Transport Of Propachlor In Water-Soil-Wheat System Affected By Surfactant Triton X-100and Dissolved Organic Matters

Soil is the environmental storage of pesticides, in which most pesticides applied into farmland remains. Pesticides, which come into the soil by chemical, physical and biological methods and have solid combination with soil, can be harmful to the agricultural production and environment.Surfactants are a class of substances which can reduce solvent surface and liquid-to-liquid interfacial tension in low concentrations and have adsorption performance. The micelles and monomers of surfactants have an effect of emulsification, dispersion, solubilization, foaming, wetting, washing and so on. Surfactants are widely used in industry, agriculture, construction, medicine and daily life. Dissolved organic matters (DOM) are a complex mixture of many organic compounds, widely discovered in the plant roots, organic waste, soil and water. The transport of pesticide residues in soil is affected by the existence of surfactants and DOM in soil and water.In this study, batch equilibrium experiments, soil thin-layer chromatography experiments, soil column leaching experiments and bioaccumulation from soil were conducted to evaluate the effect of surfactant Triton X-100and DOM (extracted from rice straw) on the mobility behavior of herbicide propachlor in soils. The results show that application of TX-100(0.5CMC and1.0CMC) and DOM (at60and120mgC L-1) decreased the sorption and increased desorption of propachlor in soils. Compared to the control, the Freundlich sorption constant Kf values of propachlor were42.9%and40.6%of control at TX-100concentration of0.5CMC and1.0CMC,86.7%and89.2%at DOM concentration of60and120mg DOC L-1, respectively. Mobility of propachlor was tested in soil plate and columns. The Rf value in soil thin-layer chromatography was0.731(0.5CMC),0.763(1.0CMC),0.791(1.5CMC),0.741(DOM60mgC L-1),0.772(DOM120 mgC L"1), respectively, all of which is bigger than the control (0.710). And it reveals that both TX-100and DOM can improve the transport of propachlor in soil thin-layer. Addition of TX-100and DOM to both systems increased the mobility of propachlor and the total concentration of propachlor in the leachate in columns. Biological analysis with wheat indicated that application of TX-100and DOM reduced the shoot biomass and increased the propachlor accumulation in both shoot and root. The values of TF were93.9%(0.5CMC),84.9%(1.0CMC),62.7%(1.5CMC),16.3%(DOM60mgC L-1),13.6%(DOM120mgC L’1) of control.