冻融循环对含铁材料稳定砷污染土壤的影响

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.