Study On Heavy Metals Pollution Of Sediments In The Three Gorges Reservoir During Its Operating Period With Low Water Level

The three gorges project is the largest water conservancy project of the construction of our country ever,is an important backbone project for the Yangtze river management and development.It is given priority to with flood control,power generation,shipping,water supply,with morethings multiple functions.Influenced by the three gorges project,the three gorges reservoir area population,economic,and obtained the rapid development of city,but also produced a series of problems of water environment.The main research on heavy metals pollution of the sediments in the three gorges reservoir during its operating period with low water level after the completion of the three gorges project implement "winter storage summer drainage" of seasonal artificial water level control management conditions.In order to investigate concentration,spatial distribution,chemical speciation,source analysis,pollution level of the heavy metals in sediments of the main stream and tributaries in the Three Gorges Reservoir?chongqing-yichang section?with a low water running stage.The 67 sediment samples were collected and tested by ICP-MS in the scope of the study area In June 2015 to measure content and form,,and assessed by using index of geoaccumulation and Hakanson ecological risk index method.Using the statistical analysis software SPSS,matlab to analyze space distribution,geometrical shape,source of heavy metals analysis.The results show that:?1?The study in the three gorges reservoir area?chongqing-yichang section?of heavy metal elements in sediments including :Cr,Ni,Cu,Zn,As,Cd,Pb,Hg,the average content is103.2 mg·kg^-1?42.8mg·kg^-1,58.8mg·kg^-1,148.5mg·kg^-1,12.3mg·kg^-1,0.90mg·kg^-1,53.1mg·kg^-1,0.123mg·kg^-1,slightly higher than it in sediment background of the Yangtze river.?2?The heavy metal content of sediments of the main stream along the trend basically has the following three situations: 1)present the obviously increasing trend,the main representative elements are: Ni,Cu,As,2)source content is higher,first increases,then decreases trend,the main representative elements are Zn,Cd,Pb,Hg,3)present the not obvious increasing trend,in some special place is extremum,representative elements: Cr.The same heavy metal of the sediment of the main stream and tributaries in tributary inlet is found that the heavy metal content of wujiang river and quxil river of the upstream section?jiangbei-fengdu?is generally greater than the main stream,the opposite happens in the middle and downstream section.?3?Using Pearson correlation analysis and principal component analysis?pca?to the pollution source of heavy metals in the sediments of the three gorges reservoir analysis found that: the natural factors dominate Ni,Cu,Zn,Pb elements content increase;Industrial pollution is mainly dominated sources of Cd,Hg;Cr element is derived from the specific industry pollution sources.?4?Using index of geoaccumulation and Hakanson ecological risk index method,the results showed that: 1)in the main stream: Cd element in the main river upstream and downstream section has reached the medium pollution level;Pb element in light pollution level;Cu and Zn elements easily by accumulating in the downstream produce light pollution.The rest of the Cr,As,Ni elements in addition to a section polluting rare,less harm to ecological environment As a whole.2)Present the mild ecological hazard of the tributary,the heavy metal in sediment in the weak ecological environment harm.But quxi river,daning river ecological damage has a tendency to increase.The Cd element pollution should be taken seriously.?5?Cr,Ni elements in surface sediment forms mainly residual fraction?accounted for more than 75% of the total?;Cu and Zn elements are mainly composed of residual and reducible fraction?total amount 80 95%?;Cd elements mainly is given priority to acid extractable and reducible fraction?respectively 55% and 23% of the total?;Pb element exist mainly to reducible residual fraction.Cd and Pb element bioavailable content is higher,than the element of the Yangtze river sediment background value;This form of heavy metal element easily into the water,and when the geochemical condition changes into form,which can be biological absorption and utilization of biological cause greater harm The upper Yangtze river?the main urban area of chongqing?and downstream river,quxi river,daning river,moda river,yandu river should be the key area of research and prevention and control of ecological harm of heavy metals.