AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Evaluating Anthropogenic Influence on Isoprene Oxidation during SOAS 2013 and GoAmazon2014/5
Lindsay Yee, GABRIEL ISAACMAN-VANWERTZ, Rebecca Wernis, Nathan Kreisberg, Susanne Hering, Suzane de Sá, Scot Martin, Lizabeth Alexander, Brett Palm, Weiwei Hu, Pedro Campuzano-Jost, Douglas Day, Jose-Luis Jimenez, Anne Maria Hansen, Mads Bering, Marianne Glasius, Matthieu Riva, Jason Surratt, Juarez Viegas, Antonio O. Manzi, Eric Edgerton, Karsten Baumann, Rodrigo A. F. Souza, Paulo Artaxo, Allen H. Goldstein, University of California, Berkeley
Abstract Number: 577 Working Group: Effects of NOx and SO2 on BVOC Oxidation and Organic Aerosol Formation
Abstract Several studies have shown that anthropogenic influence alters the chemical mechanisms leading to secondary organic aerosol (SOA) formation from isoprene. In this work, we use tracer ratios to characterize the roles of sulfate and NOx chemistry on isoprene-derived SOA in two isoprene-rich forested environments. We deployed the Semi-Volatile Thermal desorption Aerosol Gas Chromatograph (SV-TAG) during the Southern Oxidant and Aerosol Study (SOAS) in the Southeastern U.S. in summer 2013 and during the wet and dry seasons of the Green Ocean Amazon experiment (GoAmazon 2014/5) in Central Amazonia. We measured oxidation products from isoprene at the molecular level in the gas and particle phases at hourly time resolution, including the isoprene/HO2 pathway marker, 2-methyl tetrols and C5-alkene triols, and the isoprene/NOx pathway marker, 2-methyl glyceric acid. Ratios of these tracers provide a measure of the relative importance of competing chemical pathways and allow general conclusions about the mechanisms of isoprene oxidation in these environments. We also measured the concentration of isoprene-derived organosulfates collected on filters. On average, the isoprene HO2 pathway tracers contribute approximately 10% of the organic mass during both field campaigns and isoprene-derived organosulfates are prevalent at concentrations often exceeding 100 ng/m3 in both SOAS and the GoAmazon wet season. Using supporting measurements of particle composition, the influence of sulfate on isoprene-OA is clear for sulfate levels spanning three orders of magnitude across deployments. We further explore the differences in the tracer ratios across deployments to understand chemical factors affecting particle phase chemistry in these regions.