns. of hydroxycarbonyls demonstrate preferential formation of the 1,4-substituted isomers (compared with 1,2- and 1,3-isomers of the same carbon no.), which are formed during the initial oxidn. sequence of longer chain alkanes.
Percival, Carl. J., Shallcross, Dudley E., Canosa-Mas, Carlos E., Dyke, John M., Recent advances in the application of discharge-flow to the determination of gas-phase rate coefficients at pressures and temperatures of relevance to the Earth's atmosphere., J. Photochem. Photobiol., A, 176 1-3 250-259 , 2005
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Abstract
A review. The detn. of gas-phase rate coeffs. using the traditional discharge-flow system has produced a wealth of information that has informed atm. science. However, the range of pressure and temps. obsd. in the Earth's atm. cannot be accessed by such a system. In this paper we discuss the recent advances in flow tube studies such as the use of turbulent flow that have allowed one to operate flow systems at atm. pressure and over a wider range of temp. At the same time a no. of new detection methods have been coupled to flow systems, such as CIMS, CEAS and UV-PES that have greatly enhanced the versatility and range of systems that may be studied and these are briefly discussed.
Clifford, Grainne M., Thuener, Lars P., Wenger, John C., Shallcross, Dudley E., Kinetics of the gas-phase reactions of OH and NO3 radicals with aromatic aldehydes., J. Photochem. Photobiol., A, 176 1-3 172-182 , 2005
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Abstract
Rate coeffs. for the reactions of OH and NO3 radicals with benzaldehyde and the tolualdehydes have been detd. at 295 +- 2 K and atm. pressure using the relative rate technique. Expts. were performed in atm. simulation chambers using gas chromatog. for chem. anal. The rate coeffs. were detd. The reactivity of the arom. aldehydes is compared to other arom. compds. and it is shown that, for the tolualdehydes, the OH and NO3 rate coeffs. do not depend on the position of the CH3 substituent on the arom. ring. The new data are used to show that the gas-phase reactivity of the arom. aldehydes towards OH and NO3 radicals follows a linear free energy relationship typical of addn. reactions, although the net result is H-atom abstraction. The rate coeff. data are explained in terms of known mechanistic features of the reactions and simple theor. calcns. have been performed in an attempt to understand the obsd. trends in reactivity. The atm. implications are also discussed.
Jones, R. L., Ball, S. M.,
Shallcross, D. E,
Small scale structure in the atmosphere., Faraday Discuss., 130 Atmospheric Chemistry 165-179 , 2005
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Abstract
Non-linearities in chem. processes are recognized as being important in a no. of areas of atm. science. In this paper we show simulations using an idealized plume model which describes the relaxation of an urban plume into the background atm. As might be anticipated, the initial conditions of NOx, O3 and VOCs (volatile org. C) within the plume and background are important in detg. the chem. downstream of the source, but crucially for this study, the rate of mixing (on timescales appropriate to the real atm.) is found to alter the compn. of the atm. significantly. The model shows that NO3 chem. can play a major role in the oxidn. of biogenic VOCs present in the background atm. In addn., the reaction of hydrocarbons with NO3 potentially has important implications for NOy speciation because a significant fraction of org. nitrates thus formed are sufficiently long-lived to leave the planetary boundary layer. A particularly crit. result of the model is that under certain NOx conditions, O3 surface deposition can be significantly inhibited, with consequent effects on the O3 budget.
Pope, Francis D., Smith, Carina A., Davis, Peter R.,
Shallcross, Dudley E., Ashfold, Michael N. R., Orr-Ewing, Andrew J.,
Photochemistry of formaldehyde under tropospheric conditions., Faraday Discuss., 130 Atmospheric Chemistry 59-72 , 2005
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Abstract
We report new results on the absorption cross sections and photochem. quantum yields for radical (H + HCO) prodn. from formaldehyde in the wavelength interval from 308-320 nm, obtained at resolns. of better than 0.1 nm. The absorption cross sections, measured at resolns. close to the limit for Doppler broadening of HCHO, show rotationally resolved fine structure, with max. values higher than those obtained in previous, lower resoln., studies. In this wavelength region, absorption cross sections peak at 2.3 * 10-19 cm2 mol.-1, but band-integrated values are in excellent accord with previous measurements. HCO absorption coeffs., measured by cavity ring-down spectroscopy following UV photolysis of HCHO at wavelengths across the 210510, 220430 and 230410 bands of the ~A1A2-~X1A1 transition, generally mimic the parent absorption band profiles. Division of these absorption coeffs. by the high resoln. parent absorption cross sections gives relative quantum yields for the H + HCO radical product channel that can be put on an abs. scale using single-wavelength literature values. These quantum yields are obsd. to show some variation with parent excitation wavelength (and thus with excited vibronic level). Addn. of 200 Torr of N2 increases the HCO quantum yields.
Sanchez-Reyna, G., Wang, K.-Y.,
Shallcross, D. E,
Trends in particulate matter in urban and rural areas of the U.K. over the last 7 years and the potential impact of future climate change on these trends., WIT Trans. Ecol. Environ., 82 Air Pollution XIII 539-548 , 2005
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Abstract
Ambient concns. of particles at 11 sites in London and one rural site in the south of England from 1996 to 2002 were examd. A downward trend was obsd. in 11 of the 12 monitoring sites and has been mainly explained by the redn. in secondary particles in urban sites. Maximum concns. of particles were registered during summer and winter seasons, and air mass back trajectory data suggested that there was a significant contribution of imported pollution for some of the highest records of PM10. Indeed, it was found that levels of particles were higher when the wind came from the SE, corresponding to European influenced air and highlighting the importance of international collaboration for the effective redn. of particles. In the wake of climate change, potential changes in prevailing meteorol. could have a significant impact on particle loading, either by increasing or decreasing regionally imported pollution or by influencing very local street scale pollution levels. Possible explanations why one site in London has not seen a decline in particle levels are given.
Bale, Catherine S. E., Canosa-Mas, Carlos E., Shallcross, Dudley E., Wayne, Richard P., A discharge-flow study of the kinetics of the reactions of IO with CH3O2 and CF3O2., Phys. Chem. Chem. Phys., 7 10 2164-2172 , 2005
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Abstract
We have detd. the rate consts. for the reactions IO + CH3O2 Products (1) and IO + CF3O2 -> Products (2) using a discharge-flow tube equipped with off-axis cavity-enhanced absorption spectroscopy (CEAS) for the detection of IO. NO2, produced from the titrn. of RO2 with NO, was also detected using the CEAS system. The rate consts. obtained were k1 = (6.0 +- 1.3) * 10-11 cm3 mol.-1 s-1 and k2 = (3.7 +- 0.9) * 10-11 cm3 mol.-1 s-1 at T = 295 +- 2 K and P = 2.5 +- 0.3 Torr, this is the first detn. of these rate consts. The possible products and the atm. implications of reaction (1) are discussed.
Bardwell, Max W., Bacak, Asan, Raventos, M. Teresa, Percival, Carl J., Sanchez-Reyna, Gabriela, Shallcross, Dudley E., Kinetics and mechanism of the C2H5O2 + NO reaction,. Int. J. Chem. Kinet., 37 4 253-260 , 2005
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Abstract
The overall rate coeff. (k1) for the reaction of C2H5O2 + NO was measured using the turbulent flow CIMS technique. The temp. dependence of the rate coeff. was studied between 203 and 298 K. Across the temp. range, the exptl. detd. rate coeffs. showed good agreement with previous studies and were fitted using an Arrhenius type anal. to yield the expression k1 = (1.75-0.13+0.14) * 10-12 exp[(462 +- 19)/T] cm3 mol.-1 s-1. Expts. were carried out in the pressure range of 100-200 torr within the stated temp. range, where the rate coeffs. are invariant with pressure. The branching ratio of the reaction was also assessed as a function of temp. and proceeds 100 +- 5% via the C2H5O + NO2 reactive channel. This work represents the first temp. and pressure study over which the branching ratio was studied.
Dyke, J. M., Ghosh, M. V., Kinnison, D. J., Levita, G., Morris, A., Shallcross, D. E, A kinetics and mechanistic study of the atmospherically relevant reaction between molecular chlorine and dimethyl sulfide (DMS)., Phys. Chem. Chem. Phys., 7 5 866-873 , 2005
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Abstract
A gas-phase kinetics study of the atmospherically important reaction between Cl2 and di-Me sulfide (DMS) Cl2 + CH3SCH3->products (1) has been made using a flow-tube interfaced to a photoelectron spectrometer. The rate const. for this reaction has been measured at 1.6 and 3.0 torr at T = (294 +- 2) K as (3.4 +- 0.7) * 10-14 cm3 mol.-1 s-1. Reaction has been found to proceed via an intermediate, (CH3)2SCl2, to give CH3SCH2Cl and HCl as the products. The mechanism of this reaction and the structure of the intermediate were investigated using electronic structure calcns. A comparison of the mechanisms of the reactions between Cl atoms and DMS, and Cl2 and DMS has been made and the relevance of the results to atm. chem. is discussed.
Shallcross, Dudley E., Teresa Raventos-Duran, M., Bardwell, Max W., Bacak, Asan, Solman, Zachary, Percival, Carl J., A semi-empirical correlation for the rate coefficients for cross- and self-reactions of peroxy radicals in the gas-phase., Atmos. Environ., 39 4 763-771 , 2005
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Abstract
Peroxy radicals play an important role as reaction intermediates in the atm. oxidn. of volatile org. compds. (VOCs). The rate coeffs. for the self-reactions vary by up to six orders of magnitude (e.g. 3.0*10-17 cm3 mol.-1 s-1 for t-C4H9O2 and 1.5*10-11 cm3 mol.-1 s-1 for CH3C(O)O2) with, up to now, no clear pattern. This work represents the first rationalization of peroxy radical self-reaction trends in reactivity. A correlation between the logarithm of the rate coeff. of peroxy radical self-reactions with the stabilization energy, the difference in the enthalpy of formation of peroxy radicals with that of the tetraoxide adduct {Delta Hf(RO4R)-2Delta Hf(RO2)}, is presented. The equation, log10 k=-{Delta Hf(RO4R)-2Delta Hf(RO2)+235.95}/13.32 (where energy is in kJ mol-1) is given to predict the room temp. rate coeffs. of peroxy radical self-reactions. The correlation was extended to predict rate coeffs. for the cross-reactions of peroxy radicals with CH3O2. Furthermore, favorable comparisons are made between the predicted rate coeffs. and very recent studies of complex peroxy radical systems.
Reimann, Stefan, Manning, Alistair J., Simmonds, Peter G., Cunnold, Derek M., Wang, Ray H. J., Li, Jinlong, McCulloch, Archie, Prinn, Ronald G., Huang, Jin, Weiss, Ray F., Fraser, Paul J., O'Doherty, Simon, Greally, Brian R., Stemmler, Konrad, Hill, Matthias, Folini, Doris., Low European methyl chloroform emissions inferred from long-term atmospheric measurements., Nature (London, U. K.), 433 7025 506-508 , 2005
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Abstract
Me chloroform (CH3CCl3, 1,1,1,-trichloroethane) was widely used as a solvent before being recognized as an O3-depleting substance, its phase-out was introduced under the Montreal Protocol. Subsequently, atm. concns. declined steadily, recent European Me chloroform consumption and emissions were estd. to be <0.1 Gg/yr. Data from a short-term tropospheric measurement campaign (EXPORT) indicated European Me chloroform emissions could have been >20 Gg in 2000 (Krol, M.C., et al., 2003), almost doubling previously estd. global emissions. Such enhanced emissions would significantly affect results from the CH3CC13 method of deriving global abundance of OH- (Prinn, R.G., et al., 1995, 2001, Montzka, S.A., et al., 2000, Spivakovsky, C.M., et al., 2000, Krol, M. and P.J. van Leeuwen, 1998, 2003), the dominant reactive atm. chem. for removing trace gases related to air pollution, O3 depletion, and the greenhouse effect. Long-term, high-frequency data from Mace Head, Ireland and Jungfraujoch, Switzerland, were used to infer European Me chloroform emissions. European emission ests. declined from .apprx.60 Gg/yr in the mid-1990s to 0.3-1.4 and 1.9-3.4 Gg/yr in 2000-03, based on Mace Head and Jungfraujoch data, resp. Thus, European Me chloroform emission ests. were higher than calcd. from consumption data, but considerably lower than those derived from the EXPORT campaign in 2000 (Krol, M., et al., 2003).
Reimann S, A. J. Manning, P.G. Simmonds, D. M. Cunnold, R.H.J. Wang, J. Li, A. McCulloch, R. G. Prinn, J. Huang, R.F. Weiss, P.J. Fraser, S. O'Doherty, B.R. Greally, K. Stemmler, M. Hill & D. Folini, Low European methyl chloroform emissions inferred from long- term atmospheric measurements, Nature., 433, 506 - 508, doi:10.1038/nature03220, 2005 .
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Abstract
Prinn, R. G.; Huang, J.; Weiss, R. F.; Cunnold, D. M.; Fraser, P. J.; Simmonds, P. G.; McCulloch, A.; Harth, C.; Reimann, S.; Salameh, P.; O'Doherty, S.; Wang, R. H. J.; Porter, L. W.; Miller, B. R.; Krummel, P. B., Evidence for variability of atmospheric hydroxyl radicals over the past quarter century, Geophys. Res. Lett., 32, 7, doi:10.1029/2004GL022228, 2005 .
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Abstract
Hodson, E.L, R.G. Prinn, S. O'Doherty, D. Martin, D. Young, and P. Simmonds, S. A Montzka and D. Mondeel, Comparison between US and UK Landfill Gas Emissions, Conference proceedings in the Air & Waste Management Associations' annual meeting .
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Abstract
Carpenter L.J, D.J. Wevill, S. O'Doherty, G. Spain, P.G Simmonds, Atmospheric bromoform at Mace Head, Ireland: seasonality and evidence for a peatland source Atmospheric Chemistry and Physics, Atmospheric Chemistry and Physics, 5, 2927-2934, 2005 .
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Abstract
Greally, B.R., P.G. Simmonds, S. O'Doherty, A. McCulloch, B.R. Miller, P.K. Salameh, J. Mühle, T. Tanhua, C. Harth, R.F. Weiss, P.J. Fraser, P.B. Krummel, B.L. Dunse, L.W. Porter and R.G. Prinn, Improved continuous in situ measurements of C1-C3 PFCs, HFCs, HCFCs, CFCs and SF6 in Europe and Australia, Journal of Integrative Environmental Sciences, 2, 2-3, 253-261, 2005 .
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Abstract
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2004
Emmerson, K. M., MacKenzie, A. R., Owen, S. M., Evans, M. J., Shallcross, D. E, A Lagrangian model with simple primary and secondary aerosol scheme 1., Atmos. Chem. Phys., 4 8 2161-2170 , 2004
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Abstract
A Lagrangian trajectory model used to simulate photochem. has been extended to include a simple parameterisation of primary and secondary aerosol particles. The model uses emission inventories of primary particles for the UK from the NAEI (National Atm. Emissions Inventory for the UK), and for Europe from the TNO (Institute of Environmental Sciences, Energy Research and Process Innovation, the Netherlands) resp., to transport tracers representing PM10. One biogenic and two anthropogenic org. compds. were chosen as surrogates to model the formation of condensable material suitable for the prodn. of secondary org. aerosol (SOA). The SOA is added to the primary PM10 and compared to measured PM10 at one urban and two rural UK receptor sites. The results show an av. under-prediction by factors of 4.5 and 8.9 in the urban and rural cases resp. The model is also used to simulate prodn. of two secondary inorg. species, H2SO4 and HNO3, which are assumed, as a limiting case, to be present in the particle phase. The relationships between modeled and measured total PM10 improved with the addn. of secondary inorg. compds., and the overall model underprediction factors are reduced to 3.5 and 3.9 in the urban and rural cases resp. Nevertheless, our conclusion is that current emissions and chem. do not appear to provide sufficient information to model PM10 well (i.e. to within a factor of two). There is a need for further process studies to inform global climate modeling that includes climate forcing by aerosol.
Bacak, Asan, Bardwell, Max W., Raventos, M. Teresa, Percival, Carl J., Sanchez-Reyna, Gabriela, Shallcross, Dudley E., Kinetics of the Reaction of CH3O2 + NO., J. Phys. Chem. A , 108 48 10681-10687 , 2004
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Abstract
The overall rate coeff. (k4) for the reaction CH3O2 + NO -> products (4) has been measured by using the turbulent flow technique with chem. ionization mass spectrometry (CIMS) for the detection of reactants and products. The temp. dependence of the rate coeff. was investigated between 193 and 300 K. Across the temp. range the exptl. detd. rate coeffs. were fitted by using an Arrhenius type anal. to yield the expression k4 = (1.75-0.24+0.28) * 10-12 exp[(435 +- 35)/T] cm3 mol.-1 s-1. Expts. were carried out at 100 and 200 Torr total pressure within the stated temp. range, where the rate coeffs. were shown to be invariant with pressure. The branching ratio of the reaction was also assessed as a function of temp. and was found to proceed 100 +- 10% via the channel forming CH3O + NO2, there being no discernible increase in the yield of CH3ONO2 at low temps. This work represents the first study of the branching ratio as a function of temp. and pressure. Previous studies have shown that the rate coeff. displays a neg. temp. dependence, with the suggestion that the reaction rate increases with increasing pressure as well as increasing with decreasing temp. This study lends wt. to the assertion that there is no pressure effect (in agreement with a recent theor. study) and that differences between previous studies at low temp. are most likely to be exptl. errors. A model of the troposphere has been used to assess the impact of the exptl. error of the rate coeffs. detd. in this study on predicted concns. of a no. of key species, including O3, OH, HO2, NO, and NO2. In all cases it is found that the propagated error is very small and will not in itself be a major cause of uncertainty in modeled concns. However, at low temps. where there is a wide discrepancy between existing kinetic studies, modeling using the range of kinetic data in the literature shows a relatively large variation for CH3O2, HCHO, and minor reservoir species such as HO2NO2 and CH3O2NO2. Such a discrepancy may have implications for observationally driven models operating in regions of the troposphere below 240 K.
Colvile, R. N., Kaur, S., Britter, R., Robins, A., Bell, M. C., Shallcross, D., Belcher, S. E., Sustainable development of urban transport systems and human exposure to air pollution., Sci. Total Environ., 334-335 48 481-487 , 2004
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Abstract
DAPPLE (Dispersion of Air Pollution and Penetration into the Local Environment, http
Arnold, S. J., ApSimon, H., Barlow, J., Belcher, S., Bell, M., Boddy, J. W., Britter, R., Cheng, H., Clark, R., Colvile, R. N., Dimitroulopoulou, S., Dobre, A., Greally, B., Kaur, S., Knights, A., Lawton, T., Makepeace, A., Martin, D., Neophytou, M., Neville, S., Nieuwenhuijsen, M., Nickless, G., Price, C., Robins, A., Shallcross, D.E, Simmonds, P., Smalley, R. J., Tate, J., Tomlin, A. S., Wang, H., Walsh, P., Introduction to the DAPPLE Air Pollution Project., Sci. Total Environ., 332 1-3 139-153 , 2004
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Abstract
The Dispersion of Air Pollution and its Penetration into the Local Environment (DAPPLE) project brings together a multidisciplinary research group that is undertaking field measurements, wind tunnel modeling and computer simulations in order to provide better understanding of the phys. processes affecting street and neighborhood-scale flow of air, traffic and people, and their corresponding interactions with the dispersion of pollutants at street canyon intersections. The street canyon intersection is of interest as it provides the basic case study to demonstrate most of the factors that will apply in a wide range of urban situations. The aims of this paper are to introduce the background of the DAPPLE project, the study design and methodol. for data collection, some preliminary results from the first field campaign in central London (28 Apr.-24 May 2003) and the future for this work. Updated information and contact details are available on the web site at http
Wang, K.-Y., Shallcross, D. E, Hadjinicolaou, P., Giannakopoulos, C., Ambient Vehicular Pollutants in the Urban Area of Taipei., Water, Air, Soil Pollut., 156 1-4 29-55 , 2004
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Abstract
Continuous ambient monitoring data of major air pollutants (CO, NOx, NMHC [non-methane hydrocarbons]) from 1994 to 2001 were analyzed to establish the relationship between patterns of vehicular emitting species and vehicular emissions in the urban area of Taipei, Taiwan. These characteristics were consistent with measurements in London, UK, and Athens, Greece, indicating vehicular emissions are a major contributing factor to air pollution in Taipei. Sensitivity studies relating ambient air pollution to vehicular emissions in urban Taipei were performed and further examd. by analyzing special events where the overall city vehicle use were extreme. Ambient measurement anal. during the passing of Typhoon Nari showed very low CO (0.3-0.4 ppmv), NOx (5-10 ppbv), and NMHC (0.01-0.05 ppmv) concns. with no well-defined daily patterns. Measurements during Typhoon Nari were compared with measurements during the Chinese New Year and during Typhoon Herb. All analyses showed distinctive low pollution periods surrounded by elevated trace gas concns., initiated by normal working practices. This revealed the severe impact of vehicle exhaust emissions on air pollution concns. in Taipei. Other vehicle impacts were examd. by comparing post-Nari measurements with those before the typhoon arrival and comparing these data with a photochem. modeling system. As much as 15 ppmv CO, 250 ppbv NOx and 2.5 ppmv NMHC were measured during the day with an .apprx.50% increase in ambient vehicular pollutants in the first 2 days after Typhoon Nari passed. Implications for pollution-related impacts on human health within Taipei are noted.
Reimann, Stefan, Schaub, Daniel, Stemmler, Konrad, Folini, Doris, Hill, Matthias, Hofer, Peter, Buchmann, Brigitte, Simmonds, Peter G., Greally, Brian R., O'Doherty, Simon., Halogenated greenhouse gases at the Swiss high Alpine site of Jungfraujoch (3580 m asl)., J. Geophys. Res., [Atmos.] , 109 D5 D05307/1-D05307/12 , 2004
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Abstract
At the high Alpine site of Jungfraujoch (3580 m), 23 halogenated greenhouse gases are measured quasi-continuously GC/MS. Measurement data from the years 2000-2002 are analyzed for trends and pollution events. Concns. of the halogenated trace gases, which are already controlled in industrialized countries by the Montreal Protocol (e.g., chlorofluorocarbons (CFCs)) were at least stable or declining. Pos. trends in the background concns. were obsd. for substances which are used as CFC-substitutes (hydrofluorocarbons, hydrochlorofluorocarbons). Background concns. of the hydrofluorocarbons at the Jungfraujoch increased from Jan. 2000 until Dec. 2002 as follows
S. O'Doherty, D. M.Cunnold, A. Manning, B.R. Miller, R.H.J. Wang, P. B. Krummel, P.J. Fraser, P. G. Simmonds, A. McCulloch, R.F. Weiss, P. Salameh, L.W. Porter, R.G. Prinn, J.Huang, G. Sturrock, D. Ryall, R.G. Derwent and S. A. Montzka, Rapid growth of HFC-134a, HCFC-141b, HCFC-142b and HCFC-22 from AGAGE observations at Cape Grim, Tasmania and Mace Head, Ireland, J. Geophys. Res., 109, D06310, doi: 10.1029/2003JD004277, 2004 .
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Abstract
S. Reimann, D. Schaub, K. Stemmler, D. Folini, P. Hofer, B. Buchmann, P.G. Simmonds, B. R. Greally, and S. O'Doherty, Halogenated Greenhouse Gases at the Swiss High Alpine Site of Jungfraujoch (3850 m asl): Continuous Measurements and their Use for Regional European Source Allocation, J. Geophys. Res., 109, D05307, doi:10.1029/2003JD003923, 2004 .
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Abstract
P. G.Simmonds, R. G. Derwent, A. J. Manning, P. J. Fraser, P. B. Krummel, S. O'Doherty, R. G. Prinn, D. M. Cunnold, B. R. Miller, H. J. Wang, D. B. Ryall, L. W. Porter, R. F.Weiss, and P. K. Salameh, AGAGE Observations of Methyl Bromide and Methyl Chloride at Mace Head, Ireland, and Cape Grim, Tasmania, 1998-2001, J. Atmospheric Chem., 47, 3, 243-269, 2004 .
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Abstract
Stemmler K, S. O'Doherty, B Buchmann and S. Reimann, Emissions of the refrigerants HFC-134a, HCFC-22, and CFC-12 from road traffic: Results from a tunnel study (Gubrist Tunnel, Switzerland), Environmental Science & Technology, 38, 7, 1998-2004, 2004 .
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Abstract
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2003
Giannakopoulos, C., Good, P., Law, K. S., Shallcross, D. E, Wang, K-Y., Modelling the impacts of aircraft traffic on the chemical composition of the upper troposphere., Proc. Inst. Mech. Eng., Part G, 217 G5 237-243 , 2003
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Abstract
A 3-dimensional chem.-transport model assessed the impact of aircraft traffic in the upper troposphere. Aircraft engines emit NOx, which can perturb the chem. compn. at flight altitude paths, i.e., 10-12 km height for sub-sonic flights. The model included a comprehensive chem. scheme, so perturbations to other species apart from NOx could be examd. Results showed that monthly mean NO increases due to aircraft were .apprx.60 pptv (parts/trillion vol., 30% increase), for HNO3 mean aircraft-induced increases were 100 pptv (30% increase). Consequently, O3 is enhanced by 2500 pptv (5% increase) due to aircraft traffic. To assess regional and temporal variations in perturbations, a time series anal. above a central European grid cell located at 47 DegN 18 DegE was also performed. Results indicated local perturbations can be much larger than monthly mean values, reaching 200 pptv for NOx, 150 pptv for HNO3, and 5000 pptv for O3.
Petherbridge, J. R., May, P. W., Shallcross, D. E, Harvey, J. N., Fuge, G. M., Rosser, K. N., Ashfold, M. N. R., Simulation of H-C-S containing gas mixtures relevant to diamond chemical vapor deposition., Diamond Relat. Mater., 12 12 2178-2185 , 2003
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Abstract
Mole fractions of 24 species present within x%H2S/1%CH4/H2 (x = 0-1%) and 1%CS2/H2 gas mixts. have been calcd. using the CHEMKIN computer package in conjunction with a mechanism based on the composite conversion
Rivett, A. C., Martin, D., Gray, D. J., Price, C. S., Nickless, G., Simmonds, P. G., O'Doherty, S. J., Greally, B. R., Knights, A., Shallcross, D. E, The role of volatile organic compounds in the polluted urban atmosphere of Bristol, England., Atmos. Chem. Phys., 3 4 1165-1176 , 2003
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Abstract
The results of a field campaign carried out from early spring through to the late summer of 2000, in Bristol, England, are presented. Continuous measurements of over 40 hydrocarbons have been made at an urban background site, located at Bristol University, for approx. nine months using a Gas Chromatog. - Flame Ionization Detection (GC-FID) system and for a selection of halocarbons for approx. one month using a Gas Chromatog. - Electron Capture Detection (GC-ECD) system. In this paper we present the time-series of the nine halocarbons and selected hydrocarbons. Daytime and night-time hydroxyl radical concns. have been estd. based on the diurnal variations of a selection of the measured hydrocarbons. The av. summer daytime concn. of OH was found to be 2.5 * 106 mols. cm-3 and the night-time concn. to be in the range 104 to 105 mols. cm-3. In addn., the role played by certain VOCs in the formation of ozone is assessed using the POCP (photochem. ozone creation potential) concept.
Carr, Sinead, Shallcross, Dudley E., Canosa-Mas, Carlos E., Wenger, John C., Sidebottom, Howard W., Treacy, Jack J., Wayne, Richard P., A kinetic and mechanistic study of the gas-phase reactions of OH radicals and Cl atoms with some halogenated acetones and their atmospheric implications., Phys. Chem. Chem. Phys., 5 18 3874-3883 , 2003
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Abstract
Rate coeffs. for the reactions of hydroxyl radicals and chlorine atoms with a series of halogenated acetones of the type CX3COCH3 (X = H, Cl, F) have been detd. using a photolytic relative-rate technique at T = 298 K and at 760 Torr total pressure. The reactions studied and the rate coeffs. obtained are shown in the table.The errors quoted reflect an est. of the abs. uncertainty in the measured rate coeffs. of +-20%. For , Fourier transform IR spectroscopy was used to identify products. Qual. ultra-violet absorption spectra were also recorded for most of the halogenated species investigated in this study, and have been used together with the kinetic data to derive atm. lifetimes for these species.
Parkes, Alistair M., Fawcett, Beth L., Austin, Rachel E., Nakamichi, Shinji, Shallcross, Dudley E., Orr-Ewing, Andrew J., Trace detection of volatile organic compounds by diode laser cavity ring-down spectroscopy., Analyst (Cambridge, U. K.) , 128 7 960-965 , 2003
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Abstract
The use of continuous wave cavity ring-down spectroscopy (cw CRDS) with near infra-red diode lasers is demonstrated for quant. detection of trace levels of unsatd. volatile org. compds. (VOCs) at wavelengths that avoid overlapping absorptions by more abundant atm. constituents such as H2O and CO2. The current detection limit, with due allowance for pressure broadening by 1 atm of air, is 6 ppb by vol. (ppbv) for ethyne at an air wavelength of 1519.670 nm, and is sufficient for direct atm. detection of this mol. in many urban environments. Detection limits for alkenes are inferior, and, without incorporating the consequences of pressure broadening, include 78 ppbv for ethene and 900 ppbv for 1,3-butadiene. While the CRDS detection method offers several advantages over established gas chromatog. techniques for monitoring of small VOCs such as ethyne, it appears to be less well suited to study of larger org. compds. Methods are discussed for improving the instrument to reach the sensitivities required to monitor the various alkenes and other C-H contg. mols. in the troposphere.
Bardwell, Max W., Bacak, Asan, Teresa Raventos, M., Percival, Carl J., Sanchez-Reyna, Gabriela, Shallcross, Dudley E., Kinetics of the HO2 + NO reaction., Phys. Chem. Chem. Phys., 5 11 2381-2385 , 2003
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Abstract
The overall rate coeff. (k2) for the reaction HO2 + NO has been measured using the turbulent flow technique with chem. ionisation mass spectrometry (CIMS) for the detection of reactants and products. The temp. dependence of the rate coeff. was investigated between 183 and 300 K. Across the temp. range the exptl. detd. rate coeffs. showed good agreement with previous studies and were fitted using an Arrhenius type anal. to yield the expression k2 = (3.98+0.29-0.27) * 10-12 exp [(223 +- 16.5)/T] cm3 mols.-1 s-1. Expts. were carried out in the pressure range of 75 to 220 Torr within the stated temp. range, where the rate coeffs. were shown to be invariant with pressure. Such invariance with pressure is in accord with recent theor. calcns. This work represents an extension to the range of temp. and pressure over which the rate coeff. has been studied. A model of the troposphere has been used to assess the impact of the exptl. error of the rate coeffs. detd. in this study on predicted concns. of a no. of key species, including O3, OH, HO2, NO and NO2. In all cases it is found that the propagated error is rather small and will not in itself be a major cause of uncertainty in modelled concns.
Rivett, Alison C., Martin, Damien, Nickless, Graham, Simmonds, Peter G., O'Doherty, Simon J., Gray, Daniel J., Shallcross, Dudley E., In situ gas chromatographic measurements of halocarbons in an urban environment., Atmos. Environ., 37 16 2221-2235 , 2003
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Abstract
A gas chromatog.-electron capture detection system continuously measured 9 halocarbons in the urban environment of Bristol, England, over the course of .apprx.1 mo. A GC-flame ionization detection system was deployed at the same location to simultaneously monitor >30 C2-8 hydrocarbons. A halocarbon time series is presented and compared with the hydrocarbon dataset. The effect of local sources was examd. by comparing halocarbon concn. fluctuations with local weather conditions. A complex time series was obsd., with no species displaying a clear diurnal cycle. Also, large deviations from baseline concns. were obsd. for many compds. at different times. Local small-scale industry and landfill sites are postulated as the source of many of these excursions. The geog. of Bristol affects pollution levels in the city since surrounding hills trap emissions and prevent their quick dispersion.
Cotter, Eimear S. N., Canosa-Mas, Carlos E., Manners, Christopher R., Wayne, Richard P., Shallcross, Dudley E., Kinetic study of the reactions of OH with the simple alkyl iodides., Atmos. Environ., 37 8 1125-1133 , 2003
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Abstract
The atm. fate of biogenic species such as the alkyl iodides is controlled mainly by photolysis, and by oxidn. initiated by attack of Cl atoms and/or OH radicals. In order to assess the contribution made by OH attack on the simpler alkyl iodides, the abs. second-order rate coeffs. for the reactions OH + CH3I -> products, (1) OH + C2H5I -> products, (2) OH + 1-C3H7I -> products, (3) OH + 2-C3H7I -> products (4) were detd. These reactions were studied at P=1.5 and 5 Torr and at room temp. (298+-2 K) using a fast-flow discharge system with resonance-fluorescence detection of OH radicals. The abs. second-order rate coeffs. are k1=(0.99+-0.20)*10-13 cm3 mol.-1 s-1, k2=(7.7+-1.0)*10-13 cm3 mol.-1 s-1, k3=(25.0+-3.0)*10-13 cm3 mol.-1 s-1 and k4=(16.0+-2.0)*10-13 cm3 mol.-1 s-1. The reactions were pressure independent over the range measured. The major atm. global degrdn. pathway is photolysis, with OH-initiated oxidn. gaining importance for the Pr iodides. The effects of variable [Cl] on a local scale are discussed.
Mazurenka, Mikhail I., Fawcett, Beth L., Elks, John M. F., Shallcross, Dudley E., Orr-Ewing, Andrew J., 410-nm diode laser cavity ring-down spectroscopy for trace detection of NO2., Chem. Phys. Lett., 367 1,2 1-9 , 2003
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Abstract
The detection of NO2 at sub part per billion by vol. (ppbv) concns. was demonstrated using a cavity ring-down spectrometer with a blue diode laser operating at wavelengths close to 410 nm. Measurements at peaks in the absorption spectrum at wavelengths of 410.4955 and 410.3533 nm demonstrate a min. detectable no. d. of NO2 of 9.8 * 109 mols cm-3, which would correspond to 0.4 ppbv under atm. conditions in the lower troposphere. Addnl. expts. performed with a pulsed, tuneable dye laser system provide absorption cross-sections for NO2 over the restricted wavelength ranges of 408.5-410.5 and 435.0-435.5 nm, but at a resoln. of ~0.06 cm-1 that is higher than previously reported and close to the Doppler broadening limit at 295 K. These spectra show considerably more structure than is evident in published Fourier transform (FT) spectra obtained at lower resoln., but yield cross-sections that are in quant. agreement with the FT measurements.
S. O'Doherty, A. McCulloch, E. O'Leary, J. Finn and D. Cunningham, Climate Change; Emissions of Industrial Greenhouse Gases (HFCs, PFCs and Sulphur Hexafluoride), ERTDI Report Series No. 10, 2003 .
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Abstract
C. Rivett, D. Martin, D. J. Gray, C. S. Price, G. Nickless, P. G. Simmonds, S. J. O'Doherty, B. R. Greally, A. Knights, and D. E. Shallcross, The role of volatile organic compounds in the polluted urban atmosphere of Bristol, UK, Atmos. Chem. Phys., 3, 1165- 1176, 2003 .
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Abstract
M.L. Cox, G.A. Sturrock, P.J. Fraser, S. Siems, P. Krummel, and S. O'Doherty, Regional sources of methyl chloride, chloroform, and dichloromethane identified from AGAGE observations at Cape Grim, Tasmania, 1998-2000. Journal of Atmos. Chem., 45, 79-99, 2003 .
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Abstract
C. Rivett, D. Martin, G. Nickless, P. G. Simmonds, S. J.O'Doherty, D. J. Gray, and D. E. Shallcross, In-situ gas chromatic measurements of halocarbons in an urban environment, Atmospheric Environment 37, 16, 2221-2235, 2003 .
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Abstract
Manning A. J, D. B. Ryall, R. G. Derwent, P. G. Simmonds, S. O'Doherty, Estimating European Emissions of ozone-depleting and greenhouse gases using Observations and a Modelling Back-Attribution Technique, J. Geophys. Res., 18, D14, 4405, 2003 .
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Abstract
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2002
Fawcett, B. L., Parkes, A. M., Shallcross, D. E, Orr-Ewing, A. J., Trace detection of methane using continuous wave cavity ring-down spectroscopy at 1.65 micro m., Phys. Chem. Chem. Phys., 4 24 5960-5965 , 2002
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Abstract
The use of continuous wave cavity ring-down spectroscopy (cw CRDS) is demonstrated for the detection of tropospheric methane. Spectra of the 2n3 overtone band of methane at wavelengths near 1.65 micro m were recorded in both lab. air and under reduced pressures, and show quant. agreement with absorption intensities and pressure-broadened line widths reported in the HITRAN 96 database. Expts. demonstrate a min. detectable absorption coeff. that is currently alpha min = 1.5 * 10-8 cm-1, equiv. to a no. d. of CH4 at ambient temp. of 2.9 * 1011 mols. cm-3 in a low pressure environment where Doppler broadening dominates the spectral lineshapes. The effects of pressure broadening reduce the detection limit of CH4 in 1 atm of air to 1.3 * 1012 mols. cm-3, corresponding to 52 ppb by vol. This is well below the 1.72 ppm by vol. av. methane concn. in the lower troposphere.
Vipond, A., Canosa-Mas, C. E., Flugge, M. L., Gray, D. J., Shallcross, D. E, Shah, D., Wayne, R. P., A discharge-flow study of the self-reaction of IO., Phys. Chem. Chem. Phys., 4 15 3648-3658 , 2002
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Abstract
A discharge-flow tube equipped with resonance-fluorescence detection for I atoms and chemiluminescence detection for O atoms has been used to investigate the kinetics of the reaction IO + IO --> products (1) at T = 296 +- 1 K and P = 1.9-2.2 Torr. The rate const. was found to be k1 = (9.3 +- 1.9) * 10-11 cm3 mol.-1 s-1, where -d[IO]/dt = 2k1[IO]2 and the errors are 95% confidence limits of the mean of the exptl. rate consts. combined with an estd. further 20% error in other parameters. The detn. of the rate const. for also required the investigation of the kinetics of the reaction IO + CF3 --> products (2). The rate const. was found to be k2 = (1.6 +- 0.7) * 10-11 cm3 mol.-1 s-1, where errors are 95% confidence limits of the slope of the regression line of a second-order plot, combined with systematic errors of 20% for the calibration of [CF3]. Iodine atoms are generated in the reactions (1) and (2). The yields have been quantified, and indicate that k1a/k1 = 0.56 +- 0.20, with k1b/k1 = (1 - k1a/k1), and k2a/k2 = 0.4 +- 0.1. Our expts. differ from others previously reported in that the results do not rely on a value for the cross section for absorption of IO in the visible region. Atm. modeling studies show that the IO self-reaction plays a minor role in ozone depletion in the marine troposphere and that further work is required to quantify the fate of OIO, a product of this reaction.
McCulloch, A., O'Doherty, S., Greally, B., Nickless, G., Simmonds, P. G., Derwent, R. G., Ryall, D. B., Spain, T. G., Verification of fluorinated greenhouse gas emissions from Ireland., Non-CO2 Greenhouse Gases, Proc. Int. Symp., 3rd, 577-578 , 2002
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Abstract
National emissions ests. for HFCs 23, 32, 125, 134a, 152a, 143a and 227ea, PFCs 14 and 116 and SF6 during 1995 and 1998 were developed for Ireland. The most significant of these were verified against Irish source strengths calcd. independently by inverse modeling from continuous observations of their atm. concns. at Mace Head, Co Galway. The method of estg. emissions involved firstly using macroeconomic parameters to calc. the quantities used in Ireland based on known European usages of the compds. In the case of the HFCs which replace ozone depleting substances (ODS), the Irish usages were verified at this stage against historical data for consumption of ODS. Emissions were then calcd. using std. global functions that were extensively tested in other work. Similar ests. were also made for emissions of HCFCs 22, 141b, and 142b that are emitted from Ireland in much larger amts. than the Kyoto greenhouse gases. The higher emissions, however, afforded a more rigorous assessment of the methodologies for estg. emissions and verification by inverse modeling.
Stordal, F., Schmidbauer, N., Simmonds, P., Greally, B., McCulloch, A., Reimann, S., Maione, M., Mahieu, E., Notholt, J., Isaksen, I., Derwent, R. G., System for Observation of halogenated Greenhouse gases in Europe (SOGE)., Non-CO2 Greenhouse Gases, Proc. Int. Symp., 3rd, 573-574 , 2002
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Abstract
Observations of halogenated greenhouse gases are made at four locations in Europe. The observations are used to detect trends and to verify emissions. Impacts on climate and ozone are calcd.
Greally, B. R., Simmonds, P. G., O'Doherty, S. J., Nickless, G., McCulloch, A., Reimann, S., Schmidbauer, N., Maione, M., Ryall, D. B., Derwent, R. G., Manning, A. J., Observations of halogenated greenhouse gases and estimation of European source strengths., Non-CO2 Greenhouse Gases, Proc. Int. Symp., 3rd , 553-557 , 2002
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Abstract
The relative lack of information on long-term changes in atm. abundance of non-CO2 greenhouse gases in Europe is being addressed under the System for Observation of Greenhouse gases in Europe (SOGE) program. Results are presented from the in situ observations of the CFCs and their substitutes the HCFCs and HFCs at 4 European locations covering sites in Western and Northern Europe (Ireland and Spitzbergen) and include elevated mountain sites in Central and Southern Europe (Switzerland and Italy). Measurements of halogenated greenhouse gases were achieved using automated gas chromatograph-mass spectrometers combined with a specialized preconcn. device with detection limits of 0.5 pptv based on a 2-L air sample. Frequent calibration to internationally used scales was undertaken to achieve a consistent dataset. When combined with models of air dispersion these observations were used to est. European source strengths for many of the important halogenated greenhouse gases. Furthermore the measurements provide a cross-check that the available emission inventories are reasonable and that, where applicable, internationally-agreed redns. in emissions are being implemented.
Simmonds, P. G., Greally, B. R., Olivier, S., Nickless, G., Cooke, K. M., Dietz, R. N., The background atmospheric concentrations of cyclic perfluorocarbon tracers determined by negative ion-chemical ionization mass spectrometry., Atmos. Environ., 36 13 2147-2156 , 2002
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Abstract
The background atm. mixing ratios for a range of cyclic perfluorocarbons (cyclic-PFCs), widely used in atm. dispersion studies, were measured by gas chromatog.-mass spectrometry in neg. ion-chem. ionization mode. Background concns. range from <1 fL L-1 to >10 fL L-1, where femtoliter is expressed as parts in 1015 (ppqv). Because of their very long atm. lifetimes (>3000 yr) the present day concns. represent the accumulated emissions from all sources, although significant com. prodn. did not commence until the 1960s. Cyclic-PFCs are potent greenhouse gases, however, their atm. concns. are currently so low as to make an insignificant contribution to global warming.
Sebastien Biraud, Philippe Ciais, Michel Ramonet, Peter Simmonds, Victor Kazan, Patrick Monfray, Simon O'Doherty, Gerard Spain, and S. Gerard. Jennings, Quamtification of carbon dioxide, methane, nitrous oxide and chloroform emissions over Ireland from atmospheric observations at Mace Head, Tellus., 54B, 41-60, 2002 .
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Abstract
D. B. Ryall, R. G. Derwent, A. J. Manning, A. L. Redington, J. Corden, W. Millington, P. G. Simmonds, S. O'Doherty, N. Carslaw and G. W. Fuller, The origin of high particulate concentrations over the United Kingdom, March 2000, Atmospheric Environment, 36, 8, 1363-1378 2002 .
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Abstract
P.Fraser, G. Ashokkumar, S. Baly, L. Cooper, K. Courtney-Jones, N. Derek, B. Ellis, S. Glenn, H. Griffin, B. Hobson, P. Kill, P. Krummel, T.Kuhn, R. Langenfelds, M. Mann, S. O'Doherty, L. Porter, N. Reid, P. Simmonds and J. Toric, Greenhouse and Ozone Depleting Trace Gases at Disko Island, Greenland, 2001, Clean Air, 36, 2, 2002 .
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Abstract
R.G. Derwent, D.B. Ryall, A.J. Manning, P.G. Simmonds, S. O'Doherty, S. Biraud, P. Ciais, M. Ramonet, and S. G. Jennings, Continuous observations of carbon dioxide at Mace Head, Ireland from 1994-1999 and its net European ecosystem exchange, Atmospheric Environment, 36, 17, 2799-2807, 2002 .
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Abstract
B.R Greally, P.G. Simmonds, S.J. O'Doherty, G. Nickless, A. McCulloch, S. Reimann, N. Schmidbauer, M. Maione, D.B. Ryall, R. G. Derwent, and A.J. Manning, Observations of halogenated greenhouse gases and estimation of European source strengths, Non-CO2 Greenhouse Gases, Van Ham, Baede, Guicherit & Williams-Jacobse (eds), 2002, Millpress, Rotterdam, ISBN 90-77017-70-4 .
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Abstract
D. M. Cunnold, L. P. Steele, P. J. Fraser, P. G. Simmonds, R. G. Prinn, R. F. Weiss, L. W. Porter, S. O'Doherty, R. L. Langenfelds, P.B. Krummel, H. J. Wang, L. Emmons, X. X. Tie, E. J. Dlugokencky, In situ measurements of atmospheric methane at GAGE/AGAGE sites during 1985-2000 and resulting source inferences, J. Geophys. Res., 107, D14, 10.1029/2001JD001226, 2002 .
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Abstract
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2001
Aliwell, S. R., Halsall, J. F., Pratt, K. F. E., O'Sullivan, J., Jones, R. L., Cox, R. A., Utembe, S. R., Hansford, G. M., Williams, D. E., Ozone sensors based on WO3., Meas. Sci. Technol., 12 6 684-690 , 2001
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Abstract
The use of a WO3 semiconductor as a sensor for O3 at concn. levels relevant to atm. monitoring applications is an important advance in attempts to produce cheap, lightwt., and reliable instruments. Problems of stability are a possible obstacle to this application. A model that describes the response of these sensors to O3 is proposed here and using it an explanation for the drift of resistance with time at const. concns. of O3 is given. Consideration of this drift model enables a measurement routine to be employed that compensates for the drift obsd. exptl., thus producing a reliable calibration of the sensor.
Wang, K.-Y., Pyle, J. A., Shallcross, D. E, Hall, S. M., Formulation and evaluation of IMS, an interactive three-dimensional tropospheric chemical transport model 3. Comparison of modelled C2-C5 hydrocarbons with surface measurements., J. Atmos. Chem., 40 2 123-170 , 2001
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Abstract
This, part 3 of a series of papers on a new 3-dimensional global tropospheric chem. transport model using an Integrated Modeling System (IMS), evaluates model performance in simulating global distributions and seasonal variations for volatile org. compds. (VOC) in the atm. Comparisons of model OH- concns. with previous model studies showed consistent modeled OH concns. from the sub-tropics to mid-latitudes, more discrepancies occurred over the tropical low latitudes, with IMS predicting the highest OH- concns. The close agreement between modeled OH- concns. over mid-latitudes, where high surface NOx and VOC concns. are also obsd., indicates the strong photochem. coupling between NOx, VOC, and O3 over these latitudes. IMS OH- concns. in the Northern Hemisphere (NH) mid-latitudes in summer are generally lower than available measurements, implying that models generally underestimate OH- concns. at this location and time of year. Substantial differences between modeled OH- concns. over low latitudes clearly highlighted areas of uncertainty between models. Generally, IMS OH- concns. are the highest in the models compared, one possible reason is that biogenic emissions of species such as isoprene and monoterpenes are highest in IMS, leading to higher O3 levels and hence higher OH-. Generally, IMS VOC concns. showed a similar seasonality to measurements at most locations, however, IMS tends to underestimate the NH winter VOC max. and over-est. the NH summertime VOC min. Such an overestimate in summer could be due to IMS underestimating OH- concns., an overestimation of VOC emissions, or possibly a problem with model transport, all possibilities were explored. Except for n-pentane, model under-prediction of a VOC max. in the NH winter months strongly suggests a missing emission mechanism in the model or an underestimate of an existing one. It is very likely there is a lack of time varying emission sources in the model to account for seasonal change in emission behavior, such as increasing energy usage (e.g., electricity and gas), road transportation, engine performance, and other anthropogenic factors with strong seasonal characteristics. The anomalous over-prediction of winter n-pentane vs. its close summer prediction with measurements suggested emissions in this case may be too high.
Wang, K.-Y., Pyle, J. A., Shallcross, D. E, Formulation and evaluation of IMS, an interactive three-dimensional tropospheric chemical transport model 1. Model emission schemes and transport processes., J. Atmos. Chem., 38 2 195-227 , 2001
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Abstract
In part one of this series of papers on a new integrated modeling system (IMS), the interactive three-dimensional chem. transport model (CTM), we present a detailed description of the interactive emission scheme for biogenic species and outline the datasets used for anthropogenic species. In addn., we describe the transport scheme employed in this model. The biogenic emission schemes incorporate the high-resoln. Olson World Ecosystem data, the satellite-sensed terrestrial vegetation data from AVHRR (A Very High Resoln. Radiometer), and the CZCS (Coastal Zone Color Scanner) data. These datasets provide seasonal variations in surface biogenic emissions. The emission schemes are tested against other ests. (e.g., GEIA) and equil. emissions. A comparison of terrestrial biogenic fluxes, both the spatial and temporal (seasonal) variation of modeled surface net primary prodn., is consistent with the geog. variations of the global vegetation index (GVI) distribution derived from AVHRR. The annual net primary prodn. is 76,000 Tg C/yr, which compares well with the 40,500-78,000 Tg C/yr estd. by J. M. Melillo et al. (1993). This indicates that the model works well in capturing spatial and seasonal variations in the terrestrial vegetation. The modeled surface vegetation fluxes are verified against data from A. Guenther et al. (1995). While the comparison shows a generally good agreement in terms of the temporal and spatial distributions of isoprene (530 Tg/yr), large discrepancies are seen over the tropical locations, which often exhibit strong seasonality in rainfall and very small variation in temp. These differences indicate that a large difference in the estn. between an empirical relation and an LSM (land surface model) calcn. occurs if an area in which seasonal distribution of rainfall is the main factor which dets. the type of vegetation. In this paper, we assess (results are discussed in following papers) the role of changing surface biogenic distributions in surface-to-atm. biogenic fluxes (both ocean-to-atm. and land-to-atm.).
Wang, K.-Y., Pyle, J. A., Shallcross, D. E, Larry, D. J., Formulation and evaluation of IMS, an interactive three-dimensional tropospheric chemical transport model 2. Model chemistry and comparison of modelled CH4, CO, and O3 with surface measurements., J. Atmos. Chem., 38 1 31-71 , 2001
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Abstract
The chem. reaction mechanism used in an interactive, 3-dimensional tropospheric chem. transport model, IMS, was evaluated and compared to modeled CH4, CO, and O3 with a dataset of annual surface measurements. Modeled monthly and 24-h mean tropospheric OH concns. were 5-22 * 105 mols./cm3, indicating an annual averaged OH concn. of .apprx.10 * 105 mols./cm3. This value was close to the estd. 9.7 +- 0.6 * 105 mols./cm3 calcd. from the reaction of CH3CCl3 with OH radicals. Modeled and measured CH4 concns. generally showed good agreement, except for the Barrow site, where modeled wetland emissions in summer could be a factor of 3 too high. For CO, pronounced seasonality shown in measurements was generally reproduced by the model, however, modeled concns. were lower than measurement concns. This discrepancy may due to lower CO emissions, esp. from biomass burning, used in the model vs. other studies. For O3, good agreement between the model and measurements was obsd. at locations away from industrial regions. Max. discrepancy between modeled and measured results at tropical and remote marine sites was .apprx.5-10 ppbv, the discrepancy can be >30 ppbv in industrial regions. Comparisons in rural areas at European and American continental sites were highly affected by local photochem. prodn., which is difficult to model with a coarse, global chem. transport model. The very large O3 variations at these locations varied from .apprx.15-25 ppbv in Jan. to 55-65 ppbv in July-Aug. Obsd. annual O3 amplitude was .apprx.40 ppbv vs. .apprx.20 ppbv in the model. An overall comparison of modeled vs. measured O3 showed the O3 seasonal surface cycle is generally governed by the relative importance of 2 key mechanisms that drive a spring O3 max. and a summer O3 max.
Cotter, E. S. N., Booth, N. J., Canosa-Mas, C. E., Gray, D. J., Shallcross, D. E, Wayne, R. P., Reactions of Cl atoms with CH3I, C2H5I, 1-C3H7I, 2-C3H7I and CF3I., Phys. Chem. Chem. Phys., 3 3 402-408 , 2001
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Abstract
The kinetics of the reactions were studied at T=298 K using a fast-flow discharge system with resonance-fluorescence detection of Cl atoms. The rate coeffs. were found to be pressure-independent over the range 1.5-12 Torr, and were k1=(1.51+-0.15)*10-12 cm3 mol.-1 s-1, k2=(16.0+-1.7)*10-12 cm3 mol.-1 s-1, k3= (66.5+-7.5)*10-12 cm3 mol.-1 s-1, k4=(46.8+-4.9)*10-12 cm3 mol.-1 s-1 and k5=(0.85+-0.09)*10-12 cm3 mol.-1 s-1. The rates of reaction of these alkyl iodides with Cl atoms in the marine boundary layer were compared with the rates of their photolysis and their reaction with OH. For early morning conditions, it is shown that reaction with Cl atoms can compete with photolysis and dominate over reaction with OH, if Cl atom concns. are about 1*105 mol. cm-3. At. iodine may be released following reaction of Cl with the alkyl iodides, this at. I can participate in catalytic destruction of ozone in the marine boundary layer.
D.B. Ryall, R.G. Derwent, P.G. Simmonds, and S.J.O'Doherty. Estimating source regions of European emissions of trace gases from observations at Mace Head. Atmos. Environ., 35, 2, 2507-2523 2001 .
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Abstract
R.G, Prinn, R.F. Weiss, P.J. Fraser, P.G. Simmonds, D.M. Cunnold, F.N. Alyea, S. O'Doherty, P. Salameh, B.R. Miller, J. Huang, R.H.J. Wang, D.E. Hartley, C. Harth, L.P. Steele, G. Sturrock, P.M. Midgley, and A. McCulloch, A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE: 1978-2000. European Geophysical Society, 26th General Assembly, Nice, France, 2001 .
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Abstract
S. O'Doherty, D. Cunnold, G.A. Sturrock, D. Ryall, R.G. Derwent, R.H.J. Wang, P.Simmonds, P.J. Fraser, R.F. Weiss, P. Salameh, B.R. Miller and R.G. Prinn. In-Situ Chloroform Measurements at AGAGE Atmospheric Research Stations from 1994 -1998. J. Geophys. Res., 106, D17, 20,429-20,444 2001 .
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Abstract
R.G. Prinn, J. Huang, R.F.Weiss, D.M. Cunnold, P.J. Fraser, P.G. Simmonds, P. Salameh, S. O'Doherty, R.H.J. Wang, L. Porter, Evidence for substantial variations of atmospheric hydroxyl radicals in the past two decades, Science, 292, 1882-1888, 2001 .
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Abstract
Caroline Forster, Ulla Wadinger, Gerhard Wotawa, Paul James, Ina Mattis, Dietrich Althausen, Peter Simmonds, S. O'Doherty, S. Gerard Jennings, Christoph Kleefeld, Johannes Schneider, Thomas Trickl, Stephan Kreipl, Horst Jager, Andreas Stohl, Transport of boreal forest fire emissions from Canada to Europe., J. Geophys. Res., 106, D19, 22,887-22,906 2001 .
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Abstract
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2000
Bridgeman, C. H., Pyle, J. A., Shallcross, D. E, A three-dimensional model calculation of the ozone depletion potential of 1-bromopropane (1-C3H7Br)., J. Geophys. Res., [Atmos.], 105 D21 26493-26502 , 2000
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Abstract
A three-dimensional chem. transport model has been used to investigate factors affecting the potential impact of a short-lived bromine compd. on lower stratospheric ozone. The model is used to calc. the ozone depletion potential (ODP) of 1-bromopropane employing a previously used empirical approach, which depends on the lifetime of the compd. and the amt. reaching the stratosphere. We show that this approach may be unsuitable for very shortlived compds. Indeed, for a short-lived compd. the definition of the lifetime itself is ambiguous. The lifetime varies with season, region of emission, and depends on the method of calcn. A series of tracer expts. reveals that the amt. of bromine reaching the stratosphere, and hence the calcd. ODP, can also be highly dependent on the distribution of the surface emissions. Where emissions are located solely in the equatorial region, the calcd. ODP is over 3 times greater than when the emissions are centered over Europe. Vigorous convection in the tropics can lift the compd. rapidly into the lower stratosphere where the bromine can be released and contribute to ozone destruction. For surface releases at higher latitudes the lifetime in the troposphere is significant compared with the time to reach the stratosphere and a smaller ODP is calcd. This highlights a problem in calcg. ODPs for short-lived species. Uncertainties in the degrdn. mechanisms for short-lived compds., and the subsequent fate of the degrdn. intermediates, and further uncertainty to calcns. of their impact on the stratosphere. Addnl. methods need to be developed to assess their potential impact on the stratosphere.
Lary, D. J., Shallcross, D. E, Central role of carbonyl compounds in atmospheric chemistry., J. Geophys. Res., [Atmos.] , 105 D15 19771-19778 , 2000
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Abstract
With the exception of acetone, it is not generally recognized how important atm. carbonyls and alkyl radicals are in the lower stratosphere and upper troposphere. Carbonyl compds. are the crucial intermediate species for the autocatalytic prodn. of OH. For example, in the upper troposphere and lower stratosphere, it is calcd. based on data assimilation anal. of Atm. Trace Mol. Spectroscopy Expt. (ATMOS) data that CH3 prodn. due to the degrdn. of carbonyls contributes around 40% to the overall prodn. of CH3, a key initiation step for HOx prodn., with the contribution due to the photolysis of CH3CHO being comparable to that of acetone. So correctly modeling the alkyl radical concns. is of central importance and has not be given the attention it deserves to date. The reactions of carbonyls with Br and Cl are also major sources of HBr and HCl. In short, carbonyl compds. play a central role in atm. chem. close to the tropopause, and this is directly relevant to issues such as the assessment of the impact of air traffic, and ozone depletion.
Wang, K.-Y., Shallcross, D. E, A modelling study of tropospheric distributions of the trace gases CFCl3 and CH3CCl3 in the 1980s., Ann. Geophys., 18 8 972-986 , 2000
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Abstract
Interhemispheric transport is a key process affecting the accuracy of source quantification for species such as methane by inverse modeling and is a source of difference among global three-dimensional chem. transport models (CTMs). Here we use long-term observations of the atm. concn. of long-lived species such as MeCCl3 and CFCl3 for testing three-dimensional CTMs, notably their ability to model the interhemispheric transport, distribution, trend, and variability of trace gases in the troposphere. The very striking contrast between the inhomogeneous source distribution and the nearly homogeneous trend, obsd. in the global ALE/GAGE expts. for both CH3CCl3 and CFCl3, illustrates an efficient interhemispheric transport of atmospherically long-lived chem. species. Anal. of the modeling data at two tropical stations, Barbados (13 DegN, 59 DegW) and Samoa (14 DegS, 124 DegW), shows the close relationship between interhemispheric transport and cross-equator Hadley circulations. We found that cross-equator Hadley circulations play a key role in producing the globally homogeneous obsd. trends. Chem., the most rapid interaction between MeCCl3 and OH occurs in the northern summer troposphere, while the most rapid photolysis of MeCCl3 and CFCl3, and the chem. reactions between CFCl3 and O(1D), take place in the southern summer stratosphere. Therefore, the cross-equator Hadley circulation plays a key role which regulates the southward flux of chem. species. The regulation by the Hadley circulations hence dets. the amt. of air to be processed by OH, O(1D), and UV photolysis, in both hemispheres. In summary, the dynamic regulation of the Hadley circulations and the chem. processing [which crucially depends on the concn. of OH, O(1D), and on the intensity of solar insolation] of the air contribute to the seasonal variability and homogeneous growth rate of obsd. MeCCl3 and CFCl3.
Evans, M. J., Shallcross, D. E, Law, K. S., Wild, J. O. F., Simmonds, P. G., Spain, T. G., Berrisford, P., Methven, J., Lewis, A. C., McQuaid, J. B., Pilling, M. J., Bandy, B. J., Penkett, S. A., Pyle, J. A., Evaluation of a Lagrangian box model using field measurements from EASE (Eastern Atlantic Summer Experiment) 1996., Atmos. Environ., 34 23 3843-3863 , 2000
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Abstract
The Cambridge Tropospheric Trajectory model of Chem. and Transport (CiTTyCAT), a Lagrangian chem. model, has been evaluated using atm. chem. measurements collected during the East Atlantic Summer Expt. 1996 (EASE '96). The model includes a description of gas-phase tropospheric chem., and simple parameterizations for surface deposition, mixing from the free troposphere and emissions. The model generally compares well with the measurements and is used to study the prodn. and loss of O3 under a variety of conditions. The mean difference between the hourly O3 concns. calcd. by the model and those measured is 0.6 ppbv with a std. deviation of 8.7 ppbv. Three specific air-flow regimes were identified during the campaign
Wang, K.-Y., Shallcross, D. E, Modeling terrestrial biogenic isoprene fluxes and their potential impact on global chemical species using a coupled LSM-CTM model., Atmos. Environ., 34 18 2909-2925 , 2000
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Abstract
We study the role of the biogenic isoprene on tropospheric chems. using a land surface model (LSM) and a 3-dimensional (3-D) tropospheric chem. transport model (CTM). An efficient and conservative coupling scheme is used to couple the LSM to the 3-D CTM. Annual integrations of the coupled model were performed and the results compared with other ests. The comparison shows that the annual global isoprene flux from terrestrial vegetation is 530 Tg C/yr, which is in good agreement with 503 Tg C/yr estd. by a high-resoln. (0.5 Deg * 0.5 Deg) vegetation model of Guenther et al (1995). Comparison of the seasonal variations of the surface emission distribution between the coupled model and Guenther et al. (1995) also shows close agreement. The potential impact of isoprene on the levels of tropospheric species is studied by running the same coupled model for the period of June-Dec. but without biogenic isoprene emissions included, and the results are compared with the run which includes biogenic isoprene emissions. Our comparison indicates a significant difference in O3 and PAN for both hemispheres. The discrepancy between the run with and without isoprene is predominantly governed by the spatial and temporal variations of terrestrial vegetation. The largest difference is seen in the summertime northern hemisphere at locations with extensive terrestrial vegetation (e.g. North America, Europe, east and southeast Asia, South America and equatorial central Africa). For O3, there is an .apprx.4-ppbv increase over the oceanic areas and an about 8- to 12-ppbv increase over the mid-latitude land areas. For PAN, a max. of .apprx.1 order of magnitude in difference, which increases from 0.01 ppbv (without isoprene emissions) to 0.1-0.3 ppbv (with isoprene emissions), is seen in areas of extensive terrestrial vegetation.
Jenkin, Michael E., Shallcross, Dudley E., Harvey, Jeremy N., Development and application of a possible mechanism for the generation of cis-pinic acid from the ozonolysis of alpha - and beta -pinene., Atmos. Environ., 34 18 2837-2850 , 2000
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Abstract
Recent exptl. studies have identified cis-pinic acid (a C9 dicarboxylic acid) as a condensed-phase product of the ozonolysis of both alpha - and beta -pinene, and it is currently believed to be the most likely degrdn. product leading to the prompt formation of new aerosols by nucleation. The obsd. timescale of aerosol formation appears to require that cis-pinic acid is a 1st-generation product, and a possible mechanism for its formation was developed. The key step in the proposed mechanism requires that the isomerization of a complex C9 acyl-oxy radical by a 1,7 H atom shift is able to compete with the alternative decompn. to CO2 and a C8 org. radical. Thermodn. and kinetic arguments are presented, on the basis of semi-empirical electronic structure calcns., which support this proposed mechanism, and thereby the competition between the 2 pathways. The transfer of the labile aldehydic H atom is shown to be esp. facile in this case because it occurs though an unstrained transition state, this feature can in turn be attributed to the cis-substitution of the 4-membered ring, which enforces the steric proximity of the acyl-oxy and aldehyde groups. The mechanism can explain the formation of cis-pinic acid from both alpha - and beta -pinene, because the acyl-oxy radical is likely to be formed following the decompn. of excited Criegee biradicals formed in both systems. It is also possible that a similar isomerization reaction of a complex C10 alpha -carbonyl oxy radical by a 1,8 H atom shift might explain the very recently obsd. formation of cis-10-hydroxy-pinonic acid from alpha -pinene ozonolysis, and this possibility is also explored. An existing detailed scheme describing the degrdn. of alpha -pinene (part of the Master Chem. Mechanism, MCM) is updated to include the proposed cis-pinic acid and cis-10-hydroxy-pinonic acid formation mechanisms, and the values of several uncertain parameters are adjusted on the basis of reported yields of a series of org. products from the ozonolysis of alpha -pinene. The updated degrdn. scheme is incorporated into a boundary layer box model, and representative ambient concns. of the org. acids and other oxygenated products are calcd. for a range of representative conditions appropriate to the boundary layer over central Europe. The simulated concns. of the org. acids in general, and cis-pinic acid in particular, are strongly dependent on the level of NOx, and suggest that new aerosol formation from the oxidn. of alpha -pinene is likely to be more favored at lower NOx levels.
Lary, D. J., Shallcross, D. E, Potential importance of the reaction CO + HNO3., J. Geophys. Res., [Atmos.] , 105 D9 11617-11623 , 2000
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Abstract
CO has a strong thermodn. potential for reducing HNO3 to HONO. If the reaction of HNO3 with CO does proceed via heterogeneous catalysis on sulfuric acid aerosols in our atm., then this data assimilation study shows that the model is better able to reproduce the obsd. NOx/HNO3 ratio even with a gamma value as low as 1 * 10-4. This is particularly true in the upper troposphere and lower stratosphere. We highlight the possibility that elements such as Fe deposited in the lower stratosphere by meteorites may be catalyzing this and other reactions within sulfate aerosols.
Shallcross, Dudley E., Monks, Paul S., New directions., Atmos. Environ., 34 10 1659-1660 , 2000
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Abstract
CO has a strong thermodn. potential for reducing HNO3 to HONO. If the reaction of HNO3 with CO does proceed via heterogeneous catalysis on sulfuric acid aerosols in our atm., then this data assimilation study shows that the model is better able to reproduce the obsd. NOx/HNO3 ratio even with a gamma value as low as 1 * 10-4. This is particularly true in the upper troposphere and lower stratosphere. We highlight the possibility that elements such as Fe deposited in the lower stratosphere by meteorites may be catalyzing this and other reactions within sulfate aerosols.
Wang, K.-Y., Shallcross, D. E, A Lagrangian study of the three-dimensional transport of boundary-layer tracers in an idealized baroclinic-wave life-cycle., J. Atmos. Chem., 35 3 227-247 , 2000
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Abstract
The role of baroclinic-wave driven chem. transport is examd. using the framework of a Lagrangian trajectory model. The Lagrangian motion of transported trace gases are closely monitored through labeled boundary-layer tracers binned according to their latitudinal locations. From a set of 14-day Lagrangian paths, the mechanistically lifted subtropical boundary-layer tracers track along tilted poleward paths, while the subsiding high-latitude tracers track along tilted equator-ward paths. The most significant movements of tracers occur between days 6 and 8. The vertical and latitudinal displacements during this time interval are 3 km and 15 Deg latitude. During a baroclinic-wave life-cycle, boundary-layer tracers can either ascend vertically from 1 km to 7 km or descend to the surface, while they are latitudinally transported from 37 Deg to 73 Deg and from 45 Deg to near 15 Deg during the poleward and equator-ward motions, resp. Vertical mixing of tracers occurs vigorously at mid-latitudes, where more than 50%, by day 7, and a max. of 70%, between days 9 and 10, of the boundary layer tracers have been transported into the free troposphere during the baroclinic-wave life-cycle. A clear 3D picture emerges from a Lagrangian anal. Each time the tracer travels equator-ward, it descends, while when it travels poleward, it ascends. Almost all of the low latitude tracers show tilted upward and poleward paths, while high latitude tracers shows downward tilted and equator-ward path. The max. vertical displacement between poleward and equator-ward tracers are shown in mid-latitudes. Two types of the tilted upward and poleward paths are generally seen in the latitude-height projections
Giannakopoulos, C., Chipperfield, M. P., Law, K. S., Plantevin, P.-H., Pyle, J. A., Shallcross, D. E, A three-dimensional modeling study of the correlations of 210Pb with HNO3 and peroxyacetylnitrate (PAN) at remote oceanic sites., J. Geophys. Res., [Atmos.], 105 D2 1947-1956 , 2000
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Abstract
We have used 210Pb, a tracer originating from the radioactive decay of 222Rn emitted from soils, to show that tracers not affected by complex chem. reactions can provide a strong indication of the origin of air masses in the remote oceanic atm. and can help us understand the behavior of species which are affected by chem. Using our three-dimensional off-line chem. transport model (CTM), TOMCAT, we show that 210Pb tends to covary with altitude with HNO3 and peroxyacetylnitrate (PAN) at remote oceanic areas, suggesting the importance of transport for insol. species (in our case 222Rn and NOx) that are able to escape deep convective scavenging and travel long distances before being transformed to sol. species (here 210Pb and HNO3). Near the continental coast, esp. in the lower part of the troposphere, model HNO3 levels are large, evident of the continental influence. PAN and 210Pb levels are small. This indicates that 222Rn has not yet decayed to 210Pb and also PAN formation is not favored due to higher temps. near the surface. Therefore, in these young air masses, only PAN and 210Pb correlate, both having low values. Higher up, in the middle to upper troposphere, our modeling study shows that HNO3 and 210Pb tend to correlate, since in these relatively older air masses there was sufficient time for 210Pb formation.
P.G Simmonds, R.G Derwent, S. O'Doherty, D.B Ryall, L.P. Steele, R.L. Langenfelds, P.Salameh, R. Wang, and C.H. Dimmer and L.E.Hudson. Continuous High Frequency Observations of Hydrogen at the Mace Head Baseline Atmospheric Monitoring Station over the 1994-1998 Period. Atmos. Environ., 105, D10, 12105-12121, 2000 .
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Abstract
R.G, Prinn, R.F. Weiss, P.J. Fraser, P.G. Simmonds, D.M. Cunnold, F.N. Alyea, S. O'Doherty, P. Salameh, B.R. Miller, J. Huang, R.H.J. Wang, D.E. Hartley, C. Harth, L.P. Steele, G. Sturrock, P.M. Midgley, and A. McCulloch, A History of Chemically and Radiatively Important Gases in Air Deduced from ALE/GAGE/AGAGE., J. Geophys. Res., 105, D14, 17751-17792, 2000 .
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Abstract
S. Biraud, P. Ciais, M. Ramonet, P. Simmonds, V. Kazan, P. Monfray, S. O'Doherty, T.G. Spain and S. G. Jennings, European Greenhouse Gas Emissions Estimated from Continuous Atmospheric Measurements and Radon 222 at Mace Head, Ireland., J. Geophys., Res., 105, D1, 1351-1366, 2000 .
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Abstract
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1999
Stockwell, D. Z., Giannakopoulos, C., Plantevin, P.-H., Carver, G. D., Chipperfield, M. P., Law, K. S., Pyle, J. A., Shallcross, D. E, Wang, K.-Y., Modelling NOx from lightning and its impact on global chemical fields., Atmos. Environ., 33 27 4477-4493 , 1999
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Abstract
A 3-dimensional off-line chem. transport model (CTM) assessed the impact of lightning emissions in the free troposphere on NOx and other chem. species such as O3 and OH. These effects were examd. using 2 lightning emission scenarios. In the first, lightning emissions were coupled in space and time to the convective cloud top height calcd. every 6 h by the CTM moist convection scheme. In the second, lightning emissions were calcd. as a const., monthly mean field. Model performance against obsd. NOx and O3 profiles in the Atlantic and Pacific oceans improved significantly when lightning emissions were included. With the inclusion of these emissions, the CTM produced a significant increase in NOx concns. in the upper troposphere, where the NOx lifetime is long, and a smaller increase in the lower free troposphere, where surface NOx sources dominate. These changes caused a significant increase in 03 prodn. in the upper troposphere and hence higher calcd. 03 there. Results indicated that lightning emissions cause local increases of >50 parts per 1012 by vol. (pptv) in NOx, 200 pptv in HNO3, and 20 parts per 109 by vol. (ppbv) (>40%) in O3. In addn., a smaller O3 increase in the lower troposphere occurred due to an increased downward transport of O3. The O3 change was accompanied by an increase in OH which is more pronounced in the upper troposphere with a corresponding redn. in CO. The method of emission used in the model does not appear to have a significant effect globally. In the upper troposphere (above .apprx.300 hPa), NOx concns. were generally lower with monthly mean emissions, because of the de-coupling of emissions from the model's convection scheme, which vents NOx aloft more efficiently in the coupled scheme. Below the local convective outflow altitude, NOx concns. were larger when using monthly mean emissions than when coupled to the convection scheme, because the more dil. and night-time emissions led to a slower NO destruction rate. Only minor changes were predicted in the monthly av. O3 fields if lightning was emitted as a monthly const. field, however, the method of emission became important when a direct comparison of model results was made with time varying data. These differences should be accounted for when a direct comparison of O3 with measurements collected at particular times and locations is attempted.
Canosa-Mas, Carlos E., Carr, Sinead, King, Martin D., Shallcross, Dudley E., Thompson, Katherine C., Wayne, Richard P., A kinetic study of the reactions of NO3 with methyl vinyl ketone, methacrolein, acrolein, methyl acrylate and methyl methacrylate., Phys. Chem. Chem. Phys., 1 18 4195-4202 , 1999
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Abstract
Abs. and relative-rate techniques were used to obtain rate coeffs. for the reactions of NO3 with MeCOCH
Biggs, P., Canosa-Mas, C. E., Percival, C. J., Shallcross, D. E, Wayne, R. P., A study of the self reaction of CH2ClO2 and CHCl2O2 radicals at 298 K., Int. J. Chem. Kinet., 31 6 433-444 , 1999
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Abstract
A low-pressure discharge-flow system equipped with laser-induced fluorescence (LIF) detection of NO2 and resonance-fluorescence detection of OH has been employed to study the self reactions CH2ClO2 + CH2ClO2 -> products (1) and CHCl2O2 + CHCl2O2 -> products (2), at T = 298 K and P = 1-3 Torr. Possible secondary reactions involving alkoxy radicals are identified. We report the phenomenol. rate consts. (kobs) k1obs = (4.1 +- 0.2) * 10-12 cm3 mol.-1 s-1 k2obs = (8.6 +- 0.2) * 10-12 cm3 mol.-1 s-1 and the rate consts. derived from modeling the decay profiles for both peroxy radical systems, which takes into account the proposed secondary chem. involving alkoxy radicals k1 = (3.3 +- 0.7) * 10-12 cm3 mol.-1 s-1 k2 = (7.0 +- 1.8) * 10-12 cm3 mol.-1 s-1. A possible mechanism for these self reactions is proposed and QRRK calcns. are performed for reactions (1), (2) and the self-reaction of CH3O2, CH3O2 + CH3O2 -> products (3). These calcns., although only semiquant., go some way to explaining why both k1 and k2 are a factor of ten larger than k3 and why, as suggested by the products of reaction (1) and (2), it seems that the favored reaction pathway is different from that followed by reaction (3). The atm. fate of the chlorinated peroxy species, and hence the impact of their precursors (CH3Cl and CH2Cl2), in the troposphere are briefly discussed. HC(O)Cl is identified as a potentially important reservoir species produced from the photooxidn. of these precursors.
Canosa-Mas, C. E., King, M. D., Shallcross, D. E, Wayne, R. P., Kinetic investigation of the reaction between the NO3 radical and peroxymethacrylic nitric anhydride (MPAN)., Phys. Chem. Chem. Phys., 1 10 2411-2414 , 1999
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Abstract
The gas-phase reaction between the NO3.bul. radical and CH2
Fish, D. J., Shallcross, D. E, Jones, R. L., The vertical distribution of NO3 in the atmospheric boundary layer., Atmos. Environ., 33 5 687-691 , 1999
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Abstract
Recent urban measurements suggest that NO3 concns. vary significantly with altitude in the lowest few hundred meters of the atm. Calcns. using a one-dimensional boundary layer model show that NO3 concns. are low near the ground and increase with altitude to a max. near the top of the nocturnal boundary layer (NBL). These results show that the NBL is not well mixed, and that where there are surface sources and sinks two-box models of the NBL are inadequate, and surface measurements are not representative and may lead to an underestimate of the oxidizing capacity of the atm.
R.G. Derwent, N. Carslaw, P.G. Simmonds, M. Bassford, S. O'Doherty, D. B. Ryall, and M.J. Pilling, Hydroxyl Radical Concentrations Estimated from Measurements of Trichloroethylene during the EASE/ACSOE Campaign at Mace Head, Ireland during July 1996. J. Atmos. Chem., 34, 185-205, 1999 .
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Abstract
S.J. O'Doherty, G. Nickless, M. Bassford, M. Pajot, P. Simmonds, Separation of hydrohalocarbons and chlorofluorocarbons using a cyclodextrin gas solid chromatography capillary column., J. Chromatography A, 832, 253-258, 1999 .
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Abstract
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1998
Law, K. S., Plantevin, P. H., Shallcross, D. E, Rogers, H. L., Pyle, J. A., Grouhel, C., Thouret, V., Marenco, A., Evaluation of modeled O3 using measurement of ozone by Airbus In-Service Aircraft (MOZAIC) data., J. Geophys. Res., [Atmos.], 103 D19 25721-25737 , 1998
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Abstract
The O3 distribution calcd. by a global three-dimensional chem. transport model, TOMCAT, is compared to O3 data collected on Airbus A340 passenger aircraft as part of the Measurement of Ozone by Airbus In-Service Aircraft (MOZAIC) project. The model results are compared to seasonally averaged data at cruise altitudes in the upper troposphere and lower stratosphere and to individual vertical profiles collected over particular cities during takeoff and landing. In many regions, the model shows good agreement with these data, given the large variability encountered, particularly around the tropopause. There are also significant day to day variations in ozone, which, in the vertical profile data, TOMCAT captures well over northern midlatitude cities, esp. in the upper troposphere and also in the winter lower troposphere. In the tropics, the MOZAIC data often shows a lot of structure, with thin layers of high O3 which are sometimes captured in the model. Possible reasons for this and other discrepancies are discussed.
Mossinger, Juliane C., Shallcross, Dudley E., Cox, R. Anthony., UV-visible absorption cross-sections and atmospheric lifetimes of CH2Br2, CH2I2 and CH2BrI., J. Chem. Soc., Faraday Trans., 94 10 1391-1396 , 1998
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Abstract
The UV-visible absorption spectra of CH2Br2, CH2I2 and CH2BrI have been measured over the wavelength range 215-390 nm using a dual-beam diode array spectrometer. The spectra consist of broad continuous absorption bands. CH2Br2 exhibits its max. cross-section of s = 2.71(+-0.16)*10-18 cm2-mol.-1 at l = 219 nm. The magnitude of the peak cross-sections for the iodine-contg. mols. above l = 210 nm are s = 1.62(+-0.10)*10-18 cm2-mol.-1 at l = 248 nm and s = 3.78(+-0.23)*10-18 cm2-mol.-1 at l = 288 nm for CH2I2, and s = 5.67(+-0.34)*10-18 cm2-mol.-1 at l = 215 nm and s = 2.34(+-0.14)*10-18 cm2-mol.-1 at l = 267 nm for CH2BrI. The temp. dependence of the absorption cross-sections was investigated over the temp. range 348-250 K. A decline in the cross-sections with decreasing temp. was obsd. in the tail of the spectra. At the peaks the opposite effect was obsd. All three gases have been found in the atm. and the atm. photolysis rates of CH2Br2, CH2I2 and CH2BrI were calcd. as a function of altitude and solar zenith angle using the measured cross-sections. Model calcns. show that, during sunlit hours, CH2I2 and CH2BrI will be photolyzed within minutes and hours, resp. The photolysis of CH2Br2 is much slower and reaction with the OH radical is the dominant atm. loss process.
Greally, Brian R., Nickless, Graham, Simmonds, Peter G., Woodward, Michael, de Zeeuw, Jaap., Separation of mixed halocarbons of environmental interest on a new type of silica-based porous-layer open tubular capillary gas chromatographic column., J. Chromatogr., A , 810 1 + 2 119-130 , 1998
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Abstract
A new type of capillary porous-layer open tubular (PLOT) column consisting of a hydrophobic silica layer on a fused-silica capillary has been tested for the sepn. of a mixt. of environmentally sensitive halocarbons present in tropospheric air. The column shows high retention for a wide range of halocarbons, with elution orders following both b.p. order and hydrogen bonding capability. The resoln. of the halocarbons is good and only one pair of halocarbons [CHFClCF3 (HCFC 124) and CH3CF2Cl (HCFC 142b)] cannot be resolved on this column type at all column temp. profiles. Unlike alumina PLOT columns, the silica PLOT column does not dehydrohalogenate labile halocarbons. Excellent reproducibility of retention times and peak areas for halocarbons on the column are reported.
P.G. Simmonds, D.M. Cunnold, R.F. Weiss, R.G. Prinn, P.J. Fraser, A. McCulloch, F.N. Alyea, and S. O'Doherty, Global Trends and Emission Estimates of Carbon Tetrachloride (CCl4) from in-situ Background Observations from July 1978 to June 1996., Geophys., Res., 103., 16017-16028., 1998 .
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Abstract
P.G. Simmonds, S. O'Doherty, J. Huang, D. Derwent, D. Ryall, R. Prinn, G. Nickless, and D. Cunnold., Calculated Trends and Atmospheric Abundance of HFC-134a, HCFC-141b and HCFC-142b using Automated in-situ Gas Chromatographic-Mass Spectrometry Measurements Recorded at Mace Head, Ireland from October 1994 to March 1997., J. Geophys., Res., 103, 16029-16038, 1998 .
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Abstract
R.G. Derwent, P.G. Simmonds, S. O'Doherty, and D. B. Ryall, The Impact of the Montreal Protocol on Halocarbon Concentrations in Northern Hemisphere Baseline and European Air Masses at Mace Head, Ireland Over a Ten Year Period from 1987-1996., Atmos. Environ., 32, 21, 3689-3702, 1998 .
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Abstract
.G. Derwent, P.G. Simmonds, S. O'Doherty, P. Ciais and D. B. Ryall, European Source Strengths and Northern Hemisphere Baseline Concentrations of Radiatively Active Trace Gases at Mace Head, Ireland. Atmos. Environ., 32 21 3703-3715, 1998 .
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Abstract
G. Sturrock, S. O'Doherty, and P. Fraser, In Situ Measurements of CFC Replacement Chemicals at Cape Grim, Tasmania: The AGAGE GC-MS Program., Clean Air., 5, 511-516, 1998 .
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Abstract
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1997
Clemitshaw, Kevin C., Williams, Jonathan, Rattigan, Oliver V., Shallcross, Dudley E., Law, Kathy S., Cox, R. Anthony., Gas-phase ultraviolet absorption cross-sections and atmospheric lifetimes of several C2-C5 alkyl nitrates., J. Photochem. Photobiol., A , 102 2-3 117-126 , 1997
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Abstract
Gas-phase UV absorption cross-sections of Et nitrate, 1-Pr nitrate, 2-Pr nitrate, 2-Me, 1-Pr nitrate, 1-Bu nitrate and 1-pentyl nitrate have been measured over the wavelength range 220-340 nm using a dual-beam, diode array spectrometer. Each alkyl nitrate spectrum appears to be the sum of at least two Gaussian-shaped absorptions with an intense v-pi* band extending from 190-240 nm having a shoulder between 250-340 nm due to a n-pi* system. The absorption cross-sections recorded for Et nitrate, 1-Pr nitrate, 2-Pr nitrate and 1-Bu nitrate are within 10% of previous data
Chipperfield, M. P., Shallcross, D. E, Lary, D. J., A model study of the potential role of the reaction BrO + OH in the production of stratospheric HBr., Geophys. Res. Lett., 24 23 3025-3028 , 1997
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Abstract
The authors used a constrained one-dimensional photochem. model to investigate the effect of a potential minor channel of the fast reaction between BrO + OH to produce HBr. There is no direct evidence for this reaction but the analogous yield of HCl from ClO + OH is thought to be about 5%. With only a 1-2% yield of HBr the modeled HBr mixing ratio between 20-30 km increases from around 0.5 parts per 1012 by vol. (pptv) to 1-2 pptv. This brings the model into agreement with recent balloon-borne observations of stratospheric HBr. Should BrO + OH produce HBr with around 1-2% yield then its reaction will dominate HBr prodn. between 20-35 km. Since the main loss of HBr is reaction with OH this will lead to steady state HBr
Rattigan, Oliver V., Shallcross, Dudley E., Cox, R. Anthony., UV absorption cross-sections and atmospheric photolysis rates of CF3I, CH3I, C2H5I and CH2ICl., J. Chem. Soc., Faraday Trans., 93 16 2839-2846 , 1997
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Abstract
The absorption cross-sections of trifluoromethyl iodide (CF3I), Me iodide (CH3I), Et iodide (C2H5I) and chloro iodomethane (CH2ICI) have been detd. over the wavelength range 235-400 nm, with a spectral resoln. of 0.6 nm (FWHM), using a diode array spectrometer. The spectra consist of a broad continuous absorption band with max. cross-sections of (6.0 +- 0.1) * 10-19 cm2 mol.-1 for CF3I at 267 nm, (1.09 +- 0.02) * 10-18 cm2 mol.-1 for CH3I at 258 nm, (1.18 +- 0.04) * 10-18 cm2 mol.-1 for C2H5I at 258 nm and (1.21 +- 0.07) * 10-18 for CH2ICl at 270 nm. The temp. dependence of the cross-section was investigated over the range 333-243 K. A decline in the cross-section with decreasing temp. at wavelengths longer than ca. 280 nm was obsd. in all cases, the decrease being most pronounced in the long wavelength tail of the absorption band. At wavelengths shorter than ca. 270 nm the cross-section increased with decreasing temps., the effect, however, was significantly smaller (5-10%), being most pronounced around the band max. The temp. dependence was parametrized in order to calc. the atm. photolysis rate as a function of altitude, latitude and season. Model calcns. show that during sunlit hours the iodides will be rapidly photolyzed with tropospheric photo-dissocn. lifetimes of ca. 1 day for CF3I, several days for CH3I and C2H5I and several hours for CH2ICl.
Shallcross, Dudley E., Biggs, Peter, Canosa-Mas, Carlos E., Clemitshaw, Kevin C., Harrison, Mark G., Alanon, M. Reyes Lopez, Pyle, John A., Vipond, Alison, Wayne, Richard P., Rate constants for the reaction between OH and CH3ONO2 and C2H5ONO2 over a range of pressure and temperature., J. Chem. Soc., Faraday Trans., 93 16 2807-2811 , 1997
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Abstract
A discharge-flow app. equipped with resonance-fluorescence detection for OH radicals has been used to measure rate coeffs. for the two reactions OH + CH3ONO2 -> products (1) and OH + C2H5ONO2 -> products (2), over the pressure range 1-20 Torr at T = 298 K and .apprx. 1-3 Torr over the temp. range 300-400 K. The rate consts.(k1 and k2) were found to be invariant with pressure, but were found to increase with increasing temp. In light of these findings, we conclude that at low pressure the reaction mechanism is consistent with an abstraction process. The rate consts. derived are k1 = (4.1 +- 0.8) * 10-13 exp(-604 +- 121/T) cm3 mol.-1 s-1 and k2 = (3.30 +- 0.66) * 10-12 exp(-699 +- 140/T) cm3 mol.-1 s-1. The existence of pressure-dependent (assocn.) channels for reactions (1) and (2) is briefly discussed. Model calcns. are presented that imply that photolysis, and not reaction with the OH radical, is the dominant loss process in the atm. for CH3ONO2 and C2H5ONO2. Lifetimes of CH3ONO2 and C2H5ONO2 are derived for the lower atm., they vary from a few years to several days depending upon season and location. Possible sources of these alkyl nitrates in the atm. are discussed.
Biggs, Peter, Canosa-Mas, Carlos E., Shallcross, Dudley E., Vipond, Alison, Wayne, Richard P., Kinetics of the reactions of CF3O2 with OH, HO2 and H., J. Chem. Soc., Faraday Trans., 93 16 2701-2705 , 1997
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Abstract
The kinetics of the reactions
Biggs, Peter, Canosa-Mas, Carlos E., Frachebound, Jean-Marc, Shallcross, Dudley E., Wayne, Richard P., Kinetics of the reaction of F atoms with CH3ONO and CH3O, and the reaction of CH3O with a number of hydrocarbons., J. Chem. Soc., Faraday Trans., 93 15 2481-2486 , 1997
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Abstract
A discharge-flow system equipped with a laser-induced fluorescence cell to detect the methoxyl radical and a quadrupole mass spectrometer to detect products has been used to det. the kinetics of the reactions
Biggs, Peter, Canosa-Mas, Carlos E., Shallcross, Dudley E., Vipond, Alison, Wayne, Richard P., Kinetics of the reaction of CF3O2 radicals with O(3P) atoms., J. Chem. Soc., Faraday Trans., 93 15 2477-2480 , 1997
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Abstract
A discharge fast-flow tube equipped with laser-induced fluorescence detection for NO2, produced from the titrn. of CF3O2 with NO, and chemiluminescence detection for O(3P), was employed to det. the rate const. for the reaction CF3O2 + O(3P) -> products, at T = 296 +- 1 K and P = ca. 2 Torr. The rate const. was found to be (6.3 +- 1.0) * 10-11 cm3 mol.-1 s-1. Some implications of the results for atm. chem. are discussed.
Biggs, Peter, Canosa-Mas, Carlos E., Fracheboud, Jean-Marc, Percival, Carl J., Wayne, Richard P., Shallcross, Dudley E., Kinetics of the self reaction of CF3O2 radicals and their reaction with O3 at 298 K., J. Chem. Soc., Faraday Trans., 93 3 379-385 , 1997
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Abstract
Two low-pressure discharge-flow systems, one equipped with laser-induced fluorescence (LIF) detection of NO2 and the other mass spectrometric detection of NO2, have been employed to det. the rate const. for the self reaction CF3O2 + CF3O2 -> products, at T = 298 K and P = 1-3 Torr. The phenomenol. rate const. is k1 = (2.0 +- 0.1) * 10-12 cm3 mol.-1 s-1, however, after consideration of secondary chem., numerical modeling suggests that the true rate const. is k1 = (1.2 +- 0.3) * 10-12 cm3 mol.-1 s-1. In addn., an upper limit has been derived for the reaction CF3O2 + O3 -> products of k3 < 3 * 10-14 cm3 mol.-1 s-1. The mechanism of the self reaction and the atm. implications of these results are discussed briefly.
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1996
Canosa-Mas, Carlos E., King, Martin D., Lopez, Reyes, Percival, Carl J., Wayne, Richard P., Shallcross, Dudley E., Pyle, John A., Daele, Veronique., Is the reaction between CH3C(O)O2 and NO3 important in the night-time troposphere?, J. Chem. Soc., Faraday Trans., 92 12 2211-2222 , 1996
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Abstract
A discharge-flow system equipped with a laser-induced fluorescence cell to detect NO2 and a multi-pass absorption cell to detect NO3 was used to study the reaction CH3C(O)O2 + NO3 -> CH3C(O)O + NO2 + O2 at 403-443 Deg K and 2-2.4 Torr. The rate const. was independent of temp. with a value of k1 = (4+1) * 10-12 cm3/mol.-s. The likely mechanism for the reaction is discussed. The atm. implications of this reaction are investigated using a range of models and several case studies are presented, comparing model results with actual field measurements. It is concluded that this reaction participates in a cycle which can generate OH at night. This reaction can operate throughout the continental boundary layer, but may even occur in remote regions.
Morris, Noreen M., Greally, Brian R., Cairns, Peter M., An investigation of factors influencing the resolution of chiral alkyl aromatic amines on a dinitrobenzoyl-(S)-leucine HPLC column., J. Liq. Chromatogr. Relat. Technol., 19 3 489-502 , 1996
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Abstract
Normal phase HPLC methodol. was utilized to obtain sepn. of (+-)-1-(4-bromophenyl)ethylamine and (+-)-2-(1-Naphthyl)ethylamine on a 3,5-dinitrobenzoyl-(S)-Leucine Pirkle type chiral stationary phase (CSP). A proposed retention mechanism (based on a three point interaction model) is outlined where the key interaction s steric attraction/repulsion between aryl groups on the solutes and the (S) Leucine group on the CSP.
P.G. Simmonds, R.G. Derwent, A. McCulloch, S. O'Doherty, and A.Gaudry, Long-Term Trends in Concentrations of Halocarbons and Radiatively Active Trace Gases in Atlantic and European Air Masses Monitored at Mace Head, Ireland from 1987-1994, Atmos. Environ., 30, 3, 4041-4063, 1996 .
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Abstract
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1995
Monks, P. S., Nesbitt, F. L., Payne, W. A., Scanlon, M., Stief, L. J., Shallcross, D. E, Absolute Rate Constant and Product Branching Ratios for the Reaction between H and C2H3 at T = 213 and 298 K., J. Phys. Chem., 99 47 17151-9 , 1995
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Abstract
The discharge-flow kinetic technique coupled to mass-spectrometric detection has been used to det. the variable-temp. dependence of the rate const. and product branching ratios for the reaction between H and C2H3 at 1 Torr nominal pressure (He). At. hydrogen was produced from the reaction between F(2P) and H2 while the vinyl radical was produced simultaneously from the reaction between F(2P) and ethylene, which gives both C2H3 and H. The reaction was studied at T = 213 and 298 K by monitoring the decay of C2H3 in the presence of a large excess of H. The rate consts. were detd. to be k(H+C2H3)(298 K) = (1.1 +- 0.3) * 10-10 and k(H+C2H3)(213 K) = (1.0 +- 0.3) * 10-10 both in the units cm3 mol.-1 s-1, the quoted uncertainty represents total errors. The activation energy for the reaction between H and C2H3 is therefore near zero. Further, the fractional product yields for the channels H + C2D3 -> C2D3H (a) and H + C2D3 -> C2D2 + HD (b) were detd. by quant. measuring the yields of both C2D3H and HD independently. The derived fractional product yields were Gamma a(298 K) = 0.33 +- 0.13, Gamma b(298 K) = 0.67 +- 0.18, Gamma a(213 K) = 0.24 +- 0.09, and Gamma b(213 K) = 0.76 +- 0.16, where the quoted uncertainty represents total errors. Quantum RRK (QRRK) calcns. have been undertaken to investigate the relationship between the obsd. kinetics, products, and possible mechanisms. With the available data and the QRRK calcns., a mechanism of the form H + C2H3 + M .tautm. [H-C2H3]* -> C2H4 + M (a) and H + C2H3 -> H2 + C2H2 (b) is shown to be most likely. Further, Troe calcns. have been undertaken in order to suggest values for the limiting low-pressure rate coeffs. A brief comparison is made between the results of the Troe and QRRK analyses. The implications for the conversion of C2H2 to C2H6 in the relatively low temp. conditions of planetary atmospheres are briefly discussed.
Biggs, Peter, Mcnosa-Mas, Carlos E., Francheboud, Jean-Marc, Marston, George, Shallcross, Dudley E., Wayne, Richard P., Kinetics and mechanism of the reaction of CH3 and CH3O with ClO and OClO at 298 K., J. Chem. Soc., Faraday Trans., 91 18 3045-53 , 1995
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Abstract
A discharge-flow system equipped with a laser-induced fluorescence cell to detect the methoxyl radical and a quadrupole mass spectrometer to detect both the chlorine monoxide and chlorine dioxide radicals has been used to measure the rate consts. for the reactions CH3 + ClO -> products, CH3O + ClO -> products, CH3 + OClO -> products, CH3O + OClO -> products at T = 298 K and P = 1-3 Torr. The obsd. products of these reactions are CH3O for reaction (1), HOCl for reaction (2), and CH3O and ClO for reaction (3). For reaction (4), CH3OCl is a possible product. The rate consts. derived for reactions (1)-(4) are
Biggs, P., Canosa-Mas, C. E., Fracheboud, J. -M., Shallcross, D. E, Wayne, R. P., Efficiency of formation of CH3O in the reaction of CH3O2 with ClO., Geophys. Res. Lett., 22 10 1221-4 , 1995
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Abstract
A discharge-flow app. was used to det. the branching ratio alpha for the channel of the reaction of ClO with CH3O2 that leads to the formation of CH3O. The expts. were performed at 2 Torr pressure and at room temp. ClO was the excess reactant and was measured mass spectrometrically, CH3O was detected by laser-induced fluorescence. The value of alpha was shown to depend on the fraction beta of the reaction of CH3O2 with Cl atoms that leads to the formation of CH3O. For beta = 0, 0.5 and 1, the derived values of alpha are 0.28 +- 0.07, 0.32 +- 0.08 and 0.42 +- 0.09, resp. Comparison with other published results suggests the possibility of three significant product channels for the reaction of CH3O2 with ClO.
Biggs, Peter, Canosa-Mas, Carlos E., Fracheboud, Jean-Marc, Shallcross, Dudley E., Wayne, Richard P., Rate constants for the reactions of C2H5, C2H5O, and C2H5O2 radicals with NO3 at 298 K and 2.2 Torr., J. Chem. Soc., Faraday Trans., 91 5 817-25 , 1995
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Abstract
A discharge-flow system equipped with a laser-induced fluorescence cell to detect the ethoxyl radical and an optical absorption cell to detect the nitrate radical has been used to measure the rate consts. for the reactions C2H5 = NO3 -> products (1), C2H5O + NO3 -> products (2), C2H5O2 + NO3 -> products (3), at T = 298 K and P = 2.2 Torr. The major products of these reactions are C2H5O and NO2 for reaction (1), C2H5O2 and NO2 for reaction (2) and C2H5O, O2 and NO2 for reaction (3). Reactions (2) and (3) are therefore highly coupled and, in order to det. the rate consts. k2 and k3 for these reactions, two types of expt. were performed. In the first set of expts., C2H5O was generated in situ via reaction (1) and allowed to react with NO3 and, in the second set of expts., C2H5O2 was generated sep. and allowed to react with NO3. A numerical model was then used to derive the following rate consts.
P.G. Simmonds, S. O'Doherty, G. Nickless, and G.A. Sturrock, Automated Gas Chromatographic/Mass Spectrometer for Routine Atmospheric Field Measurements of the CFC Replacement Compounds, the Hydrofluorocarbons and Hydrochlorofluorocarbons, Anal. Chem., 67, 4, 717-723, 1995 .
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Abstract
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1994
Biggs, P., Canosa-Mas, C. E., Fracheboud, J. -M., Shallcross, D. E, Wayne, R. P., The reactions of alkyl, alkoxy and alkylperoxy radicals with NO3. A contribution to subproject LACTOZ., Transp. Transform. Pollut. Troposphere, Proc. EUROTRAC Symp., 3rd, 91 5 144-8 , 1994
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Abstract
The results of expts. carried out using a discharge-flow tube at room temp. and 2.2 tor are analyzed and kinetics of the reactions are studied.
Biggs, P., Canosa-Mas, C. E., Fracheboud, J-M., Shallcross, D. E, Wayne, R. P., An investigation of the kinetics of the reaction between MeO2, MeO, and Me with NO3., Comm. Eur. Communities, [Rep.] EUR , 91 15609, Physico-Chemical Behaviour of Atmospheric Pollutants, Vol. 1 77-83 , 1994
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Abstract
A low-pressure discharge-flow system equipped with laser-induced fluorescence (LIF) and optical absorption detection was employed to det. rate coeffs. for the reactions (1) MeO2 + NO3 -> products, (2) MeO + NO3 -> products, and (3) Me + NO3 -> products, at 298K and 2.4 Torr. The values obtained were
Biggs, Peter, Canosa-Mas, Carlos E., Fracheboud, Jean Marc, Shallcross, Dudley E., Wayne, Richard P., Investigation into the kinetics and mechanism of the reaction of NO3 with CH3O2 at 298 K and 2.5 Torr., J. Chem. Soc., Faraday Trans., 90 9 1205-10 , 1994
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Abstract
The kinetics of the reaction CH3O2 + N3 -> CH3O + NO2 + O2 (1) have been studied at 298 K and at pressures between 2 and 3 Torr of helium using the discharge-flow technique combined with laser-induced fluorescence detection of the methoxyl radical and measurements of the NO3 radical using visible absorption. Numerical modeling of the concn.-time profile of CH3O with or without NO3 and NO as a titrant has allowed the authors to show that CH3O is a product of reaction (1) and to derive a rate const. k1 = (1.0 +- 0.6) * 10-12 cm3 mol.-1 s-1, at 95% confidence limits. A comparison of the reactivities of NO3 and NO2 towards the species R, RO and RO2, where R = H or CH3, is given. The implication of reaction (1) in the possible prodn. of OH in the atm. at night is discussed.
Biggs, Peter, Canosa-Mas, Carlos E., Fracheboud, Jean Marc, Shallcross, Dudley E., Wayne, Richard P., Investigation into the kinetics and mechanism of the reaction of NO3 with CH3 and CH3O at 298 K between 0.6 and 8.5 Torr., J. Chem. Soc., Faraday Trans., 90 9 1197-204 , 1994
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Abstract
The reactions CH3 + NO3 -> products (1), and CH3O + NO3 -> products (2), have been studied using a flow system at T = 298 K and at pressures between 0.6 and 8.5 Torr. The laser-induced fluorescence (LIF) technique was used to detect CH3O and multi-pass optical absorption to detect NO3. The chem. systems were studied as a pair of consecutive reactions, however, a simple anal. treatment was not sufficient to describe them because CH3O2 was formed as one of the products in the major channel of reaction (2). This species also reacts with NO3 regenerating CH3O. Use a numerical model to correct for this regeneration process allowed rate parameters of k1 = (3.5 +- 1.0) * 10-11 cm3 mol.-1 s-1 and k2 = (2.3 +- 0.7) * 10-12 cm3 mol.-1 s-1 to be detd. at 2.4 Torr. There is no pressure dependence obsd. for reaction (1) between 1 and 2.4 Torr, but the possibility of a slight pressure dependence for reaction (2) exists. These pressure effects are examd. using the semi-empirical quantum RRK method.
1993
S.J. O’Doherty, P.G. Simmonds, and G. Nickless, Evaluation of Carboxen Carbon Molecular Sieves for Trapping Replacement Chlorofluorocarbons, J. Chromatogr., 630, 265-274 1993 .
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Abstract
S.J. O'Doherty, P.G. Simmonds, and G. Nickless, Analysis of Replacement Chlorofluorocarbons using Carboxen Microtraps for Isolation and Preconcentration in Gas Chromatography-Mass Spectrometry, J.Chromatogr., 657, 123-129 1993 .
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Abstract
Biggs, Peter, Canosa-Mas, Carlos E., Fracheboud, Jean Marc, Parr, A. Douglas, Shallcross, Dudley E., Wayne, Richard P., Caralp, Francoise., Investigation into the pressure dependence between 1 and 10 Torr of the reactions of NO2 with CH3 and CH3O., J. Chem. Soc., Faraday Trans., 89 23 4163-9 , 1993
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Abstract
The kinetics and pressure dependence of the reactions of NO2 with Me and MeO were studied in the gas phase at 298 K, at pressures from 1 to 10 torr. A low-pressure discharge-flow laser-induced fluorescence (LIF) technique was used. In a consecutive process, Me reacted with NO2 to form MeO, Me + NO2 -> MeO + NO (1), which further reacted with NO2 to form products, MeO + NO2 -> products (2). Reaction (1) displayed no discernible pressure dependence over the pressure range 1-7 torr, and k1 was calcd. to be (2.3 +- 0.3) * 10-11 cm3 mol.-1 s-1. Reaction (2) displayed a strong pressure dependence and an RRKM anal. yielded the following limiting low- and high-pressure rate consts. in He, ko = 5.9 * 10-29 cm6 mol.-2 s-1 and k., . = 2.1 * 10-11 cm3 mol.-1 s-1. It is unrealistic to quote errors for this type of anal. Parametrization in the std. Troe form with Fc = 0.6 yielded ko = (5.3 +- 0.2) * 10-29 cm6 mol.-2 s-1 and k., . = (1.4 +- 0.1) * 10-11 cm3 mol.-1 s-1. Atm. implications and possible reaction mechanisms are discussed.