Lower than expected volatility of secondary organic aerosols formed during α-pinene ozonolysis

Abstract

Abstract.Traditional yield curve analysis shows that semi-volatile organic compounds are a major component of secondary organic aerosols (SOAs). We investigated the volatility distribution of SOAs from α-pinene 10 ozonolysis using positive electrospray ionization mass analysis and dilution-and heat-induced evaporation measurements. Laboratory chamber experiments were conducted on α-pinene ozonolysis, in the presence and absence of OH scavengers. Among these, we identified not only semi-volatile products, but also less volatile highly oxygenated molecules (HOMs) and dimers. Ozonolysis products were further exposed to OH radicals to check the effects of photochemical aging. HOMs were also formed during OH-initiated photochemical aging. 15Most HOMs that formed from ozonolysis and photochemical aging had ten or less carbons. SOA particle evaporation after instantaneous dilution was measured at <1% and ~40% relative humidity. The particle volume fraction remaining decreased with time and stabilised more than 3 h after dilution. The formation of compounds less volatile than of semi-volatile products, and the slow SOA evaporation, contradict the assumptions of current atmospheric simulation models. 20

Criegee Intermediate Reactions with Carboxylic Acids: A Potential Source of Secondary Organic Aerosol in the Atmosphere

“…Chamber studies have shown that ozonolysis of biogenic alkenes like isoprene and α-pinene in the presence of carboxylic acids leads to the formation of adduct products in large yield. 41,42 Our observations suggest that these products could result from a single step reaction of Criegee intermediates, generated during ozonolysis, with the carboxylic acids. The volatilities of the adducts were deduced from their saturation concentrations as described in detail in section S10 of the Supporting Information.…”