Chemical oxidative potential of secondary organic aerosol (SOA) generated from the photooxidation of biogenic and anthropogenic volatile organic compounds

摘要

Particulate matter (PM), of which a significant fraction is comprised ofsecondary organic aerosols (SOA), has received considerable attention due toits health implications. In this study, the water-soluble oxidativepotential (OP) of SOA generated from the photooxidation of biogenicand anthropogenic hydrocarbon precursors (isoprene, -pinene, -caryophyllene, pentadecane, -xylene, and naphthalene) under differentreaction conditions ( vs. dominant,dry vs. humid) was characterized using dithiothreitol (DTT) consumption. Themeasured intrinsic OP values ranged from 9 to 205 pmol min µg and were highly dependent on the specific hydrocarbonprecursor, with naphthalene and isoprene SOA generating the highest andlowest OP values, respectively. Humidity and RO fate affectedOP in a hydrocarbon-specific manner, with naphthalene SOAexhibiting the most pronounced effects, likely due to the formation ofnitroaromatics. Together, these results suggest that precursor identity maybe more influential than reaction condition in determining SOA oxidativepotential, demonstrating the importance of sources, such as incompletecombustion, to aerosol toxicity. In the context of other PM sources, all SOAsystems, with the exception of naphthalene SOA, were less DTT active thanambient sources related to incomplete combustion, including diesel andgasoline combustion as well as biomass burning. Finally, naphthalene SOA wasas DTT active as biomass burning aerosol, which was found to be the most DTT-active OA source in a previous ambient study. These results highlight a needto consider SOA contributions (particularly from anthropogenic hydrocarbons)to health effects in the context of hydrocarbon emissions, SOA yields, andother PM sources.