The content and potential ecological risk assessment of heavy metals in coastal wetlands around the Bohai Sea

Coastal wetlands play a vital role in the migration and transformation of heavy metal pollutants in watersheds. There were 30 surface sediment samples that were analysed to investigate the distribution and ecological risks of heavy metals in the coastal wetlands around the Bohai Sea. Our results showed that the average concentrations of Pb, Cr, Ni, Cu, Zn, and Cd in these wetlands were 17.92 ± 5.81, 50.29 ± 20.50, 31.53 ± 9.71, 25.37 ± 4.29, 80.13 ± 15.11, and 0.92 ± 0.54 mg/kg, respectively. Relative to other wetlands, Pb (25.43 ± 2.68 mg/kg) and Cd (1.67 ± 0.06 mg/kg) contents were higher in the Liaohe Delta wetland (LHDW). Cu (28.44 ± 3.71 mg/kg), Cr (83.11 ± 5.80 mg/kg), and Ni (45.91 ± 3.02 mg/kg) contents were higher in the Yellow River Delta wetland (YRDW). The Zn (120.86 ± 7.41 mg/kg) content was higher in the Qilihai wetland. Heavy metal concentrations in coastal wetland sediments are shown to be positively correlated with organic matter content. Our results showed that the concentration of heavy metals decreases with increasing sediment particle size. In this study, Cd showed the highest pollution index and, therefore, more attention should be paid to the potential ecological risks of Cd in coastal wetlands around the Bohai Sea, especially in the LHDW and YRDW.