Distribution and evaluation of heavy metals in sediments of Zhenzhu Bay mangrove wetland in Guangxi

Heavy metals in sediments belongs to persistent pollutants, with characteristics of enrichment, recalcitrance and toxicity, which would pose a threat to the ecological environment and human safety after long-term accumulation. In order to study the distribution characteristics and quality status of heavy metals in the surface sediments of Zhenzhu Bay mangrove wetland, the authors collected 13 surface sediment samples in the mangrove distribution area of Zhenzhu Bay on September in 2021 to analyze the heavy metal content. The results shows that the content of heavy metals in the surface sediments of Zhenzhu Bay mangrove wetland is relatively low compared with other mangrove wetlands in China. Only some stations showed weak Cd and Hg pollution and most stations wasn’t plolluted by heavy metals, with two showed weak Cd and Hg pollution according to the geo-accumulation index. and all stations in the bay are at low ecological risk based on potential risk index method. Correlation analysis and principal component analysis show that Cd was mainly affected by the input of Jiangping River and mariculture in the southeast of Zhenzhu Bay, and other elements were mainly affected by the weathering and normal deposition of natural background rocks. The contribution rates of Jiangping River input and Zhenzhu Bay mariculture were 57% and 43% respectively through PCA-MLR model analysis on the heavy metal source. The results show that the overall ecological condition of the Zhenzhu Bay Mangrove Wetland is good, however, it is still necessary to pay attention to the input of Cd.