The effects of atmospheric salts on the aging of secondary organic aerosols (SOA) in cloud and fog water are not well understood. In this study, we examined SOA aging in aqueous solutions with the presence of some common atmospheric salts in cloud or fog water relevant concentrations. A common monoterpene (alpha-pinene) and a common sesquiterpene (alpha-humulene) were used to produce SOA through ozonlysis in a flowtube, and this SOA was impacted onto filters. The water-soluble portion of the SOA was then extracted from the filter into pure water or aqueous solutions containing dilute concentrations of H2O2, NaNO3, or NH4NO3. To simulate photolytic or dark processing, after dilution, aqueous samples were exposed to light in the actinic region for four hours (approximately equivalent to 64 hours in the atmosphere) or kept in the dark for four hours. The changes in composition due to aging were monitored by high-resolution electrospray ionization mass spectrometry at one hour intervals. The resultant spectra showed that the presence of salts with or without photolysis preferentially removed higher molecular weight compounds and so increased the volatility of the SOA as efficiently as or more efficiently than photolysis in pure water. This result could have importance for understanding SOA lifetimes and aging in dilute aqueous solutions such as cloud and fog water.

Aqueous photochemistry of secondary organic aerosol in the presence of common inorganic salts

2019 Fall National Meeting

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