Distribution Characteristics And Ecological Risk Assessment Of Heavy Metals In Sediment Of Dongping Lake

With the development of Industry and Economics, various pollutants entered the sediment and gradually enriched through different ways such as atmospheric deposition, waste water discharge, precipitation, soil erosion, resulting in increasing sediment contamination. Heavy metal pollution received extensive attention because of no degradation, bio-accumulation, ecological risk, and the persistence of environmental hazards. Water security of Dongping Lake which is the regulation and storage stations of national North Water Diversion Project and the source water of Shandong Province West-East water, has been generally concerned the issues. The researches on pollution characteristics of Dongping Lake have been done a lot, and most studies focused on eutrophication and heavy metal concentration in water quality. However, the distribution of heavy metals in sediment and the risk evaluation have few studies. This thesis investigates the distribution of heavy metals in sediment of Dongping Lake, and evaluates the risk through Nemerow index, Geo-accumulation index and potential ecological risk index. The basis for sediment pollution control of Dongping Lake has been provided in the thesis, such as the following conclusions.1、The content of Lead, Cadmium, Chromium, Copper, Arsenic, Mercury in normal water period and dry season can meet the secondary paddy standard of "soil environmental quality standards"(GB 15618-1995). The elements except chromium in normal water period and arsenic in dry season exceed the soil environmental background values in Shandong Province. Elemental mercury pollution is at the most severe level.2、The distribution of heavy metals in sediment of Dongping Lake has the following laws: Lead, South of the lake> Center of the Lake>North of the lake; Cadmium, South of the lake=North of the lake > Center of the lake; Cr, South of the lake> North of the lake> Center of the lake; Copper, North of the lake> Center of the lake> South of the lake; Arsenic, South of the lake>Center of the lake> North of the lake; Mercury, South of the lake= North of the lake >Center of the lake. The content of six metal elements in different period has the following laws: Lead, Chromium, Copper: dry season> normal water period; Cadmium, Arsenic and Mercury: normal water period> dry season.3、Ecological Risk Assessment of heavy metals in sediment shows that Lead, Cadmium, Chromium, Copper, Arsenic, Mercury pollution are clean, compared with the second national soil quality standards through Nemerow Index. Geo-accumulation index: Lead, Chromium, Copper, Arsenic have no pollution, and Cadmium, Mercury have moderate pollution in the normal water period. Lead, Chromium, Arsenic have no pollution, Cadmium, Copper have a little pollution, and Mercury has moderate pollution in the dry season.The mean of Geo-accumulation index in descending order is South of the lake> North of the lake> Center of the lake. There is little or moderate pollution in South of the lake and North of the lake, and there is no pollution in Center of the lake. Potential ecological risk index: The hazard trend in descending order is Hg>Cd>As>Cu>Pb>Cr. Potential ecological risk of Lead, Chromium, Copper in the normal water period is higher than that in the dry season. The potential hazards of Mercury is very strong. There is a strong potential hazard of cadmium, and there is a little potential hazards of Arsenic, Copper, Lead, Chromium. Potential ecological risk of different areas in descending order is South of the lake> North of the lake> Center of the lake.4、Chromium, Copper and Lead in sediment of Dongping Lake are mainly the result of natural deposition, and affected by the man little. Arsenic and Cadmium mainly come from man-made pollution. Mercury is affected form both natural factors and human factors, and man-made pollution is more serious.