High acetone concentrations throughout the 0-12 km altitude range over the tropical rainforest in Surinam

Airborne measurements of acetone were performed over the tropical rainforest in Surinam (2 degrees -7 degrees N, 54 degrees -58 degrees W, 0-12 km altitude) during the LBA-CLAIRE campaign in March 1998, using a novel proton transfer reaction mass spectrometer (PTR-MS) that enables the on-line monitoring of volatile organic compounds (VOC) with a higher proton affinity than water. The measured acetone volume mixing ratios ranged from similar to0.1 nmol/mol up to similar to8 nmol/mol with an overall average of 2.6 nmol/mol and a standard deviation of 1.0 nmol/mol. The observed altitude profile and correlations with CO, acetonitrile, propane and wind direction are discussed with respect to potential acetone sources. No linear correlation between acetone and CO mixing ratios was observed, at variance with results of previous measurement campaigns. The mean acetone/CO ratio (0.022) was substantially higher than typical values found before. The abundance of acetone appears to be influenced, but not dominated, by biomass burning, thus suggesting large emissions of acetone and/or acetone precursors, such as possibly 2-propanol, from living plants or decaying litter in the rainforest.