發(fā)布時(shí)間：2018-08-21 15:07

【摘要】：近年來(lái),隨著采礦和冶煉業(yè)的迅速發(fā)展,在有色金屬冶煉過(guò)程中排放的含有重金屬的廢渣、廢液和廢氣會(huì)通過(guò)各種途徑進(jìn)入土壤,致使周邊土壤生態(tài)系統(tǒng)遭到破壞,土壤環(huán)境質(zhì)量下降。土壤環(huán)境的安全不僅關(guān)系到整個(gè)生態(tài)環(huán)境安全,而且對(duì)國(guó)家農(nóng)業(yè)生產(chǎn)安全也至關(guān)重要。在眾多污染土壤修復(fù)技術(shù)中,淋洗法因具有能迅速有效的去除大部分污染物的特點(diǎn),而被認(rèn)為能用于污染現(xiàn)場(chǎng)的迅速修復(fù)治理,但當(dāng)前對(duì)不同淋洗劑的淋洗應(yīng)用潛力仍需要進(jìn)一步深入研究。本研究為探討淋洗法在修復(fù)鉛鋅廠周邊重金屬污染土壤的修復(fù)效果及淋洗后土壤的利用價(jià)值及其潛在環(huán)境風(fēng)險(xiǎn),試驗(yàn)中采用振蕩淋洗的方法比較了幾種螯合劑、有機(jī)酸及無(wú)機(jī)酸等淋洗劑對(duì)不同污染程度土壤中Cd、Cu、Zn、Pb的去除效果,并用BCR連續(xù)提取法分析了淋洗前后土壤中各重金屬形態(tài)的變化,最后通過(guò)黑麥草盆栽實(shí)驗(yàn)及土壤酶分析,探討了土壤經(jīng)淋洗后的潛在生態(tài)風(fēng)險(xiǎn)。主要研究結(jié)果如下:(1)EDTA、EDDS、EGTA、NTA等4種螯合劑對(duì)土壤重金屬Cd、Cu、Zn、Pb的去除率各不相同,但Cd的去除率均呈現(xiàn)出EDTANTAEDDSEGTA的特點(diǎn)。對(duì)于Cd、Cu、Zn和Pb等重金屬而言,EDTA是較理想的淋洗劑,EDTA在濃度100mmol/L、pH 4、淋洗時(shí)間24 h的條件下,對(duì)污染土壤中重金屬離子的去除率分別達(dá)Cd 76.4%-91.0%、Cu 38.1%-42.5%、Zn 19.2%-57.0%、Pb 45.4%-52.0%。(2)比較了乙酸、草酸、酒石酸、檸檬酸等4種有機(jī)酸對(duì)土壤中Cd、Cu、Zn、Pb的去除效果,結(jié)果表明,隨著濃度增加重金屬去除率也增加,在0.1mol/L時(shí),檸檬酸和酒石酸分別對(duì)重金屬的去除率最大;淋洗過(guò)程中,檸檬酸對(duì)Cd、Cu、Zn、Pb的去除效果略好于酒石酸,但從4種有機(jī)酸總體的去除率來(lái)看,0.1mol/L的檸檬酸和酒石酸對(duì)Cd、Cu、Zn、Pb等4種重金屬的去除效果最好,且檸檬酸更適合處理污染嚴(yán)重的區(qū)域3土壤,酒石酸適合淋洗區(qū)域污染較輕的區(qū)域1土壤。(3)相比以上4種有機(jī)酸,無(wú)機(jī)酸HCl對(duì)重金屬有較好的去除率。對(duì)Cd、Cu、Zn、Pb等4種重金屬而言,當(dāng)HCl濃度為0.1mol/L時(shí),4種重金屬去除達(dá)到最大,其大小分別為Cd(88.3%)Zn(60%)Pb(44.1%)Cu(23.7%);強(qiáng)酸對(duì)土壤的結(jié)構(gòu)和營(yíng)養(yǎng)物質(zhì)等理化性質(zhì)造成很大的破壞,因此使用HCl存在較大的環(huán)境風(fēng)險(xiǎn)。(4)淋洗前后土壤中重金屬的形態(tài)分析表明EDTA、NTA、酒石酸、檸檬酸淋洗能夠有效去除酸溶態(tài)、可還原態(tài)等有效態(tài)的重金屬,降低了土壤中的重金屬生物有效性和對(duì)環(huán)境的影響。(5)土壤經(jīng)過(guò)淋洗后,可以顯著減少黑麥草對(duì)重金屬的吸收,且與未淋洗土壤相比,EDTA和NTA淋洗后土壤種植黑麥草后土壤呼吸均未發(fā)生顯著變化,EDTA淋洗后土壤酶活性比NTA淋洗后土壤酶活性要高;與檸檬酸相比,酒石酸淋洗土壤種植黑麥草后土壤呼吸作用和土壤酶活性大小均有所增加。(6)因此,在降低土壤中重金屬含量的同時(shí)土壤能夠再利用,鑒于上述分析,考慮EDTA、NTA、酒石酸、檸檬酸和HCl的成本價(jià)格、淋洗效率和土壤潛在利用價(jià)值等因素,可認(rèn)為采用EDTA和檸檬酸淋洗修復(fù)重金屬污染土壤具有一定的實(shí)用性,并且環(huán)境風(fēng)險(xiǎn)較小。
[Abstract]:In recent years, with the rapid development of mining and smelting industry, the waste residue containing heavy metals discharged in the process of non-ferrous metals smelting will enter the soil through various ways, resulting in the destruction of the surrounding soil ecosystem and the decline of soil environmental quality. Among many remediation technologies for contaminated soils, leaching is considered to be a rapid remediation method for contaminated sites because it can remove most of the contaminants quickly and effectively. However, the potential of different leaching agents still needs further study. Remediation effect of leaching method on heavy metal contaminated soil around Pb-Zn plant and its potential environmental risk were discussed. The removal effects of several chelating agents, organic acids and inorganic acids on Cd, Cu, Zn and Pb in different contaminated soils were compared by oscillating leaching method. The removal efficiency of Cd, Cu, Zn and Pb in the soil was continuously extracted by BCR. The main results are as follows: (1) The removal rates of Cd, Cu, Zn and Pb by EDTA, EDDS, EGTA and NTA are different, but the removal rates of Cd, Zn and Pb are different. EDTA is an ideal eluent for heavy metals such as Cd, Cu, Zn and Pb. Under the conditions of 100 mmol/L, pH 4 and 24 h of elution time, the removal rates of heavy metal ions in contaminated soil by EDTA are 76.4% - 91.0%, 38.1% - 42.5%, 19.2% - 57.0% for Zn and 45.4% - 52.0% for Pb, respectively. The results showed that the removal efficiency of Cd, Cu, Zn and Pb increased with the increase of concentration, and the removal efficiency of citric acid and tartaric acid was the highest at 0.1 mol/L. The removal efficiency of Cd, Cu, Zn and Pb by citric acid was slightly better than that by tartaric acid during the leaching process. According to the total removal rate of acid, 0.1 mol/L citric acid and tartaric acid had the best removal effect on four heavy metals, such as Cd, Cu, Zn, Pb, and citric acid was more suitable for the treatment of three soils in the heavily polluted area, while tartaric acid was suitable for the treatment of one soil in the lightly polluted area. (3) Compared with the above four organic acids, HCl had a better removal rate of heavy metals. For four heavy metals, such as Cd, Cu, Zn and Pb, when HCl concentration was 0.1 mol/L, the removal of the four heavy metals reached the maximum, the size of which was Cd (88.3%) Zn (60%) Pb (44.1%) Cu (23.7%); strong acid caused great damage to soil structure and nutrient properties, so the use of HCl had a greater environmental risk. (4) Heavy gold in soil before and after leaching. Morphological analysis showed that EDTA, NTA, tartaric acid and citric acid leaching could effectively remove acid-soluble and reducible heavy metals, and reduce the bioavailability of heavy metals in soil and their impact on the environment. (5) After leaching, the uptake of heavy metals by ryegrass could be significantly reduced, and EDTA and citric acid leaching could reduce the bioavailability of heavy metals in soil and the environmental impact. Soil respiration did not change significantly after NTA leaching, and soil enzyme activity after EDTA leaching was higher than that after NTA leaching. Compared with citric acid, soil respiration and soil enzyme activity increased after planting Lolium perenne under tartaric acid leaching. In view of the above analysis, considering the cost price of EDTA, NTA, tartaric acid, citric acid and HCl, the leaching efficiency and the potential utilization value of soil, it can be concluded that EDTA and citric acid leaching for remediation of heavy metal contaminated soil has certain practicability and less environmental risk.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：X53

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本文編號(hào)：2196119