陕南金属尾矿库区土壤重金属迁移规律及其环境效应研究

发布时间：2018-04-29 00:32

本文选题：尾矿 + 土壤　；参考：《西安科技大学》2017年博士论文

【摘要】：金属尾矿砂中残留大量重金属元素,通过地表径流和渗流、风沙扬尘等作用,尾砂中重金属元素很容易进入尾矿库周边的土壤环境中,从而造成重金属土壤环境污染。一方面,土壤重金属经过漫长的积累,通过植被吸收、生物富集、生物放大等作用对生物体造成严重的危害;另一方面,土壤重金属在复杂的物理、化学和生物因素的影响下,其在土壤中的空间分布、存在形态及危害性质也不断发生变化。所以,对土壤环境中重金属迁移途径及影响因素进行研究,既有土壤污染治理指导意义,也对矿山土壤污染防治工作具有重要的参考价值。该论文采用实地调查研究与模拟研究相结合的方法,分析陕南金属尾矿区重金属在土壤中迁移的规律及其环境效应。得到以下结论:(1)土壤重金属空间分布、富集及分类结论Cu、Zn、Pb、Cd、Mn、Co是研究区域内具有普遍性污染的元素,Ni、V、Ge、Mo、Ba元素的污染区域只集中在某一个或几个尾矿库周围的小部分区域。Cu、Zn、Pb、Cd四种元素在土壤中的富集作用达到显著污染水平,Ni、Mn、Ba元素富集作用最不明显,Ge、Mo元素富集具有明显的区域差异性。Zn、Pb、Cd、Ni四种元素的可交换态比例较大,RAC生态风险编码法等级为中度风险等级,其它元素的生态风险为低风险或无风险等级。对土壤重金属含量的因子分析与聚类分析结果基本一致,11种重金属可分为3类:具有普遍的、共同污染源的Cu-Zn-Pb-Cd-Co-V,有明显污染源差异的Ge-Ba-Mo,自然污染因素的Mn-Ni。(2)距离对土壤重金属迁移的影响从Hakanson潜在生态危害评价结果确定的重金属污染安全区界:距离尾矿库400-1000m的范围,重金属潜在生态危害为低等级,单元素生态危害也为低等级,故400m的范围是潜在生态风险的安全范围。重金属元素迁移受到距离的影响显著:Ba主要迁移范围0-200m;Ni、Co主要迁移范围0-400m,Cu、Zn、Pb、Cd、V、Mn主要迁移范围是0-600m,Ge、Mo主要迁移范围是0-800m。按照迁移距离大小分析,11种元素的迁移能力排序为 Ge/MoCu/Zn/Cd/V/Pb/MnNi/CoBa。(3)高差对土壤重金属迁移的影响以尾矿坝面为高差0基准,高差范围为80-0m的区域重金属含量总体低于0-(-80)m的区域。从Hakanson潜在生态风险评价结果确定的重金属污染安全区界:在高差80-20m的范围,重金属潜在生态风险为低等级,Cd单元素生态危害为中等等级,故在尾矿坝面以上20m范围,是潜在生态风险安全范围,但要重点防控Cd元素污染;在尾矿坝面以下0-(-80)m范围,土壤重金属潜在危害为中等等级以上,故安全界限尚不能确定。金属在土壤中的迁移受到高差影响十分显著:Cu、Cd、Zn、Pb、V主要迁移范围为0-20m、超过0-(-80)m,Ba元素迁移范围为0-(-40)m,Mn主要迁移范围为0-20m和0-(-40)m,Mo迁移范围为0-20m和0-(-60)m,Ni主要迁移范围为0-20m和0-(-20)m,Ge主要迁移范围为0-(-40)m,Co迁移范围超过0-(-80)m。按照迁移高差范围分析,11种元素的向上迁移能力:Cu/Zn/Cd/V/Pb/Mn/Ni/CoBa/Ge/Mo,向下迁移能力:Cu/Zn/Cd/Pb/V/CoMoBa/Ge/MnNi。(4)土地利用类型对重金属的迁移性影响从土壤重金属元素含量分布分析,Zn、Cd、Ni、Mo、Ba、Cu、Pb、V、Co九种元素在草地土壤中的迁移累积作用比农用地、林地、撂荒地土壤明显。从Hakanson潜在生态危害指数RI看,草地土壤的等级为较高等级危害,其它3种土壤为中等,4种利用类型土壤中的Cd的单元素潜在生态危害等级均为较高等级,说明研究区域内Cd元素应是重点防控的污染元素。从金属元素化学形态分析,土地利用类型对11种元素的迁移影响作用差异性较大,如Cu元素迁移性和金属有效性在农用地最大,Zn元素在草地中最大;Pb元素在撂荒地中的迁移能力最强,在草地中的金属有效性最大;Cd元素在农用地、草地中的迁移性及金属有效性均较大;Ni、Co元素在草地迁移能力最强,金属有效性在4种土壤中相当。草地是多种金属元素迁移能力或金属有效性最强的土地利用类型(5)尾砂填埋模拟研究从迁移时间看,Cu、Zn、Pb、Cd发生明显迁移的时间分别是12、6、6、3个月,迁移能力顺序为CdPb/ZnCu;从迁移距离看,水平方向Cu、Zn、Pb、Cd迁移能力符合Zn/PbCu/Cd,垂直方向迁移能力符合CdZnCuPb;从迁移速率分析,水平和垂直迁移能力均符合CdPbZnCu规律。从迁移方位分析,受到正南方向的汉江河的影响,SE、S、SW是迁移最为明显的3个方位;从迁移发生时间、迁移距离、速率等层面分析的迁移能力排序结果有较大差异。(6)陕南金属尾矿区土壤重金属迁移数学模型模拟实验的重金属迁移模型:Cu、Zn、Pb和Cd四种元素迁移量与距离R、深度H和迁移时间T的均达到极显著负相关水平,补充了实地调研中不能反映的“重金属迁移的先后顺序”和“迁移速率”规律,该模型反映尾砂重金属向土壤迁移的初始阶段,代表微观的、较理想化的重金属迁移预测模型;实地调研的重金属迁移模型:考虑土地利用类型因素的方案B比A方案更能客观、详尽的模拟土壤重金属的迁移趋势,B方案模型证实了土地利用类型对土壤重金属的迁移有着重要的影响,同时重金属含量与距离D、高差H、砂粒S0、粘粒S2也呈现出明显相关性,该组模型反映了尾矿库区重金属在土壤中迁移的发展阶段,代表较为宏观的、客观实际的重金属迁移预测模型。
[Abstract]:Heavy metal elements are retained in the metal tailing sand. Through surface runoff, seepage, sand and dust, heavy metal elements in the tailings can easily enter the soil environment surrounding the tailings reservoir, thus causing heavy metal soil environmental pollution. On the one hand, the heavy metals in the soil accumulate through vegetation, bioaccumulation and biological release through the long accumulation of heavy metals. On the other hand, under the influence of complex physical, chemical and biological factors, the spatial distribution, the existence form and the harmfulness of heavy metals in soil are also constantly changing. Therefore, the study on the migration pathways and influencing factors of heavy metals in the soil environment, not only has soil pollution, but also has soil pollution. The guiding significance of governance also has important reference value for the prevention and control work of mine soil pollution. This paper adopts the method of field investigation and simulation study to analyze the law and environmental effects of heavy metals in the soil of Southern Shaanxi metal tailing area. The following conclusions are obtained: (1) the spatial distribution, enrichment and classification of heavy metals in the soil Conclusions Cu, Zn, Pb, Cd, Mn, Co are the elements of universal pollution in the study area. The contaminated regions of Ni, V, Ge, Mo and Ba are concentrated only in a small portion of the region around a certain or several tailing banks. The enrichment of four elements in the soil is the most obvious pollution level. The four elements of.Zn, Pb, Cd, and Ni have large exchangeable proportions. The RAC ecological risk coding method has a moderate risk grade, and the ecological risk of other elements is low risk or risk free grade. The factor analysis of soil heavy metal content is basically consistent with the results of cluster analysis, and the 11 kinds of heavy metals can be divided into 3 categories. Cu-Zn-Pb-Cd-Co-V with common pollution sources, Ge-Ba-Mo with distinct source of pollution, the Mn-Ni. (2) distance of natural pollution factors affects the heavy metal pollution safety zone determined by the potential ecological hazard assessment results of Hakanson: range from 400-1000m of tailing pond, the potential ecological harm of heavy metals is low The range of 400m is a safe range of potential ecological risk. The migration of heavy metals is significantly affected by distance: the main migration range of Ba, 0-200m, Ni, Co, 0-400M, Cu, Zn, Pb, Cd, V. The main migration range is based on the migration distance. Size analysis, the migration ability of the 11 elements is Ge/MoCu/Zn/Cd/V/Pb/MnNi/CoBa. (3) and the effect of height difference on the migration of heavy metals in the soil is 0 datum of the height difference of the tailings dam surface. The heavy metal content in the area with the range of 80-0m is lower than that of 0- (-80) m. The safety of heavy metals from the results of the potential ecological risk assessment of Hakanson is safe. Zone boundary: in the range of high difference 80-20m, the potential ecological risk of heavy metals is low grade, and the ecological harm of single element of Cd is medium grade. Therefore, the 20m range above the tailings dam surface is the potential ecological risk safety range, but it is important to prevent and control the pollution of Cd elements, and the potential hazards of heavy metals in the 0- (-80) m below the tailings dam surface are above the middle level. Therefore, the migration of metal in the soil is greatly affected by the height difference: Cu, Cd, Zn, Pb, and V migration range is 0-20M, more than 0- (-80) m, Ba element migration range is 0- (-40). The migration range is 0- (-40) m, and the migration range of Co exceeds 0- (-80) M. in accordance with the range of migration height. The upward migration ability of the 11 elements: Cu/Zn/Cd/V/Pb/Mn/Ni/CoBa/Ge/Mo, the downward migration ability: Cu/Zn/Cd/Pb/V/CoMoBa/Ge/MnNi. (4) the influence of the land use type on the heavy metal content distribution from the soil heavy metal element content, Zn, Cd, Ni, The migration accumulation of nine elements, Mo, Ba, Cu, Pb, V, Co in grassland soil is more obvious than that of agricultural land, woodland and abandoned land. From the Hakanson potential ecological hazard index RI, the grade of grassland soil is high grade, the other 3 kinds of soil are medium, and the single element potential ecological hazard grade of Cd in 4 kinds of utilization types is higher. Grade, Cd elements in the study area should be the key pollution control elements. From the analysis of metal elements chemical forms, land use types have great differences in the influence of the migration of the 11 elements, such as Cu element mobility and metal availability in the largest agricultural land, the largest Zn element in the grassland, and the most migratory capacity of Pb elements in abandoned land. Strong metal availability in grassland is the largest, Cd elements have greater mobility and metal availability in agricultural land and grassland; Ni, Co elements have the strongest migration ability in grassland, and the metal availability is equivalent in 4 kinds of soil. The grassland is the simulation study of a variety of metal elements migration ability or the most powerful metal availability type (5) tailings landfill. From the migration time, the time for Cu, Zn, Pb, Cd to migrate is 12,6,6,3 months, and the order of migration ability is CdPb/ZnCu. From the migration distance, the horizontal direction Cu, Zn, Pb, Cd migration ability conforms to Zn/PbCu/Cd, and the vertical migration ability conforms to CdZnCuPb. From the transfer rate analysis, both horizontal and vertical migration ability conform to the regularity. The migration orientation analysis is affected by the Han River in the south direction. SE, S and SW are the 3 most obvious migration directions. The migration ability sorting results from the migration time, the migration distance and the rate are different. (6) the heavy metal migration model in the simulation experiment of the heavy metal transfer model in the southern Shaanxi metal tailings area: Cu, Zn The four elements of Pb and Cd, the migration amount and distance R, the depth H and the migration time T, all reached the extremely significant negative correlation level, which supplemented the law of "the sequence of heavy metal migration" and "migration rate" which could not be reflected in the field investigation. This model reflects the initial stage of the migration of heavy metals to the soil in the tailings, representing the microscopic, more ideal weight. Metal migration prediction model; field investigation of heavy metal migration model: the scheme B considering land use type factors is more objective and more detailed to simulate the migration trend of heavy metals in soil. The B scheme model confirms that the land use type has an important influence on the migration of heavy metals in the soil, while the heavy metal content and distance are D, and the height difference H The grain S0 and the clay S2 also show a significant correlation. This model reflects the development stage of heavy metal migration in the tailings reservoir area and represents a more macroscopic, objective and actual heavy metal migration prediction model.

【学位授予单位】：西安科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X753;X53

【参考文献】