氨氮在滦河三角洲典型包气带介质上的吸附性能研究

Ammonia-nitrogen adsorption characteristics onto vadose zone soils in Luanhe Delta

包气带是地下水的天然屏障,也是氮素污染地下水的主要通道。以滦河三角洲包气带4种典型土壤粉砂、砂粉土、粉土以及粉质粘土为研究对象,通过静态吸附实验查明了4种不同土壤对氨氮的吸附性能。结果表明,4种土壤对氨氮的吸附主要发生在0~2 h,其吸附均符合二级吸附动力学方程;其等温吸附曲线均符合Langmuir模式,且最大吸附量分别为粉砂0.138 mg/g,砂粉土0.382 mg/g,粉土0.428 mg/g,粉质粘土0.534 mg/g。不同土壤对氨氮的吸附能力随着粒径的不同差异较大,表现为：粉质粘土〉粉土〉砂粉土〉粉砂。说明粉质粘土防污能力最强,粉土次之,粉砂最弱。结果为查明氨氮在包气带的迁移转化规律提供理论依据,同时对水土氮污染防治有着重要的意义。

Vadose zone is a nateral barrier for groundwater.It is also the main polluted channel through which nitrogen enter into the groundwater.In this paper,four typical soils in Luanhe delta which named silty sand,sandy silt,silt and silty clay are examined.Adsorption characteristics of ammonia-nitrogen onto four different soils were studied.The results indicated that the process of ammonia-nitrogen adsorption onto soils mainly occurred within 0~2 h,then attended to a dynamic equilibrium.Two kinetic models can describe the experimental data and the second-order kinetic model was the best.The data of the ammonia-nitrogen sorption isotherms at different initial concentration ranges can be fitted by the linear form of Langmuir model remarkably.The maximal ammonia-nitrogen sorption capacity ranged from 0.138 to 0.534 mg/g.The capacities of four soils to prevent pollution are different and the order is silty clay,silt,sandy silt and silty sand.