Study On Selective Enantiomeric Toxicology Of Two Chiral Pesticides Of Pyrethroids On Daphnia Magna

There are enantioselective differences in environmental behavior of chiral pesticides,which are common in the environment and living organisms.Because of the enantiomers of chiral pesticides may degrade at different rates in the environment,enantiomeric ratio that causes them in the environment is likely to deviate from 1:1,the toxic effects will also be completely different from the toxic effects at 1:1.In this paper,two kinds of pyrethroid chiral pesticides,lambda-cyhalothrin(LCT)and permethrin(PM),were selected.Two enantiomers of LCT and four enantiomers of PM were prepared by HPLC.Using Daphnia magna as the test organism,the toxicity difference between the two enantiomers of LCT was revealed by exploring the 48 h acute toxicity,14 d chronic toxicity and 48 h oxidative stress on Daphnia magna.The joint toxicity of different proportions of LCT enantiomers and PM enantiomers was investigated to predict and evaluate the combined toxicity effects of enantiomers.This provides data support for the comprehensive assessment of the selective differences in toxicity and interference effects of chiral pyrethroid pesticide residues on ecosystems.The experimental results show that:(1)The toxicity order of LCT to Daphnia magna is:(+)-LCT > Rac-LCT >(-)-LCT.As the proportion of(-)-LCT increased,the joint toxicity of(+)-LCT and(-)-LCT to Daphnia magna may changed;The IA model is more suitable for predicting(+)-LCT and(-)-LCT mixtures.(2)The internal rate of growth is an indicator of LCT and its enantiomers is thebest sensitivity to 14 d chronic toxicity on Daphnia magna.3 ng/L(+)-LCT and900 ng/L(-)-LCT cause negative growth in the Daphnia magna population.(3)(-)-LCT will produce oxidative stress on large fleas;The influence of Rac-LCT on Daphnia magna gradually exceeded the degree of oxidative stress,and at high concentrations it began to cause body damage to Daphnia Magna.The effect of(+)-LCT on Daphnia magna far exceeds the scope of oxidative damage,resulting in obvious body damage.(4)When PM enantiomers are separated by HPLC,as the proportion of ethanol in the flow phase increased the peak time of the four peaks of PM decreases,and the four enantiomers gradually get a good baseline separation.(5)The 48 h acute toxicity of PM and its four enantiomers to Daphnia magna is:(-)-cis-PM >(-)-trans-PM > Rac-PM >(+)-cis-PM >(+)-trans-PM;the IA model is the better predict model that predict the joint toxicity of PM enantiomers.