Study On The Distribution And Migration Of Endosulfan In Agricultural Soil

As a broad spectrum organochlorine pesticide pesticide,endosulfan was widely used in agricultural production.Due to its high toxicity,bioaccumulation,persistence and long range transport capabilities,endosulfan was listed as the elimination of substances in the"Convention of Stockholm",and then it was banned in the world.Persistent endosulfan pesticides used in industrial and agricultural production processes enter the water and soil environment and can migrate to more distant areas or even groundwater environments through physical processes such as soil release again and hydrological processes such as surface runoff and soil percolation,which will have a certain degree of impact on the terrestrial ecological environment and human health.The Guanting Reservoir basin,which used to be the drinking water source of Beijing,had developed agriculture.Therefore,the large scale use of organochlorine pesticides was inevitable,resulting in more serious non-point source pollution.Hence,the Yang River-Guanting Reservoir basin was selected as research area in this study.The distribution characteristics of endosulfan in agricultural soils were mainly investigated in this area,and the migration of endosulfan in soil environmental media was explored by the surface runoff test during the simulated rainstorm process in the field and indoor soil column leaching test.The results of this study have certain theoretical and practical significance for the formation and reduction of organochlorine pesticides in the water and soil environment of the Yang River-Guanting Reservoir basin.The main research contents and conclusions are as follows:（1）Endosulfan were common in soil,water body and sediments in the Yang River-Guanting Reservoir basin.The concentration of total endosulfan in topsoil,water and sediments ranged from 0.237 ng/g to 472.344 ng/g（on average 17.384 ng/g）,3.882ng/L to 204.791 ng/L（on average 58.341 ng/L）and 0.145 ng/g to 3.396 ng/g（on average1.121 ng/g）,respectively.With the increase of depth in the profile soil,the concentration of endosulfan decreased,and most of the endosulfan stayed in the soil layer of 0-60 cm.In the middle reaches of the Yang River（SY-2）,the net exchange flux of endosulfan between the river water and sediments was up to 50.849 ng·m^-2·d^-1.According to the ratio ofα-/β-endosulfan in the study area,the endosulfan in the Yang River-Guanting Reservoir basin mainly came from historical use.Besides,the total endosulfan concentration of topsoil and atmospheric dust in typical industrial areas（Xuanhua）ranged from 0.484 ng/g to 81.196 ng/g（on average 15.328 ng/g）and from 1.253 ng/g to 17.294 ng/g（on average7.106 ng/g）,respectively.Along the wind direction from the industrial area to the foot of the mountain,the concentration of endosulfan appeared to decrease first and then increase in atmospheric dust,indicating that the migration of endosulfan in the atmosphere was affected by wind direction,temperature and topography.（2）In the surface runoff test during the simulated rainstorm process in the field,the migration trend of endosulfan in the horizontal direction in the Yang River Basin（1DBJL）was higher than that in the vertical direction.In the Sanggan River Basin（2DBJL）,the migration capacity of endosulfan in the vertical direction was large,and the horizontal direction was also up to 25 m in 6 d.In the Chao River Basin（3DBJL）,the content of organic matter was high,and endosulfan was not suitable for migration to a distant place.The horizontal migration distance could reach 5 m in 6 d.（3）In the indoor soil column leaching test,α-endosulfan in the column A（α-endosulfan+Ca Cl₂）and column C（α-endosulfan+Ca Cl₂+Na N₃）showed accumulation in the topsoil（0-3 cm）.The migration distance ofα-endosulfan in the column A、column B（blank solution+Ca Cl₂+Na N₃）and column C was 7.5 cm in 4 d.