AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Influence of Anthropogenic Emissions on the Production of Organic Particulate Matter from Isoprene Epoxydiols in Central Amazonia
SUZANE DE SÁ, Brett Palm, Pedro Campuzano-Jost, Douglas Day, Weiwei Hu, Jose-Luis Jimenez, Matt Newburn, Lizabeth Alexander, Gabriel Isaacman-VanWertz, Lindsay Yee, Allen H. Goldstein, Joel Brito, Samara Carbone, Paulo Artaxo, Stephen Springston, Rodrigo A. F. Souza, Antonio O. Manzi, Scot Martin, Harvard University
Abstract Number: 373 Working Group: Effects of NOx and SO2 on BVOC Oxidation and Organic Aerosol Formation
Abstract The atmospheric chemistry of isoprene produces a substantial fraction of the submicron organic particulate matter (PM) over forests. Isoprene epoxydiols (IEPOX) are produced in the gas phase from the reactions of photochemically produced OH with biogenically emitted isoprene when HO$_2 pathways are favorable in the absence of extensive NO pollution. The reactive uptake of IEPOX in turn contributes significantly to the mass concentration of PM. The present study investigates anthropogenic influences on the production of IEPOX-derived PM over a tropical forest. The composition of submicron PM was measured with an Aerodyne Aerosol Mass Spectrometer (AMS) during the wet season of 2014 in central Amazonia at the GoAmazon2014/5 T3 site, downwind of Manaus, Brazil. Given the variability in local winds, the air masses sampled at T3 represented conditions ranging from background to polluted. The time series of the organic contribution to the mass spectra was analyzed by Positive Matrix Factorization (PMF). A factor associated with IEPOX-derived PM was resolved and labeled “IEPOX-SOA factor”. The temporal correlation between the loadings of the IEPOX-SOA factor and measured sulfate mass concentrations as mediated by NO levels (using NO$_y as a surrogate) is explored. Results show that sulfate can be used as a first-order predictor of IEPOX-derived PM in the central Amazon forest. In addition, NO levels show a significant modulating role on IEPOX-derived PM chemistry in the region. The net influence of the city of Manaus in this context is also assessed, and polluted air masses were associated with lower loadings of the IEPOX-SOA factor compared to background conditions. The results are discussed taking into account the pre-existing background conditions and the city’s two-lever effect as source of both sulfate and NO, improving the understanding of the roles of anthropogenic sulfate and NO$_y in the production of organic PM in a tropical environment.