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EFFECT OF ACIDITY ON SECONDARY ORGANIC AEROSOL FORMATION FROM ISOPRENE
Citation:
SURRATT, J. D., M. LEWANDOWSKI, J. H. OFFENBERG, M. JAOUI, T. E. KLEINDIENST, E. O. EDNEY, AND J. SEINFELD. EFFECT OF ACIDITY ON SECONDARY ORGANIC AEROSOL FORMATION FROM ISOPRENE. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 41(15):5363-5369, (2007).
Impact/Purpose:
The purpose/objectives are to 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; 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; in 2005 recommend improvements to AMD for the treatment of SOA chemistry in CMAQ; by the end of FY06, deliver an improved SOA chemistry model to AMD who will incorporate the model into CMAQ; and by the end of 2007, deliver an improved N2O5 chemistry model to AMD who will incorporate the model into CMAQ.
Description:
The effect of particle-phase acidity on secondary organic aerosol (SOA) formation from isoprene is investigated in a laboratory chamber study, in which the acidity of the inorganic seed aerosol was controlled systematically. The observed enhancement in SOA mass concentration is closely correlated with increasing aerosol acidity (R2 = 0.979). Direct chemical evidence for acid-catalyzed particle-phase reactions was obtained from the SOA chemical analyses. Aerosol mass concentrations for the 2-methyltetrols, as well as the newly identified sulfate esters, both of which serve as tracers for isoprene SOA in ambient aerosols, increased significantly with enhanced aerosol acidity. Aerosol acidities, as measured in nmol H+ m-3, employed in the present study are in the same range as those observed in tropospheric aerosol collected from the eastern U.S.