冻融对污染土壤中重金属稳定化性能影响研究

发布时间：2018-03-19 06:47

本文选题：冻融循环　切入点：重金属　出处：《辽宁工程技术大学》2015年硕士论文　论文类型：学位论文

【摘要】：为了分析冻融前后对污染土壤中的重金属稳定化后性能的影响,选取赤泥和硫化钠作为添加剂对土壤中的Pb、Zn和Cd进行稳定化处理。通过模拟冻融过程,分析冻融循环后重金属的浸出毒性、生物可给性、土壤pH和土壤结构的变化,通过力学渗透实验考查稳定化土壤,经过冻融处理前后的变化趋势,借助X射线衍射与扫描电镜来探讨冻融循环对稳定化处理土壤中重金属长期稳定性能的影响。结果表明：稳定化处理的土壤中Pb、Zn和Cd的浸出毒性分别比原始污染土降低了98.5%、99.8%和99.7%。养护30d后,Zn和Cd的生物可给性由28.8%和49.5%降到11.5%和21.8%,Pb的生物可给性由52.9%升到57.9%。预测Pb、Zn和Cd在土壤中的释放特征,探讨了经过60次冻融循环后3种土壤重金属稳定性的变化,其中Cd、Pb和Zn的浸出毒性与稳定化后样品相比增加了4.27、2.47和89.7mg/L,生物可给性比未冻融样品略有增高。随着养护时间与冻融时间的增长,土壤pH值呈现升高趋势。不同阶段土壤扫描电镜图片可以清晰的观察到不断的冻融循环迫使土壤空隙变大,结构松散。定性和定量分析结果表明冻融过程增加了Pb、Zn和Cd释放的环境风险。力学渗透结果表明,经过冻融的稳定化土壤渗透系数幅度与最大值均大于未经过稳定化的土壤。
[Abstract]:In order to analyze the effect of freezing and thawing on the stability of heavy metals in contaminated soil, red mud and sodium sulfide were selected as additives to stabilize Pb, Zn and CD in soil. The leaching toxicity, bioavailability, soil pH and soil structure of heavy metals after freeze-thaw cycle were analyzed. The effects of freeze-thaw cycle on the long-term stability of heavy metals in stabilized soils were investigated by means of X-ray diffraction and scanning electron microscopy. The results showed that the leaching toxicity of Pb, Zn and CD in stabilized soils was higher than that of original pollution, respectively. The bioavailability of Zn and CD decreased from 28.8% and 49.5% to 11.5% and 21.8Pb from 52.9% to 57.9%. The changes of the stability of heavy metals in three soils after 60 freeze-thaw cycles were studied. The leaching toxicity of CD _ (2 +) Pb and Zn was increased by 4.27 mg / L and 89.7 mg / L compared with the stabilized samples, and the bioavailability of CD _ (2 +) Pb and Zn was slightly higher than that of the samples without freezing and thawing, with the increase of curing time and freeze-thaw time. The soil pH values showed an increasing trend. The continuous freeze-thaw cycles forced the soil voids to become larger at different stages. The results of qualitative and quantitative analysis show that the freeze-thaw process increases the environmental risk of Pb ~ (2 +) Zn and CD release. The results of mechanical permeation show that the amplitude and maximum value of soil permeability coefficient after freezing and thawing are larger than those of unstabilized soil.
【学位授予单位】：辽宁工程技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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