Ecological risk assessment of dissolved heavy metals in the Yangtze River Estuary and Zhejiang coastal waters, China

The study applied a tiered ecological risk assessment method to evaluate the long-term status and trend of the ecological risks of dissolved heavy metals from 2011 to 2019 in the Yangtze River Estuary and Zhejiang coastal waters, China. The results for spring, summer, and autumn of 2019 indicated that Pb, Cd, and Zn posed no adverse ecological risk, Cu posed a potential ecological risk, and As posed an ecological risk. The annual results from 2011 to 2019 suggested that Pb, Cd, and Zn posed no adverse ecological risks, and As and Cu posed an ecological risk. The trend analysis in the nine years showed that the ecological risk of Cu is gradually decreasing, while that of As is still a concern. The overall trend is attributed to the environmental protection policies that reduced these contaminants' terrestrial sources and atmospheric sources.