Distribution features and ecological risk assessment of heavy metals in mangrove sediments in Zhanjiang bay, Guangdong province

With the rapid development of human society and economy, the ecological risk of mangrove sediments is more and more serious. In order to understand the heavy metals pollution status and ecological risk of mangrove sediments in Zhanjiang bay, Guangdong province, and provide support for the protection and restoration of mangroves, 25 samples were collected along the mangrove distribution area in this study. The content, correlation, enrichment factors and ecological risk of heavy metals were analyzed and evaluated, and the sources of heavy metals were discussed. The results showed that, the average contents of Cu, Pb, Zn, Cr, Co, Ni, As, Cd, Mn and Hg in mangrove sediments were (9.62 ± 6.86)×10⁻⁶, (16.70 ± 12.13)×10⁻⁶, (29.68 ± 21.33)×10⁻⁶, (24.17 ± 23.32)×10⁻⁶, (2.48 ± 2.17)×10⁻⁶, (7.22 ± 5.19)×10⁻⁶, (4.97 ± 4.15)×10⁻⁶, (0.14 ± 0.08)×10⁻⁶, (118.80 ± 115.23)×10⁻⁶ and (0.16 ± 0.04) ×10⁻⁶, respectively. The contents of Cd and Hg were 2.41 and 2.06 times higher than the background values of soil environment in Guangdong province. Heavy metals in mangrove sediments were mainly from natural sources. The content of Cd was high due to human activities. Hg was mainly from human activities. The pollution level of heavy metals in mangrove sediments is slight, and the potential ecological risk is moderate. Cd and Hg are the main pollutants in the study area.