Ecological Risk Assessment And Risk Driver Screening Of Pesticide Residues In Vegetable Ecosystem Soils In Chongqing

The vegetable planting area of Chongqing has reached 753,200 hectares,accounting for 22.5% of the total agricultural sown area,including three major vegetable industrial belts: seasonal vegetable industrial belt,processed vegetable industrial belt and alpine vegetable industrial belt.Vegetable pests and diseases are of various kinds,with heavy hazards,and are sensitive to many chemicals.Improper use of chemical pesticides is easy to cause drug damage.Long-term high input of pesticides has a negative impact on agricultural ecological environment(Hong Wenying et al.,2021),resulting in deterioration of soil properties,increase of soil erosion,and decrease of biodiversity.Agricultural non-point source pollution is becoming more and more serious,which brings great pressure to soil health.It is of great significance to master the state of soil health for the development of Chongqing vegetable industry.Based on this,this study conducted research and sampling on three vegetable industrial belts in Chongqing,carried out safety assessment and risk assessment on pesticide residues in vegetable ecosystem soil in Chongqing,combined with farmer information collected in the research to build a model,screened out key factors affecting the risk of pesticide residues in soil,summarized the problems faced by pesticide application,and carried out biopesticide substitution experiments.In order to seek reasonable control measures and put forward appropriate solutions,the specific results are as follows:(1)We improved an ecological risk assessment method applicable to soil pesticide residues to assess the ecological risk and environmental carrying capacity of soil pesticide residues in vegetable ecosystems.Among 201 surface soil samples collected in Chongqing,62.1% of the samples contained excessive pesticide residues,and 86.6% of the samples were contaminated by compound pesticides.The detection frequency of fungicide was the highest(70%),and the total content of herbicide glyphosate was the highest(87.34mg/kg).According to the results of toxic exposure ratio(TER)of agricultural residues,the fungicide phenoxymeclozole(TERmax=0.14,TERmean=4.396)and the insecticide beta-fluthrin(TERmax=2.422)had toxic exposure risks to earthworm Chizi eisenia(TER<5).The results of composite index pollution assessment showed that 75.8% of the soil collection sites were at medium and high risk(RQ>1),and 43.8% were at medium risk(RQ>0.1).By calculating the environmental carrying capacity of agricultural residues,it was found that the insecticide cypermethrin had exceeded the environmental carrying capacity(-351.6t),and the insecticides fenaponil(10.1t)and beta-cypermethrin(25.35t)would exceed the environmental carrying capacity threshold in the next 50 years.These results will help to guide the rational use of pesticides and reduce soil ecological risks,so as to realize the green development of agriculture in Chongqing.(2)In order to identify the key factors affecting soil agroresidue in the region,12 groups of variables collected by the survey were divided into three types of influencing factors according to the local vegetable planting patterns and characteristics,and stochastic forest model and structural equation model were used to model planting factors,farmer factors and soil factors.The results of stochastic forest model showed that the three most important factors to the risk of agricultural residues were soil cation exchange capacity(18.84%),planting area(14.12%)and clay content(13.01%).The results of structural equation model showed that soil factor was the key factor of pesticide residue risk(0.85),and cation exchange capacity had the greatest influence(0.65).Planting factors were secondary control factors(0.84),among which planting area had the greatest influence(0.50).The direct influence of peasant household factors was not significant,but it could indirectly influence the risk of agricultural disability by influencing planting factors(0.51)and soil factors(-0.67),among which whether the peasant household had been trained had the greatest influence(0.43).(3)Based on the current situation and safety evaluation of soil pesticide residues in Chongqing,combined with structural equation model and random forest operation results,the main risk sources of agricultural residues in Chongqing were pyrethroid insecticides and triazole fungicides.In this study,biological control experiments were carried out in Tongliang Vegetable Science and Technology Small Hospital for two years,and it was found that after the optimized control treatment,agricultural residues decreased by 15.7%,pepper yield increased by 21.54% and lotus yield increased by9.45%.Pesticide optimization treatment has achieved initial results,and then we should continue to strengthen the standard training of practitioners,vigorously promote green plant protection technology,and make contributions to the supervision of a good agricultural production environment.