中国大同盆地含砷地下水反应运移模拟研究

发布时间：2018-03-17 06:15

  本文选题：地下水　切入点：大同盆地　出处：《中国地质大学》2016年博士论文　论文类型：学位论文

【摘要】：与世界其它地区众多研究相似,多种因素导致了中国北部大同盆地高砷地下水的形成。干旱,单一依靠地下水,地下水水流缓慢(长滞留时间)和封闭的系统等条件,导致大同盆地地下水通过蒸发浓缩作用、水位波动效应,水岩相互作用和冲刷洗脱砷等方式保持较高浓度的砷。高砷地下水严重威胁人类健康,亟需对地下水中多因素活化砷的机制进行调查,为高砷地下水的修复提供科学依据和理论支持。相比基于反向模拟和水流模型对大同盆地高砷地下水进行的众多研究,基于反应运移模型开展研究将是未来研究的热点。强还原环境中高砷地下水模拟需要对反应进行精细刻画,反应运移模型在此类模拟中的应用研究更为重要。本研究的目的如下：(1)解释和揭示可能影响试验场水化学分布的因子；(2)评估沉积物地球化学特征和地下水补给对砷迁移转化的影响；(3)基于反应运移模型模拟离子交换、矿物溶解/沉淀以及本身条件对砷在时间尺度和空间尺度迁移的影响；(4)解释影响地下水中砷迁移富集的机制。研究基于大同盆地中心试验场数据对水流路径(一维)变化和二维空间分布的影响因素进行了分析。本研究的主要研究对象是埋深约20m厚度约1m的浅层含水层地下水。通过野外试验场现场测定的参数以及室内水化学和沉积物分析数据对地下水水化学特征和砷的分布进行了分析,以阐明导致地下水砷活化的潜在机制。在此基础上,本文通过TOUGHREACT和PHT3D建立了两个反应运移模型以分析和识别大同盆地地下水砷富集的主控因素。本文3-5章对结果进行了分析,并得到以下主要结论：(1)试验场水化学数据和沉积物地球化学数据在室内分析完成,试验场地下水化学类型主要为Na-HCO3,地下水中砷浓度最高为2627.1μg L-1,沉积物中砷的最高浓度为26.21mg kg-1。结果表明高浓度HCO3、高pH以及强还原环境有助于增强地下水中砷的活性。此外,Fe(Ⅱ)/Fe(Ⅲ)以及SO4/HS循环可以解释由沉积物中有机质降解作为电子供体而产生的As(Ⅲ)。然而,通过S04还原形成硫化物抑制地下水中砷的活性虽微不足道,但是仍有可能。基于非反应运移模拟(MODFLOW/MT3DMS)的砷形态分布说明,相比强还原环境,在温和的还原条件下As(V)是主要的形态,而且伴生Fe(Ⅲ)和Al。(2)基于TOUGHREACT的一维水流路径模型表明主要水化学组分、pH变化以及离子交换对砷的富集有显著影响。从模型可知Fe(Ⅲ)、 As(Ⅴ)和S04的还原影响砷的分布。此外,从模型推断砷从铁锰氢氧化去/氧化物表面解吸是大同盆地还原条件下砷富集的重要机制。模拟结果进一步显示硅酸盐风化产生大量的Na进入含水层,并通过影响沉积物的稳定性促进了砷的富集。(3)基于PHT3D对试验场砷和其他共存元素的分布进行了模拟和预测。模型显示,在考虑地下水空间演化的基础上,氧化敏感元素的分布与弱还原到强还原条件的演化保持一致的。模型结果有力支持了第三章的结论即砷的分布受到Mn、Fe氧化物/氢氧化物的影响,Mn、 Fe氧化物/氢氧化物是研究区砷的主要载体。此外,模拟的分布结果强调了除表面络合反应外,pH/pe分区和离子交换对As(Ⅲ)/As(V)浓度变化的影响的重要性。研究的创新点在于,基于针对大同盆地建立的自定义数据库应用反应运移模型对厌氧条件下偏碱性地下水中砷迁移进行了分析。首先,TOUGHREACT数据库极其缺乏,尤其是针对于还原性含水层,本研究建立为TOUGHREACT建立了适用还原含水层的数据库。其次,两个模型作为首次针对大同盆地高砷地下水建立的反应溶质运移模型,为进一步进行反应溶质运移模拟奠定了基础。最后,与大同盆地相比试验场面积虽然较小,但论文研究成果通过为地下水质量管理提供有效信息和预测地下水时空变化,有力推动了本地区的研究。
[Abstract]:Similar to other parts of the world, many studies, many factors lead to the formation of high arsenic groundwater in Datong Basin in the north of China. Drought, single rely on groundwater, groundwater flow is slow (long retention time) and the conditions of closed system, resulting in groundwater in Datong Basin by evaporation condensation, water level fluctuation, water rock interaction and scour elution arsenic and other ways to keep a higher concentration of arsenic. High arsenic groundwater is a serious threat to human health, the activation of arsenic on groundwater mechanism need many factors in the investigation, provide scientific basis and theoretical support for the repair of high arsenic groundwater. Compared to many studies of high arsenic groundwater in Datong basin simulation and reverse flow based on the model, based on research carried out reactive transport model will be the focus of future research. Strong reducing environment in simulation requires fine description of high arsenic groundwater, reactive transport Application of the model in such simulation is more important. The purpose of this study is as follows: (1) to explain and reveal the field may affect the distribution of water chemical factor; (2) assess the geochemical characteristics of sediments and groundwater recharge on the impact of migration and transformation of arsenic; (3) - migration model based on ion exchange. Mineral dissolution / precipitation and its influences on the migration of arsenic in temporal and spatial scales; (4) to explain the effects of arsenic in groundwater migration and enrichment mechanism. Research center of Datong Basin test field data based on flow path (one-dimensional) factors affecting the distribution change and the two-dimensional space are analyzed. The main research object of this research is the depth of about 20m thickness of about 1m of the shallow aquifer groundwater. Through field test field parameters and the determination of indoor water chemistry and sediment data analysis on groundwater chemical characteristics and arsenic The distribution is analyzed, in order to elucidate the potential mechanism resulting in groundwater arsenic activation. On this basis, this paper established two reactive transport model by TOUGHREACT and PHT3D to analyze and identify the Datong basin groundwater arsenic enrichment controlling factors. The 3-5 chapter analyses the results, and get the following conclusions: (1 complete the analysis field test) of hydrochemical data and sediment geochemical data in the indoor test site, chemical types of groundwater are mainly Na-HCO3, the highest arsenic concentration of 2627.1 g L-1 in groundwater, the highest concentration of arsenic in the sediments of 26.21mg kg-1. results showed that the high concentration of HCO3, high pH and strong reducing environment is helpful to the enhancement of arsenic in groundwater activity. In addition, Fe (II) /Fe (III) and SO4/HS cycle can be explained by the degradation of organic matter in sediments as the electron donor and As (III). However, through the reduction of S04 sulfide formation Inhibition of arsenic in groundwater activity is not worth mentioning, but there are still possible. The simulation of non reactive transport (MODFLOW/MT3DMS) based on the arsenic distribution, compared with the strong reducing environment, reduction in mild conditions (As V) is the main form, and the associated Fe (III) and Al. (2) one-dimensional flow path model TOUGHREACT that the main chemical components of water based on the change of pH and ion exchange on arsenic enrichment have significant effects. From the model shows that Fe (III), As (V) and S04 reduction effect of arsenic distribution. In addition, inferred from the model of arsenic from oxidation of iron and manganese oxide / hydrogen to surface desorption is an important mechanism of arsenic enrichment the Datong Basin reducing conditions. The simulation results further showed that silicate weathering produced large amounts of Na into the aquifer, and the effects of sediment stability and promote the accumulation of arsenic. (3) the test field of arsenic and its distribution he coexisting elements based on PHT3D The simulation and prediction. The model shows that considering the groundwater spatial evolution, the evolution of the distribution of oxidation sensitive elements and weak reducing to strong reducing conditions consistent. Model results support the conclusion of the third chapter is the arsenic distribution by Mn, Fe oxide / hydroxide effect, Mn, Fe oxide the study area is the main carrier of hydroxide / arsenic. In addition, the distribution of the simulation that in addition to surface complexation reactions, pH/pe partition and ion exchange of As (III) /As (V). The effects of concentration of the importance of innovation, custom database application model for reactive transport for the Datong Basin Analysis of anaerobic alkaline arsenic in groundwater migration based on TOUGHREACT database. First of all, extremely deficient, especially for the reduction of the aquifer, this study established TOUGHREACT is established with reduction Water database. Secondly, two for the first time as model reaction solute transport model of high arsenic groundwater in Datong Basin, laid the foundation for further simulation of reaction solute transport at last, compared with the field test of Datong Basin area is small, but to provide effective information and prediction of temporal and spatial variation of groundwater for groundwater quality management through the research results that has promoted the research in the area.

【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P641.3
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本文编号：1623508