Measurements of Aqueous-Phase Secondary Organic Aerosol Processing

JOHN SHILLING, Jesse Anderson, Will Cantrell, Richard Flagan, Jose Fuentes, Gourihar Kulkarni, Mikhail Pekour, Hamed Sadi, Raymond Shaw, Suryadev Singh, ManishKumar Shrivastava, Jaemin Yeom, Maria Zawadowicz, Alla Zelenyuk, Yuzhi Chen, Tania Guatam, Pacific Northwest National Lab

     Abstract Number: 434
     Working Group: Aerosol Chemistry

Abstract
Several field and modeling studies have suggested that cloud processing could be a significant and sometimes dominant source of secondary organic aerosol (SOA), which has a major influence on the Earth's energy balance. However, relatively few studies have investigated the formation and processing of SOA in authentic cloud droplets. Instead, most studies are conducted in bulk solutions or on deliquesced aerosol particles and results are extrapolated to liquid water content characteristic of clouds. We describe two types of experiments in which we investigate the role cloud processing may play in generating SOA. In the first series of experiments, SOA was generated from the photooxidation of isoprene and alpha-pinene in the Pacific Northwest National Laboratory (PNNL) environmental chamber and the SOA vapors were extracted into a second chamber where they interact with deliquesced sulfate particles at varying pH and at relative humidity (RH) approaching 100%. We measure the SOA formation efficiency and chemical composition that results under these near-saturation experiments. We shall also present preliminary measurements of the fate of isoprene expoxydiols (IEPOX) when injected into a synthetic cloud formed in the Michigan Technological University Pi cloud chamber as a function of the cloud liquid water content.