Transport of SO2 and aerosol over the Yellow sea

Aircraft measurements of air pollutants were made to investigate the charac teristic features of long-range transport of sulfur compounds over the Yell ow Sea for the periods of 26-27 April and 7-10 November in 1998, and 9-11 A pril and 19 June in 1999, together with aerosol measurements at the Taean b ackground station in Korea. The overall mean concentrations of SO2, O-3 and aerosol number in the boundary layer for the observation period ranged 0.1 -7.4 ppb 33.1-64.1 ppb and 1.0-143.6 cm(-3), respectively. II was found tha t the air mass over the Yellow Sea had a character of both the polluted con tinental air and clean background air, and the sulfur transport was mainly confined in the atmospheric boundary layer. The median of SO2 concentration within the boundary layer was about 0.1-2.2 ppb. However, on 8 November, 1 998, the mean concentrations of SO2 and aerosol number increased up to 7.4 ppb and 109.5 cm(-3), respectively, in the boundary layer, whereas O-3 conc entration decreased remarkably. This enhanced SO2 concentration occurred in low level westerly air stream from China to Korea. Aerosol analyses at the downstream site of Taean in Korea showed 2-3 times higher sulfate concentr ation than that of other sampling days, indicating a significant amount of SO2 conversion to non sea-salt sulfate during the long-range transport. (C) 2001 Elsevier Science Ltd. All rights reserved.