HR: 0800h
AN: A21C-0750    [Abstracts]
TI: Water-soluble organic carbon in coarse particles in a coastal environment: Role of cloud processing
AU: Pathak, R K
EM: pathak@ust.hk
AF: Hong Kong University of Science & Technology, Department of Chemical Engineering, Clear Water Bay, Kowloon, Hong Kong, 00000 China
AU: * Yu, J Z
EM: chjianyu@ust.hk
AF: Science & Technology, Department of Chemistry, Clear Water Bay, Kowloon, Hong Kong, 00000 China
AU: Chan, C K
EM: keckchan@ust.hk
AF: Hong Kong University of Science & Technology, Department of Chemical Engineering, Clear Water Bay, Kowloon, Hong Kong, 00000 China
AB: Water-soluble organic carbon (WSOC) components constitute a significant fraction of atmospheric aerosol carbon mass, ranging from 5% to 83%. Because of their hydrophilic nature, water-soluble organic compounds are active in modulating aerosol­_s role to act as cloud condensation nuclei. Despite the abundance of WSOC, sources and formation pathways of WSOC are still poorly understood. In this study, we measured the size distribution characteristics of coarse mode WSOC and investigated its relationship with major inorganic constituents in the coastal city of Hong Kong in summer 2004. Atmospheric particles were collected into five size bins in the coarse mode ($>$18, 18-10, 10-6.2, 6.2-3.2, 3.2-1.8 micrometer) and one size bin in the fine mode ($<$1.8 micrometer). The WSOC concentrations in two coarse bins (1.8-3.2 and 3.2-6.2 micrometer) show strong correlations with the WSOC in the fine mode ($<$1.8 micrometer). In the two coarse bins and the fine size bin, WSOC was well correlated with non-sea-salt sulfate while showed no correlation with either sea salt or crustal species. WSOC concentrations in particles larger than 6.2 micrometer were not correlated with the fine mode WSOC concentrations, and found to have a constant value of ~ 0.3 microgram per cubic meter. We postulate that cloud processing, known to be the dominant formation pathway for fine mode sulfate, was mainly responsible for the production of WSOC in the two coarse sizes of 1.8-3.2 micrometer and 3.2-6.2 micrometer and in the fine particles. On the other hand, the nearly constant presence of WSOC on larger coarse particles ($>$ 6.2 micrometer) was likely a result of primary emissions.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting