电动修复过程中电极逼近对土壤砷迁移与形态转化的影响

以高浓度砷污染土壤为修复对象，探究电极逼近法耦合捕集室对砷污染土壤的修复效果。实验设置4个处理，分别为固定电极 (FE-EK) 、阴极逼近 (AC-EK) 、阳极逼近 (AA-EK) 和两极逼近 (AAC-EK) 。结果表明，AC-EK、AA-EK以及AAC-EK对总砷[As(T)]的迁移具有促进作用，表现为捕集室中As(T)质量分数与初始值相比显著升高 (p<0.05) ，而FE-EK捕集室中As(T)质量分数与初始值相比无显著性差异 (p>0.05) ，As(T)整体迁移率以AAC-EK最高 (31.50%) ，FE-EK最低 (15.38%) 。由于土壤整体氧化还原电位升高，使得FE-EK、AC-EK、AA-EK、AAC-EK处理组三价砷平均质量分数较初始值分别降低9.78%、7.81%、13.65%、4.09%。砷的生物有效性在Fe₂O₃和电动效应的联合作用下不断降低，表现为可交换态砷、铝结合态砷、钙结合态砷向铁结合态砷、残渣态砷转化。本研究结果表明，AAC-EK促进As(T)迁移的效果最好，可交换态砷占比最低，且单位修复能耗最低，具有良好的砷污染土壤修复潜力。

Effect of the approaching electrode on the soil arsenic migration and speciation transformation during electrokinetic remediation

The remediation effect of the approaching electrode technique coupled with a capture chamber was evaluated using soil contaminated with a high concentration of arsenic. Four treatments were set up in the experiment: fixed-electrode electrokinetic (FE-EK), approaching cathode electrokinetic (AC-EK), approaching anode electrokinetic (AA-EK), and approaching anode and cathode electrokinetic (AAC-EK) techniques. The results demonstrated that AC-EK, AA-EK, and AAC-EK techniques promoted the migration of total arsenic [As(T)]: the mass fraction of As(T) in their capture chambers was significantly higher than the initial value(p<0.05), while that in the capture chamber of FE-EK did not differ significantly from the initial value(p>0.05). The overall migration rates of As(T) in AAC-EK was the highest (31.50%), and that in FE-EK was the lowest (15.38%). The average mass fraction of trivalent arsenic in FE-EK, AC-EK, AA-EK, and AAC-EK techniques decreased by 9.78%, 7.81%, 13.65%, and 4.09%, respectively, compared with the initial value owing to an increase in the overall soil redox potential. Under the combined influence of Fe2O3 and electric-influence, the bioavailability of arsenic was continuously reduced, as evidenced by the conversion of exchangeable arsenic, aluminum-bound arsenic, and calcium-bound arsenic to iron-bound arsenic and residual arsenic. This study showed that AAC-EK was associated with the highest As(T) migration, lowest proportion of exchangeable arsenic, and lowest energy consumption per unit of remediation. Thus, the AAC-EK technique had good potential for remediating arsenic-contaminated soil.