Characterization And Ecological Risk Assessment Of Pesticide Residues In Agricultural Soils And Water Bodies In The South China Crop Breedind Area Of Hainan

Pesticides have always played a very important role in agricultural production activities,playing a huge role in controlling pests and diseases and improving crop yields,especially in hot zone crop cultivation.South China Crop Breeding Area are known as a national"birthplace of new crop varieties"and"green gene pool".The variety of crops in this region and the climate conditions of high temperature and humidity make pests and diseases frequent,and there are multiple types and high frequency of pesticides input.In2016,the amount of pesticide input in crop cultivation in this region amounted to 46.9kg/hm~2,and the amount of pesticide used per unit area was much higher than other regions of China,which may pose a threat to the environmental security of producing areas.Therefore,it is necessary to carry out research on the characteristics of pesticide pollution in agricultural soil and water bodies in the South China Crop Breeding Area.In this study,soil samples and water samples from nearby irrigation areas/drainage canals in the rice and vegetable rotation in the South China Crop Breeding Area as research objects,32 pesticides used during the planting period of rice and vegetable crops and 9banned pesticides were used as research targets,and used the rapid joint detection method established in the previous to analysis their spatial and temporal distribution characteristics;ecological risks of pesticide residues in soil and water bodies were evaluated by using the risk quotient method.The main research results are as follows:(1)A total of 140 soil samples were collected for testing and analysis in South China Crop Breeding Area,and the results showed that the total pesticide residue concentrations ranged from 18.6 to 5121.3μg/kg,with the number of detections ranging from 14 to 29;the highest average residue concentration of 153.1μg/kg was found in the Sanya sample site;carbendazim,spinosad and butachlor were the pesticides with the highest average residue concentrations among the three pesticide types,which are 6.7,71.7 and 0.3μg/kg;the highest average residue levels and total pesticide residue concentration were detected at sample sites in January;according to the relevant provisions of the national soil environmental quality standards,both DDT and HCH residues in this area did not exceed the standards.(2)In the 140 water samples collected in South China Crop Breeding Area,the total pesticide residue concentration ranged from 0.7 to 373.7μg/L,with the number of detections ranging from 6 to 25;the highest average residue concentration in the sample site in Ledong County was 9.3μg/L;the highest average residue concentrations of spinosad and cypermethrin were 10.3 and 0.6μg/L,respectively;the highest average residue concentration at sample sites in November.Chlorpyrifos exceeded the EU surface water limit,with an exceedance rate of 20%,and atrazine had one residual exceedance according to China’s surface water environmental quality standards.(3)The ecological risk of fungicidal pesticides to earthworms in the soil of the three regions showed high risk characteristics as follows:2.8%in Lingshui County,5.7%in Sanya City,and 11.4%in Ledong County;among the insecticidal pesticides,only imidacloprid and acetamiprid were of medium risk;high risk characteristics of fungicidal and herbicidal pesticides existed in Baoben Primary School and Shuinei Village of Ledong County,especially carbendazim and butachlor;a total of 13 pesticides in water showed high risk characteristics to aquatic invertebrates.A total of 13 pesticides in water have ecological risk values greater than 1 for aquatic invertebrates;all three regions show high risk characteristics,and the overall ecological risk of herbicide-based pesticides is low.In summary,there is a variety of pesticide compound pollution in the agricultural soil and water bodies in this area,and the types of pesticide residues and residual concentrations vary greatly in different regions in different months,and are closely related to the type of crops grown.For areas with high ecological risk,it needs to control pesticide input strictly to reduce ecological risk.The results of this study can provide a basis for identifying typical pesticide residue characteristics and scientific management of pesticides in soil and water of rice and vegetable rotation cropland in Hainan.