The Aquatic Toxicity And Microbial Degradation Of Tetramethrin

During the past few decades, pyrethroids have become one of themain families of modern pesticides, because of their unique advantagesincluding high efficiency, low toxicity and broad spectrum. They take about30%market in world by widespread application in agricultural and urbanenvironment. Pyrethroid pesticides can enter into the aquatic environmentvia runoff facilitated primarily by sediment movement, which brings aseries of pollution. As a kind of chiral pesticides, its enantioselectivity intoxicity have caused more and more extensive attention. There are manystudies on the acute toxicity of pyrethroids now, and a few is about the fishembryonic development and endocrine disturbance. However, the study ofenantioselective effects on the immune system and endocrine system of fishspecies have only got limited attention. In this paper, we chose zebrafish asthe model organism, discussed the aquatic toxicity to zebrafish embryo，then on the basis of the research in chiral separation, the enantioselectivityof trans-tetramethrin(trans-Tet) was studied. It suggested that in the lowconcentration range (0.5-2.0mg/L), Tet could promote the haching ofzebrafish embryo at lower concentration, with the increasing concentrationsof Tet, the process would be hindered. Tet could also lead to morphologicalabnormalities of zebrafish embryo. In48h, yolk sac edema(YSE) was the main toxic end point, until72h more end points like pericardial edema(PE)and crooked body(CB) were observed. Then, a high-performance liquidchromatography method is presented for the enantioseparation oftetramethrin. A pair of trans-Tet enantiomers were achieved on ChiralpakAD using a mobile phase consisting of a mixture of n-hexane/ethanol (95:5,v/v). After that the toxicity differences between trans-Tet enantiomers werestudied. The results of acute toxicity assays indicated that trans-(+)-Tet wasmore toxic to zebrafish embryo than trans-(-)-Tet. In addition, trans-Tetand its enantiomers may promote the expression of immune genes ofzebrafish embryo, but inhibit the expression of endocrine genes. Thesignificant analysis showed a significant enantioselectivity at high exposureconcentration between the two trans-Tet enantiomers. By consideration ofthe high toxicity of Tet, it has very important to find a method to reduce itsenvironmental conentration. As a result, a Tet-degrading bacterium wasisolated, and identified as Ancylobacter sp. based on the analysis of16SrDNA gene. After7d, the degradation rate of50mg/L Tet was54%.