Combined Toxicity of Copper, Cadmium and Lead Toward Daphnia magna: Recommendation for Bioassay-Based Whole Effluent Toxicity (WET) Testing in China

Metals cause popular attention worldwide due to their non-degradability and universal distribution in the aquatic ecosystem. In this study, the single, binary, and ternary combined toxicity of copper, cadmium, and lead toward survival rate of Daphnia magna were investigated based on different level fixed equivalenteffect concentration ratios. Furthermore, the combined toxicity was predicted by concentration addition and independent action models based on an established concentration-response relationship of a single toxicant and compared with the experimental data. The results indicated both binary and ternary mixture of the three metals had a strongly synergistic effect (EC50mix<1 TU) on the survival of Daphnia magna in all designed mixture ratios, which is meaning that there may be potential risks even when the single toxicant meets the discharged standards just based on chemical analysis. So, it is suggested that biological testing of whole effluents toxicity based on aquatic organisms should be applied in environment and risk management in China.