Cooperative Institute for Research in Environmental Sciences

Volatile organic compounds (VOCs) in the South Coast Air Basin (SoCAB): Characterizing the gas-phase chemical evolution of air masses during CalNex 2010

J.B. Gilman (1,2), B.M. Lerner (1,2), W.C. Kuster (1,2), D. Bon (1,2,3), C. Warneke (1,2), E.J. Williams (1,2), J.S. Holloway (1,2), I.B. Pollack (1,2), T.B. Ryerson (1), E.L. Atlas (4), D.R. Blake (5), S.C. Herndon (6), M.S. Zahniser (6), A. Vlasenko (7), S.M. Li (7), S. Alvarez (8), B. Rappenglueck (8), J. Flynn (8), N. Grossberg (8), B. Lefer (8), J.A. de Gouw (1,2)

(1) NOAA ESRL Chemical Sciences Division, (2) CIRES at Univ. of Colorado, Boulder, (3) Now at Colorado Dept. of Public Health and Environ., (4) RSMAS at Univ. of Miami, (5)Dept of Chemistry, Univ. of CA-Irvine, (6) Aerodyne Research, (7) Environ. Canada, (8) University of Houston

Volatile organic compounds (VOCs) are critical components in the photochemical production of ozone (O3) and secondary organic aerosol (SOA). During the CalNex 2010 field campaign, an extensive set of VOCs were measured at the Pasadena ground site, and aboard the NOAA WP-3D aircraft and the WHOI Research Vessel Atlantis. The measurements from each platform provide a unique perspective into the emissions, transport, and atmospheric processing of VOCs within the South Coast Air Basin (SoCAB).

The chemical evolution of air masses as a function of the time of day is investigated in order to determine the relative impacts of primary emissions vs. secondary VOC products on OH reactivity and potential SOA formation. The reactivity of VOCs with the hydroxyl radical (•OH) at the Pasadena site was dominated by the light hydrocarbons, isoprene, and oxygenated VOCs including aldehydes (secondary products) and alcohols (primary anthropogenic emissions). Toluene and benzaldehyde, both of which are associated with primary anthropogenic emissions, are the predominant VOC precursors to the potential formation of SOA.