DISTRIBUTION PATTERN OF HEAVY METALS IN THE COASTAL SEDIMENT OF SOUTHERN HAINAN ISLAND AND ECOLOGICAL RISK ASSESSMENT

The southern coast of Hainan Island is a famous tropical beach for tourism. Careful management of environment is required. However, there is lack of ecological risks evaluation in the region for heavy metal contamination. We made a survey and data analysis of heavy metals in the region recently. 164 samples of surface sediments were collected and analyzed, and the distribution patterns, influencing factors and possible ecological risk of heavy metals discussed. The results show that the contents of Cu, Pb, Zn, Cr, As, Hg, Cd are 10.45 μg/g, 22.38 μg/g, 53.72 μg/g, 23.42 μg/g, 4.52 μg/g, 0.09 μg/g, 0.05 μg/g respectively. Heavy metals are enriched in the Yulin Bay and Xincun Harbor. Heavy metals in other areas are relatively low compared to the densely populated harbor areas. Hg is specifically high and increasing in recent years. The contents and distribution of Cu, Pb, Zn, Cr are obviously controlled by grain size. They are mainly from natural weathering and erosion. The distribution of As is affected by human factors, and it is mainly from domestic sewages, fish cage culture, oil seepages and other sources. Hg and Cd owe their origin to degradation of organic matters and human activities. Single metal pollutant has little effect on the environment, but the overall evaluation of potential ecological risk index results indicates that in some of the stations, sediments have been contaminated by multiple heavy metals, for examples, in the Yulin Bay and Xincun Lagoon, due to the impact of sewage discharge. Further control of farming and sewage contaminated areas is required in order to prevent the region from heavy metal pollution.