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SOA Formation from the Atmospheric Oxidation of 2-Methyl-3-Buten-2-ol and Its Implications for PM2.5
Citation:
JAOUI, M., T. E. KLEINDIENST, J. H. OFFENBERG, M. LEWANDOWSKI, AND W. A. LONNEMAN. SOA Formation from the Atmospheric Oxidation of 2-Methyl-3-Buten-2-ol and Its Implications for PM2.5. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, Germany, 12(4):2173-2188, (2012).
Impact/Purpose:
The National Exposure Research Laboratory′s (NERL) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA′s mission to protect human health and the environment. HEASD′s research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA′s strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools is improved regulatory programs and policies for EPA.
Description:
The formation of secondary organic aerosol (SOA) generated by irradiating 2-methyl-3-buten-2-01 (MBO) in the presence and/or absence of NOx H2O2, and/or SO2 was examined. Experiments were conducted. in smog chambers operated either in dyna.mic or steady-state mode. A filter/denuder sampling system was used for simultaneously collecting gas and particle phase products. The structural characterization of gas and particulate products was investigated using BSTFA, BSTFA + PFBHA, and DNPH derivatization techniques followed by GC-MS and liquid chromatography analysis. This analysis showed the occurrence of more than 68 oxygenated organic compounds in the gas and particle phase, 28 of which were identified. The major components observed include 2,3-dihydroxyisopenlanol (DHIP), 2-hydroxy-2-oxoisopenlanol. 2,3-dihydroxy-3-methylbutanal. 2,3-dihydroxy-2-methylsuccinic acid, 2-3 hydroxy-2-methylpropanedioic acid, acetone, glyoxal. methylglyoxal, glycolaldehyde, and formaldehyde. Most of these oxygenated compounds were detected for the first time in this study. While measurements of the gas-phase photooxidation products have been made, the focus of this work has been an examination of the particle phase. SOA from some experiments was analyzed for the organic mass to organic carbon ratio (OM/OC), the effective enthalpy of vaporization (ΔHeffvap), and the aerosol yield. Additionally, aerosol size, volume, and number concentrations were measured by a Scanning Mobility Particle Sizer coupled to a Condensation Particle Counter system. The OM/OC ratio was 2.1 in the MBO/H2O2 system. The ΔHeffvapwas 41 kJ mol-1, a value similar to that of isoprene SOA. The laboratory SOA yield measured in this study was 0.7% in MBO/H2O2 for an aerosol mass of 33 ug-3. Secondary organic aerosol was found to be negligible under conditions with oxides of nitrogen (NOx) present. Time profiles and proposed reaction schemes are provided for selected compounds. The contribution of SOA products from MBO oxidation to ambient PM2.5 was investigated by analysing a series of ambient PM2.5 samples collected in several places around the United States. In additiion to the occurrence of several organic compounds in both field and laboratory samples, DHIP was found to originate only from the oxidation of MBO, and therefore this compound could potentially serve as a tracer for MBO SOA. Initial attempts have been made to quantify the concentrations of DHIP and other compounds based on surrogate compound calibrations. The average concentrations of DHIP in ambient PM
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Atmospheric Chemistry and Physics
SOA Formation from the Atmospheric Oxidation of 2-Methyl-3-Buten-2-ol and Its Implications for PM2.5 (PDF, NA pp, 696 KB, about PDF)