Atmospheric input of silicon to the China adjacent seas: Non-negligible contributions from anthropogenic sources

Atmospheric deposition is an important source of exogenous Si in the oceans. As a typical crustal element, Si in the atmo-sphere emitted from anthropogenic sources is ignored. In this study, the atmospheric dry deposition of anthropogenic Si to China adjacent seas was calculated using WRF-CMAQ in January and July 2019 to investigate the contribution of anthro-pogenic Si to the oceans. Si emitted from 13 anthropogenic sources in China, the Korean Peninsula, Japan, and marine ships was considered. Emissions of anthropogenic Si in January and July 2019 were 30.2 and 22.0 Gg, respectively. The highest Si emissions were concentrated over eastern China, e.g. Beijing-Tianjin-Hebei region, Shandong province, Yangtze river delta area (0.2-21.3 ng m-2 s-1), while the lowest emissions were in northwestern China (< 5.2 ng m-2 s-1). Among the Bohai (BS), Yellow (YS), and East China seas (ECS), dry deposition fluxes over the southern YS were highest (4.6-16.8 mu g m-2 d-1), and those over the ECS were lowest (0.2-7.7 mu g m-2 d-1). During pollution episodes, the outflow of polluted air masses from the continent caused a 10-fold increase in Si deposition compared with clear days. The relative contribution of continental anthropogenic emissions and ship combustion varied significantly in two seasons. In winter, de-position from continental anthropogenic emissions to total anthropogenic Si deposition was higher than 96 %. While in summer, the contributions from ship combustion increased obviously, accounting for 10-38 %. Deposition flux of dissolved Si from anthropogenic sources over China adjacent seas was about 4-38 % of that of dissolved mineral dust Si. The annual Si depositions from atmospheric anthropogenic sources to the Si fluxes from rivers to the China adjacent seas were 0.03 %- 2.8 %. The marine primary productivity in the BS, YS, and ECS caused by atmospheric anthropogenic dissolved Si deposi-tion were 1.3, 1.2, and 0.7 mg C m-2 a-1, respectively.

Automated summary

In this study, the atmospheric dry deposition of anthropogenic Si to China adjacent seas was calculated using WRF-CMAQ model. The emissions of anthropogenic Si from various sources were considered and it was found that the highest Si emissions were concentrated over eastern China. The impact of pollution episodes and the contribution of continental anthropogenic emissions and ship combustion varied significantly between winter and summer.