Occurrence, source, and ecological impacts of dry depositing aerosol metal elements in the Bohai Bay

Bohai Bay, characterized as a typical semi-enclosed bay, has experienced substantial anthropogenic influence. Significant quantities of metal elements have been deposited into Bohai Bay through atmospheric dry deposition. This study focuses on the collection of aerosol samples during the summer and autumn of 2020 to investigate the spatial-temporal distribution and dry deposition fluxes of nine metal elements. The sources of these elements and their potential ecological effects were explored. Subsequently, the potential ecological risk posed by TSP (total suspended particulates)-bound heavy metals over the Bohai Bay was assessed. The mean concentrations of TSP-bound Cr, Cu, Zn, As, Cd, Pb, Mn, Fe, and Al during both seasons were found to be 17.84, 19.91, 205.95, 14.62, 1.12, 30.50, 32.78, 506.63, and 2054.63 ng/m³, respectively. Enrichment factors and correlation analysis suggested that Al and Fe in aerosols were primarily derived from soil dust, while other metal elements predominantly originated from anthropogenic activities. The potential pollution sources were identified primarily from the Bohai Bay coast and Mongolia. Despite the significant impact of dissolved metal elements on marine ecosystems, the study highlights the relatively serious pollution levels of Cd and As in TSP, as indicated by the Geo-accumulation index and potential ecological risk evaluation. Although the overall contribution of atmospheric deposition to inputs to Bohai Bay is relatively modest, inputs of specific metallic elements from atmospheric deposition cannot be ignored. Consequently, the dry deposition of aerosol metal elements significantly influences the biogeochemical cycling of metallic elements, providing organisms not only with nutrients but also with toxic substances.