Enhanced Anthropogenic Contributions to Marine Aerosols and trace elements Compared to Coastal Regions in Northern China

Terrestrial aerosols, transported by westerly winds from Asian continent, continuously deliver both natural and anthropogenic nutrients to downstream marine ecosystems. This study quantified the trace elements in fine particles (PM_2.5) collected concurrently in a coastal city (Qingdao) in Northern China, and across the adjacent sea areas (Yellow and Bohai Sea) during the spring and summer of 2018, to investigate the widespread and sources of aerosols and elements over East Asia marginal areas. Trace elements generally exhibited higher levels in Qingdao compared to marine areas. However, anthropogenic elements, like Zn, Pb, As and Cd showed even higher concentrations in summer marine envrionemnt compared to the coastal site. Through positive matrix factorization (PMF) analysis, it is identified that dust and secondary nitrate contributions to PM_2.5 decreased dramatically from an average of 48.3% in coastal to 19.7% in marine environment. Conversely, anthropogenic sources were more prevalent over the ocean, particularly vehicular emissions (18.5%) and residual oil combustion (9.0%). Specifically, coal comubstion was identified as a dominant source, contributing more than half of Fe and Mn concentrations in the summer marine environment. The disparities in elemental sources between land and sea across different seasons were influenced by several key factors, inlcuding the aerosols sources, airmass history, weather conditions and the mixing with dust. These results highlight significant interaction between sea salt and dust or anthropogenic elements, which may enhance the solubility of these trace elements. This study underscores the potential far-reaching impact of these fine particles on marine ecosystems in East Asian marginal seas.