Sulfate radical-initiated formation of isoprene-derived organosulfates in atmospheric aerosols

Abstract

Recent studies show that isoprene-derived organosulfates are an important fraction of ambient secondary organic aerosol (SOA), adding up to 20% to the organic mass. Organosulfates with m/z of 199 and 183 relating to C4 compounds are found in ambient and laboratory generated SOA and a sulfate radical induced oxidation of methacrolein (MACR) and methyl vinyl ketone (MVK) has been shown to be a possible formation mechanism. In the present study, experiments on the sulfate radical-induced oxidation of methacrolein and methyl vinyl ketone were performed in bulk aqueous phase, as well as in an aerosol chamber, and finally compared with ambient PM10 samples collected at a rural East German village during the summer 2008, to investigate their relevance in aqueous phase SOA formation. Samples from aqueous phase experiments and extracts from filters were analysed with UPLC/(-)ESI-IMS-QTOFMS. All the samples showed the abundance of highly oxidised organosulfates with m/z 153, 155, 167, 183 and 199 corresponding to the species found in ambient particle samples. In the bulk phase studies with laser-induced sulfate radical formation, the signal intensities increased with increasing number of laser pulses, indicating the sulfate radical-induced formation of these organosulfates. Additionally, the chamber experiments showed a particle mass growth of about 10 microg m(-3) and 4 microg m(-3) for experiments on the reactive uptake of MACR and MVK with a sulfate radical precursor (K2S2O8) in the seed particles. Correlations of the C2 to C5 organosulfate species (including the m/z 215, C5H11O7S-), detected in the ambient samples were found to be very strong (r > 0.8), indicating that these compounds are formed from similar mechanisms and under equal environmental conditions. This study shows that sulfate radical-induced oxidation in the aqueous particle phase provides a reasonable explanation for the formation of these organosulfates from methacrolein and methyl vinyl ketone.

Atmospheric aqueous phase radical chemistry of the isoprene oxidation products methacrolein, methyl vinyl ketone, methacrylic acid and acrylic acid – kinetics and product studies

“…48 For the investigated substances, several H atoms can possibly be abstracted. Looking at methyl vinyl ketone, the BDE calculated after Benson (1976) 73 indicates a hydrogen abstraction reaction for NO 3 75 This logical mechanism was confirmed by a recent study of Schindelka et al (2013). Section 3.5.1).…”

Linking biogenic hydrocarbons to biogenic aerosol in the Borneo rainforest

“…There are other sources that may contribute to these OS species (Shalamzari et al, 2013;Surratt et al, 2008), for example the MW 214 species may be related to 2-or 4-pentenal SOA . The formation pathways of organosulfates remains unclear with epoxides from isoprene and methacrylic acid oxidation (Lin et al, 2013) and sulfate radical chemistry (Nozière et al, 2010;Schindelka et al, 2013) both potential routes. Van Krevelen plots, where the H : C ratio is plotted against the O : C ratio, are useful tools for investigating complex data sets such as organic aerosol and have been used in a number of studies (Bateman et al, 2010;Nizkorodov et al, 2011;Reinhardt et al, 2007;Saranjampour et al, 2011).…”

Biogenic, urban, and wildfire influences on the molecular composition of dissolved organic compounds in cloud water

“…Organosulfates are suggested to be formed from acidcatalyzed reactive uptake of epoxides onto sulfate aerosol (Surratt et al, 2010), as well as in-cloud radical-radical reactions involving sulfate radicals (Nozière et al, 2010;Perri et al, 2010;Schindelka et al, 2013). Isoprene-and monoterpene-derived organosulfates have been observed in cloud water over the southeastern US (Boone et al, 2015;Pratt et al, 2013).…”