Isotopic investigation of sources and processes affecting gaseous and particulate bound mercury in the east coast, South Korea

Understanding sources and processes affecting atmospheric mercury (Hg) are key to enabling targeted Hg managements under the Minamata Convention on Mercury. We employed stable isotopes (δ202Hg, Δ199Hg, Δ201Hg, Δ200Hg, Δ204Hg) and backward air trajectories to characterize sources and processes affecting total gaseous Hg (TGM) and particulate bound Hg (PBM) in a coastal city, South Korea, subjected to atmospheric Hg sources of a local steel manufacturing industry, coastal evasion from the East Sea, and long-distance transport from East Asian countries. Based on the simulated airmasses and the isotopic comparison with TGM characterized from other urban, remote, and coastal sites, TGM evaded from the coastal surface of the East Sea (warm seasons) and from the land surface in high latitude regions (cold seasons) act as important sources relative to local anthropogenic emissions at our study location. Conversely, a significant relationship between Δ199Hg and concentrations of PBM (r2 = 0.39, p < 0.05) and a seasonally uniform Δ199Hg/Δ201Hg slope (1.15), except for summer (0.26), suggest that PBM is generally sourced from local anthropogenic emissions and subjected to Hg2+ photo-reduction on particles. The striking isotopic similarity between our PBM (δ202Hg; −0.86 to 0.49 ‰, Δ199Hg; −0.15 to 1.10 ‰) and those previously characterized along the coastal and offshore regions of the Northwest Pacific (δ202Hg; −0.78 to 1.1 ‰, Δ199Hg; −0.22 to 0.47 ‰) infer that anthropogenically emitted PBM from East Asia and those processed in the coastal atmosphere serves as a regional isotopic end-member. The implementation of air pollution control devices can reduce local PBM, while regional and/or multilateral efforts are required to manage TGM evasion and transport. We also anticipate that the regional isotopic end-member can be used to quantify the relative influence of local anthropogenic Hg emissions and complex processes affecting PBM in East Asia and other coastal regions.