Bioavailability Of 10 Pesticides To Peanut In Soil

Pesticide residues in the soil performed potential hazards to the ecological environment and human health.However,the total concentration of pesticides in soil could not really reflect bioavailability of the pesticides.The bioavailability of pesticides in soil was affected by factors of physicochemical properties of pesticides and soil characteristics.Therefore,in this work ten pesticides including thiamethoxam,imidacloprid,thiacloprid,clothianidin,simazine,atrazine,alachlor,metolachlor,acetochlor and butachlor were selected for investigating the bioavailability of ten pesticides to peanut.The four kinds different extraction methods including organic solvent extraction,water extraction,in situ pore water,polyurethane film（PU）passive sampling was used for predicting the bioavailability of 10 pesticides.The prediction model of pesticides bioavailability was established and verified with isoproturon.In addition,five types of soils including blackland,yellow brown soil,fluvo-aquic soils,red loam,and yellow clunamon soil were selected to explore the effects of soil characteristics on the bioavailability of pesticide.The results of this study provide theoretical basis and technical support for risk assessment and bioavailability prediction of pesticide residues in soil.The main results were summarized as follows:（1）The Linear relationship between the physicochemical properties of pesticides and the uptake of pesticides in peanut were explored with pot experiments.The results showed that the K_OW values of pesticides possessed well correlations with the uptake of pesticides in peanut and the value of R² was greater than 0.7714.The smaller the log K_OW value of the pesticide was,the easier it was to be uptake by the peanut plants,indicating the the bioavailability was higher to peanut.（2）The concentration of ten pesticides in soil was measured by four different extraction methods.The correlation analysis between the uptake amount of pesticides in different parts of peanut and the soil concentration measured by four extraction method revealed the the optimal method to evaluate the bioavailability of pesticides in soil.The results showed that there were no correlations between the total concentration of pesticides extracted with acetonitrile or water in soil and the concentration of pesticides in peanut.The concentration of pesticides in soil measured by the in-situ pore water and PU passive sampling performed good correlations with the pesticide concentration in peanut roots,shoots and bioconcentration factor（BCF）value.And the values of R² were 0.8183-0.9300 and 0.7556-0.9424,respectively.Therefore,the in-situ pore water method and PU passive sampling method could accurately characterize the bioavailability of pesticides in soil to peanut.The feasibility of in-situ pore water and PU film passive sampling for predicting peanut bioavailability was verified by using the herbicide isoproturon.（3）The toxicity of acetochlor to peanut was different in five different types of soil.The IC₅₀of acetochlor on peanut height were 5.90,3.38,2.74,1.09 and 0.97 mg/kg,respectively,indicating that soil types affected bioavailability of acetochlor to peanut,leading to the different toxicity of acetochlor in different soils was different.The concentration measured with in-situ pore water method and the membrane passive sampling method showed good correlations with IC₅₀ of acetochlor,the values of R²were 0.8164 and 0.8025,indicating that the in-situ pore water method and PU passive sampling method could be used to characterize the toxicity of acetochlor to peanut in soil.