(273b) Chemical Characterization of Water Soluble Organic Matter in Rural and Contrasting Urban Environments in the Southeastern United States

Atmospheric particulate matter (PM) has substantial impacts on climate, air quality, and human health. One important component of atmospheric PM is water-soluble organic matter (WSOM), which can alter the hygroscopicity and surface tension of particles and further influence climate. However, the chemical composition and sources of WSOM are poorly understood. In order to continuously measure the chemical composition of WSOM, we developed a novel system by coupling a Particle-Into-Liquid-Sampler to a High-Resolution Time-of-Flight Mass Spectrometer (denoted as PILS-AMS). This novel system was deployed in two contrasting environments, rural Centreville in Alabama (part of the Southeast Oxidant and Aerosol Study) and urban Atlanta in Georgia in summer, 2013. We found that the majority of OM is water-soluble in both rural and urban sites, which is consistent with our previous finding. We performed Positive Matrix Factorization (PMF) analysis on both ambient total OM and WSOM for source apportionment. The comparison between ambient OM and WSOM provides insights about the water solubility of OM subtypes. We found that primary OM from vehicle emissions and cooking is not water-soluble. A large fraction of biomass burning OA is water soluble. Secondary OM from different sources show different water solubility, which will be discussed in detail in the presentation. Studying the water solubility of OM subtypes largely improves our understanding of the sources of PMF factors.