Analysis of heavy metal content and ecological risk in surface seawater of Wuchuan coastal area, Guangdong Province

To understand the status and potential risks of heavy metal content in the coastal waters of Wuchuan, Guangdong Province, surface seawater samples were collected from 41 stations in October 2020, and the degree of heavy metal pollution and potential ecological risks were evaluated by comprehensive index method, Hakanson potential ecological risk index method, and correlation analysis method. The results show that the content of Cu ranged 0.48-14.1 μg/L (1.75 μg/L on average), Pb 0.07-7.79 μg/L (0.44 μg/L), Zn 3.98-65.8 μg/L (9.22 μg/L), Cu 0.48-14.1 μg/L (1.75 μg/L), Cd 0.03-0.17 μg/L (0.05 μg/L), Cr 0.62-2.69 μg/L (1.92 μg/L), Hg 0-0.039 μg/L (0.021 μg/L), As 0.39-1.42 μg/L (0.93 μg/L). The average content of heavy metal elements in Wuchuan sea area did not exceed the first-class benchmark of China’s national marine water quality criteria. By comparing the contents of heavy metals in the surface waters of other sea areas in China and the world, the contents of heavy metals in the surface waters of Wuchuan sea area are generally at a medium or low level. According to their correlation, the heavy metal elements in Wuchuan sea area were divided into three types: Cu-Pb-Zn-Cd assemblage, Cr-Hg-As assemblage, and Hg element. The main source of the first type may be the atmospheric deposition from marine vessel emission in the sea area, and the second type may be mainly from aquaculture wastewater from coastal farms and agricultural activities using pesticides and fertilizers. The average comprehensive pollution index of the Wuchuan coastal waters was 0.31, indicating an overall clean state of pollution. The single potential ecological risk index ranged from 0.2 to 38.95, and the overall potential ecological risk index ranged from 0.59 to 87.38, showing that the overall ecological hazard scale was low.