DNA Damage And Effect On Soil Microbial Diversity Induced By Chlorpyrifos And TCP

Chlorpyrifos is a broad-spectrum organophosphorus insecticide (O,O-diethyl-O-3,5,6-trichloro-2-pyridyl phosphorothioate) with numerous agricultural crop and urban pest control uses.In nowadays,chlorpyrifos is world-widely used as a substitute for some highly toxic pesticides,such as methamidophos and methyl parathion.During recent years,many countries have recognized the hazards of chlorpyrifos and gradually restrict or ban the use of chlorpyrifos.However,chlorpyrifos continues to be one of the most commonly used organophosphorus insecticides.The primary metabolites of chlorpyrifos is 3,5,6-trichloro pyridine-2-phenol(TCP),leading to the existence of a certain amount of this harmful substance in the environment. Due to its strong water-solubility and mobility,the residue of TCP in the soil and water,resulting in the large environment pollution and the harm to living things.The aim of this study was to get more comprehensive understanding on the effects of chlorpyrifos and its metabolites TCP,and information about the potential ecological risk of this pesticides on the soil ecosystem.The results could be summarized as follows:1.Micronucleus test:The roots of Vicia faba were treated separately with different solutions(chlorpyrifos:0,01,0.1,1.0,10.0 mg·L^-1,TCP 0.01,0.1,1.0, 5.0 mg·L^-1).Tissues were collected at the 12,24,36 and 48h of treatment process.The micronucleus rate of Vicia faba root tip cells induced by chlorpyrifos and TCP were studied.The results showed that:chlorpyrifos and TCP can induce Vicia faba root tip cells produce micronuclei,indicating that a certain extent genetic damage on Vicia faba root tip cells could be caused by this two substances;by comparing the micronucleus rate,we know that the primary metabolites(TCP) was greater genotoxicity on Vicia faba than chlorpyrifos.2.The single-cell gel electrophoresis test:Earthworms were exposed with chlorpyrifos concentrations of 0.01,1.0,10.0 mg·kg^-1,TCP concentrations of 0.01,0.1,1.0,5.0 mg·kg^-1 in separate artificial soil.Tissues were collected on the 7^th,14^th,21^st and 28^th days of treatment process.The results showed that: chlorpyrifos and TCP both introduced DNA damage on earthworms,DNA fragmentation showed a dose-response relationship,and significant differences were found compared to the controls;by comparing the DNA damage induced by the same treatment under the conditions of chlorpyrifos and TCP on the earthworm cells,we can see that TCP was more serious.3.The denaturing gradient gel electrophoresis test:DGGE method was applied to determine the relative genetic complexity of microbial communities in soil treated with chlorpyrifos and TCP.The result showed that there are a certain effect on bacterial communities diversity in soils treated with different concentrations of chlorpyrifos and TCP.High concerntration of chlorpyrifos (10.0mg·kg^-1)and TCP(5.0mg·kg^-1) had a significant effect on microbial diversity for a relatively short time.