Influences Of Dissolved Organic Matter On The Migration Of Organochlorine Pesticides In Soil-groundwater

Organochlorine pesticides with soil interstitial water continuously migratedownward through vadose zone is the main way to cause groundwater pollution. Byinfluencing dissolution and adsorption behavior of organochlorine pesticides in soil,the dissolved organic matter(DOM) will affect their mobility.The purpose of this paperis to study the effects of DOM on the migration of organochlorine pesticides in soil andgroundwater, through isothermal adsorption experiments and soil column leachingexperiments to complete this study. Different sources of DOM has differentcompositions, different properties, and the impacts on the migration of organochlorinepesticides are vary. In order to reveal the influence mechanism, we use the method ofultraviolet-visible spectroscopy and the three-dimensional fluorescence spectroscopyto characterize its chemical structures and to speculate its possible performance.The results showed that, in the isothermal adsorption experiment, the soilendogenous DOM (DOM extracted from soil) can inhibit absorption of organochlorinepesticides in the soil, and the addition of20mg·L-1exogenous DOM can significantlypromote the absorption of organic chlorine pesticide in soil sample of S5. Among them,silt DOM promote more strongly. In a certain range, the adsorption amount oforganochlorine pesticides in soils will not change with exogenous DOM concentrationchange. All adsorption curve can be fitting with the linear model, thus, the adsorptionperformance of organochlorine pesticides in soil shows the distribution between thesoil and the water solution.In soil column leaching experiment, HCHs class of organochlorine pesticidescompared to DDTs showed stronger migration in soil. When the soil columns wereleached with distilled water or silt DOM solution, the contents of organochlorinepesticides in the leachate were very low,which no more than3ng·L-1, but when the soilcolumn was leached with nutritional soil DOM (DOM extracted from nutritional soil)solution, it showed a higher contents of HCHs in the leachate and changed in the rangeof3.79ng·L-1~102.36ng·L-1. In addition, compared with the soil column leaching withdistilled water, the use of silt DOM and nutrient soil DOM leaching, can promote theorganochlorine pesticides moving deep into the soil,and nutritional soil DOM plays agreater role in promoting its migration.