Evaluating The Joint Toxicity Of Weak Acidic And Alkaline Organic Contaminants And Heavy Metal Cadmium To Daphnia Magna

The toxicity of Organic and inorganic chemicals to aquatic organisms is an important indicator in the assessment of water quality risk,but environmental pollutants usually occur in the form of mixture,so it is necessary to measure the toxicity of joint contaminants instead of only measuring the toxic effects of a single compound.The single toxicity of heavy metal cadmium and weak acidic and alkaline organic chemicals?11 phenols and 9 aniline compounds?to Daphnia magna were determined respectively.Based on the single toxicity of these contaminants,the joint toxicity of binary mixtures of organic pollutants and heavy metal?cadmium combined with 11 phenols and 9 anilines at different cadmium concentrations of 0.2IC₅0,0.5IC₅0 and 0.8IC₅0?were determined.The joint toxicity was evaluated by Toxic Unit?TU?,Additive Index?AI?and Mixture Toxic Index?MTI?methods.It will be very helpful for us to understand the combined toxicity of these pollutants,and provides a scientific standard for the determination of toxic effects of combined pollutants.The result showed that the single toxicity of Cd was 4.14 of log1/IC₅0?mol/L?.For phenols and anilines,the single toxicity is related to the situation,number and variety of the substituent group.The result of joint toxicity tests showed that the joint toxicity was connected with the concentration of the components.The joint toxicity of the mixture of cadmium and 11 phenols and 9 anilines was increased as the cadmium concentration increased.The joint toxicity of Cd and phenols to Daphnia magna at different combined ratios was mainly simple addition and antagonism.However for the joint toxicity of anilines and Cd,the joint effects mainly showed antagonism,while the additive effects were relatively less.The results of the assessment of joint toxicity using three methods showed that Toxicity Unit?TU?and Additive Index?AI?had good consistency,while Mixing Toxicity Index?MIT?showed some differences with the former two.The reason for this difference may come from the difference of defined range for these three methods.Furthermore,no approximate analysis was applied when using MIT method,and the division of evaluation criteria for this method was also more detailed than the other two.