Characterization of chemical composition and aerosol processing by clouds and fogs from different field studies (Baengyeong Island and Daegwallyeong, South Korea)

Fogs/clouds can play both a physical and chemical role in the fate of atmospheric species. Fogs/clouds act as processors of atmospheric aerosol particles and trace gases by aqueous oxidation of gas phase precursors and the interaction of aerosol with atmospheric water and also cleansing of the atmosphere by scavenging and removal of atmospheric particles. In addition to playing a central role in the hydrologic cycle and influencing atmospheric radiative transfer, clouds interact with a variety of chemical species. Together with gases and particles, clouds and fogs comprise a complex multiphase system. To understand the interaction of aerosol with fogs/clouds better, we conducted a fog sampling campaign and physical and chemical measurements of aerosol at the Baengyeong Island (Intensive Air Quality Monitoring Station) and Daegwallyeong (Cloud Physics Observatory), South Korea, during June 25th – July 21st, 2014 and September 15th – October 15th, 2014, respectively, using a compact version of the Caltech Active Strand Cloudwater Collector known as the CASCC2 and a two-stage fog/cloud water collector that collects “small” and “large” drops. The pH of the collected fog/cloud samples was measured on-site while sample aliquots were preserved for later analyses of S(IV), H2O2, HCHO, organic acids, total organic carbon (TOC), and major ions (Cl-, NO3-, SO42-, Na+, NH4+, K+, Ca2+, and Mg2+) in the laboratory. The chemical composition and physical properties of aerosol particles were characterized by a high resolution time of flight aerosol mass spectrometer (HR-ToF-AMS, Aerodyne), an Aerodynamic Particle Sizer (APS, TSI) and a Scanning Mobility Particle Sizer (SMPS, TSI). The presentation will provide an overview of the chemical composition of fog/cloud samples and examine changes in particle chemical composition and microphysics by fog/cloud processing in the boundary layer.