本文選題：重金屬 + 土壤修復　； 參考：《南京農(nóng)業(yè)大學》2015年碩士論文

【摘要】：我國農(nóng)田土壤重金屬污染問題不容樂觀,其中重金屬中高污染土壤占了 一定比例,研發(fā)適宜的重金屬中高污染農(nóng)田土壤治理技術(shù)具有重要的現(xiàn)實意義,本文針對重金屬中高污染農(nóng)田土壤,篩選"溫和"的淋洗劑,研究了柱淋洗對土壤重金屬的去除效果及對土壤性質(zhì)的影響,探討淋洗后土壤的改良與培肥技術(shù)以及殘留重金屬食物鏈風險,對淋洗后土壤種植伴礦景天進行吸取修復,探索了重金屬中高污染農(nóng)田土壤化學淋洗與植物吸取修復聯(lián)合技術(shù)的可行性。主要結(jié)論如下:(1)室內(nèi)振蕩實驗發(fā)現(xiàn)與三氯化鐵(FeCl3)和檸檬酸(CTA)單一淋洗劑相比,復合淋洗劑FeCl3+CTA可以提高污染土壤尤其是中性土壤的重金屬的去除,而對于酸性土壤單獨使用FeCl3即可以達到較高的去除效率;相同劑量淋洗劑分次淋洗較一次淋洗可提高重金屬的去除;重金屬的去除與其在土壤中的形態(tài)分布有關(guān),供試土壤酸溶態(tài)Cd濃度較Cu、Zn、Pb高,因此Cd的去除率明顯高于其它金屬;淋洗后土壤pH、CEC、交換性鈣鎂顯著降低。(2)采用自然淋溶的柱淋洗方式,利用20 mmol·L-1 FeCl3對污染土壤進行淋洗,結(jié)果表明,酸性土壤上隨淋洗的進行,洗出液Cd濃度很快達到最大,維持一段時間后開始下降,當液土比達到3.0時洗出液Cd濃度下降到最高時的40%左右,改用液土比為2的去離子水進行漂洗后洗出液中各元素的濃度均降至很低水平;采用3倍土壤體積的20 mmol·L-1 FeCl3淋洗+ 2倍土壤體積的去離子水漂洗,對酸性土壤Cd、Cu、Zn、Pb的去除率分別為45.2%、13%、20%、23.6%,而中性土壤的重金屬去除率很低;淋洗后土壤pH、速效NP、EC等有不同程度降低。(3)對柱淋洗后的酸性土壤進行培肥并種植小青菜,評價其食物鏈風險。結(jié)果發(fā)現(xiàn),淋洗但未予改良土壤上小青菜無法生長,添加改良劑后小青菜生物量均有增加,且以添加生石灰和有機肥的處理效果最好;與未淋洗土壤相比,淋洗后添加生石灰和有機肥改良,土壤CaCl2-Cd濃度由0.33 mg·kg-1降至0.14 mg·kg-1,降低了 58%。(4)將淋洗和改良培肥后的土壤種植鋅鎘超積累植物伴礦景天,對殘留重金屬進行吸取修復。結(jié)果表明,改良培肥可有效促進伴礦景天的生長、提高其Cd吸取修復效率,以0.18%生石灰+0.5%有機肥處理修復植物生物量最高;1%海泡石處理未明顯降低土壤Cd有效性,植物吸取修復的效率也最高,并且成本最低;因此,為使后續(xù)吸取修復保持較高效率,淋洗后土壤改良培肥以添加1%海泡石為宜。(5)單純化學淋洗對土壤Cd的去除率為45.2%,植物吸取修復Cd的去除率為35.3%,而化學淋洗、海泡石改良、植物吸取三個過程聯(lián)合,Cd去除率提高可高達63.8%,且后續(xù)伴礦景天的吸取修復還可增加土壤微生物活性,改善土壤結(jié)構(gòu)和其它理化性質(zhì)。綜上所述,對不同類型的重金屬土壤應采用不同的淋洗劑,如中性土壤可采用FeCl3+CTA復合淋洗劑,而酸性土壤則單獨使用FeCl3即可;對鎘重污染紅壤性水稻土,可采用化學淋洗+改良培肥+伴礦景天吸取的聯(lián)合修復模式,該模式既避免了單純化學淋洗成本高、環(huán)境風險大的問題,也克服了重污染土壤上單純植物修復周期長的不足,對我國南方礦冶區(qū)及周邊鎘重度污染紅壤性水稻土等的修復具有廣泛的應用前景和研究價值。
[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.
【學位授予單位】：南京農(nóng)業(yè)大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：X53

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