Research On Joint Toxicity Of Heavy Metal Chromium On Chlorella And Photobacterium

Human activity, mining emissions, waste water irrigation and heavy metal products, have lead to increasingly serious heavy metals pollution in the environment. Its pollution and influence appear more and more prominent, especially heavy metal pollution is very serious and the situation is very severe to the environment. The toxic study of the algae (primary producers of the ecosystem) and Inminescent bacteria caused by heavy metal will provide a theoretical basis for the development preventive measures of the management and have important reference value of both in heavy metal emissions and treatment.In this research, the acute toxic effects of chromium (Cr6+ and Cr3+ ) on marine plankton were studied by using the standard method. The inhibition rate on Chlorella obtained through experiments and the relationship between the concentration and the toxic response can be described with Generalized Logitâ…¡function model. And then the EC50 values of Cr6+ on Chlorella p 96 h of 27.54 mg/L and Cr3+ on Chlorella p 96 h of 15.67 mg/L were obtained through this function. At the same time, it can be concluded that the low concentration of two kinds of compounds to Chlorella were promoted the growth and both of the two EC50 values were accorded to the law that the value was more and more prolonged over time.Potassium dichromate and chromium chloride hexahydrate were used on independent toxicity and joint toxicity with Photobacterium in this thesis. The research showed that the relationship between the Cr6+ and Cr3+ concentration and the toxic response can be described with Generalized Logitâ…¡and BoxCoxLogit function model. By applying these models, the calculated EC50 values of these two substances were 7.907 mg/L for Cr6+ and 12.162 mg/L for Cr3+. The Cr6+ and Cr3+ concentrations of the typical inhibition can be calculated by the same way. Generalized Logitâ…¡and BoxCoxLogit function model can describe the relationship between the concentration of the mixture with different concentrations of mixture ratio for joint toxicity and the toxic response and the fitting effect of Generalized Logitâ…¡function is slightly better than that of BoxCoxLogit function model. For joint toxicity of the two compounds, two evaluation methods were used for joint toxicity assessment. The results showed that Cr6+and Cr3+ in the 1:1 and 4:6 ratio expressed part additivity, in the 6:4 ratio showed antagonism.The results showed that the toxicity of Cr3+ for luminous bacteria was more sensitive than Cr 6+, and the fitting effects of Cr6+ and Cr3+ for luminous bacteria were better than that of Chlorella. On these basis, this research also attempted to use the sample of algae on Inminescent bacteria to make the toxic experiment and the results were compared with the UV spectrophotometry results. It was concluded that the changes of inhibition rate according to the variation of the sample with different concentrations and the feasibility of this method which can be used to determinate concentration was confirmed.