Study On The Selective Enrichment Behavior Of Chiral Pesticide Toxic Fluoride And Phosphorus In Aquatic Animal Earthworms

In this study,acute and subchronic toxicity experiments of dufulin to aquatic animal tubifex were conducted in two different culture conditions of spiked water and spiked soil.In this study,tubifex was used as an environmental carrier,and chiral pesticide dufulin was the research object.The stereoselectivity of the accumulation of chiral pesticide dufulin in tubifex and its degradation and distribution in soil and upper water were studied at the level of enantiomers.Research results are as follows:(1)The medium concentration and culture time for spiked water and spiked soil exposure experiments were evaluated by determining the toxic effects of rac-dufulin and enantiomers on tubifex.The toxicity of rac-dufulin and enantiomers on tubifex was low.Compared with enantiomers,raceme showed a certain degree of antagonism on the toxicity of the organism and was less toxic to tubifex.The order of toxicity was rac-dufulin<R-dufulin=S-dufulin.On the basis of the tolerance of tubifex in different concentrations of exposure media and exposure times,the medium concentration and culture time were determined through exposure experiments.In the spiked water exposure experiments,the high and low rac-dufulin doses were 10 and 1 mg/L,respectively,and the high and low enantiomeric doses were 5 and 0.5 mg/L,respectively;the exposure time was 14 days.In the spiked soil experiments,the high and low doses of rac-dufulin were 50 and 5 mg/kg,respectively,and the enantiomeric doses were 25 and 2.5 mg/kg,respectively;the exposure time was 21 days.(2)A simple and efficient method for the extraction,purification,and detection of rac-dufulin and its enantiomers in tubifex,soil,and water samples was established.Through high-speed homogenate,vortex,and ultrasound methods,dufulin remained in tubifex and soil samples extracted using ethyl acetate.Dufulin in the water sample was extracted with dichloromethane and saturated brine,and all the samples were detected by high-performance liquid chromatography(HPLC).The accuracy and precision of the method were also investigated.The results showed that the recoveries of rac-dufulin enantiomers in tubifex,soil,and upper water were between 72.98% and 103.19%,and the recoveries of dufulin enantiomers in the three samples were between 77.56% and 101.23%.Meanwhile,the RSD values were less than 10%,which satisfied the requirements of pesticide residue analysis and were suitable for the accurate determination of dufulin in tubifex,soil,and water samples.(3)Spiked water and spiked soil exposure experiments were conducted on tubifex.Tubifex demonstrated a selective enrichment effect by rac-dufulin in spiked water(no soil)and spiked soil experiments,and the enrichment effect in the spiked soil experiment was significantly higher than that in the spiked water experiment.The selective enrichment directions of tubifex to dufulin were the same in the two experimental groups treated by rac-dufulin,thereby showing that the concentration of R-dufulin in tubifex was significantly higher than that of S-dufulin.However,when the exposure experiments were treated by R(S)enantiomer,tubifex had no apparent selectivity for the enrichment of dufulin.The exposure contrast experiments at different dose levels revealed a dose-effect relationship between the concentration of dufulin in tubifex and the concentration of culture medium.With the increase in the concentration of the medium,the enrichment of dufulin in tubifex also increased.(4)The influence of tubifex on the stereoselective environmental behavior of dufulin in the degradation and distribution of soil and upper water was investigated.The results showed that the presence of tubifex could accelerate the degradation of dufulin in soil,and no obvious enantioselectivity was observed for the degradation of dufulin enantiomers in the treated and controlled soils.The existence of tubifex could accelerate the repair process of the underlying solid matrix contamination,which could help convert dufulin in the adsorption state to the dissolved state,thereby accelerating the transfer of dufulin in the water environment.