Effects Of Nonionic Surfactant Tx-100and Dissolved Organic Matter On Mobility Of Herbicide Atrazine In Soil

Pesticides play a very important role in ensuring stable and high-yield crops, protecting them from insect pest. But the excess use and the negative impacts of pesticides on agricultural production and the environment have become increasingly prominent. Therefore, it is important to study the mobility of pesticides in soil for the soil environment safety and the sustainable use of soil resources.The dissolved organic matter (DOM) is organic molecules, which can dissolve in water, acid, base or salt solution and has different size and structure. It mainly comes from the ground litter, root exudates, soil humus, soil microorganisms and rainfall leaching matter. Surfactant is chemical substances, which has polar groups (hydrophilic) and non-polar groups (lipophilic). Surfactant refers to the compound, which can significantly reduce the surface tension of water at very low concentrations. If the concentration of the surfactant attains the critical micelle concentration (CMC), surfactant monomers will form micelles. Because of the DOM in soil environment and the surfactant in pesticide formulations, they have a major impact on the environmental behavior of pesticide molecules. It is significant to study the effects on the migration and transformation of pesticides in the soil environment by dissolved organic matter and surfactant.In this thesis, we choose atrazine, DOM (straw) and TX-100(non-ionic surfactant) for the study. We study the effects on adsorption, desorption, migration, leaching behavior of atrazine in the soil environment by the DOM and TX-100, as well as the migration and transformation of atrazine in the soil-plant system. In adsorption experiments, both DOM and surfactant used in this study decrease the atrazine sorption and increase desorption capacity of soil. As the concentration increases, the results are more prominent. Both the sorption and desorption coefficient dropped. The adsorption coefficient Kf value dropped from2.09(control) to0.60(under the1.5CMC treatment),0.91(under the160mgC L-1 treatment). The desorption coefficient Kf value dropped from6.84(control) to2.13(under the1.5CMC treatment),2.03(under the160mgC L-1treatment). The thin layer experimental results show that the addition of surfactant or dissolved organic matter would promote the migration of atrazine in the soil environment. The Rf value increased from0.56(control) to0.72(under the1.5CMC treatment),0.68(under the160mgC L-1treatment). The leaching experimental results show that the addition of surfactant or dissolved organic matter would promote atrazine leaching in the soil, increase the amount of atrazine from leaching soil, shorten leaching time and enhance the leaching activity. In leaching experiments, the maximum amount of atrazine of leaching was25.95μg for control, the corresponding volume was600mL; the maximum amount of atrazine of leaching was56.88μg for the1.5CMC TX-100treatment, the corresponding volume was300mL; the maximum amount of atrazine of leaching was32.99μg for160mgC L-1DOM treatment, the corresponding volume was450mL. The results of atrazine accumulation in maize show that the accumulation of atrazine in root was greater than that in shoot. The addition of surfactant (0.5CMC,1.0CMC,1.5CMC) would promote the uptake of atrazine in maize, while the addition of DOM (80mgC L-1,160mgC L-1) would inhibit the accumulation of atrazine in maize.