Spatial distribution of potentially harmful trace elements and ecological risk assessment in Zhanjiang mangrove wetland, South China

Global mangrove wetlands face increasing anthropogenic impacts along the coast. The Zhanjiang mangrove wetland is the largest and adjacent to the most developed bay area in China. Surface sediments were collected in different plant transit and used for potentially harmful trace elements (PHTEs) measurement. Mean contents of Hg, Cr, Ni, Cu, Zn, As, Cd and Pb were 0.01 mg/kg, 56.16 mg/kg, 10.06 mg/kg, 9.61 mg/kg, 43.58 mg/kg, 8.76 mg/kg, 0.25 mg/kg, 28.12 mg/kg. Most of the PHTEs were slightly enriched but the Cd pollution is significant, and the potential ecological risk is moderate. The risk of the mangrove wetland is larger than the grassland and the farmland. The PCA and PMF indicate Hg, Ni, Cu, Zn, As, and Pb mainly originated from local anthropogenic activities, Cr originated from the natural geological process, and Cd mainly originated from atmospheric deposition of regional industrial pollution. In view of the impact of surrounding industry and agriculture and the signs of PHTEs pollution, it is necessary to implement the wetland protection law more strictly to truly realize the construction of ecological civilization. This provides a valid reference for the wetland conservation and management in coastal cities.