Dianchi Lake Sediment Heavy Metal Release Mechanism Analysis And Influencing Factors

In this paper, Firstly, through the basic data research of the sediment from Dianchi Lake, the pollution characteristics were presented. Mainly with the potential ecological risk indices method and geological cumulative index method, the sediment pollution in current Dianchi Lake was effectively assessed. Secondly, using improved BCR extraction method, four different forms of heavy metals in sediment from Dianchi Lake was extracted and the results can be used to analyze the principles of the release of heavy metals and then the humic acid was extracted (HA) from the sediment of Dianchi Lake. Through adding different concentrations of HA solutions, the impact of HA on the release of heavy metals was analyze. Then, with the use of ray magnetic data acquisition software and the similar method of complexometric titration, combined with the conductivity determination of copper ions in the solution by the copper ion selective electrode, the mechanism of copper ions and HA was analyzed. Finally, using the same method of HA and copper ions, it is easy to get the Cu complexometric data in the sediment from Dianchi Lake.Research results show that:(1) According to the potential ecological pollution evaluation method it could be concluded that Cd was the most serious pollution source while Zn was lightest in the terms of the potential impact of heavy metals in the sediment from the Dianchi Lake on the environment. In the north it was easier to be secondary pollution of heavy metals in the sediment than that in the south. With the geological cumulative index method it was presented that the pollution of Pb and Cd was more serious than Cu and Zn. Combining the two methods it could draw, Cd was the main pollution problem in the sediment from Dianchi Lake while Cu, Zn and Pb pollution was lighter.(2) With the BCR distribution of heavy metals in the sediment from Dianchi Lake, it indicated that the effective form (the other froms except the residual form) decreased from north to south. On the contrary, the residual state gradually increased. The effective form was the main role played in the sediment, which was easy to come about the physical, chemical and biological reaction. And the residue state was stabilized in the sediment. (3) According to the experiment results, it showed that the influence of the changes of HA concentrations on the Pb release was greatest and the content of organic matter in the sediment was high, which were helpful to the Pb release. It was the main problem of Cd pollution in the sediment. Combining the influence of the changes of HA concentrations on the Cd release in the experiments, it indicated that with the increasing concentrations the ability of Cd release was increased. But from north to south the rate of Cd release reduced, which was maybe affected by the properties of sediment and the nature of the HA adopted.(4) The changes of HA concentrations could have a certain influence on the heavy metals. with the increasing concentrations of HA, the release of heavy metals also increased. At the same time, the influence of the changes of HA concentrations on the release of heavy metals varied with the different research points.(5) During the complexation of copper ions and HA of different concentrations, with the increasing concentrations of HA, the complexation quantity of copper ions would increase and the copper ions would be chelating with HA. In the complexation experiments of the sediment and copper ions the complexation quantity was highest in the Caohai center with the high organic matter content, which indicated that with the higher organic matter content the release of heavy metals was lower.With the research results, the space distribution and content distribution of the heavy metals such as Cu Pb Zn Cd in the sediment from the Dianchi Lake was presented, which were served as basis for the evaluation of heavy metal pollution in the sediment from the Dianchi Lake. Meanwhile with the combination of the actual samples of the sediment from the Dianchi Lake and the experiments in the laboratory, the mechanism of the release of heavy metals and the main influence factors were discussed, helpful for the treatment of heavy metal pollution in the sediment from the Dianchi Lake.