(70c) On the Nature of Water-Soluble Organic Aerosols In the Southern California Region

Water soluble organic carbon (WSOC) species are important owing to their ability to influence aerosol water-uptake properties and radiative forcing. The chemical composition, sources, and atmospheric evolution of WSOC are not well established. A particle-into-liquid sampler quantified WSOC during the airborne deployment of the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter as part of the CalNex campaign (May 2010). Eighteen flights were conducted to study the nature of aerosol particles in the San Joaquin Valley, the Los Angeles Basin and outflow regions. The measurements indicate that WSOC accounts for a significant portion of the organic aerosol mass, with likely contributions from both primary emissions and secondary production processes. The highest levels of WSOC were associated with smoke plumes in the Los Angeles Basin. On 11 of 16 flights, WSOC exhibited its highest concentration above the first 500 meters of the boundary layer, usually near the Banning and Cajon Passes, and also near the hilly terrain over corridor between San Bernadino and Riverside on the eastern edge of the Los Angeles basin. Aging and transport of polluted aerosol from the western edge of the Los Angeles basin often led to peak WSOC levels near the eastern edge of the basin near Riverside and San Bernadino during the afternoons. This work will discuss the extent to which concentrations and the spatiotemporal distribution of WSOC are dependent on secondary production, transport, meteorology, and the influence of biomass burning.