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Sediment heavy metal pollutants repository in both the potential to have an impact on the environment of heavy metals pollution sources of heavy metals in water particles with water migration from the end-result and deposited in the sediments. Under appropriate conditions, the toxic heavy metals from sediments to water again released, through a variety of ways to form secondary pollution. This study selected China's five largest freshwater lakes (Poyang Lake, Dongting Lake, Taihu Lake, Chaohu Lake) for the study to six heavy metals (Cu, Cd, Pb, Zn, Ni, Cr) in lake sediments total as the main research content and occurrence of morphological characteristics, use of the potential ecological risk index, and cumulative index method and AVS-SEM method three methods to evaluate heavy metal pollution in the five lake sediments. The results are as follows: (1) heavy metal pollution in the Poyang Lake sediments takes the shape of a large southern and northern low trend, the Raohe the Hukou nearby sediments heavy metals pollution is the most serious, followed by Poyang Lake estuary near. The five major river systems in the south have a greater impact on distribution of heavy metals in the sediment. Cu, Ni, Pb, Cr, mainly in the residual fraction, followed by the Fe / Mn oxide bound; Zn in the residual fraction, followed by the exchangeable fraction and carbonate bound; Cd Most exchangeable state and carbonate-bound form of existence. (2) to the East Dongting downstream antlers the Chenglingji segment is the most polluted area of ??Dongting Lake, the 20th overall of the most polluted. The trend of Cu, Ni, Zn, Pb content of each Sub-Lake sediments are: East Dongting Lake gt; the Chenglingji gt; South Dongting Lake gt; West Dongting Lake; Cr, Cd content trend compared: East Dongting Lake gt; Chenglingji gt; West Dongting Lake gt; South Dongting Lake. The main form of Cu, Ni, Zn, Pb, Cr are the residual fraction, three can be extracted form, Cu exchangeable fraction and carbonate, organic matter and sulfide bound form exists; Ni three more uniform effective kinds of morphological proportion; major form of Zn in the exchangeable fraction and carbonate-bound, followed by the Fe / Mn oxide bound; Fe / Mn oxide fraction is the main form of Pb; Cr organics and sulfide was bound mainly; the Cd form is exchangeable fraction and carbonate-bound. (3) Meiliang Bay in northern Lake Gonghu Zhushan Bay is a heavy metal pollution in the most polluted area in the sediments of Taihu Lake, Xu bays and lake areas are relatively less polluted. The whole lake Ni, Pb, Cd pollution heavier, Cr contamination is relatively light. Zn, Cr mainly in the residual fraction, you can exchange the state and is bound to carbonate, the largest proportion of Cd, Cu, Pb, followed by; Pb Fe / Mn oxide bound proportion (about 40%), Cu, Ni, Zn, of Cd proportion is small; various metal organics and sulfide bound very small proportion. (4) Hongze Cu, Ni, Zn, Pb Cr pollution mainly distributed in the eastern and northern part of the Lake District, Cd pollution in the western Lake District. Pb is the most polluting heavy metals in the whole lake. Cu, Ni, Zn, Pb, \Exchangeable fraction and carbonate in the form of three extracted Cu bound to organic matter and sulfide bound form exists; Ni major form of organic matter and sulfide bound more uniform, the other two forms of proportion; Zn Fe / Mn oxide bound mainly followed the exchangeable fraction and carbonate-bound; Fe / Mn oxide bound is the main form of Pb; mainly Cr bound to organic matter and sulfides. Cd main form of exchangeable fraction and carbonate-bound. (5) Chaohu western Lake District's most polluted. The whole lake Cu, Ni pollution lighter; western Lake District Zn, Pb significant enrichment; between points Cr content changes; Central Lake District Cd content belonging to a soil environmental quality standard. Cu, Ni, Pb, Cr, mainly in the residual fraction, followed by Fe / Mn oxide bound exchangeable fraction and carbonate-bound organics and sulfide proportion of state rarely; Zn mainly in residual state, followed by the exchangeable fraction and carbonate-bound. Cd vast majority of the exchangeable fraction and carbonate-bound form of existence, followed by the Fe / Mn oxide bound. (6) the use of the potential ecological risk index method found: five major lakes, Cu, Ni, Zn, Pb, potential ecological hazards of Cr are small (low-risk), the potential ecological risk of Cd, Cd of the total potential ecological hazards The index of the largest contribution. Use cumulative index method to come: the five lakes Cd accumulation index than other metals, pollution is more serious, and other metals have different degrees of pollution (light pollution). The five largest lakes only Poyang Lake into the estuary at the heavy metal bioavailability may cause adverse effects on aquatic organisms and humans, Bioavailability of heavy metals in the rest of the lakes in the regional sediment benthos.
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