陕西潼关重金属污染土壤的修复及应用潜力研究

发布时间：2018-05-11 10:40

本文选题：重金属 + 土壤污染　；参考：《西北农林科技大学》2017年硕士论文

【摘要】：矿山开采和选冶过程会形成露天采矿场、尾矿库等废弃场地,产生大量固体废物。尾矿渣中的重金属在降雨和风蚀的作用下逐渐向周围扩散,破坏生态环境,对水体和土壤造成了严重污染。因此,对重金属污染土壤进行修复,使其恢复植被功能至关重要。本研究以陕西省潼关县饮用水源保护地及历史遗留重金属企业周边的土壤修复示范工程为例,从土壤污染现状调查、工程修复技术的筛选、修复效果评价以及修复后土壤农业生产安全性评价等角度进行了系统分析,科学评估了客土法,石灰、磷酸钙、粉煤灰和Na_2S作为重金属钝化剂的原位稳定化修复技术在实际重金属污染土壤修复中的应用潜力。研究得到的结果如下:(1)“三小”冶炼行为和铅锌矿的冶炼对周边土壤造成了严重的污染。西街子土壤的污染源为矿渣堆,主要受Pb、Cd、Hg的污染,其浓度范围分别为25.1～1116mg·kg~(-1),2.30～5.20mg·kg~(-1),0.15～20.0mg·kg~(-1)。鑫欣土壤的污染源为废渣堆、堆料场和冶炼区,主要受Zn、Cd、Pb和Hg的污染,其浓度范围分别为89.2～742mg·kg~(-1),1.59～362mg·kg~(-1),88.4～7622mg·kg~(-1),0.21～35.0mg·kg~(-1)。(2)重金属的浓度呈现出由污染源向周边农田土壤逐渐递减且在污染源处向下迁移的特点。部分剖面土壤污染严重,在0～120cm范围内重金属浓度全部超过土壤环境质量二级标准。(3)西街子表层土壤的污染评价结果:内梅罗综合污染指数分析表明项目区域土壤都受到污染,97.1%的土样受到重污染。采用潜在生态危害指数法进行评价,Cd、Hg和Pb是项目区域土壤重金属污染的主要贡献因子。该区域潜在生态危害指数(RI)范围为668～10969,具有很强的生态危害。地积累指数法的统计结果表明5种重金属污染程度由强到弱依次为:CdPbHgZnCu。(4)鑫欣表层土壤的污染评价结果:内梅罗综合污染指数分析表明土样受到轻污染、中污染和重污染的比例分别为5.88%、35.3%和58.8%。从潜在生态危害指数(Eri)来看,Cd是潜在生态危害最严重的金属元素,所有的土样都存在极强的生态危害。从综合潜在生态风险(RI)分析,该项目区域土壤具有很强的生态危害。(5)对两个项目区域重污染土壤采用客土法,轻污染土壤采用原位稳定化进行修复,修复效果显著,土壤中重金属的总量和有效态浓度均明显降低。除Cd外,工程修复后的土壤中重金属的总量均低于土壤二级标准中的限值。土壤重金属有效态浓度与土壤pH、有机质浓度和重金属全量之间存在显著的相关关系。随着修复时间的增长,土壤有效态的浓度有增加趋势。(6)西街子修复后的土壤上主要种植玉米、花生、四季豆和毛豆,鑫欣修复后的土壤上主要种植玉米和芝麻,对农作物的重金属污染评价发现:部分农作物中Cd、Pb和Hg的累积量高于国家食品安全标准中规定的限值,因此修复后土壤上种植的农作物不能进入市场流通,需要统一进行处理。(7)为了探索最适宜的种植模式,在西街子修复后第二年的土壤上尝试种植一些常见蔬菜,发现不同蔬菜对重金属的富集能力有差异,具体表现为:叶菜类蔬菜非叶菜类蔬菜。(8)并非所有农作物可食部分中重金属的浓度与土壤中重金属全量、有效态浓度之间都存在显著相关性。Cd、Pb和Hg在作物中转移系数(TF)值很小,说明重金属在修复后的土壤-作物系统中迁移量较小。玉米各重金属元素的转移系数(TF)均最高,因此继续大面积种植存在一定的风险。(9)在重金属污染修复后的土壤上不建议立刻进行粮食生产,应改变原有生产模式同时持续监测,在确保粮食安全后再进行生产。
[Abstract]:Mining and smelting process will form open pit, tailings and other waste sites, producing a large amount of solid waste. Heavy metals in the tailings slag gradually spread to the surrounding area under the action of rainfall and wind erosion, destroying the ecological environment and causing serious pollution to the water and soil. Therefore, the heavy metal contaminated soil is restored to restore the vegetation. This study takes the example of the demonstration project of soil remediation around the drinking water source in Tongguan County of Shaanxi and the surrounding heavy metal enterprises left over by history, and systematically analyzes the status of soil pollution, the screening of Engineering remediation technology, the evaluation of restoration effect and the safety evaluation of soil agricultural production after restoration. The application potential of soil method, lime, calcium phosphate, fly ash and Na_2S as heavy metal passivating agent in situ remediation technology in the remediation of heavy metal contaminated soil was evaluated. The results were as follows: (1) "three small" smelting behavior and lead-zinc smelting have caused serious pollution to the surrounding soil. The source is slag pile, which is mainly contaminated by Pb, Cd and Hg, and its concentration ranges from 25.1 to 1116mg. Kg~ (-1), 2.30 to 5.20mg. Kg~ (-1), 0.15 to 20.0mg. Kg~ (-1). The pollution sources of Xinxin soil are waste residue, heap yard and smelting area. The concentration range is 89.2 ~ 1.59. 8 8.4 ~ 7622mg / kg~ (-1), 0.21 to 35.0mg. Kg~ (-1). (2) the concentration of heavy metals is gradually decreasing from the pollution source to the surrounding farmland and moving downward in the source of pollution. The soil pollution is serious in some sections, and the concentration of heavy metals in the range of 0 to 120cm is more than the standard of the soil environmental quality two. (3) the surface soil of the West Street subsoil The results of pollution assessment: the analysis of Nemero's comprehensive pollution index indicates that the soil in the project area is polluted and 97.1% of the soil samples are heavily polluted. The potential ecological hazard index method is used to evaluate the soil heavy metal pollution in the project area. Cd, Hg and Pb are the main contributors to the soil heavy metal pollution in the project area. The area of the potential ecological hazard index (RI) in this region is 668~10969. The statistical results of the land accumulation index method showed that the pollution degree of 5 kinds of heavy metals from strong to weak was in turn: CdPbHgZnCu. (4) Xinxin surface soil pollution evaluation result: the Nemero comprehensive pollution index analysis showed that the soil samples were exposed to light pollution, the proportion of medium pollution and heavy pollution were 5.88%, 35.3% and 58.8%. from potential birth, respectively. The state hazard index (Eri) shows that Cd is the most serious metal element of potential ecological hazards, and all soil samples have very strong ecological hazards. From the comprehensive potential ecological risk (RI) analysis, the soil of this project has a strong ecological hazard. (5) the soil method is used for the heavy polluted soil in the two projects, and the soil in the light polluted soil is stabilized in situ. In addition to Cd, the total amount of heavy metals in soil after engineering repair is lower than that in the two level of soil. There is a significant correlation between the effective concentration of soil heavy metals and soil pH, the concentration of organic matter and the total heavy metal content. The concentration of soil effective state increased. (6) corn, peanuts, four season beans and peas were mainly planted on the soil after the restoration of West Street. The main planting corn and sesame on the soil after Xinxin restoration showed that the accumulation of Cd, Pb and Hg in some crops was higher than that of national food. The limit set in the safety standard, therefore, the crops planted on the soil after repair can not enter the market circulation and need to be treated in a unified way. (7) in order to explore the most suitable planting pattern, we try to plant some common vegetables on the soil of second years after the restoration of West Street, and find that the enrichment ability of different vegetables on heavy metals is different. The leaf vegetables are not leafy vegetables. (8) there is a significant correlation between the concentration of heavy metals in the edible parts of the crops and the total heavy metals in the soil, and the significant correlation between the effective concentrations and the.Cd. The transfer coefficient (TF) of the Pb and Hg in the crops is small, indicating that the heavy metal has a small migration in the soil crop system after the restoration. The transfer coefficient (TF) of each heavy metal element is the highest, so there is a certain risk for continuing large area planting. (9) it is not recommended to carry out grain production immediately after the remediation of heavy metal pollution. It should change the original production mode and keep monitoring at the same time, and then make production after the food security is ensured.

【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X53

【参考文献】