Source-resolved atmospheric metal emissions, concentrations, and their deposition fluxes into the East Asian Seas

Abstract. Atmospheric deposition is an important source of marine metallic elements, which have a non-negligible impact on marine ecology. Atmospheric trace metals come from different sources, undergo their respective transport processes, and are deposited into seas finally. This study aims to provide gridded data on sea-wide concentrations, deposition fluxes, and soluble deposition fluxes with detailed source categories of metals by the modified Community Multiscale Air Quality (CMAQ) model. A monthly emission inventory of six metals – Fe, Al, V, Ni, Zn, and Cu – from land anthropogenic, ship, and dust sources in East Asia (0–55° N, 85–150° E) in 2017 was developed. Most metals came mainly from land-based sources, contributing over 80 %. The annual marine atmospheric deposition fluxes of Fe, Al, V, Ni, Zn, and Cu were 9614, 15000, 102, 84, 171, 88 μg·m^-2, and soluble deposition fluxes were 646.8, 1799.6, 43.3, 36.3, 118.4, 42.9 μg·m^-2, respectively. Contributions of each source for trace metals varied in emissions, atmospheric concentrations, and depositions. Dust source, as a main contributor of Fe and Al, accounted for a higher proportion of emissions (~90 %) than marine deposition fluxes (~20 %). However, anthropogenic sources have larger shares of marine deposition flux compared with emissions. The deposition of Zn, Cu, and soluble Fe in East Asian seas was dominated by land anthropogenic sources, while V and Ni were dominated by shipping. The seasonal gridded data and the identification of the dominant source of metal deposition offer a foundation for dynamic assessments of the marine ecological effects of atmospheric trace metals. This study also implies the importance of potential co-synthesis and complementation effects of multiple trace elements deposited into marine ecosystems.