Uptake and Release of Gaseous Species Accompanying the Reactions of Isoprene Photo-Oxidation Products with Sulfate Particles (Invited Presentation)

Gaseous species produced via the HO2 reaction pathways of isoprene photo-oxidation were reacted with liquid, partially neutralized sulfate aerosol particles. Isoprene-derived epoxydiols (IEPOX) were taken up for all neutralizations so long as the liquid phase was maintained. By comparison, isoprene-derived hydroperoxides (ISOPOOHs) were taken up only for low neutralization. The release of product molecules to the gas phase increased for low neutralization. More than half of the ISOPOOH molecules taken up into the particles subsequently released volatile products to the gas phase, indicating a major pathway of hydroperoxide cleavage in the particle phase to produce volatile products. Some product species larger than the C5 chain of isoprene were also released to the gas phase, implying that some accretion products in the particle phase were sufficiently volatile to partition to the gas phase. The results call attention to the idea that the dependence of reactive uptake on neutralization can vary by species. Not just functionalization and accretion but also decomposition and re-volatilization should be considered when formulating the mass balance of reactive uptake processes of atmospheric organic particles.