Environmental isotopic and hydrochemical characteristics of groundwater systems in Daying and Qicun geothermal fields,Xinzhou Basin,Shanxi, China

The conceptual hydrogeological model of the low to medium temperature Daying and Qicun geothermal fields has been proposed, based on hydrochemical characteristics and isotopic compositions. The two geothermal fields are located in the Xinzhou basin of Shanxi, China and exhibit similarities in their broad‐scale flow patterns. Geothermal water is derived from the regional groundwater flow system of the basin and is characterized by Cl·SO₄‐Na type. Thermal water is hydrochemically distinct from cold groundwater having higher total dissolved solids (TDS) (>0·8 g/l) and Sr contents, but relatively low Ca, Mg and HCO₃ contents. Most shallow groundwater belongs to local flow systems which are subject to evaporation and mixing with irrigation returns. The groundwater residence times estimated by tritium and ¹⁴C activities indicate that deep non‐thermal groundwater (130–160 m) in the Daying region range from modern (post‐1950s) in the piedmont area to more than 9·4 ka BP (Before Present) in the downriver area and imply that this water belong to an intermediate flow system. Thermal water in the two geothermal fields contains no detectable active ¹⁴C, indicating long residence times (>50 ka), consistent with this water being part of a large regional flow system. The mean recharge elevation estimated by using the obtained relationship Altitude (m) = ? 23·8 × δ²H (‰ ) ? 121·3, is 1980 and 1880 m for the Daying and Qicun geothermal fields, respectively. The annual infiltration rates in the Daying and Qicun geothermal fields can be estimated to be 9029 × 10³ and 4107 × 10³ m³/a, respectively. The variable ⁸⁶Sr/⁸⁷Sr values in the thermal and non‐thermal groundwater in the two fields reflect different lithologies encountered along the flow path(s) and possibly different extents of water‐rock interaction. Based on the analysis of groundwater flow systems in the two geothermal fields, hydrogeochemical inverse modelling was performed to indicate the possible water‐rock interaction processes that occur under different scenarios. Copyright © 2010 John Wiley & Sons, Ltd.     

山西忻州奇村水汞观测干扰因素浅析

为进一步明确山西忻州奇村水汞观测过程中存在的干扰因素,分别对硫酸单一试剂、综合试剂、空气湿度、同一个水样多次观测等项进行了试验。试验表明,现用硫酸及其他试剂的汞污染均不明显,对水汞观测构不成于扰;观测室内空气高湿度对水汞观测有一定干扰,且湿度越大,干扰越强,高湿度导致测值大幅突跳;通常所测的水汞含量实为在鼓泡延续时间及空气流量固定不变特定情况下的相对含量,两者的改变会对测值的可比性产生人为干扰。     

山西忻州奇村井水汞高值原因分析

通过对比观测实验,对水汞观测中出现的大幅度高值异常变化原因进行分析,认为汞标准源长时间置于观测室,造成室内汞污染;捕汞管、取样瓶、还原器等长时间不清洗受到污染等是造成水汞高值的主要原因。对观测过程中存在的问题提出几点建议,以利于提高水汞观测质量及在地震分析预报中的作用。     

山西忻州奇村热水井水氡干扰分析

2000年4月，奇村热水井出现水氡高值“异常”。本文从水点的水文地质条件、水氡异常变化特点、水氡变化的影响因素及其机理等方面，对该“异常”的干扰做了比较系统的论证。认为水氡“异常”变化，与周围冷水井抽水有关，而不是地震前兆。     

杭嘉湖地区水化学及同位素特征初步分析

本文通过初步分析杭嘉湖地区地下水化学和同位素特征,认为地下水的水化学分布存在着一定的分带性。浅层地下水化学类型为Cl,HCO3-Ca,Na型,代表了降水或地表水补给的形成过程,且补给前受到不同程度的蒸发。深层承压水化学类型为HCO3-Ca,Na和HCO3-Na型,代表了以铝硅酸盐矿物溶解为主的形成过程,其补给源为古气候条件下的降水补给。利用氘过量参数d值判断了第承压水（120~150 m）总体流向为南西至北东,即由杭州和湖州向嘉兴方向径流。     

山西忻州奇村水化站水汞观测干扰动态识别方法初探

通过对山西忻州奇村水化站水汞观测水样与空白样测值曲线所含信息的研究,论述了两者产生同步现象的原因及其动态特征,进而提出排除水汞干扰、识别水汞异常的方法。     

生态补水对白洋淀流域地表水和地下水水化学特征的影响

生态补水是维持和改善白洋淀生态环境的重要途径.为研究生态补水对白洋淀水环境的影响,分别在补水前与补水后采集淀水、河水及地下水样品,分析区域地表水和地下水水化学特征.结果表明：（1）白洋淀补水前、后地表水与地下水的水化学组成中Na⁺为主要阳离子,补水后阴离子以HCO₃^-为主,淀区南部地表水电导率高;补水后地表水与地下水Ca²⁺、Mg²⁺和HCO₃^-浓度显著增加,水体电导率降低.（2）补水前地下水为Na-HCO₃型水,地表水主要为Na-Cl·SO₄及Na-Cl·HCO₃类型;补水后地表水与浅层地下水向Ca·Mg-HCO₃型演化,深层地下水水化学类型基本保持不变.（3）生态补水使白洋淀水位升高,淀区水面积增大,缓解了水资源短缺的问题;同时也使浅层地下水水化学组成发生改变,而深层地下水暂未受到影响.生态补水后,受稀释和混合作用的影响,水体Na⁺、Cl^-和SO₄^2-浓度显著下降,Ca²⁺、Mg²⁺及HCO₃^-浓度增加.在白洋淀生态补水中应"先治污,后补水",以减少补水过程中污染物向淀区的运移,还应注意区域地下水位上升过程中的阳离子交换及水岩相互作用,为合理调配生态补水及改善白洋淀生态环境提供科学依据.     

Isotopic and hydrochemical insights into the groundwater characteristics along an arid to semi-humid climate gradient in China

In arid to semi-arid regions, groundwater is a critical water resource heavily relied upon, with the recharge sources and patterns being predominantly shaped by climate change and regional disparities. To compare the characteristics of groundwater in the endorheic and exorheic river basins with the climate transition zone of Gansu Province, this study uses isotopic hydrochemical analyses. This study summarizes the differences in regional groundwater recharge and evolutionary patterns. The results shows that the distribution patterns of precipitation isotopes in endorheic and exorheic river basins are opposite to those of groundwater isotopes. Specifically, the precipitation in the endorheic areas is more depleted in heavy isotopes, whereas the groundwater is more enriched. Both endorheic areas and exorheic areas exhibit similar characteristics of groundwater hydrochemical evolution, evolving from low-mineralization Mg²⁺ HC ${\mathrm{O}}_3^{-}$ recharge water to Na⁺ Cl⁻ type water with saline characteristics. The former is primarily replenished by surface water, whereas the latter is primarily replenished by precipitation. Variations in recharge patterns along with the differences in climatic conditions lead to distinct groundwater conditions in the two regions.     

A hydrochemical study of the Hammam Righa geothermal waters in north-central Algeria

This study focuses on the hydrochemical characteristics of 47 water samples collected from thermal and cold springs that emerge from the Hammam Righa geothermal ?eld, located in north-central Algeria. The aquifer that feeds these springs is mainly situated in the deeply fractured Jurassic limestone and dolomite of the Zaccar Mount. Measured discharge temperatures of the cold waters range from 16.0 to 26.5 °C and the hot waters from 32.1 to 68.2 °C. All waters exhibited a near-neutral p H of 6.0–7.6. The thermal waters had a high total dissolved solids(TDS) content of up to 2527 mg/l, while the TDS for cold waters was 659.0–852.0 mg/l. Chemical analyses suggest that two main types of water exist: hot waters in the up?ow area of the Ca–Na–SO_4type(Hammam Righa) and cold waters in the recharge zone of the Ca–Na–HCO_3type(Zaccar Mount). Reservoir temperatures were estimated using silica geothermometers and?uid/mineral equilibria at 78, 92, and 95 °C for HR4, HR2,and HR1, respectively. Stable isotopic analyses of the δ~(18)O and δD composition of the waters suggest that the thermal waters of Hammam Righa are of meteoric origin. We conclude that meteoric recharge in?ltrates through the fractured dolomitic limestones of the Zaccar Mount and is conductively heated at a depth of 2.1–2.2 km. The hot waters then interact at depth with Triassic evaporites located in the hydrothermal conduit(fault), giving rise to the Ca–Na–SO_4water type. As they ascend to the surface,the thermal waters mix with shallower Mg-rich groundwater, resulting in waters that plot in the immature water?eld in the Na–K–Mg diagram. The mixing trend between cold groundwaters from the recharge zone area(Zaccar Mount) and hot waters in the up?ow area(Hammam Righa) is apparent via a chloride-enthalpy diagram that shows a mixing ratio of 22.6 \ R \ 29.2 %. We summarize these results with a geothermal conceptual model of the Hammam Righa geothermal ?eld.     

Scaling of flow and transport behavior in heterogeneous groundwater systems

Three-dimensional numerical simulations using a detailed synthetic hydraulic conductivity field developed from geological considerations provide insight into the scaling of subsurface flow and transport processes. Flow and advective transport in the highly resolved heterogeneous field were modeled using massively parallel computers, providing a realistic baseline for evaluation of the impacts of parameter scaling. Upscaling of hydraulic conductivity was performed at a variety of scales using a flexible power law averaging technique. A series of tests were performed to determine the effects of varying the scaling exponent on a number of metrics of flow and transport behavior. Flow and transport simulation on high-performance computers and three-dimensional scientific visualization combine to form a powerful tool for gaining insight into the behavior of complex heterogeneous systems.Many quantitative groundwater models utilize upscaled hydraulic conductivity parameters, either implicitly or explicitly. These parameters are designed to reproduce the bulk flow characteristics at the grid or field scale while not requiring detailed quantification of local-scale conductivity variations. An example from applied groundwater modeling is the common practice of calibrating grid-scale model hydraulic conductivity or transmissivity parameters so as to approximate observed hydraulic head and boundary flux values. Such parameterizations, perhaps with a bulk dispersivity imposed, are then sometimes used to predict transport of reactive or non-reactive solutes. However, this work demonstrates that those parameters that lead to the best upscaling for hydraulic conductivity and head do not necessarily correspond to the best upscaling for prediction of a variety of transport behaviors. This result reflects the fact that transport is strongly impacted by the existence and connectedness of extreme-valued hydraulic conductivities, in contrast to bulk flow which depends more strongly on mean values. It provides motivation for continued research into upscaling methods for transport that directly address advection in heterogeneous porous media.An electronic version of this article is available online at the journal's homepage at http://www.elsevier.nl/locate/advwatres or http://www.elsevier.com/locate/advwatres (see “Special section on vizualization”. The online version contains additional supporting information, graphics, and a 3D animation of simulated particle movement.©1998 Elsevier Science Limited. All rights reserved     

The use of mixing models and chemical geothermometers for estimating underground temperatures in geothermal systems

Application of various chemical geothermometers and mixing models indicate underground temperatures of 260°C, 280°C and 265°C in the Geysir, Hveravellir and Landmannalaugar geothermal fields in Iceland, respectively. Mixing of the hot water with cold water occurs in the upflow zones of all these geothermal systems. Linear relations between chloride, boron and δ¹⁸O constitute the main evidence for mixing, which is further substantiated by chloride, silica and sulphate relations in the Geysir and Hveravellir fields.A new carbonate-silica mixing model is proposed which is useful in distinguishing boiled and non-boiled geothermal waters. This model can also be used to estimate underground temperatures using data from warm springs. This model, as well as the chloride-enthalpy model and the Na-Li, and CO₂-gas geothermometers, invariably yield similar results as the quartz geothermometer sometimes also does. By contrast, the Na-K and the Na-K-Ca geothermometers yield low values in the case of boiling hot springs, largely due to loss of potassium from solution in the upflow. The results of these geothermometers are unreliable for mixed waters due to leaching subsequent to mixing.     

Complementary use of dating and hydrochemical tools to assess mixing processes involving centenarian groundwater in a geologically complex alpine karst aquifer

Environmental dating tracers (³H, ³He, ⁴He, CFC-12, CFC-11, and SF₆) and the natural spring response (hydrochemistry, water temperature, and hydrodynamics) were jointly used to assess mixing processes and to characterize groundwater flow in a relatively small carbonate aquifer with complex geology in southern Spain. Results evidence a marked karst behaviour of some temporary outlets, with sharp and rapid responses to precipitation events, while some perennial springs show buffer and delayed variations with respect to recharge periods. The general geochemical evolution shows a pattern, from higher to lower altitudes, in which mineralization and the Mg/Ca ratio rise, evidencing longer water–rock interaction. The large SF₆ concentrations in groundwater suggest terrigenic production, whereas CFC-11 values are affected by sorption or degradation. The groundwater age in the perennial springs—as deduced from CFC-12 and ³H/³He—points to mean residence times of several decades, although the large amount of radiogenic ⁴He in samples indicate a contribution of old groundwater (free of ³H and CFC-12). Lumped parameter models and shape-free models were created based on ³H, tritiogenic ³He, CFC-12, and radiogenic ⁴He data in order to interpret the age distribution of the samples. Results evidence the existence of two mixing components, with an old fraction ranging between 160 and 220 years in age. The correlation of physicochemical parameters with some dating parameters, derived from the mixing models, serves to explain the hydrogeochemical processes occurring within the system. Altogether, long residence times are shown to be possible in small alpine systems with a clearly karst behaviour if the geological setting features highly tectonized media including units with diverse hydrogeological characteristics. These findings highlight the importance of applying different approaches, including groundwater dating techniques, when studying such groundwater flow regimes.     

Electrical resistivity imaging and hydrochemical analysis for groundwater investigation in Kuala Langat,Malaysia

ABSTRACT

Integrated two-dimensional electrical resistivity imaging (ERI) and hydrochemical surveys were used to investigate the groundwater alluvial aquifer in Kuala Langat, Malaysia. The study in the Langat basin considered the thickness of the aquifer, the depth of the bedrock, the regions influenced by seawater intrusion, and the monitoring of water levels. The resistivity imaging results show that the upper layer consists of clay, while the second layer is an aquifer whose thickness varies mostly in the range of 10–30 m, and in some cases extends to 40 m. The bedrock depth varies from 30 to 65 m. The chemical analyses were carried out on groundwater samples from nine boreholes collected between 2008 and 2012. The analyses indicate that the total dissolved solids (TDS) exceed 1000 mg L^-1 near the coastal area and are often less than 500 mg L^-1 further inland. The ERI and hydrochemical analyses reveal that groundwater in the study area, especially towards the coast, is a mixture of brackish and fresh waters.

EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR M.D. Fidelibus     

安徽池州南郊地下水水化学类型的演化与成因

通过对安徽池州南郊地下水调查及样品测试分析,发现近22年来该地区地下水水化学类型已由简单变为复杂.与1990年比,2012年HCO3-Ca和HCO3-Ca＋ Mg型地下水分布面积显著缩小,HCO3-Na＋ Ca型地下水完全消失,HCO3 ＋SO4-Ca型地下水出现并大面积分布.认为造成这种现象的主要原因是该地区近年来酸雨频发及工矿企业污染物排放.     

Evaluation of groundwater quality using pollution index of groundwater(PIG) and non-carcinogenic health risk assessment in part of the Gangetic Basin

The aim of this study was to evaluate groundwater fitness for domestic and irrigational use in Unnao district of Uttar Pradesh,India.For this study,block wise(n=16) groundwater samples were collected,and measured parameters were analyzed using the pollution index of groundwater(PIG),various irrigational indices,and graphical techniques.The results of this study suggested that most of the parameters were within the prescribed limits of WHO and BIS,excluding F~-(0.4 to 2.6 mg L~(-1))and Fe~(2+)(0.1 to 1.7 mg L~(-1)).Concentrations of total dissolved solids(TDS) were exceeded the desirable limit( 500 mg L~(-1)) in 43.75% of samples at some sites.The Gibbs plot revealed that groundwater chemistry was governed by rock-water interaction in the region,especially silicate weathering.The Piper plot suggested that Ca~(2+)-HCO_3~-is dominant hydrochemical facies in the area followed by mixed Ca~(2+)-Na~+-HCO_3~-type,Na~+-Cl~-type,and Na~+-HCO_3~-type.PIG evaluation revealed that the contribution of F~-and Fe~(2+) in groundwater degradation is high in comparison to other elements in the region,about 18.75% samples showed low pollution,while about 6.25% samples shows moderate pollution,and 6.25%samples reflected high pollution.The human health risk(HHR) assessment finding suggested that children(mean:1.36) are more vulnerable than adults(mean:1.01).Sodium absorption ration(SAR),Residual sodium carbonate(RSC),and Permeability index(PI) indicated that most of the groundwater was suitable for irrigation,whereas,Magnesium hazard ration(MHR) and Potential salinity(PS) indices suggested that only 37.5% and 56.25%of the samples were suitable for irrigational use,respectively.This regional study would help in decision making for stakeholders and relevant authorities in the execution of groundwater management and remediation plans in the area.     

Environmental isotopes and hydrochemical study applied to surface water and groundwater interaction in the Awash River basin

An environmental isotope and hydrochemical study was carried out to conceptualize the surface water and groundwater interaction and to explore the groundwater flow pattern in relation to the geological setting. More emphasis is given to the Afar Depression where groundwater is a vital source of water supply. Conventional field hydrogeological study and river discharge records support the isotope and hydrochemical analysis. The region is tectonically active, comprising rift volcanic terrain bordered by highlands. The result revealed that recent meteoric water is the major source of recharge. Three distinct groundwater zones were identified associated with the highlands, transitional escarpment and the rift. Towards the rift, the ionic concentration and isotopic enrichment (δ²H and δ^18degO) increases following the groundwater flow paths, which is strongly controlled by axial rift faults. The groundwater flow converges to the seismically active volcano–tectonic depressions with internal drainage and to the Awash River. Within the Afar Depression, at least four groundwater regimen are identified: (1) fresh and shallow groundwater associated with alluvial deposits ultimately recharged by isotopically depleted recent highland rainfall and the evaporated Awash River; (2) cold and relatively younger groundwater within localized fractured volcanics showing mixed origin in axial fault zones; (3) old groundwater with very high ionic concentration and low isotopic signature localized in deep volcanic aquifers; and (4) old and hot saline groundwaters connected to geothermal systems. The study demonstrated that dependable groundwater can only be obtained from the first two aquifer types in aerially restricted zones in flat plains following river courses, local wadis and volcano–tectonic depressions. The conventional hydrogeological survey and discharge records indicate substantial channel losses from the Awash River, which becomes a more dominant source of recharge in central and lower Awash valleys. Copyright © 2007 John Wiley & Sons, Ltd.     

新疆艾比湖主要入湖河流同位素及水化学特征的季节变化

通过野外调查取样和室内测试分析,利用水文化学以及氢氧稳定同位素技术,分析艾比湖主要入湖河流氢氧同位素及水化学的组成特征,并探讨其季节性变化.结果表明：地表水水质指标高值多出现于博乐市、温泉市和精河县及艾比湖湿地附近,主要污染为水体富营养化、工矿业污染以及有机质污染,其污染程度夏、秋季高于春、冬季.河水的δ¹⁸O与δ²H存在明显的线性关系,其相关指数为夏季（R²=0.99） > 春季（R²=0.98） > 秋季（R²=0.96） > 冬季（R²=0.90）,均沿当地大气降水线分布,受西北干旱区强烈的蒸发作用影响,各季节河流斜率均小于8,氘过量参数值多为正值.博尔塔拉河与精河地表水体δ¹⁸O值整体上表现为沿流程逐渐偏正的趋势,博尔塔拉河水体氢氧同位素与高程相关指数表现为春季（R²=0.70） > 冬季（R²=0.57） > 夏季（R²=0.45） > 秋季（R²=0.30）,精河因其海拔差异不大,流程简短,与高程相关性低.博尔塔拉河和精河氢氧同位素与氯化物、硫酸盐、五日生物需氧量等指标间存在相关性,且在夏、秋季最大,相关系数R>0.75,与总磷、Cu²⁺、色度、浊度等指标基本都不显著相关,相关系数R<0.25.     

Chloride,hydrochemical and isotope methods of groundwater recharge estimation in eastern Mediterranean areas: a case study in Jordan

Jordan is classified as an arid to semi‐arid country with a population according to 1999 estimates of 4·8 millions inhabitants and a growth rate of 3·4%. Efficient use of Jordan's scarce water is becoming increasingly important as the urban population grows. This study was carried out within the framework of the joint European Research project ‘Groundwater recharge in the eastern Mediterranean’ and describes a combined methodology for groundwater recharge estimation in Jordan, the chloride method, as well as isotopic and hydrochemical approaches. Recharge estimations using the chloride method range from 14 mm year^?1 (mean annual precipitation of 500 mm) for a shallow and stony soil to values of 3·7 mm year^?1 for a thick desert soil (mean annual precipitation of 100 mm) and values of well below 1 mm year^?1 for thick alluvial deposits (mean annual rainfall of 250 mm). Isotopically, most of the groundwater in the Hammad basin, east Jordan, falls below the global meteoric water line and far away from the Mediterranean meteoric water line, suggesting that the waters are ancient and were recharged in a climate different than Mediterranean. Tritium levels in the groundwater of the Hammad basin are less than the detection limit (<1·3 TU). However, three samples in east Hammad, where the aquifer is unconfined, present tritium values between 1 and 4 TU. Copyright © 2007 John Wiley & Sons, Ltd.     

Numerical modeling of geothermal groundwater flow in karst aquifer system in eastern Weibei,Shaanxi Province,China

The quantitative assessment of geothermal water resources is important to the exploitation and utilization of geothermal resources. In the geothermal water systems the density of groundwater changes with the temperature, therefore the variations in hydraulic heads and temperatures are very complicated. A three-dimensional density-dependent model coupling the groundwater flow and heat transport is established and used to simulate the geothermal water flow in the karst aquifers in eastern Weibei, Shaanxi Province, China. The multilayered karst aquifer system in the study area is cut by some major faults which control the regional groundwater flow. In order to calibrate and simulate the effect of the major faults, each fault is discretized as a belt of elements with special hydrological parameters in the numerical model. The groundwater dating data are used to be integrated with the groundwater flow pattern and calibrate the model. Simulation results show that the calculated hydraulic heads and temperature fit with the observed data well.

     

Using hydrochemical tracers to assess impacts of unsewered urban catchments on hydrochemistry and nutrients in groundwater

We applied graphical methods and multivariate statistics to understand impacts of an unsewered slum catchment on nutrients and hydrochemistry of groundwater in Kampala, Uganda. Data were collected from 56 springs (groundwater), 22 surface water sites and 13 rain samples. Groundwater was acidic and dominated by Na, Cl and NO₃. These ions were strongly correlated, indicating pollution originating from wastewater infiltration from on‐site sanitation systems. Results also showed that rain, which was acidic, impacted on groundwater chemistry. Using Q‐mode hierarchical cluster analysis, we identified three distinct water quality groups. The first group had springs dominated by Ca‐Cl‐NO₃, low values of electrical conductivity (EC), pH and cations, and relatively high NO₃ values. These springs were shown to have originated from the acidic rains because their chemistry closely corresponded to ion concentrations that would occur from rainfall recharge, which was around 3.3 times concentrated by evaporation. The second group had springs dominated by Na‐K‐Cl‐NO₃ and Ca‐Cl‐NO₃, low pH but with higher values of EC, NO₃ and cations. We interpreted these as groundwater affected by both acid rain and infiltration of wastewater from urban areas. The third group had the highest EC values (average of 688 μS/cm), low pH and very high concentrations of NO₃ (average of 2.15 mmol/l) and cations. Since these springs were all located in slum areas, we interpreted them as groundwater affected by infiltration of wastewater from poorly sanitized slums areas. Surface water was slightly reducing and eutrophic because of wastewater effluents, but the contribution of groundwater to nutrients in surface water was minimal because o‐PO₄ was absent, whereas NO₃ was lost by denitification. Our findings suggest that groundwater chemistry in the catchment is strongly influenced by anthropogenic inputs derived from nitrogen‐containing rains and domestic wastewater. Copyright © 2013 John Wiley & Sons, Ltd.