Assessment Of The Heavy Metal Pollution Of The Sediments In Liaohe Estuary

In this paper, surface sediments and core sediments from coastal wetland of Liao River Estuary were chosen as the research object. By testing grain-size, organic carbon, element content and 210Pb/137 Cs activity ratio of surface sediments and core sediments this paper analyzes distribution of heavy metals and their relationship with each other and influencing factors in surface sediments from coastal wetland of Liao River estuary and uses two kinds of heavy metal pollution evaluation methods to assess the quality of the study area and the pollution history in core sediments which has been discussed in the 30 years. The main conclusions are as follows:(1)The heavy metal elements had formed a certain degree of enrichment in surface sediments of this study area. The distribution was roughly divided into four categories: The highest concentration of element Cr, Cu and Zn appeared in the sediments of upstream Liuzigou River; Element As and Pb appeared in the sediments of the narrow upstream of Xiaodao River; Element Cd appeared in the sediments of the upstream of Xiaodao River; Element Hg appeared in the north research area. All the seven heavy metals reflected the lower concentrations appeared near the mouth.(2)In the core sediments, element As, Hg, Cr, Cd, Cu, Pb and Zn enriched in clay parts and all had a good positive correlation with organic carbon content, which proved that water dynamics, fine particulate matter and organic carbon content were important factors to control the distribution of heavy metal elements.(3)The deposition rate of Liao River estuary core sediments was 3.00cm/a between 1984 and 1998, and 3.73cm/a between 1998 and 2013.(4)The results of geoaccumulation index and single potential ecologic risk index showed that the heavy metal pollution in surface sediment in research area was in a low level in element Cd and Pb, and in a low ecologic risk in element Cd. In the core sediments the element Cd also had a serious pollution during the 30 years history. Other elements had mild pollution or non-pollution.