Non-sea-salt sulfate in the marine boundary layer and its possible impact on chloride depletion

Aerosol samples were collected on board the research vessel Xuelong during the Fifteenth Chinese Antarctic Research Expedition (CHINARE XV) in November 1998-April 1999 and the First Chinese Arctic Research Expedition in July-September 1999.The areas traversed by the expeditionary cruises include the Arctic Ocean, the western North Pacific Ocean and the eastern Indian Ocean,covering 75°N-69°S and 75°E-133°W. Aerosol samples were also taken at the Chinese Zhongshan Station in East Antarctica during the CHINARE XV. Analysis of the samples yielded concentrations of non-sea-salt sulfate and other soluble chemical species in the marine boundary layer. The data suggest that the chemical composition of the marine aerosols is influenced by three major sources:continental air masses, primary oceanic emissions, and secondary marine aerosols originated from oceanic emissions. The results show that, awing to strong anthropogenic sulfur emissions from the Asian continent, non-sea-salt sulfate concentrations in the Northern Hemisphere (the western North Pacific) marine aerosol are significantly higher than those in the Southern Hemisphere (the eastern Indian Ocean). Aerosol non-sea-salt sulfate concentrations appear to be inversely correlated with aerosol non-sea-salt chloride which shows significantly negative values, indicating the loss of chloride by sea salts, in most aerosol samples. Since gaseous HCl may be involved in chemical reactions that deplete atmospheric ozone in the marine boundary layer (MBL), high levels of acidic non-sea-salt-sulfate released by human activities in the low and mid-latitudes of the Northern Hemisphere may become an important potential contributor to the loss of atmospheric ozone in the MBL.