AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Evidence for Unrecognized Anthropogenic Sources of Organosulfates: Gas-Phase Oxidation of Anthropogenic Precursors in the Presence of Sulfate Aerosol
MATTHIEU RIVA, Tianqu Cui, Avram Gold, Jason Surratt, University of North Carolina at Chapel Hill
Abstract Number: 109 Working Group: Source Apportionment
Abstract Organosulfates are important components of atmospheric fine organic aerosol. However, chemical structures, abundance and sources of many organosulfates remain unclear. Formation of organosulfates from the oxidation of biogenic compounds (isoprene, monoterpenes) in the presence of acidified sulfate aerosol has been characterized in both laboratory-generated and ambient secondary organic aerosol (SOA). Enhancement of SOA mass by increased aerosol acidity has been explained in part by the presence of organosulfates in the aerosol phase. Recent studies have identified and quantified aromatic and aliphatic organosulfates in the fine aerosol collected from several major urban locations, although the sources of compounds remain unknown.
The aim of the present study was to examine the potential for organosulfate formation from the photooxidation of intermediate volatility organic compounds (IVOCs) such as polycyclic aromatic hydrocarbons (PAHs) and long-chain alkanes, which are recognized to be a "missing" source of SOA, particularly in urban areas. Low-molecular weight PAHs (naphthalene and 2-methyl-naphthalene) and C10-C12 alkanes (dodecane, cyclodecane, decalin) were selected for photooxidation experiments in the UNC outdoor smog chamber in the presence of non-acidified and acidified sulfate seed aerosol. These IVOCs are representative of anthropogenic compounds abundantly emitted into the urban atmosphere and could contribute substantially to SOA formation. Impacts of relative humidity, acidity and structure of the IVOCs on organosulfur compound formation were examined. Organosulfates in SOA collected onto filters from smog chamber experiments were chemically characterized by ultra performance liquid chromatography coupled to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-QTOFMS).
Organosulfur compounds identified in the smog chamber experiments were also measured in urban fine aerosols from Lahore, Pakistan, and Pasadena, USA. This work suggests that the gas-phase oxidation of anthropogenic precursors in the presence of sulfate aerosol is a hitherto unrecognized source of anthropogenic secondary organosulfur, and provides new anthropogenic SOA tracers.