中文摘要：

采用批量平衡试验方法,研究了柠檬酸对黄棕壤、棕红壤和红壤吸附五氯酚（PCP）的影响.结果表明,供试3种土样对PCP的等温吸附曲线均可用Freundlich吸附等温方程描述,对PCP的吸附容量大小为黄棕壤〉棕红壤≥红壤,与其有机质含量大小顺序一致.实验条件下,随着柠檬酸加入浓度的提高（0~100mmol/L）,棕红壤和红壤对PCP的吸附容量和吸附强度表现为先升高后下降的趋势,较低浓度（≤50mmol/L）的柠檬酸处理显著促进了它们对PCP的吸附,而较高浓度柠檬酸处理则抑制其吸附.供试浓度范围内,柠檬酸对PCP在黄棕壤中的吸附容量和吸附强度均表现为促进作用,但较高浓度柠檬酸处理下促进作用减弱.加入柠檬酸后,土壤吸附PCP的平衡溶液的pH值显著降低,这可促进PCP在土壤中的吸附,同时土壤固相有机质的释放和溶液中溶解性有机质（DOM）浓度的增加则可减少土壤对PCP的吸附.

英文摘要：

The impacts of citric acid on sorption of pentachlorophenol（PCP） by three typical zonal soils in China,including yellow-brown soil,brown-red soil,and red soil,were investigated by a batch experimental technique.The sorption isotherm of PCP by soils can be well described by Freundlich equation.The sorption capacity of PCP by three test soils was in the order of yellow-brown soil〉 brown-red soil 〉 red soil,which was positively correlated to the soil organic matter contents（foc）.The presence of citric acid dramatically affected the PCP sorption.The sorption capacity of PCP by brown-red soil and red soil increased firstly and decreased thereafter with the increment of citric acid concentrations from 0 to 100 mmol/L.The addition of citric acid significantly enhanced the sorption of PCP in yellow-brown soil.However,the enhancement tended to weaken with the presence of citric acid at higher concentrations.It was observed that the pH values lowered and dissolved organic matter（DOM） concentrations enlarged in the equilibrium solution with the increase of added citric acid concentrations.The sorption of PCP by soil enhanced at the lower pH value and weakened by the higher DOM concentration in solution.