【作者】 缪德仁；

【导师】 陈鸿汉； 刘菲；

【作者基本信息】 中国地质大学（北京） ， 环境工程， 2010， 博士

【摘要】 随着工业化与城市化发展,土壤重金属污染已成为全球关注的环境问题之一。化学稳定化是控制污染物扩散的修复技术,稳定试剂的选择和重金属长期稳定性问题是其研究的主题。土壤重金属污染方式可分为突发性和累积性,在突发性污染方式下,土壤重金属的优势存在形态为水溶态和可交换态,重金属移动性强,生物活性大;在累积性污染方式下,次稳定态（如碳酸盐结合态）为土壤重金属的优势存在形态,重金属对环境的危害长期而持久,目前鲜见对其进行区别并加以研究的报道。本文采集不同酸碱度土壤,以外源添加污染物方式制备模拟突发性污染方式的土壤重金属复合污染样品,对CaCO₃、Na₂S₂O₃、Fe（OH）₃、K₃PO₄、K₂HPO₄、Ca（H₂PO₄）2和磷矿石进行快速化学稳定化稳定试剂筛选实验研究;采集原沈阳冶炼厂累积性污染方式的土壤重金属复合污染样品,采用三种稳定试剂组合方式（即T1:H₃PO₄+CaO、T2:Na₂S+CaCO₃和T3:H₃PO₄+Na₂S+CaCO₃）进行室内长期化学稳定化试验研究,通过去离子水、TCLP（Toxicity Characteristic Leaching Procedure）和SBET（Simple Bio accessi- bility Extraction Test）浸出方法对不同稳定时间各试剂组合对各目标元素的稳定效率进行评价。采用Tessier化学形态连续提取、MINTEQ化学形态平衡模型和光谱显微镜（XRD和EMPA）分析等技术相结合的手段对稳定后各目标元素在土壤中的形态转化、可能控制矿物和新形成矿物进行分析、预测和鉴定,得到以下主要研究成果。对突发性污染方式的重金属复合污染土壤来说,CaCO₃能快速控制Cu、Zn、Cd、Hg、Ni和Cr的扩散和迁移,土壤粘土矿物含量越高,控制效果越好;Na₂S₂O₃能有效控制Cr的扩散和迁移,土壤pH值越高,控制效果越好;Fe（OH）₃能有效控制As的扩散和迁移,6%（w/w）Fe（OH）₃可使土壤TCLP浸出液中As离子浓度降至低于0.18 mg·L^-1;含磷物质能有效控制Pb的扩散和迁移,Ca元素的存在对伴生污染元素Cd、Ni、Cu和Zn的控制有利;2%（w/w）Ca（H₂PO₄）₂对酸性土壤中Pb的稳定效率可达90%以上;然而CaCO₃、Na₂S₂O₃和含磷物质均能提高土壤As的活性。对累积性污染方式的重金属复合污染土壤来说,H₃PO₄能有效降低Pb的活性但增强了As的活性;Na₂S能有效降低Cu的活性。TCLP方法的稳定效率评价结果表明,经T1稳定后,各土壤Pb、Cd、Cu和Zn的稳定效率分别在:80.77～93.16%、64.64～73.07%、5.95～62.47%和9.67～38.17%之间;经T2稳定后,各土壤Pb、Cd、Cu和Zn的稳定效率分别在:47.33～75.44%、13.30～59.89%、54.75～83.08%和26.08～57.41%之间;经T3稳定后,各土壤Pb、Cd、Cu和Zn的稳定效率分别在:75.60～97.24%、74.75～78.77%、75.99～95.12%和25.67～42.41%之间。Tessier提取结果表明,经T1稳定后,各土壤Pb和Cd的残渣态转化率分别在:19.71～44.64%和5.89～35.32%之间;经T3稳定后,各土壤Pb和Cd的残渣态转化率分别在:23.39-45.03%和8.13-39.95%之间。SBET评价结果表明,经T1和T3稳定后,Pb和Cd的生物可给度降低但As的生物可给度升高;经T2稳定后,As、Pb和Cd的生物可给度均降低。MINTEQ模型模拟结果表明,经T1和T3稳定后,土壤Pb的可能控制矿物是PbHPO₄;经T2稳定后,土壤Pb的可能控制矿物是PbCO₃和PbSO₄。XRD和EPMA分析表明,经T1和T3稳定后,土壤中有磷氯铅矿[Pb5（PO₄）₃Cl]矿物形成,经T2和T3稳定后,土壤中有以Cu硫化物为主的多金属硫化物沉淀/矿物生成。T3试剂组合方式对各目标元素的稳定效率及长期稳定性优于T1和T2。更多还原

【Abstract】 Heavy metals contamination in soils is increasingly under environmental concern, as a result of the rapid industrialization and urbanization. Accumulation of heavy metals in soils and subsequently in waters or in food chain is potential threat to human health. Hence, increasing awareness of the hazard makes it necessary to remediate metal contaminated soils. Heavy metal contaminants cannot be destroyed like organic contaminants but only be relocated from one place to another or transferred its environmental existing speciation. Conventional soil remediation technologies based on the excavation, transport, and landfill of metal contaminated soils are highly effective at a low risk, but the cost is high. In situ chemical immobilization technique is of particular interest because it is relatively cost-effective and less disruptive to the environment.The amendments selection and immobile mechanism are the two key aspects which should be taken into account on chemical immobilization study. However, heavy metals speciation distributions in soils between emergency contaminated style and accumulative contaminated style are quite different. Water soluble and exchangeable fractions are the predominant existing species in emergency contaminated soils. In order to hinder the spread of heavy metals in the environment immediately, amendments quick immobile effectiveness should be considered firstly. In accumulative contaminated soils, on the other hand, secondary stable fractions, e.g. carbonate associated fraction, are the predominant existing species, and pose a permanent threat to the environment. Thus, the immobile efficiencies and the long-term stabilities should be taken into account. Unfortunately, discriminatively chemical immobilization research on soils contaminated between these two contamination styles is limited. The purpose of this paper are to select the most effective amendments for emergency multi-heavy metals contaminated soils, to identify immobile efficiencies of different amendments combination for accumulative ones, and to predict metals long-term stability mended by chemical immobile technique.In the present study, four soils with various pH values have been sampled. Experimental soils, mimicking emergency multi-heavy metals contaminated soils, synthesized by adding the corresponding soluble metal salts. The quick immobile effectiveness of CaCO₃, Na₂S₂O₃, Fe （OH） 3, K₃PO₄, K₂HPO₄, Ca （H₂PO₄）2 and phosphate rock for each target metal has been examined by using TCLP （Toxicity Characteristic Leaching Procedure） method. The accumulative multi-heavy metals contaminated soils, sampled from an inoperative smelter site in Shenyang, were immobilized with three chemical immobilization treatments, i.e. T1: H₃PO₄+CaO, T2: Na₂S+CaCO₃ and T3: H₃PO₄+Na₂S+CaCO₃. The effectiveness of every treatment for the tested soils was evaluated by using water extraction, TCLP, and Tessier’s sequential extraction method. Metals bioaccessibilities were evaluated by an SBET （simple bioaccessibility extraction test） method mimicking metal uptake in the acidic environment of human stomach. The possible mechanisms for metal immobilization were elucidated using XRD （X-ray diffraction）, EPMA （electron probe micro-analyzer） and chemical speciation program Visual MINTEQ. Results listed as follow:In emergency multi-heavy metals contaminated soils:1. CaCO₃ could effectively hinder the spread and translocation of Cu, Zn, Cd, Hg, Ni and Cr in the environment. With the same dosage, the higher clay contents the higher immobile effectiveness.2. Na₂S₂O₃ could effectively hinder the spread and translocation of Cr in the environment. Added 2% （w/w） Na₂S₂O₃ to acidic and alkaline soils, the immobile effectiveness of Cr were above 74% and 98%, respectively.3. Fe （OH）₃ could effectively hinder the spread and translocation of As in the environment. Added 6% （w/w） Fe （OH）₃, the concentrations of As in TCLP leachates decreased below 0.18 mg·L^-1 in all tested soils.4. Phosphorus-containing materials could effectively hinder the spread and translocation of Pb in the environment. The presence of Ca element would be favor to immobilize Cd, Ni, Cu and Zn, added 2% （w/w） Ca （H₂PO₄）₂ to acidic soils, the immobile effectiveness of soil Pb achieved above 90%.5. CaCO₃, Na₂S₂O₃ and phosphorus-containing materials increased the concentrations of As in TCLP leachates.In accumulative multi-heavy metals contaminated soils:a. In T1-treated soils, the immobile effectiveness of Pb, Cd, Cu and Zn evaluated by TCLP are at the range of 80.77-93.16%, 64.64-73.07%, 5.95-62.47% and 9.67-38.17%, respectively.b. In T2-treated soils, the immobile effectiveness of Pb, Cd, Cu and Zn evaluated by TCLP are at the range of 47.33-75.44%, 13.30-59.89%, 54.75-83.08% and 26.08-57.41%, respectively.c. In T3-treated soils, the immobile effectiveness of Pb, Cd, Cu and Zn evaluated by TCLP are at the range of 75.60-97.24%, 74.75-78.77%, 75.99-95.12% and 25.67-42.41%, respectively.d. T1 and T3 treatments significantly increased the availability of soil As.e. Sequential extraction results indicated that the residual fraction conversion ratio of soil Pb and Cd in T1 treated soils at the range of 19.71-44.64% and 5.89-35.32%, respectively, and in T2 treated soils at the range of 23.39-45.03% and 8.13-39.95%, respectively.f. SBET results indicated that T1 and T3 treatments were effective in reducing soil Pb and soil Cd bioaccessibilities while significantly increasing soil As bioaccessibility, T2 treatment was effective in reducing Pb, Cd and As bioaccessibilities in all tested soils.g. MINTEQ model and activity-ratio diagram indicated that PbHPO₄ controlled Pb²⁺ activities in T1 and T3 treated soils. However, PbCO₃ controlled Pb²⁺ activities in T2 treated soils.h. XRD and EPMA elucidated that the mechanism for Pb immobilization were via formation of insoluble chloropyromorphite minerals in T1 and T3 treated soils. The mechanism for Cu, Zn and Cd immobilization were via formation of multi-metal sulfide precipitates （minerals）. However, the Cu-sulfide is predominant in multi-metals sulfide precipitates （minerals）.In conclusion, T3 treatment proved an effective approach to immobilize Pb, Cd, Cu and Zn for accumulatively multiple contaminated soils. Further research needs to be done on the sequential extraction procedure for Fe-rich industrial contaminated soils.更多还原