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SECONDARY ORGANIC CARBON AND AEROSOL YIELDS FROM THE IRRADIATIONS OF ISOPRENE AND á-PINENE IN THE PRESENCE OF NO X AND SO 2
Citation:
KLEINDIENST, T. E., E. O. EDNEY, M. LEWANDOWSKI, J. H. OFFENBERG, AND M. JAOUI. SECONDARY ORGANIC CARBON AND AEROSOL YIELDS FROM THE IRRADIATIONS OF ISOPRENE AND á-PINENE IN THE PRESENCE OF NO X AND SO 2. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 40(12):3807-3828, (2006).
Impact/Purpose:
1. Conduct laboratory studies with scientists from Caltech, the University of Antwerp, and the NOAA Aeronomy Laboratory to improve treatments of SOA Chemistry and N2O5 chemistry in CMAQ.
2. Analyze ambient PM2.5 samples in Research Triangle Park, NC, Detroit, MI and Pasadena, CA and when available compare field data with CMAQ predictions obtained from AMD.
3. In 2005 recommend improvements to AMD for the treatment of SOA chemistry in CMAQ.
4. By the end of FY06, deliver an improved SOA chemistry model to AMD who will incorporate the model into CMAQ.
5. By the end of 2007, deliver an improved N2O5 chemistry model to AMD who will incorporate the model into CMAQ.
Description:
A laboratory study was carried out to investigate the secondary organic carbon (SOC) yields of a-pinene and isoprene in the presence of SO2, which produces acidic aerosol in the system. Experiments were based on irradiating each hydrocarbon (HC) with NOx in a 14.5 m3 smog chamber operated in the dynamic mode. The experimental design consisted of several multi-part experiments or each HC. In the first part of each experiment, an HC/NOx irradiation was conducted in the absence of SO2 and was followed by irradiations with the addition of SO2 in subsequent parts. Filter-based analyses for organic carbon were made using a thermal-optical approach either with an off-line instrument or in situ with an automated instrument. For isoprene in the absence of SO2, the SOC yield was approximately 0.001, a value consistent with earlier work from this laboratory. With the addition of up to 200 ppb SO2, the yield increased by a factor of 7. For α-pinene in the absence of SO2, the SOC yield of the irradiated mixture was found to average 0.096 from two experiments. With SO2 in the system, the SOC yield increased on average to 0.132. These results suggest that SO2, and by inference acidic aerosol, may play a role in increasing the yield of SOC from the photooxidation products of biogenic hydrocarbons or by the direct uptake of biogenic hydrocarbons onto acidic aerosol.