Dissolved and particulate heavy metal pollution status in seawater and sedimentary heavy metals of the Bohai Bay

Heavy metal contamination has been the focus of many studies owing to its potential risk on the health of coastal ecosystems. The Bohai Bay (BHB) is the second largest bay of Bohai Sea and subjected to serious anthropogenic perturbations. The aim of this study was to evaluate the distribution and pollution status of toxic heavy metals in seawater with two fractions (dissolved and suspended particulate phases) and surface sediments of this coastal system. Therefore, several hydrochemical parameters and concentration of seawater metals and sediment metals were measured at two cruises of 2020 summer and autumn. The spatial distribution and potential ecological risks were examined and their inter-element relationships were analyzed to identify potential geochemical processes. By comparing historical data since 1978, we find declining trends in contents of most trace metals in seawater and sediments, suggesting that recent pollution control in BHB have an effect on diminishing metal pollution. Dissolved metals showed no significant dependence on their particulate phase. The seawater posed a moderate to high level of ecological risk. The hydrochemical factors mainly had a greater impact on dissolved metals during summer, whereas they influenced suspended metals more significantly during autumn. These results provide fundamental information to support environmental quality management and ecological protection in coastal systems.