铬污染土壤的还原稳定化修复

以湖南某工业场地的铬污染土壤为修复对象，投加不同比例的FeSO4·7H2O、FeSO4·7H2O和Ca（OH）2混合物及NaHSO3，通过测定土壤及浸出液中六价铬、总铬以及铬的形态，比较3种稳定剂对该污染土壤的还原稳定化作用。结果表明，FeSO4·7H2O和NaHSO3对铬污染土壤的还原稳定效果都较好，可以有效还原土壤中六价铬并能降低土壤中总铬的浸出浓度。当FeSO4·7H2O投加量为2%时，土壤六价铬和总铬浸出浓度降幅分别达到99.0%和57.5%；当NaHSO3投加量为0.8%时，六价铬和总铬浸出浓度降幅分别达到97.7%和42.2%，与前二者相比，FeSO4·7H2O和Ca（OH）2混合物还原稳定化效果较差。投加FeSO4·7H2O能够将土壤中活性大的可交换态和碳酸盐态铬转化为稳定的有机态和残渣态铬；而NaHSO3主要将可交换态和碳酸盐态铬转化为相对稳定的铁锰氧化态铬，其稳定化效果要差于FeSO4·7H2O。

Experimental research onstabilization remediation of chromium contaminated soil

Different proportions of FeSO4·7H2O, mixture of FeSO4·7H2O and Ca(OH)2 and NaHSO3, were added in the chromium polluted soil collected from an industrial area in Hunan Province. The efficiencies of 3 different stabilizers on the remediation of chromium contaminated soil were compared based on the contents of hexavalent chromium, total chromium and chromium of different forms in soil and leaching liquids. The results show that both FeSO4·7H2Oand NaHSO3 can effectively reduce the leaching concentration of hexavalent chromium and total chromium. When dosing quantity of FeSO4·7H2O was 2%, reduction of hexavalent chromium and total chromium in the leaching liquid of the contaminated soil were 99.0% and 57.5%, respectively.When dosing quantity of NaHSO3 was 0.8%, reduction of hexavalent chromium and total chromium in the leaching liquids of the contaminated soil were 97.7% and 42.2%, respectively. Compared with the former two stabilizers, stabilization effect of the mixture of FeSO4·7H2O and Ca(OH)2 was poor. FeSO4·7H2O can transform the active exchangeable and carbonate chromium to the stable organic and residual chromium;NaHSO3 can mainly transform exchangeable and carbonate chromium to the relatively stable manganese-iron combination state, which is the reason why its stabilization efficiency is worse than FeSO4·7H2O.