重金属中高污染农田土壤的化学淋洗—植物吸取联合修复技术研究

发布时间：2018-07-06 21:35

本文选题：重金属 + 土壤修复　；参考：《南京农业大学》2015年硕士论文

【摘要】：我国农田土壤重金属污染问题不容乐观,其中重金属中高污染土壤占了一定比例,研发适宜的重金属中高污染农田土壤治理技术具有重要的现实意义,本文针对重金属中高污染农田土壤,筛选"温和"的淋洗剂,研究了柱淋洗对土壤重金属的去除效果及对土壤性质的影响,探讨淋洗后土壤的改良与培肥技术以及残留重金属食物链风险,对淋洗后土壤种植伴矿景天进行吸取修复,探索了重金属中高污染农田土壤化学淋洗与植物吸取修复联合技术的可行性。主要结论如下:(1)室内振荡实验发现与三氯化铁(FeCl3)和柠檬酸(CTA)单一淋洗剂相比,复合淋洗剂FeCl3+CTA可以提高污染土壤尤其是中性土壤的重金属的去除,而对于酸性土壤单独使用FeCl3即可以达到较高的去除效率;相同剂量淋洗剂分次淋洗较一次淋洗可提高重金属的去除;重金属的去除与其在土壤中的形态分布有关,供试土壤酸溶态Cd浓度较Cu、Zn、Pb高,因此Cd的去除率明显高于其它金属;淋洗后土壤pH、CEC、交换性钙镁显著降低。(2)采用自然淋溶的柱淋洗方式,利用20 mmol·L-1 FeCl3对污染土壤进行淋洗,结果表明,酸性土壤上随淋洗的进行,洗出液Cd浓度很快达到最大,维持一段时间后开始下降,当液土比达到3.0时洗出液Cd浓度下降到最高时的40%左右,改用液土比为2的去离子水进行漂洗后洗出液中各元素的浓度均降至很低水平;采用3倍土壤体积的20 mmol·L-1 FeCl3淋洗+ 2倍土壤体积的去离子水漂洗,对酸性土壤Cd、Cu、Zn、Pb的去除率分别为45.2%、13%、20%、23.6%,而中性土壤的重金属去除率很低;淋洗后土壤pH、速效NP、EC等有不同程度降低。(3)对柱淋洗后的酸性土壤进行培肥并种植小青菜,评价其食物链风险。结果发现,淋洗但未予改良土壤上小青菜无法生长,添加改良剂后小青菜生物量均有增加,且以添加生石灰和有机肥的处理效果最好;与未淋洗土壤相比,淋洗后添加生石灰和有机肥改良,土壤CaCl2-Cd浓度由0.33 mg·kg-1降至0.14 mg·kg-1,降低了 58%。(4)将淋洗和改良培肥后的土壤种植锌镉超积累植物伴矿景天,对残留重金属进行吸取修复。结果表明,改良培肥可有效促进伴矿景天的生长、提高其Cd吸取修复效率,以0.18%生石灰+0.5%有机肥处理修复植物生物量最高;1%海泡石处理未明显降低土壤Cd有效性,植物吸取修复的效率也最高,并且成本最低;因此,为使后续吸取修复保持较高效率,淋洗后土壤改良培肥以添加1%海泡石为宜。(5)单纯化学淋洗对土壤Cd的去除率为45.2%,植物吸取修复Cd的去除率为35.3%,而化学淋洗、海泡石改良、植物吸取三个过程联合,Cd去除率提高可高达63.8%,且后续伴矿景天的吸取修复还可增加土壤微生物活性,改善土壤结构和其它理化性质。综上所述,对不同类型的重金属土壤应采用不同的淋洗剂,如中性土壤可采用FeCl3+CTA复合淋洗剂,而酸性土壤则单独使用FeCl3即可;对镉重污染红壤性水稻土,可采用化学淋洗+改良培肥+伴矿景天吸取的联合修复模式,该模式既避免了单纯化学淋洗成本高、环境风险大的问题,也克服了重污染土壤上单纯植物修复周期长的不足,对我国南方矿冶区及周边镉重度污染红壤性水稻土等的修复具有广泛的应用前景和研究价值。
[Abstract]:The problem of heavy metal pollution in farmland soil in China is not optimistic, among which the high pollution soil of heavy metals is a certain proportion. It is of great practical significance to research and develop the suitable technology for soil treatment of high polluted farmland in heavy metals. In this paper, a "mild" leaching agent is selected for the high polluted farmland soil in heavy metals, and the heavy soil gold is studied by the column leaching. The effect of the removal of the genus and the soil properties, the improvement of the soil and the risk of the residual heavy metal food chain after leaching are discussed. The feasibility of the combined technology of soil chemical leaching and plant extraction in high polluted farmland is explored. The main conclusions are as follows. (1) (1) indoor oscillation experiment found that the compound leaching agent FeCl3+CTA can improve the removal of heavy metals in contaminated soil, especially in neutral soil compared with the single drenching agent of iron trichloride (FeCl3) and citric acid (CTA), and higher removal efficiency can be achieved by using FeCl3 alone in acid soil, and the same dosage of leaching agent is more than one leaching. The removal of heavy metals by secondary leaching can improve the removal of heavy metals; the removal of heavy metals is related to their distribution in the soil. The concentration of acid soluble Cd in the tested soil is higher than that of Cu, Zn and Pb. Therefore, the removal rate of Cd is significantly higher than that of other metals; the soil pH, CEC, and exchangeable calcium and magnesium are significantly reduced after leaching. (2) 20 mmol. L-1 FeCl3 is used in natural leaching. The leaching of contaminated soil shows that the concentration of Cd in the acid leaching solution reaches the maximum quickly with the leaching of the acid soil, and begins to decline after a period of time. When the ratio of liquid to soil reaches 3, the concentration of Cd drops to about 40%, and the concentration of each element in the rinse solution after the rinse of liquid soil is 2. To a very low level, the removal rate of Cd, Cu, Zn, Pb in acid soil was 45.2%, 13%, 20%, 23.6% in acid soil Cd, Cu, Zn, and Pb, using 3 times the soil volume of 20 mmol. FeCl3 and Pb, and the removal rate of heavy metals in neutral soil was very low; the soil pH, quick acting NP, EC and so on after leaching were reduced in varying degrees. (3) the acid after leaching of the column was acidic. The soil was fertilized and planted with small green vegetables to evaluate the risk of food chain. It was found that the small green cabbage could not grow on the soil without improvement, and the biomass of small green vegetables increased after the addition of the modifier, and the treatment effect was best with the addition of lime and organic fertilizer. The soil CaCl2-Cd concentration decreased from 0.33 mg to kg-1 to 0.14 mg. Kg-1, and reduced 58%. (4) to plant zinc and cadmium superaccumulating plant with Rhodiola in soil after leaching and improvement. The results showed that the modified fertilizer could effectively promote the growth of the companion mine, improve the efficiency of Cd absorption and repair, and take 0.18% lime +0.5. The 1% sepiolite treatment did not significantly reduce the soil Cd efficiency, and the efficiency of plant remediation was the highest and the cost was the lowest. Therefore, in order to keep the follow-up and repair to maintain high efficiency, the soil improved after leaching to add 1% sea blister is suitable. (5) pure chemical leaching of soil Cd removal rate For 45.2%, the removal rate of Cd was 35.3%, while chemical leaching, sepiolite improvement, plant absorption three processes combined, and the removal rate of Cd increased by up to 63.8%. Furthermore, the soil microbial activity, soil structure and its physicochemical properties could be increased, and the soil structure and its physicochemical properties were also improved. Different leaching agents should be used in the soil, such as FeCl3+CTA compound lotion in neutral soil and FeCl3 in acid soil, and the combined remediation model of chemical leaching + improved fertilizer and absorption of Sedum in red soil paddy soil with cadmium heavy pollution can be used. This model not only avoids high cost of pure chemical leaching, but also has great environmental risk. The problem has also overcome the long shortage of simple plant repair cycle in heavy polluted soil, which has extensive application prospect and research value for the restoration of red soil paddy soil in Southern Mining and metallurgy areas and the surrounding cadmium polluted red soil paddy soil.
【学位授予单位】：南京农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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