Pollution Characteristics And Risk Assessment Of Organophosphorus And Pyrethroid Pesticides In Typical Agricultural Areas In Shaanxi

As an indispensable means of production in human society,pesticides have made great contributions to the development of human society,but their unreasonable application has caused inevitable negative impacts on the environment.Therefore,it is necessary to understand the current situation of pesticide residues in soil and agricultural products in agricultural production and the impact of pesticide residue pollution on the ecological environment.This thesis intends to take typical agricultural production areas in Shaanxi as the study area,and use chlorpyrifos,lambda-cyhalothrin,cypermethrin and deltamethrin,the main Organophosphorus pesticides and Pyrethroids,as the target pollutants,in combination with soil properties and the study will reveal the levels,distribution characteristics and influencing factors of pesticide residues in agricultural soils and products,and assess the risk based on the current status of residues.The results of the study are as follows.To investigate the residues of Organophosphorus pesticides and Pyrethroids in agricultural fields in Shaanxi,soil samples were collected from agricultural fields in Guanzhong,northern Shaanxi and southern Shaanxi and determined and analyzed by GC-MS on soil samples from agricultural fields in Shaanxi.The detection rates of chlorpyrifos,cypermethrin,deltamethrin and lambdacyhalothrin were 70%,51%,41%and 9%,respectively,in the soils of the studied areas.Soils showed different distribution characteristics:the detection rates of chlorpyrifos and cypermethrin were higher in the soils of Guanzhong,northern Shaanxi and southern Shaanxi,and the detection rates of deltamethrin were higher in the greenhouses than in the fields in Guanzhong,and the detection rates of chlorpyrifos and deltamethrin were higher in the greenhouses than in the fields in northern Shaanxi and southern Shaanxi.The average levels of lambda-cyhalothrin and deltamethrin were highest in Guanzhong,while the average levels of chlorpyrifos and cypermethrin both reached the highest in southern Shaanxi.The level of pesticide content in different utilization types of soils showed that field>orchard>vegetable field,and chlorpyrifos residues were much higher than several other pesticides.Correlation analysis showed that soil organic carbon was not significantly correlated with the four pesticides;lambda-cyhalothrin was significantly and positively correlated with cypermethrin,and the two may have the same or similar source;while cypermethrin and pH were significantly and negatively correlated,and soil pH may affect the degradation of cypermethrin;while deltamethrin and soil cation exchange were significantly and positively correlated with each other.The residue levels of Organophosphorus pesticides and Pyrethroids in agricultural products from typical agricultural production areas in Shaanxi were determined by GC-MS to explore the bioconcentration characteristics of the pesticides in the crops and to perform correlation analysis.The results showed that all four pesticides were detected in agricultural products in this study area to different degrees,and the content levels were overall chlorpyrifos>deltamethrin>cypermethrin>lambda-cyhalothrin.The enrichment ability of pesticides varied widely among crops,with chlorpyrifos being stronger in vegetable crops(cabbage,eggplant and pepper,etc.)and relatively weaker in fruit and field crop categories;the bioenrichment of deltamethrin was significantly stronger in hollow cabbage than in other vegetable categories,and the bioenrichment of deltamethrin was weakest in fruit crops.Correlation analysis showed that there was a positive correlation between soil-agricultural products and chlorpyrifos,while there was no correlation between soil-agricultural products and chlorpyrifos;there was a negative correlation between soil-agricultural products and deltamethrin and a weak correlation between soil-agricultural products and lambda-cyhalothrin.The residues of the four pesticides in different regions and different types of agricultural products varied.The residues of chlorpyrifos>deltamethrin>lambda-cyhalothrin>cypermethrin in agricultural products in Guanzhong were generally higher than those in maize;the residues of chlorpyrifos>deltamethrin>cypermethrin>lambda-cyhalothrin;the residues of chlorpyrifos in agricultural products in southern Shaanxi were the highest overall.Pesticide residues were detected in maize in all three regions of Guanzhong,northern Shaanxi and southern Shaanxi,with the pesticide residues in maize and wheat samples in Guanzhong being higher than those in southern Shaanxi;the residues of lambdacyhalothrin in tomato samples were much higher than those in other crops.In this study,we evaluated the toxic effects of contaminated soil on Eisenia foetida by adding different concentration gradients of pesticides to artificial soil based on the actual pesticide residue levels,using the Eisenia foetida as indicator organisms.The results showed that the soil environment treated with pesticide additions was significantly biotoxic to Eisenia foetida,and external morphological changes visible to the naked eye occurred in the Eisenia foetida epidermis during the storm toxicity period,along with significant avoidance behavior,with avoidance rates above 55%in all cases.The ecological risk assessment of soil pesticide residue levels showed that the soil ecological risk indices were all less than 1,indicating that the soil ecological risk of the agricultural product origins in the study area was small and would not pose a threat to the soil environment and quality.Except for the low risk phenomenon of lambda-cyhalothrin in potato fields in southern Shaanxi,the overall risk index of lambda-cyhalothrin in soils of Guanzhong,northern Shaanxi and southern Shaanxi was less than 0.001,indicating that the risk of lambda-cyhalothrin was basically negligible.The risk indices for chlorpyrifos,cypermethrin and deltamethrin in soils from Guanzhong and northern Shaanxi were in the range of 0.001 to 0.1,which is low risk;in soils from southern Shaanxi,cypermethrin was individually at medium risk in potato and maize fields.The bioaccessibility data obtained from simulated artificial gastrointestinal fluid experiments on agricultural products with artificial gastric and intestinal environments showed that a large proportion of all four pesticides in agriculturall products ingested via the stomach could not be absorbed by the human body,and the bioaccessibility ranges of chlorpyrifos,cypermethrin,deltamethrin and lambda-cyhalothrin were 4.59%～34.88%,0～16.77%,0～16.77%,0～45.34%and 0～16.24%respectively.The bioaccessibility ranges in the intestinal stage were 4.26%～24.83%,0～21.37%,0～25.65%and 0～9.04%,respectively.Some of the agricultural products had pesticide residues exceeding the limit values in GB 2762-2017 National Standard for Food Safety Limits for Contaminants in Food.Dietary exposure risk assessment based on the levels of pesticide residues in agricultural products showed that the human health risk indices were all less than 1 and within the acceptable range,indicating that pesticide residues in agricultural products do not pose a significant health risk to the dietary population.