AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Characterizing the Behavior of Ambient Organic Aerosols Under Conditions of Aerosol Liquid Water Evaporation
MARWA EL-SAYED, Dziedzorm Amenumey, Christopher Hennigan, University of Maryland, Baltimore County
Abstract Number: 52 Working Group: There Must be Something in the Water: Cloud, Fog and Aerosol Aqueous Chemistry for Aerosol Production
Abstract Aerosol liquid water (ALW) can affect the quantity and chemical composition of organic aerosols; however, the interaction between ALW and ambient organic aerosol compounds is highly uncertain at present. To characterize the behavior of organic aerosols under conditions of drying, water-soluble organic matter (WSOM) in PM2.5 was measured during two consecutive summers in Baltimore, MD. The WSOM measurements were alternated through an unperturbed ambient channel and through a ‘dried’ channel maintained at ~35% relative humidity (RH). Sample drying induced systematic evaporation of the WSOM during both summers. The quantity of evaporated WSOM was strongly related to RH, WSOM concentrations, and isoprene emissions. Significant differences in meteorological conditions (including RH), isoprene emissions, and overall WSOM concentrations were observed between the two summers. This led to major differences in the amount of evaporated WSOM during summer 2016 in comparison to summer 2015. We used the sensitivity of evaporated mass to each of the aforementioned parameters to build a statistical model describing the effect of liquid water evaporation on ambient organic matter in the eastern United States. These results have implications for secondary organic aerosols formed through aqueous pathways (aqSOA), and for a measurement approach that is widely applied in aerosol science.