Oxygenated compounds in aged biomass burning plumes over the Eastern Mediterranean: evidence for strong secondary production of methanol and acetone

• Published in: Atmospheric chemistry and physics discussions 2004-10, Vol.4 (5), p.6321-6340
• Main Authors: Holzinger, R., Williams, J., Salisbury, G., Klüpfel, T., de Reus, M., Traub, M., Crutzen, P. J., Lelieveld, J.
• Format: Article
• Language: English
• Subjects: Ocean, Atmosphere; Sciences of the Universe
• ISSN: 1680-7367; 1680-7375

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.