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环境化学

摘要：采用振荡平衡法测定了低浓度范围内(<30mg·L^-1)灭草松和莠去津单、双溶质在4种土壤中的吸附等温线.单溶质吸附结果表明,4种土壤中灭草松存在不吸附、吸附2种类型,吸附等温线类型有L和C型;莠去津的吸附等温线有L、S和C型;有机质、矿物质及农药疏水性是影响灭草松和莠去津在土壤中吸附的重要因素.通过比较单溶质和双溶质溶液中灭草松和莠去津的等温吸附线,发现混合溶液中它们的吸附行为相互之间随土壤类型不同存在竞争、无影响和协同作用,并且竞争程度与溶质浓度有关.用理想溶液吸附理论(IAST)和单溶质吸附等温线参数,模拟了双溶质溶液中灭草松和莠去津的吸附等温线,结果显示,该模型不能很好的预测实验结果.进一步结合吸附机理分析认为,不同土壤中的竞争结果是由于2种农药在其中共同占有吸附点的情况不同造成的.

Abstract：Two series of adsorption experiments with a primary solute (atrazine or bentazone) in the absence and presence of secondary solute (bentazone or atrazine) at different concentrations(<30 mg·L^-1) were carried out in the laboratory using the batch equilibrium techniques. For single solute systems the L-, S-or C-type isotherms were observed for the adsorption of bentazone and atrazine in all soils except one soil with no sorption of bentazone holding the lowest organic matter and higher pH. The organic matter, mineral and hydrophobicity of pesticides were found to be the main factors controlling the sorption of herbicides in soils. Effect of the mixture solutes on the adsorption of bentazone and atrazine was evaluated by comparison with each single solution. The competitive, unaffected or cooperative sorption was observed in mixed systems, which depended on the components of soil. In addition, the extent of competition was also found to be a function of the concentration of sorbate and competitor. The ideal adsorbed solution theory was introduced to predict the competitive effects from single-solute sorption isotherms, but it failed to model accurately binary sorption due to restrictive hypothesis. It was proposed that the adsorption sites were available to both herbicides varying from soil to soil as a plausible cause for their varying competitive behavior in soils.