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Anthropogenic Influences on Amazonian Organic Aerosol: A Molecular-Level Analysis
EMILY BARNES, Lindsay Yee, Gabriel Isaacman-VanWertz, Rebecca Wernis, Nathan Kreisberg, Robert Weber, Scot T. Martin, Brett Palm, Weiwei Hu, Pedro Campuzano-Jost, Douglas Day, Jose-Luis Jimenez, Paulo Artaxo, Allen Goldstein, University of California, Berkeley
Abstract Number: 135
Working Group: Aerosol Chemistry
Abstract
The formation processes of secondary organic aerosols (SOA) in remote, biogenically dominated regions such as the Amazon are as yet incompletely understood and characterized. While the majority of SOA mass in such areas is understood to result from the oxidation of biogenic volatile organic compounds (BVOCs) including isoprene, monoterpenes, and sesquiterpenes, the processes by which anthropogenic emissions, biomass burning activities, and climatological conditions influence oxidation pathways and aerosol yields remain obscure. By changing the concentrations and classes of atmospheric oxidants present, anthropogenic emission plumes can significantly alter the yield and characteristics of biogenic SOA formed. In this work, we analyze a series of quartz fiber filters collected during the wet and dry season intensive operating periods (IOP’s) of the 2014/5 GoAmazon field campaign at a semi-remote site in central Amazonia. These filters were analyzed using thermal desorption two-dimensional gas chromatography coupled with high resolution time-of-flight mass spectrometry. Hundreds of compounds were separated and resolved from each sample. From 11 samples representing a wide range of Amazonian conditions, 1,484 unique compounds were identified and compiled into a custom mass spectral library. These compounds were traced through ~3 week periods of each IOP with 12 hour resolution in the wet season and 4 hour resolution in the dry season. Compounds without authentic standards or published mass spectra are categorized through a variety of techniques including mass spectral similarities to known compounds, identification in filters from laboratory oxidation experiments, and time series correlation with known tracers of specific sources and oxidant-influenced reaction pathways. Relevant source categories include biomass burning derived OA, isoprene OA, monoterpene OA, and sesquiterpene OA. The relative abundances of individual tracer compounds and total contributions of the various categories under varying degrees of anthropogenic influence are compared and contrasted to probe the processes by which anthropogenic emissions alter biogenic SOA.