【作者】 杨晓婷；

【导师】 王文科；

【作者基本信息】 长安大学 ， 地质工程， 2011， 博士

【摘要】 近年来，随着工业化经济的迅猛发展和人口的快速增加，未达标排放的工业废水和生活污水，大量排入河流，使得河流污染日益严重，除此之外，近年来突发性水污染事件频繁发生，这些不仅加剧了当地的水资源危机，而且也严重的影响了经济发展和社会安定，均引起国际社会的广泛关注。河流与地下水之间具有着密切的联系，河流中的污染物在浓度梯度和（或）水力梯度作用下进入地下水，造成地下水的污染。傍河地下水水源地在我国北方地区城市供水尤其是饮用水的供给方面发挥着不可替代的作用。傍河地下水开采强度的增加，加速了河流污染物向地下水的运移。因此，河流污染或发生突发性水污染事件后，如何保障沿岸居民饮水安全和社会稳定是当前最为敏感和急待解决的问题。污染河流对沿岸地下水以及傍河水源地水质污染的机理研究，是一个急需解决的科学问题，也是保障我国北方地区城市饮水安全的国家目标和重大科技需求。为此，论文以国家自然科学基金“河流污染对地下水的影响模拟研究”为依托，利用砂槽来模拟河流与地下水系统，选择直线河流的一个断面，并选择保守性物质NaCl和非保守性物质硝基苯作为典型污染物，考虑影响污染物运移的因素：河流形态、河水位、河床介质、结构、排泄水位，来模拟河流与地下水关系演化过程中污染物的运移规律；构建河流与地下水关系演化过程中地下水流与污染质协同运移相耦合的数学模型；利用所建数值仿真模型，预测不同抽水强度下河流污染对沿河地下水环境的影响程度，分析影响污染物运移的因素，探讨污染物在河流与地下水关系演化过程中的运移机理；对傍河水源地供水安全问题提出相应对策。通过本次研究获得以下阶段性结论：1傍河水源地开采中，只要开采量超过河流的极限补给量，河水位与地下水位就会脱节。影响河流与地下水关系演化的因素有：含水层介质岩性、结构，河床形状、宽度、河水深度以及开采水位。这些因素不仅影响着河水与地下水的水力联系，同时也影响着污染物的运移。2在人类抽水驱动下，随着开采水位的下降，不仅河流—地下水含水系统、浸润曲线形状、河流补给方式，补给量、渗流途径发生了变化，而且河流污染物的运移方式也发生了改变，并具有明显的分带性。对流带、过渡带、弥散带是以河流为中心，以水流方向为轴，不断的扩大、移动。3无论河流与地下水的关系如何，河流污染物都会不断扩散，污染地下水。距离河流越近，就越容易污染。对傍河开采井来说，在河流与地下水脱节之前，随着开采水位的降低，污染物到达该点的时间越短；脱节之后，开采水位再继续降低，河流污染物到达该点的时间增加。4在相同水力梯度下，污染物的扩散距离随着时间而增加，最终趋于稳定；污染物的扩散速度随时间而减小，最后趋于零；污染前缘扩散的速度比污染峰值快。在不同水力梯度下，河流与地下水脱节前，水力梯度越大，污染物的扩散距离就越远，当开采水位达到临界脱节水位时扩散距离最远；脱节以后，水力梯度越大，污染物的扩散范围有所减小并基本保持不变；含水层中水力梯度越大，污染前缘运移的越快，但污染峰值运移却越慢。5在河流与地下水位关系的演化过程中，当河流—地下水含水层水力梯度J0.15时，开采井位于弥散带中；当0.15J0.65时，开采井位于过渡带中；当水力梯度J0.65时，开采井位于对流带中。因此，在傍河水源地的开采中，为了保证水源地的水质尽可能的使开采井位于弥散带中。6综合考虑水量、水质、经济三方面的问题，在傍河地下水水源地的开采过程中，在水质较好的河流中上游地段，可以使开采水位达到河流与地下水的临界脱节水位，来激发河流的最大补给量；在水质较差的河流中下游地段，开采水位不能太低，以保证开采井位于弥散带中。更多还原

【Abstract】 In recent years, with the rapid development of industrialized economies and increase ofpopulation, some non-standard industrial waster and domestic sewage have been dischargedinto rivers, it caused more and more serious river contamination. Besides that, some abruptwater pollution events happen frequently. All of these not only aggravate the local waterresource crisis, but also seriously affected the economic development and social stabilization,as well as was comprehensively paid attention by international society. There is closerelationship between river and groundwater, because river contaminants enter subsurfaceaquifers under concentration gradient and/or hydraulic gradient and result in groundwatercontamination. Riverside groundwater source field play a non-substituent role on city supplywater especially drinking water supply in the northern regions of China. At the meanwhile,the increase of riverside groundwater exploitation intensity will accelerate transportation ofriver contaminants in groundwater. So how to ensure drinking water safety along river banksand social stabilization is a sensitive and urgent problem once river pollution and abruptwater pollution events exist. Mechanism researches of the influence of polluted river ongroundwater and water quality contamination of riverside groundwater source field, is notonly an urgent problem to solve exactly, but also a national goal and significant science andtechnology remand to ensure city drinking water safety in the northern regions.This paper, relying on the national natural science funding “simulation of influence ofriver pollution on groundwater”, designing a sand trough to simulate the relationshipbetween river and groundwater, choosing one section of a linear river and typicalcontaminants of one kind of conservative matters named NaCl and another kind ofun-conservative those named nitrobenzene, and considering influence factors of contaminanttransportation: river shape, river level, river bed media, structure and discharge level, baseon saturated and un-saturated flow theory, systemically stimulate transportation rules ofcontaminants during the evolution process between river and groundwater, construct themathematic model of coupling groundwater flow with contaminants transportation duringthe process. And it also predicts the influence extent under different groundwater pumpingintensity by the model, analyzes influence factors of contaminants transportation. And then it discusses transportation mechanism of contaminants during the evolution process of therelationship of river and groundwater. Finally it puts forward to the measurements of watersupply safety of riverside groundwater source field.Some conclusion has achieved from this study:1. Once groundwater withdrawal is larger than the maximum recharge of a river, water levelbetween river and groundwater will disjoint during exploitation of a riverside groundwatersource field. The related factors, which affect the evolution process of relationship betweenriver and groundwater, are lithology and structure of aquifers, shape and width of riverbed,water deepness and discharge level of a river, etc. These factors affect not only hydraulicconnection between river and groundwater, but also pollution transportation.2Under drive of pumping groundwater, with decline of groundwater level, not only therive-groundwater aquifer system, shape of soakage curves, recharge, recharge pattern of theriver and leakage paths have changed, but also transportation style of river pollutions haschanged and has obvious zonation. The convection zone, transition zone and dispersion zonecenter on river, enlarging and moving along river flow direction.3No matter how the relationship between river and groundwater changes, rivercontaminants will diffuse in groundwater and pollute groundwater. The closer distance from ariver, the more easily groundwater is polluted. To pumping wells along rivers, it takespollutants shorter time to reach these wells before water level between river and groundwaterdisjointed, however, after the water level between them disjointed, it takes pollutants a longertime to reach these wells with decline of exploitation water level.4Under the same hydraulic gradient, pollutant diffusion distance increases with theincrease of time, and tends to a stable value, however, pollutant diffusion velocity decreases,and tends to zero. Velocity of the front pollution diffusion is faster than that of pollution peak.Under different hydraulic gradient, the bigger hydraulic gradient is, the farther pollutantdiffusion distance is before level disjointed between river and groundwater. Then thepollutant diffusion distance is the farthest when discharge water level has access to its criticaldisjointed water level. After disjointed between them, the bigger hydraulic gradient is, theless pollutant diffusion areas reduce, then keeps stable. The bigger hydraulic gradient is, thefaster velocity of the front pollutant diffusion, but the more slowly speed of the pollution migration peak.5. During the evolution process of relationship between river level and groundwater level, ifhydraulic gradient of river-aquifer is smaller than0.15, wells will be in dispersion zones; if itshydraulic gradient is smaller than0.65, wells will be in transition zones; while if its hydraulicgradient is bigger than0.65, wells will be in advection zones. So wells should be indispersion zones as possible to ensure better water quality during exploitation of watersources near a river.6. During explorations of riverside groundwater source field, comprehensively consideringwater quality, quantity and economic efficiency, exploitation level may reach the criticaldisjointed level between a river and groundwater to stimulate the maximum recharge if waterquality of its middle and upperstream sections is better. However, exploitation level should behigher to ensure wells are always in dispersion zones if water quality of its middle andlowerstream sections is worse.更多还原