Preliminary Study On Ecological Risk And Environmental Carrying Capacity Assessment Of Pesticides In Soil

In recent years,soil environmental security has attracted much attention because of its important role in the development of agricultural economy,ecosystem and human health risks.The source of soil pollution is mainly related to human activities,among which the residue of pesticide in soil is one of the main problems of soil pollution.Organophosphorus pesticides（OPPs）and synthesis pyrethroids（SYPs）were widely used in agricultural production,which resulted in residue of pesticides in soil.Based on the concept of the Central Plains Urban Agglomeration（CPUA）proposed by China,this study targeted 16 cities in the core development area of CPUA,and divided the 197 soil samples collected into three soil regional types:industrial（69）,residential（68）,and agricultural（60）based on the division of different industrial structures.At the same time,88 samples of soil and leaves of different plant types in the main urban area of Zhengzhou,the central city of the core development area,were collected for analysis.12 OPPs and 8 SYPs were detected,and the pollution characteristics of OPPs and SYPs in the core development area were studied through their concentration level,regional distribution,relative abundance,environmental carrying capacity assess ment,ecological risk,human health risk and migration and transformation between soil and plants.It provides information for better management of soil safety in the core development area of CPUA,protects the ecosystem and reduces the risk of human soil pesticide residues.The main research results are as follows:（1）The total average concentration level（dry weight,dw）of∑₁₂OPPs in industrial,residential and agricultural soils in the core development area is 194.26 ng/g,216.9 ng/g and266.57 ng/g respectively.There is an obvious trend of industry<resident<agriculture in the three soil types.Malathion is the highest concentration in the three soil types in the core development area.Due to the diversity and complexity of agricultural activities,the type and content of OPPs in agricultural areas are significantly different from industrial and residential areas.The residual amount of OPPs in the eastern of the core development area was higher than that in the western.The results of the environmental carrying capacity assessment show that acephate and malathion in OPPs have high environmental loads and are predicted to exist in soil for a longer period of time,exceeding 500 years.Omethoate is the pesticide type with the highest ecological risk among all OPPs in the core development area.Among the 16 cities,Shangqiu has the highest frequency of high ecological risk,which deserves more attention.The 12 types of OPPs,including total OPPs,have no significant impact on adult non-carcinogenic risk,while in children’s non-carcinogenic risk,the HI value of total OPPs is greater than 1,which has significant human health risk.（2）The total average concentration level（dry weight,dw）of∑₈SYPs in industrial,residential and agricultural soils in the core development area is 26.78 ng/g,35.66 ng/g and25.47 ng/g respectively.Different from the trend of OPPs,the concentration level of SYPs is agricultural<industrial<residential,and the concentration of fenpermethrin was the highest among the three soil types in the core development area and presented the highest ecological risk.At the same time,it shows the highest ecological risk in the 16 cities in the core development area.Since bifenthrin has good insecticidal and mosquito killing effect and low toxicity,individual sampling points in residential and agricultural areas also diapaly higher concentrations and occupy larger components.The overall concentration distribution of SYPs in the core development area shows that it is more affected by point sources,especially the Xingyang Square and Shangqiu Farmland in Zhengzhou.Although the concentration level of fenpropathrin is the highest in the three soil regions,the assessment of environmental carrying capacity shows that cypermethrin is the SYPs with the highest environmental load,and only the cypermethrin is predicted to exist in the soil for a short period of time,less than 100 years.The total SYPs showed a significant impact on the non-carcinogenic risk of adults and children in residential areas,and fenvalerate and fenvalerate even showed a significant impact on the non-carcinogenic risk of adults and children at individual sampling points,HI<1.0.（3）Among the 7 plant（Photinia serratifolia,Euonymus japonicus Thunb,Ligustrum lucidum,Eriobotrya japonica,Pittosporum tobira,Thuja occidentalis,Ophiopogon bodinieri）leaf types in the main urban area of Zhengzhou,the central city of the core development area,methamidophos,acephate and omethoate are the main pesticide types in OPPs,while allethrin,fenpropathrin and cypermethrin are the main pesticide types in SYPs.The leaves of Pittosporum tobira had detected the highest concentrations of OPPs,while the leaves of Ligustrum lucidum had detected the highest concentration of SYPs.In the division of the six main urban areas of Zhengzhou,the Green Valley Park and Science Avenue in Zhongyua n District respectively showed the highest accumulation of OPPs and SYPs.Through the calculation of biological sediment accumulation factor,the relationship between pesticide concentration in plant leaves and soil concentration was analyzed and studied.It was found that OPPs in Euonymus japonicus and Ligustrum lucidum were more susceptible to the influence of octanol-water partition coefficient.SYPs only had a significant positive correlation with octanol-water partition coefficient in Ligustrum lucidum.For other plant types,pesticides in plant tissues were more controlled by transpiration flux,while transpiration flux was related to water solubility.