Aerosol chemical properties and related pollutants measured in Dongsha Island in the northern South China Sea during 7-SEAS/Dongsha Experiment

摘要

Aerosol observations were conducted at Dongsha Island in two batches from 19 to 23 March and 10 to 19 April 2010. Dongsha Island is located in a remote area over the northern South China Sea (SCS), distantly surrounded by southern China, Taiwan, the Philippines, and the Indochinese Peninsula. During the study period, the average PM_(10) and PM_(2.5) mass concentrations were 26.5 ± 19.4 and 12.6 ± 6.0 μg m~(-3) respectively. In particular, a daily PM_(10) concentration of 94.1 μg m~(-3) caused by a yellow-dust event originating from the Asian Continent was recorded on 21 March. Other than this event, the PM_(2.5) and PM_(10-2.5) daily levels were 7.1 ± 1.2 and 12.6 ± 5.0 μg m~(-3), respectively, on days without pollution from anthropogenic sources in the surrounding areas. Water-soluble ions (WSIs) were the predominant components that accounted for 58.7% ± 10.5% and 51.1% ± 7.2% of the PM_(10) and PM_(2.5) mass. The second most abundant component was carbonaceous content, which accounted for 9.5% ± 4.7% and 17.5% ± 5.3% of PM_(10) and PM_(2.5), respectively. SO_4~(2-) was the most abundant PM_(2.5) WSI, whereas the Na~+ and Cl pair was the most abundant PM_(10-2.5) WSI. Based on the U.S. IMPROVE protocol, the resolved carbonaceous fractions were mainly distributed in PM_(2.5) and influenced by coal combustion, mobile vehicles, and biomass burning. Most of the resolved WSIs in particles were in the liquid phase due to the humid environment around the northern SCS.