Acute Toxicity And Oxidative Stress Of Chlorpyrifos And TCP To Earthworm Under Different Soil Types

Chlorpyrifos,as a common organophosphate pesticide,is used on a large scale in agricultural production.However,the large and unreasonable use has led to the continuous accumulation of chlorpyrifos in the environment,which has caused an inevitable threat to the soil ecosystem.Toxicity of chlorpyrifos to earthworms in artificial soil has been reported in studies,but chlorpyrifos is applied to natural soil in actual life,and the physical and chemical properties of natural soils are significantly different from artificial soils.The toxicity of earthworms cannot fully evaluate the effects of chlorpyrifos on earthworms in actual soil environment.TCP is a major degradation product of chlorpyrifos.It has higher solubility in water than chlorpyrifos and has strong mobility in the environment.Because TCP is environmentally toxic,the toxicity of TCP should be considered when evaluating the toxicity of chlorpyrifos.Therefore,this paper studied the toxic effects of chlorpyrifos and TCP on Eisenia fetida in artificial soil and three typical natural soils.In this study,the chlorpyrifos acute toxicity test to earthworms was first performed using the soil method,and the LC₅₀ values were calculated on the 7th and 14th days.Then,the subchronic toxicity of chlorpyrifos and TCP to the earthworm was tested using the soil method.The oxidative stress and oxidative damage in earthworms were measured within 56 days,and the comprehensive chronic biotoxicity index was evaluated using the integrated biomarker index（IBR）.Finally,combined with the physical and chemical properties of the soil,the ecological risks of chlorpyrifos and TCP in different soils were analyzed and evaluated,which provided a scientific basis for guiding chlorpyrifos in practical applications.The main findings are as follows:（1）Acute toxicity:The acute toxicity of chlorpyrifos to Eisenia fetida in four kinds of soils is different.The 14 d LC₅₀ in artificial soil,fluvo-aquic soil,black soil and red clay are:116.8,33.1,233.5 and 27.4 mg kg^-1.It can be seen from LC₅₀ that the acute toxicity of chlorpyrifos to Eisenia fetida in natural soils is quite different from that of artificial soils,and the range is 0.5to 4 times.（2）Active oxygen,antioxidant enzymes,and detoxifying enzymes:Affected by chlorpyrifos and TCP,the ROS content of earthworms showed a significant dose-response relationship,and they tended to increase and then decrease with time.Antioxidant enzymes,after being affected by ROS,were activated at medium and low concentrations(0.01 and 0.1mg kg^-1)and then recovered to control level,while high concentration(chlorpyrifos concentration was 1 mg kg^-1;TCP concentration 0.5 mg kg^-1)is first activated and then inhibited.Affected by chlorpyrifos and TCP,GST activity was inhibited at 56 days,compared with 7days,GST enzyme activity was reduced.（3）Oxidative damage and DNA damage:Earthworms have suffered oxidative damage after exposure to chlorpyrifos and TCP,which are mainly manifested in the MDA content of lipid peroxidation products and the 8-OHdG content of DNA damage markers.increase.（4）Comprehensive evaluation of subchronic toxicity:IBR index showed that chlorpyrifos and TCP had subchronic toxicity to Eisenia fetida in four soils.The results showed that the IBR value of chlorpyrifos on the 56 d was 14.1,15.3,13.2 and 16.3 in the artificial soil,fluvo-aquic soil,black soil and red clay;the IBR value of TCP on the 56 d was 13.6,18.6,17.1 and 14.9.（5）Correlation analysis:The content of sand grains and clay particles affect the toxicity of chlorpyrifos to earthworms.Sand grains have a negative correlation with toxicity,and clay particles have a positive correlation with toxicity.The amount of soil cation exchange will affect the toxicity of TCP to earthworms,and the amount of cation exchange is positively correlated with the toxicity.