Study on the bioremediation of alachlor-contaminated farmland soil and the toxicity of its metabolites by dominant bacterial

Abstract

The widespread use of the herbicide alachlor disrupted the endocrine system of organisms in the soil and severely contaminated the soil. Biodegradable herbicides have become a hot research topic. In this study, the efficient degrading strain Trichoderma harzianum H12 was isolated from the soil which is applied with amide herbicides for a long time. The effects of temperature, pH, strain dosage and oncentration of alachlor on the degradation of alachlor by dominant bacteria were studied. The changing trend of malondialdehyde (MDA) content and related typical enzyme activities in earthworms were analyzed to characterize the changes in toxicity of alachlor and its metabolites. Finally, the dominant bacteria were added into the rhizosphere soil of corn to establish a corn-microorganism combined remediation system. The research results showed that: after 5d, the degradation rate of strain H12 to 50 mg/L alachlor under the optimal conditions was 96.1%. The activities of superoxide dismutase (SOD) and catalase (CAT) in earthworms were increased, and the content of MDA was always significantly higher than that in the control group, resulting in lipid peroxidation in earthworms. However, the activity of acetylcholinesterase (AchE) finally recovered to the level of the control group, and the toxicity of metabolites was less than that of alachlor. The degradation rate of the corn and strain H12 combined in the remediation of alachlor-contaminated soil was as high as 85.9%, and the addition of strain H12 alleviated the toxic effects of alachlor on corn.