Development of a secondary organic aerosol formation mechanism: Comparison with smog chamber experiments and atmospheric measurements

L. E. OLCESE; J. E. PENNER; S. SILLMAN

Davis, ISA

Congreso; INTERNATIONAL AEROSOL MODELLING ALGORITHMS; 2007

The Air Quality Research Center

<!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:1; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:0 0 0 0 0 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; mso-hyphenate:none; font-size:12.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman"; mso-fareast-language:AR-SA;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.0in 1.0in 1.0in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} --> A new mechanism to simulate the formation of secondary organic aerosols (SOA) from reactive primary hydrocarbons is presented, together with comparisons with experimental smog chamber results and ambient measurement. The SOA formation mechanism is based on an approach using calculated vapor pressures and a selection of species that can partition to the aerosol phase from a gas phase photochemical mechanism. The mechanism has been validated against smog chamber measurements using a-pinene, xylene, toluene and isoprene as SOA precursors, and the average difference between the model and observations was 16%. The average difference between the model and the observed SOA in the TORCH 2003 experiment (atmospheric measurements) was only 12%. This contrasts with previous efforts, in which it was necessary to increase partition coefficients by a factor of 500 in order to match these observed values. Calculations for rural and urban-influenced regions in the eastern U.S. suggest that most of the SOA is biogenic in origin, and is produced mainly from the oxidation products of isoprene. A zero-dimensional calculation based on the New England Air Quality Study also showed good agreement with estimated SOA, with about 40% of the total SOA from anthropogenic precursors. This mechanism can be implemented in a general circulation model to estimate global SOA formation under ambient NOx and HOx levels.