Significant Seasonal Variations in Isotopic Composition of Atmospheric Total Gaseous Mercury at Forest Sites in China Caused by Vegetation and Mercury Sources

作者：Xuewu Fu, Hui Zhang, Chen Liu, Hui Zhang, Che‐Jen Lin, Xinbin Feng · 发表于：Environmental Science & Technology · 年份：2019 · DOI：10.1021/acs.est.9b05016 · 被引用次数：94 · 研究领域：Mercury impact and mitigation studies、Heavy Metal Exposure and Toxicity、Heavy metals in environment

In this study, isotopic compositions of atmospheric total gaseous mercury (TGM) were measured in the Mt. Changbai (MCB) temperate deciduous forest and the Mt. Ailao (MAL) subtropical evergreen forest over a 1-year period. Higher δ 202 Hg TGM values were observed under the forest canopy than above the forest canopy in the MCB forest. The vertical gradients in δ 202 Hg TGM and Δ 199 Hg TGM are positively correlated with the satellite-based normalized difference vegetation index (NDVI, representing the vegetation photosynthetic activity), suggesting that a strong vegetation activity (high NDVI) induces both mass-dependent and mass-independent fractionation of TGM isotopes. The observed δ 202 Hg TGM and Δ 199 Hg TGM showed seasonal variations. Mean δ 202 Hg TGM and Δ 199 Hg TGM in summer were 0.35–0.99‰ and 0.06–0.09‰ higher than those in other seasons in the MCB forest. In contrast, the highest seasonal δ 202 Hg TGM in the MAL forest was observed in winter at 0.07–0.40‰ higher than the values found in other seasons. The variability of δ 202 Hg TGM and Δ 199 Hg TGM in MCB was attributed to vegetation activities, whereas the seasonal δ 202 Hg TGM in the MAL forest was driven by the exposure of air masses to anthropogenic emissions. Using the data in this study and in the literature, we concluded that vegetation activity and anthropogenic Hg release are the main drivers for the spatial variations in TGM isotopic compositions in the northern hemisphere.