几种典型土壤对电动修复镉污染效果的影响

Influence of several typical soils on removal of cadmium contaminants during electrokinetic remediation

选择5种典型土壤进行了镉污染的电动修复研究。结果表明,经12 d电动修复后,黑土、潮土、红壤、水稻土和黄棕壤中镉的去除率依次为16.7%、21.0%、47.1%、10.7%和12.6%。红壤靠阳极附近Cd含量由初期435 mg·kg-1降至32.4 mg·kg-1,迁移率高达92.5%。黑土、红壤和潮土都维持了较高的电流强度和电渗流量,但由于红壤对碱的缓冲能力较强,修复效果最好。水稻土中电渗流量高,但由于电流低,镉的去除率不高,说明电动修复中电迁移作用强于电渗析。修复后,土壤中可交换态镉、碳酸盐结合态镉、铁锰氧化物结合态镉总量减少,残渣态镉总量增加,有机结合态在阳极附近总量减少、阴极附近总量增加。上述结论揭示了电动修复的土壤镉污染的主要机制,通过镉的运动轨迹和形态分布,可预测不同土壤的电动修复效果,同时能改变不同土壤的电动修复策略,为场地修复提供参考。

Five typical soils were selected as cadmium（ Cd）-contaminated media for an electrokinetic remediation experiment. Results indicated that after 12 days of remediation,removal efficiencies of total Cd from paddy soil,fluvo-aquic soil,yellow-brown soil,red soil,and black soil were 16. 7%,21. 0%,47. 1%,10. 7%,and12. 6%,respectively. In the red soil,92. 5% of Cd near the anode migrated to the cathode,and the amount of Cd decreased from 435 mg ·kg^-1to 32. 4 mg ·kg^-1. High levels of current intensity and electroosmotic flow were observed in the red soil,black soil,and fluvo-aquic soil. Due to its high alkaline buffering capacity,the red soil showed the greatest remediation potential among these soils. Despite high electroosmotic flow in the paddy soil,low current intensity led to low removal efficiency of Cd,showing that electromigration played a more important role than electroosmosis did during Cd migration. The amount of exchangeable fractions,bound to carbonates fractions,and bound to Fe-Mn oxides fractions of Cd decreased after remediation,whereas residual fractions increased,other than in the anode. These results revealed the main mechanism of Cd migration in different soils,via electrokinetic remediation. Removal efficiencies may be predicted by analyzing Cd movement and distribution in soil; thus remediation strategies can be adjusted according to soil type,allowing effective guidance for site remediation work.