Host: Abstracts of Annual Meeting of the Geochemical Society of Japan
Pages 208-
Fine airborne particulate matters (PM2.5) were collected weekly at four remote sites in China, which were located at Mt. Waliguan (northwestern China), Mt. Ailao (southwestern China), Mt. Changbai (northeastern China) and Huaniao Island (East China Sea). The averaged mercury (Hg) concentrations in PM2.5 at the studied sites ranged from 18.9 to 46.1 pg m-3, which are 2-5 times greater than that observed from the North America and Europe. We identified that long-range transport from industrial and urbanized areas in eastern, northern, southwestern, northwestern China played a primary role in distribution of Hg in PM2.5 in remote areas of China. Hg in PM2.5 overall displayed negative δ202Hg values ranging from -2.5‰ to -0.30‰. The negative δ202Hg values were partly attributed to direct emission of PM2.5 from anthropogenic sources, as most previous studies suggested that PM2.5 Hg released from coal fired power plants were characterized by negative δ202Hg values. Also, Hg isotopes fractionation during atmospheric transformation including oxidation of Hg0 in the atmospheric followed by gas-particle partitioning could also induce negative shift in PM2.5 δ202Hg values. We also observed significant mass independent fractionation (MIF) in PM2.5 with ∆199Hg values ranging from -0.20‰ to 1.17‰. The PM2.5 ∆199Hg values were significantly anti-correlated with PM2.5 Hg concentrations. As most of high PM2.5 Hg samples were directly related to anthropogenic Hg emission in mainland China, we suggest that PM2.5 released from anthropogenic sources of China were characterized by ∆199Hg values near zero. This conclusion is consistent with previous studies which showed that MIF signatures in world coal and during coal combustion were all close to zero. On the other hand, atmospheric processes including oxidation of Hg0 and photo reduction of PM2.5 Hg are thought to drive isotopic composition of PM2.5 Hg toward high positive ∆199Hg values. This may explain the high positive ∆199Hg values in low PM2.5 Hg samples.
