ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-5281-2010 Measurements of volatile organic compounds over West Africa Murphy J. G. 1 2 Oram D. E. 1 Reeves C. E. 1 School of Environmental Sciences, University of East Anglia, Norwich, UK now at: Department of Chemistry, University of Toronto, Toronto, Canada 16 06 2010 10 12 5281 5294 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/10/5281/2010/acp-10-5281-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/5281/2010/acp-10-5281-2010.pdf

In this paper we describe measurements of volatile organic compounds (VOC) made using a Proton Transfer Reaction Mass Spectrometer (PTR-MS) aboard the UK Facility for Atmospheric Airborne Measurements during the African Monsoon Multidisciplinary Analyses (AMMA) campaign. Observations were made during approximately 85 h of flying time between 17 July and 17 August 2006, above an area between 4° N and 18° N and 3° W and 4° E, encompassing ocean, mosaic forest, and the Sahel desert. High time resolution observations of counts at mass to charge (<i>m/z</i>) ratios of 42, 59, 69, 71, and 79 were used to calculate mixing ratios of acetonitrile, acetone, isoprene, the sum of methyl vinyl ketone and methacrolein, and benzene respectively using laboratory-derived humidity-dependent calibration factors. Strong spatial associations between vegetation and isoprene and its oxidation products were observed in the boundary layer, consistent with biogenic emissions followed by rapid atmospheric oxidation. Acetonitrile, benzene, and acetone were all enhanced in airmasses which had been heavily influenced by biomass burning. Benzene and acetone were also elevated in airmasses with urban influence from cities such as Lagos, Cotonou, and Niamey. The observations provide evidence that both deep convection and mixing associated with fair-weather cumulus were responsible for vertical redistribution of VOC emitted from the surface. Profiles over the ocean showed a depletion of acetone in the marine boundary layer, but no significant decrease for acetonitrile.

 References Aghedo, A. M., Schultz, M. G., and Rast, S.: The influence of African air pollution on regional and global tropospheric ozone, Atmos. Chem. Phys., 7, 1193–1212, doi:10.5194/acp-7-1193-2007, 2007. Andreae, M. O., Artaxo, P., Fischer, H., Freitas, S. R., Gregoire, J. M., Hansel, A., Hoor, P., Kormann, R., Krejci, R., Lange, L., Lelieveld, J., Lindinger, W., Longo, K., Peters, W., de Reus, M., Scheeren, B., Dias, M. A. F. S., Strom, J., van Velthoven, P. F. J., and Williams, J.: Transport of biomass burning smoke to the upper troposphere by deep convection in the equatorial region, Geophys. Res. Lett., 28, 951–954, 2001. Andrés-Hernández, M. D., Kartal, D., Reichert, L., Burrows, J. P., Meyer Arnek, J., Lichtenstern, M., Stock, P., and Schlager, H.: Peroxy radical observations over West Africa during AMMA~2006: photochemical activity in the outflow of convective systems, Atmos. Chem. Phys., 9, 3681–3695, doi:10.5194/acp-9-3681-2009, 2009. Arnold, S. R., Spracklen, D. V., Williams, J., Yassaa, N., Sciare, J., Bonsang, B., Gros, V., Peeken, I., Lewis, A. C., Alvain, S., and Moulin, C.: Evaluation of the global oceanic isoprene source and its impacts on marine organic carbon aerosol, Atmos. Chem. Phys., 9, 1253–1262, doi:10.5194/acp-9-1253-2009, 2009. Atkinson, R., Baulch, D. L., Cox, R. A., Crowley, J. N., Hampson, R. F., Hynes, R. G., Jenkin, M. E., Rossi, M. J., Troe, J., and IUPAC Subcommittee: Evaluated kinetic and photochemical data for atmospheric chemistry: Volume~II - gas phase reactions of organic species, Atmos. Chem. Phys., 6, 3625–4055, doi:10.5194/acp-6-3625-2006, 2006. Bange, H. W. and Williams, J.: New Directions: Acetonitrile in atmospheric and biogeochemical cycles, Atmos. Environ., 34, 4959–4960, 2000. Barret, B., Ricaud, P., Mari, C., Attié, J.-L., Bousserez, N., Josse, B., Le Flochmo\"en, E., Livesey, N. J., Massart, S., Peuch, V.-H., Piacentini, A., Sauvage, B., Thouret, V., and Cammas, J.-P.: Transport pathways of CO in the African upper troposphere during the monsoon season: a study based upon the assimilation of spaceborne observations, Atmos. Chem. Phys., 8, 3231–3246, doi:10.5194/acp-8-3231-2008, 2008. Bechara, J., Borbon, A., Jambert, C., and Perros, P. E.: New off-line aircraft instrumentation for non-methane hydrocarbon measurements, Anal. Bioanal. Chem., 392, 865–876, 2008. Capes, G., Murphy, J. G., Reeves, C. E., McQuaid, J. B., Hamilton, J. F., Hopkins, J. R., Crosier, J., Williams, P. I., and Coe, H.: Secondary organic aerosol from biogenic VOCs over West Africa during AMMA, Atmos. Chem. Phys., 9, 3841–3850, doi:10.5194/acp-9-3841-2009, 2009. Christian, T. J., Kleiss, B., Yokelson, R. J., Holzinger, R., Crutzen, P. J., Hao, W. M., Saharjo, B. H., and Ward, D. E.: Comprehensive laboratory measurements of biomass-burning emissions: 1 Emissions from Indonesian, African, and other fuels, J. Geophys. Res.-Atmos., 108, 4719, doi:10.1029/2003JD003704, 2003. Christian, T. J., Yokelson, R. J., Cárdenas, B., Molina, L. T., Engling, G., and Hsu, S.-C.: Trace gas and particle emissions from domestic and industrial biofuel use and garbage burning in central Mexico, Atmos. Chem. Phys., 10, 565–584, doi:10.5194/acp-10-565-2010, 2010. Collins, W. J., Stevenson, D. S., Johnson, C. E., and Derwent, R. G.: Role of convection in determining the budget of odd hydrogen in the upper troposphere, J. Geophys. Res.-Atmos., 104, 26927–26941, 1999. Colomb, A., Williams, J., Crowley, J., Gros, V., Hofmann, R., Salisbury, G., Klupfel, T., Kormann, R., Stickler, A., Forster, C., and Lelieveld, J.: Airborne measurements of trace organic species in the upper troposphere over Europe: the impact of deep convection, Environ. Chem., 3, 244–259, 2006. Commane, R., Floquet, C. F. A., Ingham, T., Stone, D., Evans, M. J., and Heard, D. E.: Observations of OH and HO<sub>2</sub> radicals over West Africa, Atmos. Chem. Phys. Discuss., 10, 7265–7322, doi:10.5194/acpd-10-7265-2010, 2010. Crutzen, P. J. and Andreae, M. O.: Biomass Burning in the Tropics – Impact on Atmospheric Chemistry and Biogeochemical Cycles, Science, 250, 1669–1678, 1990. de Gouw, J., Warneke, C., Karl, T., Eerdekens, G., van der Veen, C., and Fall, R.: Sensitivity and specificity of atmospheric trace gas detection by proton-transfer-reaction mass spectrometry, Int. J. Mass. Spectrom., 223, 365–382, 2003a. de Gouw, J. A., Goldan, P. D., Warneke, C., Kuster, W. C., Roberts, J. M., Marchewka, M., Bertman, S. B., Pszenny, A. A. P., and Keene, W. C.: Validation of proton transfer reaction-mass spectrometry (PTR-MS) measurements of gas-phase organic compounds in the atmosphere during the New England Air Quality Study (NEAQS) in 2002, J. Geophys. Res.-Atmos., 108, 4682, doi:10.1029/2003JD003863, 2003b. de Gouw, J. A., Warneke, C., Parrish, D. D., Holloway, J. S., Trainer, M., and Fehsenfeld, F. C.: Emission sources and ocean uptake of acetonitrile (CH3CN) in the atmosphere, J. Geophys. Res.-Atmos., 108, 4329, doi:10.1029/2002JD002897, 2003c. de Gouw, J. A., Warneke, C., Stohl, A., Wollny, A. G., Brock, C. A., Cooper, O. R., Holloway, J. S., Trainer, M., Fehsenfeld, F. C., Atlas, E. L., Donnelly, S. G., Stroud, V., and Lueb, A.: Volatile organic compounds composition of merged and aged forest fire plumes from Alaska and western Canada, J. Geophys. Res.-Atmos., 111, D10303, doi:10.1029/2005JD006175, 2006. de Reus, M., Fischer, H., Arnold, F., de Gouw, J., Holzinger, R., Warneke, C., and Williams, J.: On the relationship between acetone and carbon monoxide in different air masses, Atmos. Chem. Phys., 3, 1709–1723, doi:10.5194/acp-3-1709-2003, 2003. Eerdekens, G., Ganzeveld, L., Vilà-Guerau de Arellano, J., Klüpfel, T., Sinha, V., Yassaa, N., Williams, J., Harder, H., Kubistin, D., Martinez, M., and Lelieveld, J.: Flux estimates of isoprene, methanol and acetone from airborne PTR-MS measurements over the tropical rainforest during the GABRIEL~2005 campaign, Atmos. Chem. Phys., 9, 4207–4227, doi:10.5194/acp-9-4207-2009, 2009. Ferreira, J., Reeves, C. E., Murphy, J. G., Garcia-Carreras, L., Parker, D. J., and Oram, D. E.: Isoprene emissions modelling for West Africa using MEGAN, Atmos. Chem. Phys. Discuss., 10, 6923–6953, doi:10.5194/acpd-10-6923-2010, 2010. Garcia-Carreras, L., Parker, D. J., Taylor, C. M., Reeves, C. E., and Murphy, J. G.: The impact of mesoscale vegetation heterogeneities on the dynamical and thermodynamic properties of the planetary boundary layer, J. Geophys. Res.-Atmos., 115, D03102, doi:10.1029/2009JD012811, 2010. Guenther, A., Karl, T., Harley, P., Wiedinmyer, C., Palmer, P. I., and Geron, C.: Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature), Atmos. Chem. Phys., 6, 3181–3210, doi:10.5194/acp-6-3181-2006, 2006. Hamm, S., Hahn, J., Helas, G., and Warneck, P.: Acetonitrile in the Troposphere – Residence Time Due to Rainout and Uptake by the Ocean, Geophys. Res. Lett., 11, 1207–1210, 1984. Holzinger, R., Warneke, C., Hansel, A., Jordan, A., Lindinger, W., Scharffe, D. H., Schade, G., and Crutzen, P. J.: Biomass burning as a source of formaldehyde, acetaldehyde, methanol, acetone, acetonitrile, and hydrogen cyanide, Geophys. Res. Lett., 26, 1161–1164, 1999. Holzinger, R., Williams, J., Salisbury, G., Klüpfel, T., de Reus, M., Traub, M., Crutzen, P. J., and Lelieveld, J.: Oxygenated compounds in aged biomass burning plumes over the Eastern Mediterranean: evidence for strong secondary production of methanol and acetone, Atmos. Chem. Phys., 5, 39–46, doi:10.5194/acp-5-39-2005, 2005. Hopkins, J. R., Lewis, A. C., and Read, K. A.: A two-column method for long-term monitoring of non-methane hydrocarbons (NMHCs) and oxygenated volatile organic compounds (o-VOCs), J. Environ. Monitor., 5, 8–13, 2003. Hopkins, J. R., Evans, M. J., Lee, J. D., Lewis, A. C., H Marsham, J., McQuaid, J. B., Parker, D. J., Stewart, D. J., Reeves, C. E., and Purvis, R. M.: Direct estimates of emissions from the megacity of Lagos, Atmos. Chem. Phys., 9, 8471–8477, doi:10.5194/acp-9-8471-2009, 2009. Jacob, D. J., Field, B. D., Jin, E. M., Bey, I., Li, Q. B., Logan, J. A., Yantosca, R. M., and Singh, H. B.: Atmospheric budget of acetone, J. Geophys. Res.-Atmos., 107, 4100, doi:10.1029/2001JD000694, 2002. Janicot, S., Thorncroft, C. D., Ali, A., Asencio, N., Berry, G., Bock, O., Bourles, B., Caniaux, G., Chauvin, F., Deme, A., Kergoat, L., Lafore, J.-P., Lavaysse, C., Lebel, T., Marticorena, B., Mounier, F., Nedelec, P., Redelsperger, J.-L., Ravegnani, F., Reeves, C. E., Roca, R., de Rosnay, P., Schlager, H., Sultan, B., Tomasini, M., Ulanovsky, A., and ACMAD forecasters team: Large-scale overview of the summer monsoon over West Africa during the AMMA field experiment in 2006, Ann. Geophys., 26, 2569–2595, 2008. Jost, C., Trentmann, J., Sprung, D., Andreae, M. O., and Dewey, K.: Deposition of acetonitrile to the Atlantic Ocean off Namibia and Angola and its implications for the atmospheric budget of acetonitrile, Geophys. Res. Lett., 30, 1837, doi:10.1029/2003GL017347, 2003a. Jost, C., Trentmann, J., Sprung, D., Andreae, M. O., McQuaid, J. B., and Barjat, H.: Trace gas chemistry in a young biomass burning plume over Namibia: Observations and model simulations, J. Geophys. Res.-Atmos., 108, 8482, doi:10.1029/2002JD002431, 2003b. Karl, T., Hansel, A., Mark, T., Lindinger, W., and Hoffmann, D.: Trace gas monitoring at the Mauna Loa Baseline observatory using proton-transfer reaction mass spectrometry, Int. J. Mass. Spectrom., 223, 527–538, 2003. Lee, A., Schade, G. W., Holzinger, R., and Goldstein, A. H.: A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux, Atmos. Chem. Phys., 5, 505–513, doi:10.5194/acp-5-505-2005, 2005. Lim, H. J., Carlton, A. G., and Turpin, B. J.: Isoprene forms secondary organic aerosol through cloud processing: Model simulations, Environ. Sci. Technol., 39, 4441–4446, 2005. Lindinger, W., Hansel, A., and Jordan, A.: On-line monitoring of volatile organic compounds at pptv levels by means of proton-transfer-reaction mass spectrometry (PTR-MS) – Medical applications, food control and environmental research, Int. J. Mass. Spectrom., 173, 191–241, 1998. Marandino, C. A., De Bruyn, W. J., Miller, S. D., Prather, M. J., and Saltzman, E. S.: Oceanic uptake and the global atmospheric acetone budget, Geophys. Res. Lett., 32, L15806, doi:10.1029/2005GL023285, 2005. Marandino, C. A., De Bruyn, W. J., Miller, S. D., Prather, M. J., and Saltzman, E. S.: Correction to "Oceanic uptake and the global atmospheric acetone budget", Geophys. Res. Lett., 33, L24801, doi:10.1029/2006GL028225, 2006. Mari, C. H., Cailley, G., Corre, L., Saunois, M., Attié, J. L., Thouret, V., and Stohl, A.: Tracing biomass burning plumes from the Southern Hemisphere during the AMMA~2006 wet season experiment, Atmos. Chem. Phys., 8, 3951–3961, doi:10.5194/acp-8-3951-2008, 2008. Murphy, J. G., Oram, D. E., Reeves, C. E., Lee, J. D., Hopkins, J. R., Taylor, C. M., McQuaid, J. B., and Parker, D. J.: Observations of Isoprene and Its Oxidation Products Over West Africa, EOS Trans AGU Fall Meeting, 2006. Northway, M. J., de Gouw, J. A., Fahey, D. W., Gao, R. S., Warneke, C., Roberts, J. M., and Flocke, F.: Evaluation of the role of heterogeneous oxidation of alkenes in the detection of atmospheric acetaldehyde, Atmos. Environ., 38, 6017–6028, 2004. Pfister, G. G., Emmons, L. K., Hess, P. G., Lamarque, J. F., Orlando, J. J., Walters, S., Guenther, A., Palmer, P. I., and Lawrence, P. J.: Contribution of isoprene to chemical budgets: A model tracer study with the NCAR~CTM MOZART-4, J. Geophys. Res.-Atmos., 113, D05308, doi:10.1029/2007JD008948, 2008. Real, E., Orlandi, E., Law, K. S., Fierli, F., Josset, D., Cairo, F., Schlager, H., Borrmann, S., Kunkel, D., Volk, C. M., McQuaid, J. B., Stewart, D. J., Lee, J., Lewis, A. C., Hopkins, J. R., Ravegnani, F., Ulanovski, A., and Liousse, C.: Cross-hemispheric transport of central African biomass burning pollutants: implications for downwind ozone production, Atmos. Chem. Phys., 10, 3027–3046, doi:10.5194/acp-10-3027-2010, 2010. Reeves, C. E., Formenti, P., Afif, C., Ancellet, G., Attie, J.-L., Bechara, J., Borbon, A., Cairo, F., Coe, H., Crumeyrolle, S., Fierli, F., Flamant, C., Gomes, L., Hamburger, T., Lambert, C., Law, K. S., Mari, C., Matsuki, A., Methven, J., Mills, G. P., Minikin, A., Murphy, J. G., Nielsen, J. K., Oram, D. E., Parker, D. J., Richter, A., Schlager, H., Schwarzenboeck, A., and Thouret, V.: Chemical and aerosol characterisation of the troposphere over West Africa during the monsoon period as part of AMMA, Atmos. Chem. Phys. Discuss., 10, 7115–7183, doi:10.5194/acpd-10-7115-2010, 2010. Sanhueza, E., Holzinger, R., Kleiss, B., Donoso, L., and Crutzen, P. J.: New insights in the global cycle of acetonitrile: release from theocean and dry deposition in the tropical savanna of Venezuela, Atmos. Chem. Phys., 4, 275–280, doi:10.5194/acp-4-275-2004, 2004. Saunois, M., Reeves, C. E., Mari, C. H., Murphy, J. G., Stewart, D. J., Mills, G. P., Oram, D. E., and Purvis, R. M.: Factors controlling the distribution of ozone in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis) wet season campaign, Atmos. Chem. Phys., 9, 6135–6155, doi:10.5194/acp-9-6135-2009, 2009. Sauvage, B., Thouret, V., Cammas, J.-P., Gheusi, F., Athier, G., and N\"edélec, P.: Tropospheric ozone over Equatorial Africa: regional aspects from the MOZAIC data, Atmos. Chem. Phys., 5, 311–335, doi:10.5194/acp-5-311-2005, 2005. Saxton, J. E., Lewis, A. C., Kettlewell, J. H., Ozel, M. Z., Gogus, F., Boni, Y., Korogone, S. O. U., and Serça, D.: Isoprene and monoterpene measurements in a secondary forest in northern Benin, Atmos. Chem. Phys., 7, 4095–4106, doi:10.5194/acp-7-4095-2007, 2007. Schade, G. W. and Goldstein, A. H.: Seasonal measurements of acetone and methanol: Abundances and implications for atmospheric budgets, Global Biogeochem. Cy., 20, GB1011, doi:10.1029/2005GB002566, 2006. Singh, H. B., Salas, L., Herlth, D., Kolyer, R., Czech, E., Viezee, W., Li, Q., Jacob, D. J., Blake, D., Sachse, G., Harward, C. N., Fuelberg, H., Kiley, C. M., Zhao, Y., and Kondo, Y.: In situ measurements of HCN and CH<sub>3</sub>CN over the Pacific Ocean: Sources, sinks, and budgets, J. Geophys. Res.-Atmos., 108, 8795, doi:10.1029/2002JD003006, 2003. Sinha, V., Williams, J., Meyerhöfer, M., Riebesell, U., Paulino, A. I., and Larsen, A.: Air-sea fluxes of methanol, acetone, acetaldehyde, isoprene and DMS from a Norwegian fjord following a phytoplankton bloom in a mesocosm experiment, Atmos. Chem. Phys., 7, 739–755, doi:10.5194/acp-7-739-2007, 2007. Stavrakou, T., Müller, J.-F., De Smedt, I., Van Roozendael, M., Kanakidou, M., Vrekoussis, M., Wittrock, F., Richter, A., and Burrows, J. P.: The continental source of glyoxal estimated by the synergistic use of spaceborne measurements and inverse modelling, Atmos. Chem. Phys., 9, 8431–8446, doi:10.5194/acp-9-8431-2009, 2009. Taddei, S., Toscano, P., Gioli, B., Matese, A., Miglietta, F., Vaccari, F. P., Zaldei, A., Custer, T., and Williams, J.: Carbon Dioxide and Acetone Air-Sea Fluxes over the Southern Atlantic, Environ. Sci. Technol., 43, 5218–5222, 2009. Thouret, V., Saunois, M., Minga, A., Mariscal, A., Sauvage, B., Solete, A., Agbangla, D., Nédélec, P., Mari, C., Reeves, C. E., and Schlager, H.: An overview of two years of ozone radio soundings over Cotonou as part of AMMA, Atmos. Chem. Phys., 9, 6157–6174, doi:10.5194/acp-9-6157-2009, 2009. Vrekoussis, M., Wittrock, F., Richter, A., and Burrows, J. P.: Temporal and spatial variability of glyoxal as observed from space, Atmos. Chem. Phys., 9, 4485–4504, doi:10.5194/acp-9-4485-2009, 2009. Warneke, C. and de Gouw, J. A.: Organic trace gas composition of the marine boundary layer over the northwest Indian Ocean in April~2000, Atmos. Environ., 35, 5923–5933, 2001. Warneke, C., de Gouw, J. A., Kuster, W. C., Goldan, P. D., and Fall, R.: Validation of atmospheric VOC measurements by proton-transfer-reaction mass spectrometry using a gas-chromatographic preseparation method, Environ. Sci. Technol., 37, 2494–2501, 2003. Williams, J., Holzinger, R., Gros, V., Xu, X., Atlas, E., and Wallace, D. W. R.: Measurements of organic species in air and seawater from the tropical Atlantic, Geophys. Res. Lett., 31, L23S06, doi:10.1029/2004GL020012, 2004. Williams, J. E., Scheele, M. P., van Velthoven, P. F. J., Cammas, J.-P., Thouret, V., Galy-Lacaux, C., and Volz-Thomas, A.: The influence of biogenic emissions from Africa on tropical tropospheric ozone during 2006: a global modeling study, Atmos. Chem. Phys., 9, 5729–5749, doi:10.5194/acp-9-5729-2009, 2009. Yokelson, R. J., Christian, T. J., Karl, T. G., and Guenther, A.: The tropical forest and fire emissions experiment: laboratory fire measurements and synthesis of campaign data, Atmos. Chem. Phys., 8, 3509–3527, doi:10.5194/acp-8-3509-2008, 2008. Yokelson, R. J., Crounse, J. D., DeCarlo, P. F., Karl, T., Urbanski, S., Atlas, E., Campos, T., Shinozuka, Y., Kapustin, V., Clarke, A. D., Weinheimer, A., Knapp, D. J., Montzka, D. D., Holloway, J., Weibring, P., Flocke, F., Zheng, W., Toohey, D., Wennberg, P. O., Wiedinmyer, C., Mauldin, L., Fried, A., Richter, D., Walega, J., Jimenez, J. L., Adachi, K., Buseck, P. R., Hall, S. R., and Shetter, R.: Emissions from biomass burning in the Yucatan, Atmos. Chem. Phys., 9, 5785–5812, doi:10.5194/acp-9-5785-2009, 2009.