Relative contributions of local sources vs. long-range transport to the atmospheric speciated mercury concentrations at a remote island off the coast of Korea

Abstract:

In this study, total gaseous mercury (TGM), gaseous oxidized mercury (GOM), and particulate bound mercury (PBM) were measured on Yongheung Island off the coast of Korea between mainland Korea and Eastern China. Yongheung Island is a small island located about 15~20 km west from the mainland Korea. Because of the geographical location of the sampling site, the effect of long-range transport of Hg emitted from China could be observed with the westerly winds, and the effect of Korean domestic sources including inland industrial/metropolitan areas and coal-fired power plants could be also evaluated with the easterly and southerly winds, respectively. Average concentrations of TGM, GOM, and PBM were 2.8 ± 1.1 ng m^-3, 9.8 ± 9.9 pg m^-3,and 10.6 ± 12.0 pg m^-3 at the sampling site, respectively. CPF plot shows that the top 25% of TGM concentrations were associated with the winds from NNW and ENE, pointing out the significance of Northeast Chinese emissions and inland Korean emissions; however, when the criterion was used as the top 10% TGM concentration the regional transport from China became less important and the sources located in southern and eastern areas were magnified as important source areas. For GOM, the highest concentration was observed with the wind direction from mainland Korean sources. On the other hand, it was presumed that long-range transport from North Korea and China significantly enhanced PBM concentrations. PSCF also identified Chinese sources for TGM and PBM while mainland Korean sources including coal power plants located in southern part of the sampling site were determined for possible source areas of GOM. Also, we found that the ratio of GOM/PBM was reduced with the increasing contribution of long-range transport and enhanced with the significant impact of local sources, suggesting that the ratio of GOM/PBM can be used as an indicator to determine the relative importance of long-range transport vs. local sources.