Distribution of heavy metals in tidal flats wetlands around Hainan Island and analysis of their sources and sinks

In order to find out the history of the heavy metal pollution in the tidal flats of Hainan Island and provide the basic data for the monitoring， prevention and control of the pollution in the area， in the report， the geo-accumulation index method， the enrichment factor method， and the potential ecological hazard index method were used to analyze the seven heavy metals in 613 surface sediments in the tidal flats of Hainan Island. The results showed that the heavy metals have the similar geochemical spatial distribution patterns， with an increasing trend from the south to the north. The contribution rates of the heavy metals from the natural sources， the agricultural sources， the industrial and agricultural mixed sources， and the traffic sources to the tidal flats sediments around Hainan Island is 33.62%， 18.37%， 23.31%， and 24.71%， respectively. The overall level of the heavy metal pollution in the study area is low. However， the pollution near the small bay of Wanning City in the southeastern in Hainan Island are serious， the concentrations of some elements exceed Class 3 of the marine sediment quality in some areas. The combined analysis results of the three methods suggested that As and Cd are the most severely polluted heavy metals locally. Combining the data with Geographic Detector， the analysis results indicated that Hg element has the highest potential ecological hazard degree， and it is very likely that the mangrove wetlands distributed in the tidal flats are the sink for Hg element.