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What Aerosol Water do Organic Compounds See?
Citation:
Pye, H., A. Zuend, AND G. Isaacman-Van-Wertz. What Aerosol Water do Organic Compounds See? 2017 AAAR Annual Conference, Raleigh, North Carolina, October 16 - 20, 2017.
Impact/Purpose:
The National Exposure Research Laboratory (NERL) Computational Exposure Division (CED) develops and evaluates data, decision-support tools, and models to be applied to media-specific or receptor-specific problem areas. CED uses modeling-based approaches to characterize exposures, evaluate fate and transport, and support environmental diagnostics/forensics with input from multiple data sources. It also develops media- and receptor-specific models, process models, and decision support tools for use both within and outside of EPA.
Description:
Large amounts of aerosol water are associated with inorganic salts such as ammonium sulfate with generally smaller but important contributions from hydrophilic organics. Ambient aerosols can be externally or internally mixed in addition to containing one or multiple phases. The degree to which organic compounds in a particle interact with water associated with inorganic salts will influence their partitioning between the gas and aerosol phase as well as opportunity to participate in aqueous chemistry. In this work, we examine the potential for liquid-liquid phase separation, or lack thereof, within PM2.5 particles to affect the partitioning of compounds between the gas and aerosol phases. We examine partitioning of ammonia and several isoprene- and monoterpene-derived organic compounds using common (absorptive partitioning, ISORROPIA) and advanced (AIOMFAC) approaches to describing gas-aerosol partitioning for conditions during the Southern Oxidant and Aerosol Study (SOAS). We aim to address the degree to which sophisticated techniques accounting for organic-inorganic interactions, deviations in ideality, and phase separation reproduce observations and the information gained.
