Distribution and risk assessment of heavy metals in surface sediments of coastal mudflats on Leizhou Peninsula,China

Mudflats play a vital role in maintaining the dynamic balance between sea and land. To understand the characteristics, sources, and pollution risks of six heavy metals (As, Cd, Cr, Cu, Hg, and Pb) in the coastal mudflats on the Leizhou Peninsula, 257 surface sediment samples were studied using mathematical statistics, correlation analysis, and factor analysis. The results show that the overall concentrations of these heavy metals are low although there are several high abnormal points in the local areas. The strong correlation between these heavy metals indicates that the sources of some of the metals are similar, yet their elemental combinations in different cities (counties) varied. According to the calculated enrichment factor (EF), anthropogenic activity-induced heavy metals were determined in order of decreasing influence: As, Cd, Pb, Cr, Cu, and Hg. The low EF values of Hg indicate that it does not present as a contaminant in the study area, while low values of Cr and Cu from the Lianjiang City suggest that these two metals were also attributed to natural sources. The presence of As, Cd, Cr, Cu, and Pb from the remaining cities (counties) should be influenced by anthropogenic activities. The overall potential ecological risk index indicates that the ecological risks posed by the six analyzed heavy metals to the Leizhou Peninsula mudflats, in order of decreasing risk, are Cd, As, Hg, Pb, Cu, and Cr. It is noteworthy that only Cd in Lianjiang City demonstrated substantial ecological risk. Other examined heavy metals in other cities of the study area showed slight ecological risk.