北京城近郊区土壤对镉的吸附特征研究

Research on Adsorption Characters of Cadmium in Soils from the Suburbs of Beijing

在0.1～1200 mg/L不同Cd2+浓度条件下,进行了五个地区土壤对重金属Cd2+的静态吸附实验.土壤分别采自于北京城近郊丰台区北天堂村、大兴区庑殿村、通州区永乐店镇、海淀区四季青乡和朝阳区来广营乡五个地区.实验结果表明:常温常压下,土壤对Cd2+的吸附量与加入到土壤中的Cd2+总量呈现出一定的正相关.四季青、永乐店的重粉质壤土、庑殿的中粉质壤土及北天堂的轻壤土对Cd2+的吸附量S与土壤溶液中的平衡浓度C都基本满足直线拟合.在相同外源Cd2+浓度下,土壤对Cd2+的吸附量为:庑殿的中粉质壤土>四季青的重粉质壤土>永乐店的重粉质壤土>来广营的重粉质壤土>北天堂的轻壤土.在所拟实验条件下,土壤对镉的吸附很大程度上受到土壤有机质含量、土壤的粘粒和粉粒所占比例的控制,而酸碱度pH和氧化还原电位Eh对类型不同的土壤的吸附影响效应不很明显.

Five soil samples were collected from the suburbs of Beijing, namely Beitiantang Village in Fengtai District, Wudian Village in Daxing District, Yongledian Town of Tongzhou District, Sijiqing Town in Haidian District and Laiguangying Town in Chaoyang District. The static adsorption experiment of Cd^2＋ form the five soils was conducted under the Cd^2 ＋ concentration of 0.1 - 1200 mg/L. The results showed that under normal temperature and pressure, the adsorption capacity of Cd^2＋ by soils, namely the value of S, presented positive correlation with the total quantity of Cd^2＋ in the soils. The Cd^2＋ adsorption （S values） by the heavy silty soils from Sijiqing and Yongledian, the medium silty soils from Wudian and the light silty soils from Beitiantang basically conformed to the linear model with equilibrium concentration in soil solution （C values）. With the same Cd^2＋ concentration, the Cd^2＋ adsorption value S of five soil samples behaved as midium silty soils from Wudian 〉 heavy silty soils from Sijiqing 〉 heavy silty soils from Yongledian 〉 heavy silty soils from Laiguangying 〉 light silty soils from Beitiantang. The analytical results displayed that adsorption of cadmium by soils was greatly controlled by concentrations of organic matter, clayey grain and silty grain, while pH and Eh had little influence on it.