【作者】 冯娟；

【导师】 刘贯群； 赵全升；

【作者基本信息】 中国海洋大学 ， 环境工程， 2011， 博士

【摘要】 进入20世纪80年代以来,黄河下游冲积平原地区的地下水资源紧缺、水质恶化和环境地质等问题日趋严重,水资源供需矛盾愈来愈突出。这不仅源于气候变化,还与人类活动密切相关。本研究以黄河下游冲积平原的德州地区为对象,以地下水位监测、水质监测和同位素测试分析等为获取源信息的主要技术手段,研究确定地下水的补给来源及径流、排泄方式,揭示地下水降落漏斗形成和演化规律,识别和确定地下水降落漏斗形成与变化的主导因素。分析研究开采条件下地下水在空间和时间尺度上的演化过程与趋势,揭示地下水水质演化机制,阐明地下水水质不良演化的主要因素。针对研究区地下水水质演化新趋势,提出地下水良性演化的水质调控措施。德州位于华北平原的中东部地区,属于典型的黄河下游冲积平原孔隙水水文地质区。该冲积平原地区具有咸、淡两种水体共存的独特水环境特征,在这样一种复杂的地下水系统中,淡水天然的水环境条件非常敏感和脆弱。由于人类大规模超量开采地下水,使该区域地下水的水动力场和水化学场发生了较大变化,从而进一步加剧了地下水水质恶化趋势。针对日趋严重的水环境安全问题,开展地下水水质演化研究,可为该地区水资源可持续利用和在持续开采淡水条件下不致使淡水脆弱的水环境条件逐渐恶化以至被破坏等提供科学依据。根据研究区1996~2009年地下水动态监测数据,采用地下水动态分析、水文地球化学、同位素技术、灰色模型及数值模型多种方法进行水质演化研究。结果表明:(1)研究区浅层潜水在开采条件和自然条件的共同作用下水质不断演化,其中变化比较明显的水质指标是总硬度、矿化度和氯离子等。在区内的齐河县、夏津县苏留庄等一带,浅层潜水的矿化度、总硬度有所降低,水质趋向淡化。而在宁津县、禹城市张庄镇等一带,浅层潜水的矿化度、总硬度明显升高,水质持续咸化。受自然因素和人为因素的影响程度不同,其离子含量变化的幅度也不一样,阴离子含量的变化幅度大于阳离子,其中重碳酸根离子的含量变化幅度最大,其次为硫酸根离子。水中各离子的含量变化导致两种结果:一是改变地下水的水化学类型,二是改变地下水水质。地下水化学类型变化是一个比较复杂的水文地球化学过程,除与自然因素有关外,人类活动的影响越来越明显。(2)研究区内深层承压水的阴离子中重碳酸根离子占优势,表现为补给区大气降水淋滤水的特征。阳离子中钠离子占优势,表明其在径流过程中或产生阳离子交换,钠离子置换出大量的钙镁离子,或遭遇多次海侵干扰。深层地下水降落漏斗中心地带以重碳酸钠型水占优势,远离漏斗中心出现重碳酸硫酸钠型、重碳酸氯钠型或重碳酸硫酸氯钠型水。随着深度增加,水化学类型由重碳酸氯钠镁型渐变成氯硫酸钠镁型。钠离子、钙离子、镁离子、氯离子和硫酸根离子由小变大,越过中间的咸水层又逐渐变小,在深部略有回升。总硬度和矿化度在200m处出现峰值后开始回落。以德城区深层地下水降落漏斗区为模拟区,选取能较好反映水质演化趋势的矿化度、氯离子特征指标为模拟因子。根据研究区水文地质条件和地下水动态监测资料,建立深层地下水水质演化预测模型。模拟区水均衡计算结果为地下水处于超采状态。深层地下水位动态变化为:深层地下水降落漏斗中心位于德城区西北部的陈庄乡张庄一带,模拟区地下水位呈逐年下降趋势,地下水位由漏斗中心向外围逐渐递增。漏斗中心水位标高从2009年的-126.80m(水位埋深147.91m)降低至2015年的-137.21m(水位埋深158.31m),平均以1.76m/a的速率下降。深层地下水矿化度动态变化为:从2009年到2015年,矿化度小于1000mg/L的区域面积减少至93.48km~2,矿化度大于1200mg/L的区域面积增加至21.22km~2。深层地下水氯离子浓度动态变化为:从2009年到2015年,氯离子浓度小于60mg/L等值线圈闭面积减少至32.02km~2,氯离子浓度小于90mg/L等值线圈闭面积减少至194.47km~2,氯离子浓度大于110mg/L等值线圈闭面积增加至112.02km~2。模拟区深层地下水水质变化趋势是:地下水中矿化度、氯离子浓度随着时间的推移有不同程度的升高,但其深层地下水的化学组分未发生明显变化,且季节性变化较小。这表明:深层地下水水化学动态并不随季节而变化,由于深层地下水的径流十分缓慢或径流量较小,在过去30年的开采过程中,外围地区的地下水还没有明显影响到区内水质的变化;由于持续开采地下水造成水位下降、压力降低,导致咸、淡水之间的水力坡度增大、天然平衡遭到破坏,继而引起深层淡水含水层中矿化度和氯离子水质指标呈现升高趋势。这表明,在持续开采条件下,深层淡水上部普遍存在的咸水体有通过越流作用侵入淡水含水层的趋势。研究区地下水水质不良演化的因素主要是:地下水持续性超采、地下水开采布局不合理、含水层疏干空间持续性扩大、咸水体呈现区域性扩散、地下水环境不断恶化。针对地下水水质演化新趋势,研究区应采取分阶段、分层位开采深层地下水,开发利用浅层微咸水资源及咸水淡化等水质调控措施以修复和涵养超采区含水层。更多还原

【Abstract】 Since the 1980s, the problems of groundwater resources shortage, water quality deterioration and environmental geology in the alluvial plain of downstream of Yellow River has been more and more severe, the conflict between water resources supply and need is also obvious, which have a close relationship to the climate change and mans activity. As Dezhou District chosen the experimental objects, where locates in alluvial plain of downstream of Yellow River, groundwater level monitoring, groundwater quality monitoring and Isotopic samples analysis is main technology for acquisition source information. The research confirms the source of groundwater recharge, underground runoff and groundwater discharge, reveals formation and evolution of Dezhou confined water depression cone, identifies and determines dominant factors inducing formation and evolution of depression cone. The study discusses the evolution progress and the developing trend of groundwater at spatial and temporal scales as well as predicts the evolution mechanism of groundwater, and then illustrates the main reasons for bad evolution of groundwater quality. According to the groundwater quality evolution tendency in study area, water adjustment measures put forward to make for benign evolution of groundwater quality.Dezhou City locates in the middle and eastern part of North China Plain, which is a typical Yellow River downstream alluvial plain pore water hydrogeology area, where the salt and fresh water coexists with each other and forms a unique aquatic environment. In such a complex groundwater system, the natural aquatic environment condition of fresh water is rather sensitive and fragile. A large-scale excessive exploitation of groundwater influenced the hydrodynamic force field and hydrochemical field in this area and intensified the trend of water quality deterioration in this area. Aiming at solving this serious aquatic environment security problem, the research of the groundwater quality evolution can provide scientific basis for several areas which will benefit the sustainable usage of water resources in this area and prevent the fragile aquatic environment from deteriorating under continuous exploitation.Based on the dynamic monitoring data of groundwater quality in the study area from 1996²009, the research analyzes the water quality evolution of groundwater by the groundwater dynamic analysis method, hydrogeochemical method, isotope technology, gray model and numerical model etc. Results indicate that the water quality of phreatic water evolves constantly influenced by combined action of exploitation condition and natural conditions, in which the water quality index of total hardness, degree of mineralization and Cl^- changes obviously. The total hardness and degree of mineralization decreases to some extent and the water quality has a tendency of desalinization in the area of Qihe County and Suliuzhuang Town of Xiajin County; whereas the total hardness and degree of mineralization increases to some extent and the water quality has a tendency of salinization in Ningjin County and Zhangzhuang Town of Yucheng City. Influenced by varying degrees of both natural processes and anthropogenic activity, the changing range of ion content is different, which the anions vary more than the cations. The greatest changing range is HCO₃^- and in the next place is SO₄^2-. The variation of ion content brings about changes of the hydrochemical type as well as changes of groundwater quality. The change of the hydrochemical type is a complicated hydrogeochemical process, on which the impacts of human activities are becoming more and more obvious besides relative to natural processes.In the confined water of the study area, there is a superiority of anion HCO₃^- that displays the feature of atmosphere water leaching character. The cation is mainly Na⁺. It can indicate that cations exchange happen, which more Ca²⁺ and Mg²⁺ are replaced by Na⁺ through runoff process, or many times of marine transgression happen. In the heartland of the confined water drawdown, the hydrochemical type of is mainly HCO₃–Na. At the farthest from the center of the funnel, the hydrochemical type is HCO₃·SO₄–Na, HCO₃·Cl–Na or HCO₃·SO₄·Cl–Na. The hydrochemical type changes from HCO₃·Cl–Na·Mg to Cl·SO₄–Na·Mg with increasing depth. The concentration of Na⁺, Ca²⁺, Mg²⁺, Cl^- and SO₄^2- increase, gradually decrease through the saline water aquifer, and then recover slightly in deep part. Total hardness and degree of mineralization have emerged a strengthening peak when the water level buried depth is 200 meters, and then gradually fall.Confined water depression cone of Decheng district is selected as simulated zone as well as the degree of mineralization and Cl^- taken as the simulated factors which can reflect the changing tendency of groundwater quality evolution well. Based on the hydrogeological condition and the dynamic monitoring data of groundwater, the issue establishes water quality evolution prediction models of the confined water. Water equilibrium calculations results indicate the deep aquifers are over-exploited. As is predicted, the center of confined water depression cone will fix at Zhangzhuang of Chenzhuang village in Decheng District in 2015. The groundwater level of the simulated zone descends gradually by year, meanwhile there is an increasing tendency of groundwater level from the center of confined water depression cone to its outskirts. The groundwater level elevation of funnel center decreases from -126.80m （Buried depth is 147.91m） in 2009 to -137.21m （Buried depth is 158.31m） in 2015, which descending at 1.76m/a. Across the whole region in 2009²015, areas with the degree of mineralization of less than 1000mg/L will decrease to 93.48km². Areas with the degree of mineralization of more than 1200mg/L will increase to 21.22km². Areas with the concentration of Cl^- of less than 60mg/L will decrease to 32.02km². Areas with the concentration of Cl^- of less than 90mg/L will decrease to 194.47m². Areas with the concentration of Cl^- of less than 110mg/L will increase to 112.02m². The water quality tendency of confined water in the simulated zone is that the degree of mineralization and the concentration of Cl^- show an increase to a certain extent over time whereas the hydrochemical type of confined water has not obviously changed and little seasonal variation. It represents that the hydrochemical type of confined water has not changed with the season. As a result of slow and small underground runoff, the water quality has not yet been obviously affected by periphery water in the process of the exploitation in current 20 years. With the groundwater levels falling and the pressure drop by over-exploitation of the groundwater resource, sharp hydraulic gradient causes damage to natural balance between salt and fresh water, and then the degree of mineralization and the concentration of Cl^- of the deep fresh groundwater in aquifers tends to increase gradually. It indicates that saline water aquifer on the top of deep fresh water aquifer can invade fresh water by leakage under continuous exploitation condition.The main reasons for bad evolution of groundwater quality are sustained groundwater over-exploitation, unreasonable exploitation distribution, further expanded depleted space in aquifer, regional spread of saline water and continuous deterioration of groundwater environment. According to the groundwater quality evolution tendency in study area, water quality regulation should be implemented for the aquifer’s restoration and conservation where the groundwater has been excessively exploited in study area, including confined water exploitation according to the stages and layers, exploitation and utilization of the shallow slight saline groundwater resource, saline water desalination and so forth.更多还原