Evaluation Of Heavy Metal Combined Biotoxicity By Zebrafish Embryonic Developmental Toxicity Test

With the rapid development of industry and agriculture, heavy metal emissions has inrreased year by year, and different kinds of heavy metal pollution events occurred frequently. The heavy metal pollution has become a global problem and has caused more and more extensive concern of the public. O n the basis of physical and chemical analysis, researchers investigated the biological toxicity and the ecological risk assessment of heavy metal pollution constantly. In view of the huge number and multifarious combinations of heavy metal pollution, single heavy metal pollution detection cannot be well applied in environmental pollution monitoring, so we need to evaluate the biological toxicity of mixed system of heavy metals.This study selected 5 kind of heavy metals as the research objec ts, used the zebrafish embryo developmental toxicity test as the technical means to investigate and evaluate the single and binary mixtures’ biological toxicity. The main conclusions are as follows:（1） The single biological toxicity of heavy metals. The result showed that: The acute and developmental toxicity on zebrafish embryos have big differences between different heavy metals. Zebrafish embryos in the process of the test showed different toxic effects, one of the most sensitive toxicity endpoint is the 72 h incubation inhibition rate. With zebrafish embryo 24 h- LC50 value as reference, 5 kinds of heavy metals’ biological toxicity in the high dose exposure test of zebrafish embryos from big to small in the order: Cu²⁺>Pb²⁺>Cr⁶⁺>Cd²⁺>Zn²⁺. Zebrafish embryos were sensitive to C u²⁺ and Cd²⁺ and could provide biological early warning for C u²⁺ and Cd²⁺ pollution.（2） Heavy metal binary mixture system joint toxicity study. The mixture of C u²⁺ with Pb²⁺ or Cr⁶⁺ showed the antagonism effect; C u²⁺ /Cd²⁺ mixture showed the synergies; low concentration of C u²⁺ had antagonist effect on Zn²⁺ toxicity, while high concentration mixture performed as synergies. The interactions of Zn²⁺ with other heavy metals were more complicated: with the increase of Zn²⁺ concentration, the Zn²⁺/Cd²⁺ mixed system performed as antagonism on zebrafish embryos incubation inhibition toxicity; while with the increase of Zn²⁺ concentration, the Zn²⁺/Cr⁶⁺ mixture’s joint effect on zebrafish embryos gradually translated from antagonism to synergies. The joint action of binary mixture of Pb²⁺ with C u²⁺, Zn²⁺, Cd²⁺ or Cr⁶⁺ performed as antagonistic effect. Due to its influence on cell membrane permeability, most combined effects of mixture of Cd²⁺ with other heavy metals were synergy.（3） Binary mixed system joint toxicity evaluation. The results showed that: because of different metals had different toxic effect mechanisms and each component’s toxicity intensity would change as the extension of infected time, thus different heavy metals mixed systems had various biological toxicity on zebrafish embryos. Under different proportion the same components also had different toxic effects. The aquatic toxicology combined effect additive index method could be effective on evaluation of heavy metals joint toxicity while there also had many deficiencies. So we need more thorough evaluation method to assess the combined effect of pollutants hybrid system.