凹凸棒石对Cd污染土壤的钝化修复研究

Stabilization Remediation of Soil Polluted by Cd Using Attapulgite

以甘肃临泽地区凹凸棒石为钝化材料,人工配制镉(Cd)浓度为2 mg/kg、4 mg/kg、6 mg/kg、8 mg/kg、12 mg/kg和16 mg/kg的污染土壤,按投加量分别为10 g/kg、20 g/kg、40 g/kg、60 g/kg和80 g/kg添加凹凸棒石,保持75%的田间持水量进行钝化试验和盆栽试验。结果表明,在同一污染水平下,随着投加量增大,二乙烯三胺五乙酸(DTPA)提取态Cd含量先降低后升高,当凹凸棒石添加量为60 g/kg时取得最小值。采用欧洲共同体参考机构(BCR)连续提取法,凹凸棒石能显著降低土壤中Cd的酸溶态含量,提高Cd的残渣态含量,促进重金属Cd向低毒性形态转化。凹凸棒石能显著抑制玉米对土壤中Cd的吸收和Cd从地下部分向地上部分转移,施加凹凸棒石处理组的生物吸收因子均显著低于对照组,当凹凸棒石添加量为60 g/kg时,生物吸收因子达到最小值,与对照组相比分别降低34.94%、24.10%、26.92%、32.43%、42.17%和51.69%。

Attapulgite was used as stabilization material in Linze area of Gansu Province.The contaminated soil with Cd concentration of 2 mg/kg,4 mg/kg,6 mg/kg,8 mg/kg,12 mg/kg and 16 mg/kg was prepared.The dosage of attapulgite was 10 g/kg,20 g/kg,40 g/kg,60 g/kg and 80%respectively.The stabilization experiment and pot experiment were carried out with 75%field water holding capacity.The results showed that at the same pollution level,the content of extracted Cd of diethylenetriamine pentaacetic acid(DTPA)decreased at first and then increased with the increase of dosage,and the minimum value was obtained when the amount of attapulgite was 60 g/kg.The results of continuous extraction by European Community Reference Agency(BCR)showed that attapulgite could significantly reduce the acid-soluble content of Cd in soil and increase the residue content of Cd,and promote the transformation of heavy metal Cd from highly toxic speciation to less toxic speciation.Attapulgite can significantly inhibit the absorption of corn to Cd in soil and the transfer of underground part to the aboveground part.Compared with the control group,the biological concentration factor in the attapulgite treatment group were significantly lower than those in the control group.At 60 g/kg the amount of attapulgite,biological concentration factor decreased by 34.94%,24.10%,26.92%,32.43%,42.17%and 51.69%compared with the control group.