| Xiangjiang River, as the largest river in the Dongting Lake water system, is notonly a major drinking water source，but also a major container for the waste water fromthe cities on shore．Therefore it is taken as a crucial lifeline for the economic andsocial development of Hunan province. During China’s national “10th Five-Year Plan"period, Xiangjiang River valley has got rapid economic development that both itseconomic aggregate and industrial development level came to be top of Hunanprovince. But due to the imperfect industrial structure and regional distributions andthe undeveloped technological level of metallurgy, chemical industries, the rapideconomic development has also raised a lot of serious environmental issues atXiangjiang River valley. One of the issues is the growing frequency and speed that thepoisonous and harmful heavy metal content exceeds the safe standard in some parts ofthe River. And the metal content in certain part have already exceeded the designedassimilative capacity of the environmental function, which is threatening the safety ofdrinking water and the using water in agriculture and industry.According to “The Characteristics of Xiangjiang River heavy metals pollution inwater environment”, Task2of the “Research on target management and monitoringtechniques of heavy metals water quality in Xiangjiang River”, a major science andtechnology item of the “State water pollution control and management technology”under the “11th Five-Year Plan”, this paper takes the water-sediment at“Changsha-Zhuzhou-Xiangtan” section of Xiangjiang River as the objective to makeresearch on the heavy metals pollution.Firstly, the paper analyzes the characters of heavy metals pollution in thewater-sediment system in “Changsha-Zhuzhou-Xiangtan” section of Xiangjiang River.The varying characteristics of heavy metal As、Hg and Cd in water according to timeand space is studied: Annual Change is rainless period> normal-water period> highflow period. Inter annual variation of Hg and As is2006>2005>2007, and Cg is2005>2006>2007. The relation between Hg contents and flow rate is positivecorrelation while that of As is negative. The relation between Cd content and flow rateis positive correlation in2005while negative in2006and2007. The varyingcharacteristics of heavy metals in sediment is that: the longitudinal variation of Aschanges slightly, but most sampling points exceed the standard; One sampling point exceeds the standard for Pb, no exceeding point for Cr; Zn and Hg are erraticallydistributed and have a quite high value at most sampling points. Mn is well-distributedbut higher in value at most sampling points than the standard. Cd is erraticallydistributed of which the maximum value is at the Xiawan section.Secondly, the geo-accumulation index, potential ecological risk index andsediment pollution index were used to assess the pollution level of heavy metals at“Changsha-Zhuzhou-Xiangtan” section of Xiangjiang River. The result is that Cd, Hg,Zn and Pb are serious contamination elements, and the serious contaminatedmonitoring sections are Xiawan, sewage draining exit of Blast furnace plant, lowerreaches of Liuyang River and so on.In addition, chemical formations of the main heavy metals in the key polluted areain surface sediment in Xiangjiang River were studied. The results show that chemicalformations of heavy metal Cd and Zn in surface sediment are mainly compoundscombined by oxidants of Fe and Mn and water and acid soluble phase. The Pb ismainly found in compounds combined by oxidants of Fe and Mn and residual form.The Cu in organic bound and residual form is very great in quantity.Finally, this paper use correlation analysis, cluster analysis, principal componentanalysis (PCA) and positive matrix factorization to apportion the heavy metal sourcesin sediment of Xiangjiang River. Through qualitative analysis by the four methods, thepollution sources are divided into three major types. And in this study, PCA andpositive matrix factorization model was applied to apportion the mass concentrationsof each heavy metal source and its chemical species. |
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