The Toxicity And Mechanisms Of The Triazine Herbicide Metribuzin On E.Fetida

The triazine herbicide diazinon is widely used worldwide as a conductive selective herbicide which,when applied to the soil,will not only inhibit the target plant for weed control purposes,but will also inevitably have some effect on non-target organisms in the soil.Earthworms are an integral part of the material cycle in terrestrial ecosystems and play an important role in agricultural production,as well as being used as model organisms to assess the risk of pollutants to soil organisms.In this paper,the acute toxicity and subacute toxicity of metribuzin stress on earthworms were investigated.Finally,metabolomics was used to analyze the mechanism of disturbance of metabolites and metabolic pathways in earthworms.The main results were as follows:（1）The results of the acute toxicity test for metribuzin exposure showed that the 24 h-LC₅₀and 48 h-LC₅₀for earthworms in filter paper contact were 28.33μg·cm^-2and 18.00μg·cm^-2,respectively,and the 7 d-LC₅₀and 14 d-LC₅₀for earthworms in artificial soil were 213.90 mg·kg^-1and 181.28 mg·kg^-1,respectively,indicating that the acute toxicity of zinfandel The results indicated that the acute toxicity of metribuzin to earthworms was of low toxicity level.Metribuzin was able to inhibit the growth of earthworms,leading to a reduction in body weight,with 41.10% inhibition when metribuzin concentrations reached 20 mg·kg^-1.The results of the avoidance response behaviour test showed that the avoidance behaviour of earthworms gradually increased as the concentration of metribuzin increased,and when the concentration of metribuzin reached 20mg·kg^-1,earthworms showed an obvious avoidance response,with the avoidance rate reaching 83.00%.（2）The toxic effects of metribuzin on earthworms were evaluated at the tissue level and at the molecular level in terms of oxidative damage and genotoxicity by the artificial soil method.The results showed that metribuzin inhibited the antioxidant defense system of earthworms and reduced the activities of SOD,CAT and POD enzymes,with a decrease of 43.92%,41.93%and 26.63%in the activities of 20 mg·kg^-1for 28 d.This caused oxidative damage to the earthworms,resulting in an increase in ROS content in the earthworms,which accumulated in the body and stimulated the body to produce lipid peroxidation.The MDA content of earthworms was 1.60 and1.61 times higher than that of the control group at 21 and 28 d of stress at 20 mg·kg^-1of metribuzin,respectively.In addition,it can increase the 8-OHd G content in earthworms and cause DNA damage in earthworms.On this basis,the integrated biomarker response（IBRv2）was used to calculate the degree of integrated biomarker response.The results showed that metribuzin stress produced biomarkers in earthworms,and MDA was screened as an indicator of biomarkers.（3）Metabolomics was used to study changes in the earthworm’s own metabolites and metabolic levels under metribuzin stress conditions and to analyse the relevant metabolic pathways.In this study we screened a total of 81 differential metabolites.Among them there were 34 up-regulated metabolites and 47 down-regulated metabolites.The results indicate that metribuzin stress causes disturbances in the metabolic levels of earthworms.On this basis,we screened 12 differential metabolic pathways.Among them,the results of disrupted purine metabolism suggest that metribuzin stress inhibits nucleotide metabolism in earthworms,which in turn leads to the possibility that metribuzin may cause DNA damage to earthworms.Meanwhile,disturbances in the metabolic pathways of alanine,aspartate and glutamate indicated that amino acid metabolic pathways were disturbed,resulting in disturbed amino acid synthesis in the earthworm,suggesting that protein synthesis in the earthworm was hindered.