Atmospheric Mercury Isotopes and Meteorological Variables Reveal Local-Scale Impacts from Anthropogenic Emission...

Mercury (Hg) isotopes provide valuable insights into understanding the sources and fate of Hg in the environment. To better understand the spatiotemporal variability of Hg isotopes after emissions at a local scale, total gaseous mercury (TGM) and particulate-bound mercury (PBM) were systematically sampled near a large-scale zinc smelter. The TGM samples exhibited a significant diel variation in δ²⁰²Hg values, with nighttime samples displaying higher values than corresponding daytime samples. In contrast, PBM samples displayed a significant diel variation in Δ¹⁹⁹Hg values, with mean Δ¹⁹⁹Hg values being significantly higher during the daytime than at nighttime. Combining these findings with meteorological variables, we found that the TGM and PBM samples directly impacted by the smelter showed near-zero Δ¹⁹⁹Hg and Δ²⁰⁰Hg values, indicating that atmospheric Hg was mainly attributed to the changes in Hg sources resulting from wind direction shifts. Furthermore, the seasonal and spatial variations in TGM and PBM isotopes were mainly caused by varied sources mixing. Using Hg isotopes for source apportionment, we estimated that the annual contributions of the zinc smelter to ambient TGM and PBM were 63.0 ± 19.2% and 72.3 ± 21.3%, respectively. This study suggests that no significant mass-independent fractionation (MIF) of flue gas Hg was observed during short-range transport, highlighting the potential of Hg isotopes as a useful tool for tracing the fate of environmental Hg.