Distribution, sources and risk assessment of heavy metals in Yangshan port and its adjacent sea areas

Heavy metals play an important role in marine ecosystems, but excessive heavy metals can harm aquatic life and human health. The Yangshan Port is located near an important agricultural and fishing area in China, with rich fishery resources. However, there is a lack of research on the impact of heavy metal pollution on local fishery and environment. This study assessed the concentrations of seven metals (Cu, Zn, Pb, Cr, Cd, As, Hg) in the water, sediments and two organisms (fish and benthic organisms) of Yangshan Port, aiming to get a comprehensive information about the heavy metal pollution in Yangshan Port and its adjacent sea areas. The results showed that the concentration of heavy metals in the sediments was higher than that observed in the water. The concentrations of heavy metals in water and sediments were influenced by human activities. The main reason for this regional distribution difference was human factors such as industrial wastewater discharges, household pollution, and agricultural and fishery discharges, followed by various natural factors, such as organic content and sulfate, as well as hydrodynamic self-disturbance. It is worth noting that As is affected not only by emissions from land-based sources, but also by riverine inputs and human marine engineering activities. The ecological risk indicated that two of seven metals (As and Hg) posed a risk to the marine environment in this region. In addition, the content and accumulation level of heavy metals in benthic organisms was significantly higher than that in fish. Human health risk assessments showed that the heavy metal posed a potential carcinogenic risk to human health, particularly to children. Overall, the health risks from seafood intake by humans were low, with As having the greatest impact on human health, and metal concentrations being the most sensitive factor affecting metal health risk assessment, with As being the most sensitive element. This study provided new insight into the heterogeneity of heavy metal pollution accumulation in the Yangshan Port and its adjacent sea areas and offered a scientific basis and favorable support for port ecological environment protection and prevention of heavy metal pollution-related ecological risks.