上海市第三、四承压含水层间存在直接水力联系地段

以往上海地区地质、水文地质有关报告和文章都以为上海地区第三、四承压含水砂层间的隔水粘性土层(顶板一般埋深为140米左右)层位稳定,分布普遍,隔水性能良好。第三、四承压含水层无垂向直接水力联系。这就在一定程度上,简化了水文地质条件和相应的地下水资源计算、水化学评价等方面的工作。     

上海市第四承压含水层变形特征研究

上海市自1968年调整开采层次以后,第四承压含水层逐渐成为地下水主要开采层次,历史上曾因过度开采利用地下水而成为主要的压缩土层。本文依据上海市长期的地下水位和地面沉降监测资料,总结了第四承压含水层在不同水位变化条件下的变形特征,同时根据压缩试验资料,对第四承压含水层变形机理探讨,为合理开发利用地下水资源提供理论依据。     

上海市第四承压含水层应力-应变分析

上海市区完善的监测网络系统地记录了在第四承压含水层地下水资源开发过程中，其地下水位变化、土层压缩变形的历史。随着第四承压含水层开采量的增加，总体上地下水位呈不断下降、土层压缩变形逐年增大的趋势，并具有明显的非线性特征。第四承压含水层随地下水位降低、有效应力的增加，经历了弹性→弹塑性→塑性的变形历程，反映出地下水位（应力）状态对含水层的变形速率及相态具明显的制约作用。不同的地下水位（应力）状态下，第四含水层表现出不同的变形相态和应力-应变形迹，由弹塑性进入塑性变形时所对应的年度最低水位是含水层变形的“临界水位”。上海地区第四承压含水层的临界水位约的在-28～-32m。     

地下水控采条件下上海土层变形特征研究

根据上海地区分层标和水位孔的实测资料,分析了2001~2012年间地下水控采条件下地下水位变化及土层变形特征。上海地区潜水层和第一承压含水层水位基本保持不变,第二至第五承压含水层水位都呈现出明显的回升趋势。三个软土层仍在发生压缩变形,其中第三软土层随着水位的回升变形得到了控制,部分地区已出现回弹趋势。在水位全面回升情况下,第一到第四承压含水层表现为明显的塑性和蠕变变形,当水位持续回升时土层仍有沉降,且变形滞后于水位变化;而第五承压含水层主要以弹性变形为主,当水位不断回升时,含水砂层也随之持续回弹,滞后不明显。将上海地区近年来含水层与水位变化关系归纳出四种模式。砂性土单向蠕变试验的结果表明,双屈服流变模型可以较好地反映砂土蠕变变形特征。     

越流区开采条件下承压含水层易污染性机理研究——以单井开采为例

地下水易污染性分析是合理开发利用地下水资源、保护地下水环境的一项重要的基础性工作.长期以来针对潜水含水层易污染性的研究进行的较为深入,而对承压含水层易污染性的研究较为少见.同时,易污染性评价方法又以经验方法为主,受人为主观因素影响较大,因此需要通过对承压含水层污染机理进行研究,以减少人为主观因素对评价结果的影响.本文以单井开采承压含水层为例,通过分析承压含水层受污染的原因,以单位面积上越流补给量占开采量的比重为承压含水层易污染性指数,在建立越流区承压水向完整井稳定运动的微分方程的基础上,得到易污染性指数的解析表达式,并分析了各参数对易污染性的影响,使承压含水层易污染性评价有了一定的理论依据,对合理开发利用承压含水层有一定的指导意义.     

复合含水层系统地下水资源评价三维数值模型

江苏省盐城市地下含水系统为一复合含水层系统,采用真三维模型,将其概化为三度空间上的非均质各向异性.在对模型进行识别、验证的基础上,结合对地面沉降、咸水入侵等地质环境控制的要求,规划、预测了到2020年12月底,第Ⅱ承压含水层、第Ⅲ承压含水层和第Ⅳ承压含水层中的最低地下水位分别恢复到-20 m、-30 m和-40 m时,各含水层中地下水的开采量及地下水的最优开采布局,并预测了未来各含水层地下水位降落漏斗趋于稳定的地下水开采量.     

地下水回灌技术在浅层承压含水层中的实践与探讨

上海地区承压含水层埋深较深,深基坑围护的止水帷幕难以深入到承压含水层底板进行地下水水平向的完全阻隔,减压降水过程势必对周边环境产生一定影响。以上海盛大国际金融中心深基坑回灌试验为依据,表明人工回灌地下水对控制承压水位具有一定效果,并运用数值方法模拟了不同回灌条件下坑外承压水位的变化。     

历史海平面变化对上海地区地下水的影响

在总结海平面变化及长江三角洲古河道分布的基础上,通过上海地区第Ⅱ至第Ⅴ承压含水层地下水化学、~(14)C年龄特证的分析,探讨了因海平面变化引起的长江及支流河道的侵蚀、堆积对地下水径流交替的影响,提出了滨海三角洲地区地下水补给、径流、排泄的一种模式。     

上海第四纪地层温度场分布特征与影响因素分析

地源热泵是上海开发利用浅层地温能的主要形式。通过对上海地区不同地点、不同埋深范围内第四纪地层地温实测数据,分析了本地区浅层岩土温度场分布的一般规律,并与历史数据比较。40余年来,上海地区第一承压含水层的平均地温有小幅升高,而第二承压含水层则有小幅下降。影响浅层地温场分布的主要因素有太阳辐射的周期变化、城市热岛效应、地表植被、地下水径流、人工回灌等。本文可为本地区地埋管地源热泵系统的勘察设计提供参考。     

上海市区承压含水层结构类型分区

上海地区与工程建设密切相关的承压水主要赋存于微承压、第一、第二承压含水层中。本文在上海市区关键土层地质编图的基础上,针对与工程建设密切相关的承压含水层的分布特征,进行承压含水层的结构类型分区,为工程降水设计提供参考。     

Hydrogeochemistry and groundwater origin of the Basses-Laurentides sedimentary rock aquifer system, St. Lawrence Lowlands, Québec, Canada

A comprehensive hydrogeochemical study was carried out in the Paleozoic Basses-Laurentides sedimentary rock aquifer system in Québec over a 1500 km² study area. Groundwater samples were collected at 153 sites, characterizing all geological and hydrogeological units to a maximum depth of 140 m. Groundwater was analyzed for major, minor and trace inorganic constituents, stable isotopes δ ²H, δ ¹⁸O, and δ ¹³C of dissolved inorganic carbon (DIC), and some samples were analyzed for ³H, and ¹⁴C of DIC. The regional distribution of groundwater types shows that the hydrogeological conditions exert a dominant control on the major ions chemistry of groundwater. Preferential recharge areas are characterized by tritiated Ca-Mg-HCO₃ groundwater, and confined conditions by submodern Na-HCO₃ and Na-Cl groundwater types. Two groundwater end-members are identified in the aquifer system, modern meteoric water and Pleistocene Champlain Sea water. The region displays significant variations of groundwater geochemistry and quality controlled by glaciation, Champlain Sea invasion, lithological rock diversity, and flow system scales. This situation leads to varied groundwater types and origins within a restricted area.     

Application of multiple-point geostatistics on modelling groundwater flow and transport in a cross-bedded aquifer (Belgium)

Sedimentological processes often result in complex three-dimensional subsurface heterogeneity of hydrogeological parameter values. Variogram-based stochastic approaches are often not able to describe heterogeneity in such complex geological environments. This work shows how multiple-point geostatistics can be applied in a realistic hydrogeological application to determine the impact of complex geological heterogeneity on groundwater flow and transport. The approach is applied to a real aquifer in Belgium that exhibits a complex sedimentary heterogeneity and anisotropy. A training image is constructed based on geological and hydrogeological field data. Multiple-point statistics are borrowed from this training image to simulate hydrofacies occurrence, while intrafacies permeability variability is simulated using conventional variogram-based geostatistical methods. The simulated hydraulic conductivity realizations are used as input to a groundwater flow and transport model to investigate the effect of small-scale sedimentary heterogeneity on contaminant plume migration. Results show that small-scale sedimentary heterogeneity has a significant effect on contaminant transport in the studied aquifer. The uncertainty on the spatial facies distribution and intrafacies hydraulic conductivity distribution results in a significant uncertainty on the calculated concentration distribution. Comparison with standard variogram-based techniques shows that multiple-point geostatistics allow better reproduction of irregularly shaped low-permeability clay drapes that influence solute transport.     

Small scale study of groundwater flow in a fractured carbonate-rock aquifer at the St-Eustache quarry, Québec, Canada

A small-scale hydrogeological study was conducted in a fractured carbonate-rock aquifer located in a quarry to relate groundwater flow to the fracture network. The field study in the St-Eustache quarry, which integrates structural surveys, well logging and hydraulic tests, showed that the most important features that affect groundwater flow in the sedimentary aquifer are high hydraulic conductivity horizontal bedding planes. Vertical fractures are abundant in the quarry and throughout the region, but they have a minor effect on groundwater flow. To have a significant impact on the flow regime and lead to vertical groundwater flow, the permeability of all vertical joints need to be enhanced compared to what was generally observed at the site. Such an increase in permeability could potentially occur where dissolution and fracturing is more intense or at stress release locations such as near the surface in the quarry.     

鲁西南地区高氟水分布规律与成因分析

地方性氟中毒是我国北方地区最为典型的地方病之一,查明高氟地下水的空间分布及其成因是除氟改水、防治氟害的前提。通过对鲁西南地区不同层位地下水水质分析结果及水文地质、地质条件等多个环境影响因素的综合分析,查明了鲁西南地区高氟水的空间分布规律,并分析了影响浅层和深层高氟水形成的环境因素。浅层高氟水呈片状分布于洼地、缓平坡地等地势较低的区域,占鲁西南地区总面积的47%,大部分地区高氟水氟离子含量为1.2～2.0 mg/L,局部大于4.0 mg/L,其形成受气候、地质环境、地形地貌特征及水化学环境等多个因素的影响,成因类型为溶滤-蒸发浓缩型。深层高氟水具有水平分带性,占鲁西南地区总面积的65%,大部分高氟水氟离子含量为2.0～4.0 mg/L,氟离子含量分布与晚更新世沉积相带呈现很好的相似性,推测其为地质历史时期形成的古地下水。     

Groundwater flow modelling within a coastal alluvial plain setting using a high-resolution hydrofacies approach; Bells Creek plain, Australia

Ground penetrating radar (GPR) has proved to be an extremely useful geophysical tool, in conjunction with direct geological data, to develop a realistic, macroscopic, subjective-based conceptual model of aquifer architecture within a shallow coastal alluvial plain. Subsequent finite-difference groundwater modelling has not only enabled determination of the dominant groundwater flow paths for the plain, but has also quantified the effects of within-facies and between-facies sedimentary heterogeneity on those flow paths. The interconnection of narrow, unconfined alluvial channels and a broad, semi-confined alluvial delta is ensuring that most fresh groundwater that enters the plain in the form of precipitation or recharge from lateral bedrock hills, is discharged into the eastern coastal wetlands via that alluvial delta aquifer.     

Modeling of lithology induced chemical anomalies in the aquifer systems of the Kazan Trona deposit area, Ankara, Turkey

The study was carried out in order to investigate existing hydrogeochemical relationships between groundwater environment and geological units in the Kazan trona deposit area, Ankara, Turkey. Evaluations indicate that concentrations of alkalinity, boron, chloride and sodium in the upgradient groundwater of the Eocene sedimentary units gradually increase toward downgradient by the interactions of saline minerals (searlesite, shortite, northupite and pyrite) present in the secondary structures (microfractures and irregular voids) at various levels. Inverse modeling calculations suggest that the range of dissolved mass amounts in millimoles per kilogram of water for searlesite, shortite and northupite minerals are 0.05–28.67, 2.62–24.39 and 0.01–24.19, respectively, in the aquifer between the upgradient and downgradient locations. The ranges of accompanying calcite and dolomite precipitations are 4.54–48.71 and 2.16–24.08 mmol per kg of water, respectively. Chemical composition of the groundwater in the overlying Neogene sedimentary unit includes also higher concentrations of the major ions as measured in groundwater of the underlying units. However the lack of saline mineral zones in the Neogene unit indicates that upward groundwater mixing takes place from the underlying aquifer as also suggested by the measured upward gradient. The mixing percentage of the underlying groundwater as determined from the nested wells ranges from 2.7 to 48.3%, from upgradient to downgradient, respectively. The unconfined alluvium aquifer overlying the Neogene unit includes relatively dilute groundwater except in two locations, where high-ion concentrations detected in groundwater of the underlying units are also high in these locations, suggesting upward groundwater mixing from the underlying aquifer due to upward gradient. However, groundwater input investigations from the alluvium aquifer to the nearby Ova stream indicate that the detected high concentrations in these locations are diluted or sorbed by the aquifer material toward downgradient (Ova Stream).     

The effect of typical geological heterogeneities on the performance of managed aquifer recharge: physical experiments and numerical simulations

Understanding the role of geological heterogeneity on the performance of managed aquifer recharge (MAR) in terms of effective groundwater storage is crucial to design MAR systems. Natural aquifers are affected by a variety of geologic strata and structures at different scales, which are responsible for wide ranging hydraulic properties. This study combines physical experiments and numerical modeling to investigate the effect of geologic structures commonly encountered in sedimentary environments, on MAR-induced groundwater flow patterns using injection wells. Models were conceptualized and parametrized based on the hydrogeological conditions of Tailan River basin in arid NW China, which hosts a typical, structurally complex, alluvial-fan aquifer system affected by sediment layering, clay lenses and anticline barriers, and is extensively studied for the strategic potential of MAR in addressing water shortages in the region. Results showed that, compared to a homogeneous scenario, high-permeability aquifer layers shortened groundwater ages, decreased the thickness of the artificially recharged water lenses (ARWLs), and shifted the stagnation points downstream. Clay lenses increased groundwater residence times but had little effect on spatial flow patterns due to their elongation parallel-to-flow direction. Overall groundwater ages, as well as the thickness of ARWLs created through injection on the upstream side of an anticline, increased, and this to a larger extent than through injection on the downstream side, which did not increase significantly compared to the homogeneous scenario. Results provide insights for MAR optimization in naturally heterogeneous aquifer systems, along with a benchmark tool for application to a wide range of typical geological conditions.

     

苏锡常地区浅层地下水rNa/rCl特征及其成因初探

本文从苏锡常地区浅层地下水含水介质及包气带沉积环境的角度,阐明了浅层地下水中Cl-和Na 浓度东高西低的分布特征。根据数据分析,浅层地下水中Na 与Cl-的毫克当量比值rNa/rCl与海侵形成的沉积环境和沉积历史关系密切。地下水淡化历史越长,含水层介质中吸附的Na 与地下水中的Ca2 和Mg2 之间的阳离子交换吸附程度越高,大量的Na 进入地下水中,使得rNa/rCl比值越高。     

上海市承压含水层系统应力-应变特征及地面沉降防治对策

1990年以来，上海市地下水开采与人工回灌格局发生了较大的变化。承压含水层地下水位变化与压缩变形均表现为新的特点与发展趋势。通过对上海中心城区含水层系统的应力一应变特点分析，总结了承压含水层随地下水位下降所表现出的弹性一弹塑性一塑性变形的演化规律。上海中心城区第Ⅱ、Ⅲ承压含水层总体上处于地下水开采与人工回灌的平衡状态，表现为弹性变形；而第Ⅳ、Ⅴ承压含水层由于地下水位目前已严重低于其“临界水位”，表现为持续压缩的塑性变形。目前，第Ⅳ承压含水层对中心城区地面沉降贡献率已达到了49．3％，西部华漕地区第Ⅴ承压含水层变形的贡献率为46．7％。针对各承压含水层不同的变形特点，提出了地下水资源管理与地面沉降防治对策。     

鄂尔多斯盆地白垩系主要含水岩组沉积岩相古地理对地下水水化学场形成和水质分布的影响

通过典型水文钻孔和露头剖面沉积地质、水文地质调查、样品测试及综合研究表明,鄂尔多斯盆地白垩系含水层形成时,北部环河组、洛河组均广泛发育河流相沉积,而南部环河组湖泊相为主、洛河组沙漠沙丘相广泛分布的沉积古地理格局,这对含水岩石中长石、粘土矿物、方解石、石膏等重要矿物组成和易溶盐含量及其空间分布形成明显控制,也控制了含水层和隔水层空间分布,并显著影响了深层地下水循环交替条件的区域分布变化。在沉积-成岩环境条件下,影响地下水水化学场形成和水质分布变化的主要水-岩作用包括硫酸盐、碳酸盐及硅酸盐矿物的溶解溶滤和阳离子交换作用等水文地球化学作用。受含水层沉积岩相古地理、地下水循环及水岩作用等因素控制,环河组、洛河组地下水总体表现为盆地北区TDS低、淡水发育、以HCO3型为主,南区TDS高、微咸水和咸水发育、以HCO3.SO4型为主的分布规律,地下水水化学和水质分布在北区分布变化小、在南区上下含水层分布变化复杂。