Investigation On The Relationship Between Critical Body Residue And Toxicological Kinetics Of Nitrobenzenes In Zebrafish

With the production of a large number of organic compounds,more and more organic pollutants have been discharged into the aquatic environment,which has caused many environmental pollution problems.The mechanism,transformation and ecological toxicological effects of organic pollutants in natural water play important roles in the risk evaluation in the environment.In order to evaluate the ecological risk of nitrobenzene compounds to aquatic organisms,the relationships between toxicological kinetics or critical body residue and bioconcentration factors of nitrobenzene compounds were studied by determining the acute toxicity and critical body concentration of five nitrobenzenes in fish.The results of the study are not only helpful in determining the ecological toxicity of organic pollutants more accurately,but also helpful to deeply analyze the toxic mechanism of nitrobenzene compounds to zebrafish.In this study,the acute toxicities and critical body residues of five nitrobenzenes to zebrafish were determined by experiments.The toxic effects of these five compounds were evaluated by the toxic ratio.The relationships between the critical body residue and the bioconcentration factor or hydrophobicity were investigated.The toxic mechanism of nitrobenzene compounds to zebrafish was discussed.The obtained results are listed as following:(1)The acute toxicity of five nitrobenzene compounds to zebrafish were determined by experiments.The excess toxicity was calculated by the toxic ratio.The mode of toxic action of nitrobenzene compounds to zebrafish was evaluated.The results show that p-nitrophenol and o-nitroaniline are reactive compounds,and o-nitrotoluene,p-nitrotoluene and o-nitrophenol are narcotic compounds.(2)Investigation of the relationship between the estimated critical body residue and the observed critical body residue shows that the measured critical body residue differs from the predicted values due to the ionization of the compounds,the metabolism in the body and the loss in the experimental process.The narcotic compounds,such as o-nitrotoluene,p-nitrotoluene,o-nitrophenol,have high CBR values.There toxic effects mainly depend on the bioconcentration factor.The reactive compounds such as p-nitrophenol and o-nitroaniline,have low CBR values.The toxicity of these two compounds is not only related to the bioconcentration factor,but also related to the reactivity of the compounds.The toxic effects of the nitrobenzene compounds were different because of the difference in the toxic action,resulting in a significant difference in the critical body residue of the compounds in the organism.(3)The relationships between the concentration and time of the five compounds in zebrafish was investigated by the ten days toxicological experiment.The calculated toxicological rate constants calculated showed that the concentrations of nitrobenzene compounds in zebrafish increased significantly in the first 48 hours,and reached the equilibrium state in zebrafish after 48 hours.The elimination rate constants and the half-lives of the five nitrobenzene compounds in zebrafish were compared with that of trinitrotoluene(TNT)in Cyprinodon variegatus and Mytilus galloprovincialis obtained from the literature.The results showed that the elimination rates of nitrobenzene compounds in fish were similar,but the elimination rates in shellfish were very different.The reason for this difference could be due to the different biotransformation and metabolism of different species.