北京市朝阳区沙子营垃圾污染物在潜水含水层中迁移规律的现场模拟实验

选择北京平原区水文地质、环境地质等方面都比较典型的沙子营垃圾堆放场,建立了其水文地质模型。在充分收集资料、分析得出部分计算所需参数后,采用现场弥散实验、勘查取样测试等方法,求得了该含水层的弥散系数等参数;用二维非稳定流溶质运移方程对污染物在此含水层中的迁移扩散规律、速度和污染范围等进行了模拟计算;采用现场钻探、取样测试分析等方法,评价了该含水层的实际污染状况。实验模拟计算和现场调查结果表明:污染物在潜水含水层中的运移规律遵循二维非稳定流场中的溶质运移方程,污染物在潜水含水层中的运移速度约为86.25m/a,迁移扩散主要发生在地下水流向上,侧向扩散宽度极小,是地下水流向上的1/17。     

悦康药业地下水环境数值模拟预测与评价

悦康药业在开发和生产过程中可能会对区域地下水环境造成影响。基于研究区水文地质条件,建立水文地质概念模型,分别对拟开采的第Ⅲ承压含水层,运用水流运动方程对项目开采15年后的地下水位进行模拟预测;运用溶质运移数学模型对药厂建成后污水处理站对潜水和第Ⅰ承压水进行污染物模拟预测。水位模拟结果表明,15年后含水层(组)中形成降落漏斗大于1 m的范围为0. 45 km~2,形成地面沉降的可能性较小。污染物模拟预测选取COD_(Mn)、氨氮作为预测因子,分别预测污染发生100天、720天及1 800天后污染物迁移情况。污染物模拟结果表明污水站溶质扩散范围较小,5年后COD_(Mn)最大迁移距离为40 m,中心体积质量降为5. 0 mg/L;氨氮最大迁移距离为35 m,中心体积质量降为0. 3 mg/L,对区域地下水水质影响不大。     

Study on numerical simulation of organic pollutant transport in groundwater northwest of Laixi

The construction and hydrogeological area in the low hill, which is northwest of Laixi City and in the east of Shandong Province more precisely, is one of Dagu River’s groundwater source. Regarding COD as the typical pollutant according to general situation of groundwater pollution in aforementioned area, a three-dimensional advection-dispersion model was established to simulate the transport of organic pollutants under two accident conditions. In addition, the effect of corresponding dispersity was analyzed. The results show that COD transport is mainly in accordance with the direction of groundwater flow, pollutant concentration and its gradient as well as the rule of narrower pollution range in deeper stratum. Moreover, COD is mainly transported and diffused in groundwater of sandy soil in the first and second layers. However, under accident condition II, the pollutant concentration begins to decay gradually after its transport and diffusion tends to be stable. Besides, in terms of dominance, dispersion is to transverse transport of pollutants what advection is to longitudinal transport. If considering random dispersion, the final results see higher peak concentration of COD and longer transverse distance from pollution center compared to transport route. What’s more, the pollution plume changes and concentration isocline becomes slightly irregular.     

Groundwater deterioration in Nankou—a suburban area of Beijing: data assessment and remediation scenarios

Since the 1980s, high-nitrate concentration in one of the groundwater sampling wells at the Nankou site, northwest of the Beijing Plain, has become a major concern for the local water authority. In a previous study (Sun et?al. in Environ Earth Sci 64(5):1323?C1333, 2011), a hydrogeological structural model was developed based on the borehole logs of this area and the steady, as well as transient groundwater-flow models, were calibrated using the measured hydraulic heads. In this paper, the potential pollution sources in this area are investigated. The chemical analysis of the groundwater is also presented. The results demonstrate that the most likely pollution source is the untreated wastewater discharge from a nearby fertilizer factory. Furthermore, a mass transport model is developed to reproduce the nitrate transport process in the aquifer at the Nankou site under different pollution sources, i.e., a fertilizer factory, river with wastewater and an agriculture field. The combined effects of the river and agriculture fields present a better understanding of the nitrate transport in the local aquifer. In addition, a pumping scenario is designed to clean up the current nitrate concentration. The pumping rate and the well location are first estimated with 2-D analytical solutions of the type curves method. Then a 3-D numerical model is used to calculate the nitrate-concentration changes after the pumping activities start. In the downstream direction of the regional groundwater flow, three pumping wells are set up for the clean-up strategy. The calculated pumping rate in each well is about 1,500 m³/day. After 1?year, the nitrate concentration in the observation well recedes to 68?mg/l from the initial value of 72.9?mg/l, and it will be lower than the limitation value (20?mg/l) after 5,400 days of groundwater extraction. The data assessment and clean-up scenarios reported in this paper are fundamental for the contaminated aquifer management in the future.     

Modeling of transient groundwater flow,pollutant transport,and biodegradation in an aquifer with large hydraulic head variations

Industrially sourced dense non-aqueous phase liquids (DNAPLs) contaminated an alluvial aquifer in France decades ago. The location(s) and nature of the pollution source zone(s) were unknown, and the dissolved concentrations of volatile organic compounds in the monitoring wells varied greatly with time. The aquifer was in hydraulic equilibrium with an artificial canal whose water level was highly variable (up to 5 m). These variations propagated into the aquifer, causing changes in the groundwater flow direction; a transient numerical model of flow and solute transport showed that they correlate with the concentration variations because the changes in the flow direction resulted in the contaminant plume shifting. The transient hydrogeological numerical model was built, taking into account solvent biodegradation with first-order chain, since biodegradation has a significant influence on the pollutant concentration evolution. The model parameterization confirms the position of the source zones among the potential troughs in the bedrock where DNAPLs could have accumulated. The groundwater model was successfully calibrated to reproduce the observed concentration variations over several years and allowed a rapid validation of the hypotheses on the functioning of the polluted system.     

地下水VOCs污染修复技术探讨

污染物事故性排放、工矿企业搬迁后遗留的污染场地修复面临各种问题,给地下水资源的使用带来严重威胁。地下水VOCs污染,具有易扩散迁移、毒性高、风险大的特点,修复难度较高。本文结合典型深层地下水修复案例,充分分析场地地质背景、水文地质条件等,根据污染物的特性、污染范围和分布特征,探讨各种修复技术的修复机理、修复对象和技术特点,针对VOCs污染修复进行性能比较及适用性分析。同时通过两个阶段的试验综合研究,原位和异位技术相结合,为开展类似地下水VOCs污染修复实践和管理提供了依据和思路。     

中国地下水污染修复方法和技术应用展望

[研究目的]:中国地下水污染调查和修复日益受到科学界的重视,了解和掌握地下水污染修复方法和技术有助于对污染场地进行科学修复.[研究方法]:本文在系统分析国内外地下水污染修复案例的基础上,对中国地下水污染修复现场实施的技术方法进行总结.[研究结果]:结合中国区域经济发展特征和地下水污染调查评价成果认为,复杂的水文地质条件...     

Assessment of groundwater contamination from a hazardous dump site in Ranipet, Tamil Nadu, India

Tanneries located in an industrial development area of Ranipet (India) manufactured chromate chemicals during 1976?C1996. A large quantity of associated hazardous solid wastes has been stacked about 5-m high above ground level, spread over 3.5?ha inside one of the factory premises. The study area receives an average annual rainfall of 1,100?mm. The granitic formation in the northern part of Palar River catchment has high infiltration rates and has resulted in fast migration of the contamination to the water table. Chromium levels in the groundwater were found up to 275?mg/l. The available hydrogeological, geophysical and groundwater quality data bases have been used to construct a groundwater flow and mass transport model for assessing the groundwater contamination and it has been calibrated for the next 30?years. The migration has been found to be very slow, with a groundwater velocity of 10?m/year. This is the first field-scale study of its kind in this industrial area. The findings are of relevance to addressing the groundwater pollution due to indiscriminate disposal practices of hazardous waste in areas located on the phreatic aquifer. Further, it has been reported that the untreated effluent discharge adjacent to the chromium dump site is most influential in the migration of contaminants.     

Delineation of groundwater protection zones based on tracer tests and transport modeling in alluvial sediments

 Regulations aiming to protect exploitable groundwater resources were edicted in Belgium a few years ago. Therefore, prevention and protection zones are defined by law and must be determined practically around each pumping well or spring, based on local hydrogeological conditions. The determination of hydrodynamic and hydrodispersive parameters, characterizing the local flow and transport properties of the aquifer, requires pumping and tracing tests. The interpretation of these field experiments, considering the heterogeneity of the geological layers, is performed through the use of numerical FEM simulations of the groundwater flow and pollutant transport conditions in a deterministic framework. After calibration of the model on experimental measurements, multiple simulations with contaminant injections at various points of the modeled domain allow the determination of the transfer time of the pollutant in the studied aquifer whilst taking the updated heterogeneity into account. On the basis of the computed transfer times in the saturated zone, the various prevention and protection areas can be assessed based on provisions of the law. Received: 27 June 1997 · Accepted: 29 July 1997     

宁东煤炭基地梅花井矿区地下水三氮特征及成因

为研究大规模综合机械化采煤氮污染来源及影响程度,选取宁东煤炭基地侏罗纪煤田鸳鸯湖矿区的梅花井井田为研究对象,通过调查取样分析,对梅花井井田地下水三氮污染分布、物源、水文地质条件进行研究。结果表明:(1)宁东煤炭基地鸳鸯湖矿区梅花井井田三氮NH4+、NO3-、NO2-含量范围分别为0.06～0.12mg/L、4.67～234mg/L、0.01～2.01mg/L,与国家地下水质量标准Ⅲ类水质限值对比,NO2-达到重度或极严重污染,主要分布在潜水含水层;NO3-污染级别为中度、轻度污染,超标样点占调查样点的75%,垂向上已延伸到承压含水层。水平空间上无论矿权范围还是矿权外,污染样点均有存在。(2)部分水样中NO3-毫克当量百分数超过25%,对水化学类型产生影响。(3)煤矿区NO3-、NO2-的污染首先与丰富的物源有关,还受煤矿开采扰动、地形地貌条件、垂向补给径流、水文地球化学条件等因素的影响。研究结果为风积沙大型机械化煤矿开采区地下水氮污染的防治提供了可参考依据。     

Determination of groundwater solute transport parameters in finite element modelling using tracer injection and withdrawal testing data

The groundwater tracer injection and withdrawal tests are often carried out for the determination of aquifer solute transport parameters. However, the parameter analyses encounter a great difficulty due to the radial flow nature and the variability of the temporal boundary conditions. An adaptive methodology for the determination of groundwater solute transport parameters using tracer injection and withdrawal test data had been developed and illustrated through an actual case. The methodology includes the treatment of the tracer boundary condition at the tracer injection well, the normalization of tracer concentration, the groundwater solute transport finite element modelling and the method of least squares to optimize the parameters. An application of this methodology was carried out in a field test in the South of Hanoi city. The tested aquifer is Pleistocene aquifer, which is a main aquifer and has been providing domestic water supply to the city since the French time. Effective porosity of 0.31, longitudinal dispersivity of 2.2 m, and hydrodynamic dispersion coefficients from D = 220 m²/d right outside the pumping well screen to D =15.8 m²/d right outside the tracer injection well screen have been obtained for the aquifer at the test site. The minimal sum of squares of the differences between the observed and model normalized tracer concentration is 0.00119, which is corresponding to the average absolute difference between observed and model normalized concentrations of 0.035 5 (while 1 is the worst and 0 is the best fit).     

用地下水潮汐效应确定潜水含水层水文地质参数

目前对潜水含水层地下水潮汐效应和水文地质参数求解方法的研究相对较少.通过对福建古雷半岛滨海潜水含水层地下水潮汐效应和海水潮汐动态的观测, 运用Fourier频谱分析方法确定了研究区海水潮汐波动方程(波动特征参数), 并以此作为地下水的边界条件, 推导了潜水含水层地下水潮汐效应的波动方程, 利用最小二乘法以地下水水位波动观测值为目标函数对潜水含水层的渗透系数与重力给水度的比值进行了反演识别, 为类似地区水文地质参数的确定提供了借鉴, 也为该区后续地下水中溶质迁移规律的研究奠定了基础.      

Groundwater pollution risk mapping for the Eocene aquifer of the Oum Er-Rabia basin, Morocco

Sustainable development requires the management and preservation of water resources indispensable for all human activities. When groundwater constitutes the main water resource, vulnerability maps therefore are an important tool for identifying zones of high pollution risk and taking preventive measures in potential pollution sites. The vulnerability assessment for the Eocene aquifer in the Moroccan basin of Oum Er-Rabia is based on the DRASTIC method that uses seven parameters summarizing climatic, geological, and hydrogeological conditions controlling the seepage of pollutant substances to groundwater. Vulnerability maps were produced by using GIS techniques and applying the “generic” and “agricultural” models according to the DRASTIC charter. Resulting maps revealed that the aquifer is highly vulnerable in the western part of the basin and areas being under high contamination risk are more extensive when the “agricultural” model was applied.     

某石化污染场地含水层自然降解BTEX能力评估

地下水污染问题是国家关注的重要环境问题之一,监测与评估含水层自然降解污染物能力是防治地下水污染的基本手段,也是国外地下水中修复技术研究热点课题。以华北平原某石油化工类场地为案例,通过调查场地水文地质条件、土壤及地下水污染现状,监测场地地下水中苯系物(BTEX)浓度及相关化学参数变化,运用微生物水文地球化学方法和水文地质方法,估算了该场地含水层自然降解苯系物量。这一研究成果为评估我国石油类场地地下水污染的自然修复能力提供了实证和基础数据。     

焦作地区浅层地下水铬(Ⅵ)污染机理及迁移预测

通过对焦作地区浅层地下水中铬(Ⅵ)污染物分布特征进行调查,分析了研究区浅层地下水中铬(Ⅵ)的污染机理,并运用Visual MODFLOW建立地下水流模型及溶质运移模型,模拟预测了浅层地下水中铬(Ⅵ)的迁移规律。结果表明:研究区浅层地下水铬(Ⅵ)污染严重,污染源是位于老君庙西南方向的焦作某电厂堆灰场,主要原因是露天堆放的粉煤灰中的铬(Ⅵ)污染物在长期淋滤作用下下渗污染含水层。气候条件、包气带岩性、地下水化学环境以及人为因素等也间接使浅层地下水铬(Ⅵ)浓度升高;模拟结果显示在未来的五年时间内,受地形和地下水动力场的影响,浅层地下水中铬(Ⅵ)的迁移方向与地下径流方向一致,沿大沙河水流方向上扩散速度更快,污染区域面积逐渐增大。      

Chloride as tracer of solute transport in the aquifer–aquitard system in the Pearl River Delta,China

A 1D numerical model is constructed to investigate the impact of sedimentation and sea level changes on transport of Cl^? in the aquifer–aquitard system in the Pearl River Delta (PRD), China. The model simulates the evolution of the vertical Cl^? concentration profiles during the Holocene. Sedimentation is modeled as a moving boundary problem. Chloride concentration profiles are reconstructed for nine boreholes, covering a wide area of the PRD, from northwest to southeast. Satisfactory agreement is obtained between simulated and measured Cl^? concentration profiles. Diffusion solely is adequate to reproduce the vertical Cl^? concentration profiles, which indicates that diffusion is the regionally dominant vertical transport mechanism across the aquitards in the PRD. The estimated effective diffusion coefficients of the aquitards range from 2.0?×?10^–11 to 2.0?×?10^–10 m²/s. The effective diffusion coefficients of the aquifers range from 3.0?×?10^–11 to 4.0?×?10^–10 m²/s. Advective transport tends to underestimate Cl^? concentrations in the aquitard and overestimate Cl^? concentrations in the basal aquifer. The results of this study will help understand the mechanisms of solute transport in the PRD and other deltas with similar geological and hydrogeological characteristics.     

The geochemical and isotopic composition of aquifer systems in the deltaic region of the Po River plain (northern Italy)

The chemical and hydrodynamic characteristics of groundwater in deltaic regions are strongly influenced by the complex stratigraphy of these areas, caused by the continuously varying depositional environments associated with their recent hydrographic evolution. As a case study, the eastern sector of the Po River plain, northern Italy, has been investigated to understand the quality of the available groundwater resources. Based on the analysis of hydrochemical and isotopic data, the recharge characteristics, the groundwater residence time and the aquifer vulnerability are defined. The results show significant qualitative degradation of the unconfined aquifer due to the shallow depth to water, while in the underlying confined aquifer, a hydrochemical facies of Ca–HCO₃ type prevails. The spatial variation and relationship between oxygen-18 and deuterium determine: firstly, hydraulic separation of the two hydrogeological units; secondly, direct infiltration of local precipitation to the unconfined aquifer; thirdly, the occurrence of waters originating in the Alps and locally from the Apennines, pervading the confined aquifer. The tritium results suggest local mixing between the superficial waters and the confined aquifer, occurring along the palaeo-river channels. This increases the pollution vulnerability of the confined hydrogeological unit within the plain, which is the only natural groundwater resource exploited for water supply.     

Hydrogeological investigation of groundwater artificial recharge by treated wastewater in semi-arid regions: Korba aquifer (Cap-Bon Tunisia)

Korba aquifer is one of the most typical examples of overexploited coastal aquifer in the Mediterranean countries. In fact, from 1985, a considerable piezometric level drop, water salinization, and seawater intrusion were registered in the aquifer. In December 2008, Tunisian authorities initiated a general plan to groundwater management in order to augment groundwater resources, restore the piezometric levels, and improve water quality. The plan consists of artificial recharge of groundwater used treated wastewater through three infiltration basins. During the first 4 years (from December 2008 to December 2012), 1.41 Mm³ of treated wastewater was injected to the Korba aquifer. This study presents a hydrogeological assessment of groundwater evolution during the recharge processes. In this study, 32 piezometric and chemical surveys of 70 piezometers and observed wells are used to present hydrogeological investigation and water quality evolution of wastewater reuse through artificial recharge in Korba coastal aquifer. The piezometric evolution maps are used to specify the positive effect in groundwater level that exceeding 1.5 m in some regions. The interpretation of salinity evolution maps are used to indicate the improving of groundwater quality.     

Modeling the effects of the variability of temperature-related dynamic viscosity on the thermal-affected zone of groundwater heat-pump systems

Thermal perturbation in the subsurface produced in an open-loop groundwater heat pump (GWHP) plant is a complex transport phenomenon affected by several factors, including the exploited aquifer’s hydrogeological and thermal characteristics, well construction features, and the temporal dynamics of the plant’s groundwater abstraction and reinjection system. Hydraulic conductivity has a major influence on heat transport because plume propagation, which occurs primarily through advection, tends to degrade following conductive heat transport and convection within moving water. Hydraulic conductivity is, in turn, influenced by water reinjection because the dynamic viscosity of groundwater varies with temperature. This paper reports on a computational analysis conducted using FEFLOW software to quantify how the thermal-affected zone (TAZ) is influenced by the variation in dynamic viscosity due to reinjected groundwater in a well-doublet scheme. The modeling results demonstrate non-negligible groundwater dynamic-viscosity variation that affects thermal plume propagation in the aquifer. This influence on TAZ calculation was enhanced for aquifers with high intrinsic permeability and/or substantial temperature differences between abstracted and post-heat-pump-reinjected groundwater.

     

Potential nitrate pollution of groundwater in Germany: A supraregional differentiated model

Implemented on behalf of the Federal Ministry for Research and Technology (BMFT), a model is developed to trace the nutrient flow of nitrate in the soil and the groundwater on a supraregional scale. Research work is intended to indicate regionally differentiated hazardous potentials and thereby provide a basis for recommending comprehensive measures to protect groundwater in Germany. The adaption of the model to the hydrogeological and agricultural conditions of other states is possible in principle. This article focuses on the hydrogeological model parts. A high nitrate pollution of groundwater can be expected in all regions with intensive agricultural use of the topsoil. In particular, groundwater in solid rock areas is susceptible to nitrate pollution. There a rapid groundwater turnover and thus a short residence time for the groundwater in the aquifer is typical. Oxidizing aquifer conditions usually prevail in solid rock aquifers, preventing nitrate degradation. In many loose rock areas, in contrast, the groundwater has a low flow velocity and a long residence time in the aquifer. Because of a lack of free oxygen, a complete degradation of nitrate can occur, as long as iron sulfide compounds and/or organic carbon are available in the aquifer. A more detailed presentation of the whole research work is given in Wendland et al. (1993).