Toxic Effect Study Of Copper、Lead、Zinc On Daphnia Magna

Today, with the rapid economic development, environmental pollution has beenaggravated, especially the heavy metal pollution in the water environment which isthe most harmful one both to the environment and to human being. Not only can theheavy metal pollution in the water environment result in great economic loss, it canalso severely threaten the survival and health of various beings including human being,thus worthy of reflection.Taking the Daphnia magna as the experimental animal and the heavy metal Cu,Pb and Zn as the experimental poison, the present study, by way of static exposure,investigated the effect of three heavy metals on the Daphnia magna’s single toxicity,joint toxicity and its antioxidant system under the combined exposure mode, whichaccumulates the basic data for the scientific evaluation of heavy metal pollution inaquatic ecological environment.The experimental result of the effect of Cu²⁺, Pb²⁺and Zn²⁺on the Daphniamagna’s single toxicity indicates that the toxicity degree to the Daphnia magnadiffers from different poisons, with number0.123mg/L,2.392mg/L and4.084mg/Lrespectively to its24hLC₅₀,0.108mg/L,1.912mg/L and3.628mg/L respectively to its24hEC₅₀,0.102mg/L,1.136mg/L and2.732mg/L respectively to its48hLC₅₀and0.098mg/L、0.953mg/L and2.504mg/L respectively to its48h EC₅₀.Judging from this,it is clear that the toxicity degree to the Daphnia magna of the three heavy metals arein the following order: Cu²⁺>Pb²⁺>Zn²⁺.In the experiment exploring the effect of Cu²⁺, Pb²⁺and Zn²⁺on the Daphniamagna’s joint toxicity, aquatic toxicology combined effects and Marking’s additiveindex were adopted. And two ways of mixture, i.e. the toxicity rate1:1andconcentration rate1:1were carried out to experiment in pairs and all at the same time.This experimental results shows that the joint toxicity of the three groups i.e.Cu²⁺-Zn²⁺, Cu²⁺-Pb²⁺and Cu²⁺-Pb²⁺-Zn²⁺all assume the synergistic effect, despite thetoxicity rate1:1and concentration rate1:1. While the joint toxicity of Pb²⁺-Zn²⁺assumes the antagonistic effect, which is only correlated to poison combinationinstead of poison proportioning and exposure time.In addition, the experiment investigating the effect on Daphnia magna’s antioxidant system under the combined exposure mode of the three heavy metalsmainly explored the impact on the activity of SOD and CAT. The results reveal thatthe joint toxicity of Cu²⁺, Pb²⁺and Zn²⁺all significantly affect the SOD and CATwithin the Daphnia magna. Besides, with exposure density and exposure timechanging, both SOD and CAT can be activated or suppressed in varying degrees. Thusthe activity change of the SOD and CAT within the Daphnia magna can be taken assensitive index to monitor and assess the heavy metal ion pollution in the waterenvironment.