Assessing the drivers of Isoprene SOA: laboratory studies, calculations and modeling

Description

A potentially important natural source of aerosol particle mass that can be modulated by anthropogenic activities associated with energy production is through secondary organic aerosol (SOA) from isoprene, a hydrocarbon emitted by vegetation. More carbon is emitted to the atmosphere in the form of isoprene than any other non-methane hydrocarbon. Its contribution to SOA, even at low efficiency, can be globally significant. Isoprene photochemistry produces epoxy diols (IEPOX), hydroxy hydroperoxides (ISOPOOH), and other water soluble gases which partition to aqueous aerosol or clouds and undergo subsequent chemistry to form aqueous SOA (aqSOA). This project investigates the solubility rules of isoprene-SOA precursors that affect the rate of SOA formation and SOA properties from aqueous pathways. Solubility of water soluble organics is modified by the presence of inorganic aerosol components that are associated with anthropogenic activities such as energy production (i.e., NOx, SO2 emissions). A series of laboratory experiments is being conducted to measure Setschenow salting constants in organic and inorganic mixtures, and study mixed inorganic/organic systems to develop a database of structure-activity relationships. These measurements are accompanied by quantum calculations to better understand Setschenow salting effects in multiphase reactions and aqSOA formation, and their possible relevance to modify ambient aerosol size distributions.