Anthropogenic aerosols observed in Asian continental outflow at Jeju Island, Korea, in spring 2005

Abstract

Anthropogenic aerosols were measured together with CO at Gosan (33°17′N, 126°10′E) on Jeju Island, South Korea, between 17 March and 5 April 2005. Outflow of these aerosols from the Asian continent was associated with a high‐pressure system centered over the northern region of China and Mongolia. Air masses are classified into five distinct categories on the basis of origin: marine, free troposphere, Yellow Sea, Korea, and China. The concentrations of aerosols and CO show large variations because of the alternation of air masses, while wet scavenging of aerosols was another important factor during precipitation events at Gosan. The average mass concentrations of black carbon (BC), organic carbon (OC), water‐soluble organic carbon (WSOC), and sulfate (SO42−) aerosols were 1.2 ± 0.8 μgC m−3, 4.2 ± 1.6 μgC m−3, 1.3 ± 1.0 μgC m−3, and 4.0 ± 3.4 μg m−3, respectively. Almost all species concentrations were highest in Chinese air masses, while they were lowest in marine air masses. The observed ΔBC/ΔCO slope of 9.7 ng m−3 ppbv−1 in Chinese outflow agrees reasonably with the estimates of the BC/CO emission ratios over northeastern China. The transport efficiencies of SOx (SO2 + SO42−) are calculated to be 40–45% from the observed SOx‐CO correlation. The relationships of the SO42−/BC and WSOC/BC ratios with transport time from the continent suggest that a majority of SO42− and WSOC aerosols were formed by about 1.5 days after the air masses left the East Asian continent.