Analyses And Investigation On Heavy Metal Contamination In Sediment Of Xiangjiang River Section Flowing Through Changsha, Zhuzhou, Xiangtan

This passage sets the sediment of Changsha-Zhuzhou-Xiangtan section of Xiangjiang River as the research object, and carries out the heavy metal element pollution research. Nineteen representative samples of ten cross-sections are selected from upriver to downriver and the concentration of heavy metals including Cr Mn Ni Cu Zn Pb and Cd are evaluated . The methods of Index of Geoaccumulation , Sediment Quality Guidelines and Potential ecological risk evaluation are applied to evaluate the heavy metal element contamination of superficial sediment in Xiangjiang River.First of all, the article analyzes the changes of heavy metals in sediment along river as well as its existing patterns . The changes of the contamination of different heavy metals in sediment of Xiangjiang River appears vary .The contamination of Mn along the river changes a lot ,which is serrated . Six other metal content doesn't change greatly . The contamination of Cu Pb Cd and Zn is in downward trend roughly . This shows that the industrial wastewater pollution of Xiawan of Zhuzhou is the main source of heavy metals-Cu, Pb, Cd and Zn in sediment of Changsha- Zhuzhou-Xiangtan section. With self-purification , the density of heavy metals is gradually reduced . The contamination of heavy metals- Cr and Ni is showing up and down distribution along the river . Among all the samples , the pollution of Xiawan, the Third Bridge of Xiangtan and the Southern Bridge of Changsha is very serious . Most of the heavy metal elements here are showing various degree of high-value. Comparing with the background value of the main stream of Yangtze River, the contamination of Zn Pb and Cd in sediments of Changsha-Zhuzhou-Xiangtan section is far beyond the maximum value . This indicates the pollution of these three elements is already rather serious .Correlation analysis of heavy metals shows that Cd,Pb,Cu and Zn are in a significant correlation .The pollution discharge of plants along the river bank may be their common source of pollution . The relevance of organic and heavy metal elements reaches an outstanding level, which shows that organic and clay minerals in sediment play an important role in the distribution and concentration of heavy metals .The results of Morphological analysis shows that Cr and Ni in seven heavy metal elements mainly exist in a residue state, thus the environmental impact isn't very great. The bound state of iron-manganese oxide in Mn,Cu and Pb is relatively high , which is a threat to the surrounding ecosystem . Although Zn and Cd mainly exist in a residue state, the acid-soluble state is also taking up a considerable proportion , thus the potential ecological harm can not be ignored.On this basis, three methods are applied to evaluate the pollution of heavy metals in sediment . The results are basically the same . The Index of Geoaccumulation of the heavy metal elements in superficial sediment of Changsha-Zhuzhou-Xiangtan section is roughly in this order: Cd (very strong)>Zn(moderate-strong)>Pb (moderate-strong) > Mn(moderate) >Cu(light-moderate) >Ni(light) >Cr(light) .On the whole , the pollution is moderate. To evaluate according to the Quality Guidelines, the harmful effect on ecology of Zn Cd and Pb in each cross-section is relatively great .The pollution order is :Zn>Cd>Pb>Ni>Cu>Cr, which reaches an average-high level in ecological harm. The Potential Ecological Risk Evaluation shows that the ecological harm of heavy metals in sediment of Changsha-Zhuzhou-Xiangtan section of Xiangjiang River is very strong on the whole , Cd is the main factor in this part , followed by Pb. Combined with the regional geology background and man-made activities , the area discussed above has already been contaminated by heavy metals–Cd,Pb and Zn in particular.Through the research of the plant in the polluted soil of Mn mine in Xiangtan, we find that several plants including Phytolacca esculenta VAN HOUTTE,Poa pratensts,Cudweed,Ditch reed,Comnyza Canadensis (L.) Cronqs and so on have strong tolerance and concentration ability for the heavy metals. It provides reference for the comprehensive management and restoration of polluted rivers as well as the vegetation of sediment buried plants . Hence, it possesses value to go on the research. Finally, the comprehensive management of contaminated river and the resorting measures of plants in sediment are discussed initially.