Factors influencing concentrations of atmospheric speciated mercury measured at the farthest island West of South Korea

East Asia is the largest emitter of mercury (Hg) in the world, but only a few studies of speciated Hg have been carried out in South Korea. In this study, total gaseous mercury (TGM), gaseous oxidized mercury (GOM), and particulate bound mercury (PBM) were measured at one of the most northwestern islands of South Korea. Concentrations of TGM and GOM were similar to those measured in other regions of Korea; however, PBM was found in much higher concentrations during cold months, most likely from coal and biomass burning in North Korea. Sources outside Korea significantly affected TGM and PBM, and GOM increased as air masses transported from domestic coal-burning power plants. During the warm months, GOM increased as gaseous elemental mercury (GEM) decreased when air masses were confined within the ocean area with minimal influence from anthropogenic emissions. This implies that there is an efficient process for the oxidation of GEM and GOM production in the marine boundary layer. The concentrations of ozone also decreased as an increase in GOM was observed, suggesting that halogens are primarily responsible for GEM oxidation.