Spatial Patterns of Total and Water-Soluble Trace Metals in Various Marine Total Suspended Particulate Over the Northwest Pacific Ocean

Abstract

Atmospheric deposition of trace metals has been widely evidenced to impact oceanic primary production. However, the onboard observations of water-soluble trace metals that the phytoplankton can directly assimilate are still insufficient. In this study, springtime total suspended particulates (TSPs) were collected from the Yellow Sea and East China Seas (ECSs) to the northwest Pacific Ocean (NWPO) by the cruise in 2014, and concentrations of total and water-soluble trace metals were analyzed. Total and water-soluble trace metal concentrations in ECSs were higher than those in NWPO, suggesting anthropogenic and terrestrial emissions had greater impacts on TSPs in ECSs. Total and water-soluble trace metal concentrations in dust TSPs were higher than those in normal TSPs in NWPO, indicating that dust plumes mixed with anthropogenic emissions can be transported to NWPO. Based on enrichment factors, correlation analysis, positive matrix factorization model, and characteristics of trace metals from different sources, four emission sources (crustal mineral, ship exhaust, fossil fuel combustion, and marine emissions) of trace metals in marine TSPs in NWPO were identified. Aerosol sources, aerosol pH values, aging processing, and dust loading significantly affect trace metal solubility in different types of TSPs. Dry deposition fluxes of trace metals in ECSs were higher than those in NWPO. Atmospheric deposition of water-soluble Fe-estimated nitrogen fixation (N₂ fixation) fluxes in NWPO were comparable to in situ observations, indicating that atmospheric Fe may be an important micronutrient supporting new primary production in the open ocean of NWPO.