Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 4 5 2004 10.5194/acpd-4-6321-2004 http://www.atmos-chem-phys-discuss.net/4/6321/2004/ http://www.atmos-chem-phys-discuss.net/4/6321/2004/acpd-4-6321-2004.html http://www.atmos-chem-phys-discuss.net/4/6321/2004/acpd-4-6321-2004.pdf 6321 6340 2004-10-07 Oxygenated compounds in aged biomass burning plumes over the Eastern Mediterranean: evidence for strong secondary production of methanol and acetone R. Holzinger holzing@nature.berkeley.edu J. Williams G. Salisbury T. Klüpfel M. de Reus M. Traub P. J. Crutzen J. Lelieveld Max-Planck-Institut für Chemie, Postfach 3060, 55020 Mainz, Germany now at: University of California at Berkeley, Dept. Environm. Sci. Policy and Management, Berkeley, CA 94720, USA Airborne measurements of acetone, methanol, PAN, acetonitrile (by Proton Transfer Reaction Mass Spectrometry), and CO (by Tunable Diode Laser Absorption Spectroscopy) have been performed during the Mediterranean Intensive Oxidants Study (MINOS, August 2001). In the course of the campaign 10 biomass burning plumes, identified by strongly elevated acetonitrile mixing ratios, were found. The characteristic biomass burning signatures obtained from these plumes reveal secondary production of acetone and methanol, while CO photochemically declines in the plumes. Mean excess mixing ratios – normalized to CO – of 1.8%, 0.20%, 3.8%, and 0.65% for acetone, acetonitrile, methanol, and PAN, respectively, were found in the plumes. By scaling to an assumed global annual source of 663–807 Tg CO, biomass burning emissions of 25–31 and 29–35 Tg/yr for acetone and methanol are estimated, respectively. Our measurements suggest that the present biomass burning contributions of acetone and methanol are significantly underestimated due to the neglect of secondary formation. Median acetonitrile mixing ratios throughout the troposphere were around 150 pmol/mol; this is in accord with current biomass burning inventories and an atmospheric lifetime of ~6 months.