本文關(guān)鍵詞： 土壤 Pb Cd 競(jìng)爭(zhēng)吸附 形態(tài) 水分　出處：《西安建筑科技大學(xué)》2017年碩士論文　論文類(lèi)型：學(xué)位論文

【摘要】：隨著現(xiàn)代化和工業(yè)化的不斷發(fā)展,土壤重金屬污染問(wèn)題逐漸成為我們關(guān)注的焦點(diǎn)。污染土壤中往往不止含有某一種特定重金屬離子而是多離子共同污染,離子之間相互影響,從而影響其生物有效性和遷移特征。本文以?shī)渫翞閷?duì)象,采用吸附等溫實(shí)驗(yàn)及室內(nèi)培養(yǎng)實(shí)驗(yàn)研究了單一Pb、Cd元素及其共存時(shí)的吸附特征、存賦形態(tài)及其含水量變化的影響,得到了下面的主要結(jié)論:1.單一的Pb在婁土耕層、黏化層和鈣積層的分配系數(shù)為8.00、8.11和6.05,Langmuir方程最大吸附量為6.07、5.75和6.01mmol/kg;而Cd的分配系數(shù)為4.19、7.05和4.72,最大吸附量為5.54、4.77和2.95mmol/kg;均表現(xiàn)出Pb在三種土壤上比Cd具有強(qiáng)的吸附性能。當(dāng)Pb、Cd共存時(shí),兩種離子具有競(jìng)爭(zhēng)吸附作用,致使土壤對(duì)Pb、Cd的吸附量均降低,Pb、Cd互為競(jìng)爭(zhēng)性吸附離子的親和力效應(yīng)在0.8-0.9之間,修正得到雙離子的競(jìng)爭(zhēng)性Langmuir吸附方程可用于描述Pb、Cd的競(jìng)爭(zhēng)吸附。2.耕層、黏化層和鈣積層土壤中Pb、Cd的形態(tài)分布具有相似性,Pb、Cd總量中以殘?jiān)鼞B(tài)為主,交換態(tài)的含量都小于10%。當(dāng)外源Pb、Cd加入土壤后,交換態(tài)含量隨時(shí)間進(jìn)程逐漸降低,碳酸鹽結(jié)合態(tài)在起始階段呈現(xiàn)短暫上升,而在培養(yǎng)后期含量逐漸下降,Pb、Cd的鐵錳氧化物結(jié)合態(tài)與有機(jī)化合態(tài)的含量隨時(shí)間進(jìn)程逐漸增加,而在較短的培養(yǎng)時(shí)間內(nèi),重金屬離子較難進(jìn)入土壤礦物的晶格中,殘?jiān)鼞B(tài)含量基本保持不變。3.水分條件對(duì)于重金屬在土壤中的形態(tài)及其重新分配具有重要的影響,Pb、Cd在三個(gè)不同層次土壤中在干濕交替條件下交換態(tài)向其他形態(tài)轉(zhuǎn)變的速率最快,其次是75%田間持水量,干旱條件下轉(zhuǎn)變的速率最慢,即干濕交替75%田間持水量50%田間持水量干旱條件。4.存在競(jìng)爭(zhēng)離子條件下,Pb和Cd的形態(tài)轉(zhuǎn)化方向與單一離子存在下有顯著不同,其中交換態(tài)與碳酸鹽態(tài)的相對(duì)含量增加,殘?jiān)鼞B(tài)的含量相對(duì)降低,鐵錳氧化物結(jié)合態(tài)與有機(jī)結(jié)合態(tài)的含量變化不大,Pb和Cd更傾向于向交換態(tài)和易受外界環(huán)境影響的碳酸鹽結(jié)合態(tài)轉(zhuǎn)化。重金屬在土壤中的共存和競(jìng)爭(zhēng),可顯著影響其生物有效性和遷移性,研究重金屬?gòu)?fù)合污染的特征是治理的基礎(chǔ),本文僅僅在這些方面做了初步的工作,有待于進(jìn)一步深入的研究。
[Abstract]:With the development of modernization and industrialization, the problem of soil heavy metal pollution has gradually become the focus of our attention. In this paper, adsorption isotherm experiment and indoor culture experiment were used to study the adsorption characteristics of single Pb ~ (2 +) CD element and its coexistence, and the effects of storage forms and water content on the bioavailability and migration characteristics. The following main conclusions are obtained: 1. A single Pb in the plow layer of Lou soil, The partition coefficients of the viscous layer and the calcium layer are 8.11 and 6.05% Langmuir equation respectively. The maximum adsorption capacity of Pb is 6.07 ~ 5.75 and 6.01 mmol 路kg ~ (-1), while that of CD is 4.19 ~ 7.05 and 4.72, and the maximum adsorption capacity is 5.54 ~ 4.77 and 2.95 mmol 路kg ~ (-1) respectively. The results show that Pb has a stronger adsorption performance than CD on the three soils, and when Pb ~ (+) CD coexists with CD, the distribution coefficients of CD are 4.19 ~ 7.05 and 4.72, and the maximum adsorption capacity is 5.54 ~ 4.77 and 2.95 mmol 路kg ~ (-1) 路kg ~ (-1), respectively. The adsorption capacity of Pb ~ (2 +) and CD ~ (2 +) in soil was decreased by competitive adsorption, and the affinity effect of PbN ~ (2 +) was between 0.8-0.9, and the adsorption capacity of Pb ~ (2 +) ~ (2 +) was 0.8-0.9 (P < 0.05). The modified competitive Langmuir adsorption equation can be used to describe the competitive adsorption of Pb ~ (2 +) CD. 2. The speciation distribution of Pb ~ (2 +) CD in topsoil, clay layer and calcium accumulation layer is similar. The contents of exchangeable state were all less than 10. When exogenous PBO / CD was added into soil, the content of exchangeable state decreased gradually with time, and the carbonate bound state increased briefly in the initial stage. However, the content of ferromanganese oxide bound and organic compounds of PbPbPbCd decreased gradually during the later period of culture, and the heavy metal ions were difficult to enter the lattice of soil minerals during the short incubation period, and the content of Fe / mn oxides and organic compounds increased with the time course of culture. The residual state content remained basically unchanged .3.Water condition had the most important influence on the speciation and redistribution of heavy metals in soil. In three different layers of soils, the rate of transformation of exchange state to other forms of heavy metals was the fastest in three different layers of soils under the alternate conditions of dry and wet. The second was 75% field water holding capacity, and the rate of transformation was the slowest under drought, That is, dry and wet alternate 75% field water holding capacity 50% field water holding capacity drought condition. 4. The direction of speciation transformation of Pb and CD in the presence of competitive ions is significantly different from that in the presence of a single ion, and the relative content of exchange state and carbonate state increases. The content of residuals is relatively low, and the contents of Fe and mn oxides bound to organic compounds are not changed much, Pb and CD tend to convert to exchangeable and carbonate-bound forms which are easy to be affected by external environment, and the coexistence and competition of heavy metals in soil. The study of the characteristics of heavy metal compound pollution is the basis of treatment. This paper has only done some preliminary work in these aspects, which needs to be further studied.
【學(xué)位授予單位】：西安建筑科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：X53

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