Atmospheric volatile organic compounds (VOC) at a remote tropical forest site in central Amazonia

According to recent assessments, tropical woodlands contribute about half o f all global natural non-methane volatile organic compound (VOC) emissions. Large uncertainties exist especially about fluxes of compounds other than isoprene and monoterpenes. During the Large-Scale Biosphere/Atmosphere Expe riment in Amazonia - Cooperative LBA Airborne Regional Experiment 1998 (LBA -CLAIRE-98) campaign, we measured the atmospheric mixing ratios of differen t species of VOC at a ground station at Balbina, Amazonia, The station was located 100 km north of Manaus, SE of the Balbina reservoir, with 200-1000 km of pristine forest in the prevailing wind directions. Sampling methods i ncluded DNPH-coated cartridges for carbonyls and cartridges filled with gra phitic carbons of different surface characteristics for other VOCs. The mos t prominent VOC species present in air were formaldehyde and isoprene, each up to several ppb. Concentrations of methylvinyl ketone as well as methacr oleine, both oxidation products of isoprene, were relatively low, indicatin g a very low oxidation capacity in the lower atmospheric boundary layer, wh ich is in agreement with a daily ozone maximum of < 20 ppb. Total monoterpe ne concentration was below 1 ppb, We detected only very low amounts of VOC species, such as benzene, deriving exclusively from anthropogenic sources. (C) 2000 Elsevier Science Ltd. All rights reserved.