冻融循环对含铁材料稳定砷污染土壤的影响

为分析冻融循环对污染土壤砷（As）的稳定化性能的影响，投加4种含铁材料（FeSO4、FeS、Fe2（SO4）3和Fe0）对土壤中的As进行稳定化处理，并通过实验室模拟冻融过程，研究4种含铁材料稳定化处理后土壤中无定形氧化铁含量、氧化铁活化度、pH和As的浸出毒性随冻融循环的变化。结果表明：4种含铁材料稳定化土壤无定形氧化铁含量与氧化铁活化度随冻融循环的变化趋势基本一致；冻融循环降低了无定形氧化铁的含量，促进了铁氧化物的结晶老化。与未冻融土壤相比，冻融循环增加了稳定化土壤As的浸出毒性，但在冻融后期，As浸出毒性的增加量呈降低的趋势。4种含铁材料稳定化土壤As的浸出毒性随冻融循环表现出不同的变化趋势。1% Fe0稳定化土壤经过冻融循环As的稳定性最高，1% FeSO4和1% Fe2（SO4）3稳定化土壤次之，而1% FeS稳定化土壤最低。因此，冻融循环增加了稳定化土壤As再释放的环境风险，Fe0用做冻融地区As污染土壤稳定化药剂较为合适。

Effect of freeze-thaw cycles on stabilizing arsenic contaminated soil by iron-containing materials

In order to analyze the effects of freeze-thaw cycles on the stabilization performance of arsenic (As), four kinds of iron-containing materials (FeSO4, FeS, Fe2(SO4)3 and Fe0) were used as stabilizing agents to treat As contaminated soil. The effects of freeze-thaw cycles on the amorphous iron oxide content, activation rate of iron oxide, soil pH and leaching toxicity of As in stabilized soil were studied by laboratory simulation. The results showed that the variation trends of amorphous iron oxide content and activation rate of iron oxide with freeze-thaw cycles were similar in stabilized soil. The freeze-thaw cycles decreased the content of the amorphous iron oxide, promoting crystallization and aging of the iron oxide. The leaching toxicity of As in stabilized soil after freeze-thaw treatment was higher than that in the samples without freeze-thaw treatment. However, the increment of As leaching toxicity showed a reducing trend during the late freeze-thaw cycles. The leaching toxicity of As in soil stabilized by four kinds of iron-containing materials presented different variation trends. The stabilization efficiency of As in 1% Fe0 stabilized soil after continuous freeze-thaw cycles was the best, 1% FeSO4 stabilized soil and 1% Fe2(SO4)3 stabilized soil second, and 1% FeS stabilized soil was most poor. The results of qualitative and quantitative analysis indicated that the freeze-thaw process increased the release risks of As in stabilized soil, and Fe0 was a more suitable stabilizing agent for As contaminated soil in freeze-thaw areas.