Source-resolved atmospheric metal emissions, concentrations, and 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. Trace metals from different sources undergo their respective transport processes in the atmosphere, ultimately depositing into the ocean. This study aims to provide gridded data on sea-wide concentrations, deposition fluxes, and soluble deposition fluxes with detailed source categories of metals using the modified Community Multiscale Air Quality (CMAQ) model. A monthly emission inventory of six metals-Fe, Al, V, Ni, Zn, and Cu-from terrestrial anthropogenic, ship, and dust sources in East Asia (0-55° N, 85-150° E) in 2017 was developed. Most metals came primarily from land-based sources, contributing over 80 %. The annual marine atmospheric deposition fluxes of Fe, Al, V, Ni, Zn, and Cu were 8827.0, 13 384.3, 99.3, 82.4, 162.7, and 86.5 μgm-2, respectively, and the corresponding soluble deposition fluxes were 634.3, 1701.6, 74.3, 46.1, 113.0, and 42.0 μgm-2. The contributions of each source of trace metals varied in emissions, atmospheric concentrations, and depositions. Dust sources, as a main contributor of Fe and Al, accounted for a higher proportion of emissions (1/490 %) than marine deposition fluxes (1/420 %). However, anthropogenic sources have larger shares of the marine deposition flux compared with emissions. The deposition of Zn, Cu, and soluble Fe in East Asian seas was dominated by terrestrial anthropogenic sources, while V and Ni were dominated by shipping. The identification of the dominant source of metal deposition offers a foundation for dynamic assessments of the marine ecological effects of atmospheric trace metals. The source-resolved seasonal gridded data make it possible to calculate the soluble metal deposition flux on a source-by-source basis.