Distribution, source analysis and ecological risk assessment of heavy metals in surface seawater near Qisha peninsula, Guangxi

In order to study the distribution characteristics and quality status of heavy metals (HMs) in the surface seawater near Qisha peninsula, 67 surface seawater samples were collected in the coastal waters of Qisha peninsula in November 2020 to analyze the physical and chemical properties and HMs content in seawater. The results showed that the contents of As, Cd, Cr, Cu, Pb and Zn were (2.06 ± 0.89) μg/L, (0.08±0.06) μg/L,(2.13±0.76) μg/L, (1.91±0.74) μg/L, (0.22±0.19) μg/L and (16.17±12.89) μg/L respectively. Compared with the data in the past 10 years, the concentration of Cr and As was increased, and other elements were roughly the same as or slightly decreased. The distribution range of HMs has no obvious similarity, indicating that they may have different sources. Most of the seawater meets the seawater quality class I, and a few sites are in class II and class III. The elements affected the water quality were mainly Cu and Zn. The comprehensive water quality index (WQI) showed that the surface seawater was at clean level. Using risk quotient (RQ) to evaluate the ecological risk of HMs to marine organisms, it was considered that the main risk elements were Cu, Zn and As. With the correlation analysis and cluster analysis, it was considered that the content of HMs had a certain relationship with total phosphorus and salinity. PCA-MLR model was used to analyze the sources of HMS. Three sources such as hull coating and wastewater, natural background rock weathering and industrial and aquaculture wastewater were get, and the contribution rates were 41%, 48% and 11% respectively.