Research On Joint Toxicity Control Of Heavy Metals To Photobacteriumr Phosphoreum

Firstly, taking6heavy metal binary systems Cu-Cd, Cu-Pb, Cu-Zn, Cu-Cr, Cu-Ni and Cu-Co as research objects, the impacts of physicochemical properties and concentration ratio of heavy metals on joint toxicity to photobacterium phosphoreum were researched. And on this basis, taking heavy metal binary system Cu-Pb as research object, and selecting3inorganic ions K, Ca and Mg and2organic acids oxalic acid (OA) and tartaric acid (TA), the impacts of the5foreign chemical substances and their interactions on joint toxicity for heavy metal binary system Cu-Pb were researched.For each kind of heavy metal binary system, Cu was fixed concentration of0.1,0.3,0.5,0.7and0.9times as much as EC50for Cu existing alone to photobacterium phosphoreum, in turn. Thus heavy metal binary systems of different kinds and diffenrent concentration ratios were30sets. EC50for each set of heavy metal binary system to photobacterium phosphoreum was calculated through photobacterium phosphoreum toxicity test. Then joint toxicity for each set of heavy metal binary system was evaluated by Toxic Unit, Additive Index and Mixture Toxicity Index, respectively. The results show joint toxicity of different kinds of heavy metal binary system is different, joint toxicity of different concentration ratios for same kind of heavy metal binary system is different, and different evaluation methods can also cause different joint toxicity of heavy metal binary systems.QICAR model reflecting quantitative relation between metal ion properties and biological activity was introduced. Joint toxicity of heavy metal binary systems was analyzed from the aspect of physicochemical properties of heavy metals. It is found there are some correlations between metal ion properties and inhibition ratio for heavy metal binary system to photobacterium phosphoreum, showing that joint toxicity of heavy metal binary systems to photobacterium phosphoreum can be predicted by QICAR model.5foreign chemical substances K, Ca, Mg, OA and TA were doped into heavy metal binary system Cu-Pb at the same time by means of factorial design. Multiple linear regression models with concentration of the5foreign chemical substances and their interactions and inhibition ratio for the heavy metal binary system to photobacterium phosphoreum was built. Based on analysis of the model, we find all the5foreign chemical substances can reduce joint toxicity of the heavy metal binary system. Through mechanism analysis, it is believed the effective concentration of Cu and Pb to photobacterium phosphoreum was reduced due to the competition of the5foreign chemical substances with Cu and Pb for adsorption site of photobacterium phosphoreum, or the combination of the5foreign chemical substances and Cu and Pb. Thus the concentration ratio of the heavy metal binary system was changed, and the synergistic effect of the heavy metal binary system was weakened. In addition, for the interaction of the5foreign chemical substances, Ca*Mg, Ca*OA, K*Ca*Mg*OA and K*Ca*OA*TA have significant impact on joint toxicity of the heavy metal binary system. Ca*Mg and Ca*OA inhibited the joint toxicity, while K*Ca*Mg*OA and K*Ca*OA*TA brought synergistic effect on the joint toxicity. It is shown that the doping of foreign chemical substances can effectively reduce joint toxicity of heavy metal binary systems. Proper doping of foreign chemical substances can be used as a way to control joint toxicity of heavy metal binary systems.