Hydrogeochemical Processes of Carboniferous Limestone Groundwater in the Yangzhuang Coal Mine,Huaibei Coalfield,China

We examined the primary mechanisms controlling water quality evolution in the Carboniferous aquifer in the Yangzhuang coal mine (Huaibei coalfield). Q-mode factor analysis explained how the Na⁺ and SO₄^2? concentrations gradually increase and the hydrochemical type transforms from Ca-HCO₃ to Ca·Na-HCO₃ and Ca·Na-HCO₃·SO₄ along the flow path. The high bicarbonate concentration appears to be due to dissolution of calcite and dolomite and an open carbonate system, while frequent water inrushes and the declining water level provide evidence for the relative closure of the Carboniferous limestone aquifer. Gypsum dissolution is the main SO₄^2? source. Inverse geochemical modeling sufficiently explained the hydrogeochemical processes that control the water quality evolution. These findings should aid the interpretation of groundwater hydrochemical evolution and groundwater quality management in the study area and other north China coalfields.

     

Groundwater Geochemical Variation and Controls in Coal Seams and Overlying Strata in the Shennan Mining Area,Shaanxi, China

Water resource conservation and ecological protection are key coal mining issues in northern Shaanxi Province and the Yellow River Basin. Revealing the characteristics and variation patterns of groundwater quality in the coal series and its overlying aquifers can provide a geological foundation for solving or optimizing these issues. Taking the Zhangjiamao coal mine of the Shennan mining area in northern Shaanxi Province, western China, as an example, water samples were collected for analysis from the: quaternary strata, weathered bedrock, burnt rock, coal series, and coal seam. Test parameters included conventional ion concentrations, total dissolved solids (TDS), and pH. Key water chemistry indicators such as oxidation/reduction index (ORI) and groundwater chemical closure index (GCCI) were used to explain the water quality differences. The Quaternary water, burnt rock water, and weathered bedrock water were dominantly the Ca–HCO₃ type, the coal series water (Yan’an Formation) was dominantly Ca–HCO₃ and Na–Cl types, and the coal seam water was dominantly Na–Cl type. From the shallow groundwater to coal seam water, dissolution and leaching gradually decrease and degree of retention gradually increases. Coal seam water was characterized by high TDS, high GCCI, and low ORI, reflecting a closed hydrogeochemical environment and moderate sulfate reduction. Leaching, salt accumulation, sulfate reduction, and cation exchange jointly control the groundwater chemical characteristics and evolution of the coal series and its overlying aquifers. Salt accumulation and cation exchange reactions of the stagnant coal seam water in the arid and semiarid climates and shallow buried conditions result in increased mineralization; the water quality is vastly different from that of the overlying aquifers, which are dominated by leaching. Groundwater circulation in the coal series and coal seam are of the infiltration–retention type, and the overlying aquifer of the coal series are of the infiltration–runoff type. A comprehensive hydrogeological model was constructed of the Middle Jurassic coal series and its overlying aquifers in the area. The results of this study have implications for the identification of mine water influx sources in the Shennan mining area, and the understanding of controls on the groundwater geochemical variation in Jurassic coal field of western China.

     

Comparison of Antimony Sources and Hydrogeochemical Processes in Shallow and Deep Groundwater Near the Xikuangshan Mine,Hunan Province,China

Antimony pollution in the groundwater of the Xikuangshan (XKS) antimony (Sb) mine area in China’s Hunan Province has attracted increasing attention. A total of 43 water samples were collected to help understand the hydrogeochemical characteristics, identify the Sb source, and evaluate the water–rock interactions of the Shetianqiao aquifer (SA). The Sb concentrations in shallow and deep SA water samples were 0.1–47.4 mg L^?1 and 0.3–19.2 mg L^?1, respectively. Stibnite oxidation and leaching from arsenic alkali residue mine wastes were the main Sb sources for the shallow SA water, whereas stibnite oxidation and stronger water–rock interaction were the predominant Sb sources for the deep SA water. The higher Sb concentration (>?10.0 mg L^?1) in shallow SA water was predominantly induced by weathering of Sb-bearing minerals, evaporation/concentration effects, and cation exchange, whereas the higher Sb concentration in deep SA water was largely caused by weathering of Sb-bearing minerals, evaporation/concentration effects, ion exchange, and competitive adsorption. These findings provide a more detailed understanding of the geochemical behavior of Sb in groundwater and can be used to develop suitable Sb pollution management strategies.

     

辛置煤矿主要含水层的自由排水柱淋滤实验与水岩作用机理

辛置煤矿石炭系太原组K_2灰岩含水层与奥陶系峰峰组O_2f灰岩含水层水质参数相互重叠,利用传统的判别方法无法对这两个水源进行有效判别。为了解决辛置煤矿水源判别的问题,并揭示该矿4个主要含水层的水岩相互作用机理,对辛置煤矿4个主要含水层的岩芯样品进行自由排水柱淋滤实验。研究结果表明:①岩芯样品含有非矿物相的硫酸盐,4个主要含水层地层同样也含有硫酸盐和石膏矿物,造成淋滤液和灰岩含水层水样均富含硫酸根离子;②K_8,K_3,K_2和O_2岩芯淋滤液中SO_4~(2-)离子当量百分比均超过74%,Ca离子当量百分比均超过40%,所有淋滤液对应的水化学类型均为SO_4-Ca型;③所有淋滤液中阴离子含量大小顺序均为:SO_4~(2-)HCO_3~-Cl~-,K_8,K_3,K_2和O_2f岩芯淋滤液中阳离子含量顺序分别为:CaMgKNa,CaNaMgK,CaMgNaK和CaMgKNa;④K_2灰岩岩芯样品和淋滤液中Mo,Sb,U和Sr含量均高于奥陶系O_2f灰岩岩芯样品及其淋滤液,但Fe离子含量分布规律正好相反,该特征可以作为判别K_2和O_2f灰岩含水层的参考因素。辛置煤矿含水层的水化学特征受岩性、埋藏条件、地下水补径排及水动力条件的控制,含水层实际水质比淋滤液更为复杂多变。K_8砂岩含水层和K_3灰岩含水层的水化学类型分别为HCO_3-Na型和SO_4-Na型,与对应的淋滤液水化学类型差异较大;但K_2和O_2f灰岩含水层的实际水化学类型与淋滤液基本一致。二叠系K_8砂岩含水层中主要的水岩相互作用为溶解斜长石为主,部分区域中可能存在少量的硫酸盐溶解反应。太原组K_3灰岩含水层中的水岩相互作用主要为方解石和白云石矿物的溶解,以及部分硫酸盐和钠盐的溶解反应。太原组K_2灰岩含水层和奥陶系峰峰组O_2f灰岩含水层中主要的水岩相互作用均为方解石、白云石和硫酸盐的溶解,以及局部地段的脱硫酸作用。     

布尔台煤矿高氟地下水分布特征及形成机制研究

为研究布尔台煤矿高氟地下水的来源及形成机制，采用数理统计、离子分析等手段，在矿物的溶解沉淀、蒸发浓缩、离子交换和竞争吸附等方面对高氟地下水中F-质量浓度特征及分布规律进行研究。结果表明：布尔台煤矿地下水中C(F-)范围为0.31～11.15mg/L，平均值1.7mg/L。从空间分布上看，高氟地下水主要分布在1～5mg/L范围内，占总样品数的48.48%|从垂向分布上看，高氟地下水主要分布于侏罗系含水层组，其主要补给水源为第四系与第三系孔隙水和侏罗系孔隙、裂隙水。含氟矿物的溶解是高氟地下水的主要控制因素。Ca2+与固相中的Na+、K+发生强烈的离子交换反应，HCO-3的竞争吸附置换出吸附在黏土矿物表面的F-，促使F-富集。     

顾北煤矿煤系砂岩裂隙水水文地球化学特征及其成因分析

采用水化学测试、统计分析、水文地球化学分析等方法,对顾北煤矿4个主采煤层顶板的76组砂岩水样进行系统研究,查明了各煤层顶板水的水化学作用类型,并对其成因进行了详细分析。研究结果表明:在顾北煤矿煤层埋藏条件和水化学环境控制下,13-1煤层为Cl-Na型,以溶滤和阳离子交替吸附作用为主;11-2煤层为HCO3·Cl-Na型,以溶滤作用为主;6-2煤层为SO4·HCO3-Na型,以脱硫酸和阳离子交替吸附作用为主;1煤层为HCO3·Cl·SO4-Na型,以溶滤溶解作用为主。研究成果可为查清含水层富水性和地下水径流特征提供指导,进而为制订矿山防治水决策提供重要依据。     

华北隐伏型煤矿区地下水化学及其控制因素分析——以宿县矿区主要突水含水层为例

采用宿县矿区主要突水含水层四含、煤系、太灰地下水样常规离子(K~++Na~+,Ca~(2+),Mg~(2+),Cl~-,SO_4~(2-),HCO_3~-,CO_3~(2-))、pH值、TDS等数据,利用离子组合比和主成分分析方法探讨了水化学成分的形成机制,进一步通过研究主成分荷载得分与水化学类型的空间分布规律,分析了矿区地下水水化学形成及其控制因素。研究结果表明:宿县矿区主要突水含水层水化学数据差异是不同地下水化学成分形成作用的综合反映,其中煤系以阳离子交替吸附或脱硫酸作用最为显著,而四含、太灰以黄铁矿氧化或碳酸盐、硫酸盐溶解作用最为显著。宿县矿区采矿活动与地质背景条件不同程度地影响了主要突水含水层水化学成分形成作用与水化学类型的空间分布,其中四含主要受采矿活动控制,煤系主要受断裂(层)控制,太灰主要受采矿活动、断裂(层)与褶皱控制。     

Hydrogeochemical Evolution of an Ordovician Limestone Aquifer Influenced by Coal Mining: A Case Study in the Hancheng Mining Area,China

Statistical analysis was used to study the hydrogeochemical evolution of an Ordovician limestone aquifer group in the Hancheng mining area. Before mining, the groundwater flowed from northwest to southeast, the water type was primarily SO₄–HCO₃, and was mainly controlled by the tectonic structure and the specific hydrogeological conditions. After 40 years of mining, two large groundwater depression cones had formed, centered on the Sangshuping and Xiangshan coal mines in the north and south zones, respectively. The groundwater dropped by ≈?20 m in the center of the depression cones due to over-exploration and mine water inrush, which changed the groundwater flow field significantly. Both the total dissolved solids and the concentrations of major ions increased 2.3- to 4.7-fold, and the water type changed to SO₄–Cl. The saturation indices (SI) of the minerals along the two simulated paths both increased, indicating that the groundwater would dissolve minerals as it flowed, which verified the groundwater flow field. Groundwater quality deteriorated due to a mixture of old acidic pit water and hypersaline water intruding from the deep district. When studied vertically, the concentrations of major ions and SI of calcite and limestone increased, due to the limited cycling of water from shallow to deep. The coincidental Ca²⁺ and Mg²⁺ increases were caused by calcite-replacing dolomitization reactions. To summarize, long-term coal mining adversely affected the area’s groundwater flow field and hydrogeochemical evolution, and effective action should be taken to prevent the Ordovician groundwater from continuing to deteriorate.     

地下水溶解碳酸盐中碳氧稳定同位素组成特征与演化规律

利用任楼井田及所在的临涣矿区生产矿井常观孔、矿井出水点,从上而下分别取第四系第四含水层、二叠系煤系砂岩含水层、石炭系太原组岩溶含水层及奥陶系岩溶含水层24个水样,测试溶解碳酸盐中δ¹³C与δ¹⁸O,分析¹³C与¹⁸O组成特征与演化规律.研究结果表明：任楼井田及所在的临涣矿区地下水溶解碳酸盐δ¹³C变化幅度大,碳循环复杂,土壤水补给机理、同位素交换反应机理和含水层围岩成分溶解机理明显;含水层碳酸盐岩含量决定溶解碳酸盐δ¹³C与δ¹⁸O的变化关系,碳酸盐岩含量越高,δ¹³C随δ¹⁸O变化斜率减小;四含水因埋藏较浅并受煤层开采影响,处于相对“开放”系统内进行地下水循环,煤系水循环系统相对比较封闭,岩溶含水层虽然埋藏深,水循环系统相比四含“封闭”,但地下水径流速度快,补给源区水力梯度大,可能为山区补给.     

Geochemistry,Hydraulic Connectivity and Quality Appraisal of Multilayered Groundwater in the Hongdunzi Coal Mine,Northwest China

This study assessed the geochemistry and quality of groundwater in the Hongdunzi coal mining area in northwest China and investigated the mechanisms governing its hydrogeochemistry and the hydraulic connectivity between adjacent aquifers. Thirty-four groundwater samples were collected for physicochemical analyses and bivariate analyses were used to investigate groundwater quality evolution. The groundwater in the mine was determined to be neutral to slightly alkaline, with high levels of salinity and hardness; most samples were of SO₄·Cl–Na type. Fluoride and nitrate pollution in the confined aquifers were identified, primarily sourced from coals. Natural geochemical processes, such as mineral dissolution, cation exchange, and groundwater evaporation, largely control groundwater chemistry. Anthropogenic inputs from agricultural and mining activities were also identified in both shallow unconfined aquifers and the deeper confined aquifers, respectively. It was determined that the middle confined aquifer has a high hydraulic connectivity with the lower coal-bearing aquifer due to developed fractures. Careful management of the overlying aquifers is required to avoid mine water inrush geohazards and groundwater quality deterioration. The groundwater in the mining area is generally of poor quality, and is unsuitable for direct human consumption or irrigation. Na⁺, SO₄^2?, Cl^?, F^?, TH, TDS, NO₃^?, and COD_Mn are the major factors responsible for the poor quality of the phreatic water, while Na⁺, SO₄^2?, F^?, and TDS are the major constituents affecting the confined groundwater quality. This study is beneficial for understanding the impacts of coal mine development on groundwater quality, and safeguarding sustainable mining in arid areas.     

Tracing the Origin and Evolution of Geochemical Characteristics of Waters from the Candiota Coal Mine Area (Southern Brazil): Part I

This work correlates surface and ground water composition to the substrata, and traces how water chemistry evolves at Brazil’s largest coal mine, the Candiota Mine. The water is dominated by SO₄, Fe, Ca, and Mg. A pH range of 2.7–3 in the pit lakes is attributed through chemical models to concomitant pyrite oxidation and carbonate dissolution along with slow hydrolysis of aluminosilicate minerals and buffering provided by several iron oxy-hydroxide species. The Fe deficit of the surface water relative to the expected values is mainly due to precipitation of Fe sulfate salts, hydroxysulfates, and oxyhydroxides in the waste piles and their runoff. A progressive decrease in oxygen partial pressure with increased lake depth leads to destabilization of the iron oxyhydroxides/hydroxysulfates formed near the surface, which explains their absence from the lake sediment. Although interacting with similar rock types, the groundwater has a significantly different composition than the surface water, with less salinity and a pH of 5–6.5, due to limited oxygen and its evolution in a nearly closed system that stabilizes at higher pH values, which is controlled by carbonate/bicarbonate buffering.     

Hydrogeologic impacts in the Estonian oil shale deposit

The article describes the hydrogeological problems related to water influx to the mine and water sulphate content association with underground oil shale mining in an environmentally sensitive area of Estonia. The water balance method was used to calculate the ratio of mine water outflow/inflow. Water balance calculations are needed for estimating the groundwater transversal flow into closed mines. Before oil shale mining groundwater geochemical processes are characterised by low sulphate content. Dewatering of oil shale mines lowered groundwater level in the Keila–Kukruse aquifer, and caused an about 50-fold increase in sulphate by intensive oxidation of pyrite of natural origin. The mobile sulphate ion may serve as an indicator of changes occurring in the sulphate content of groundwater stored in the Keila–Kukruse and Lasnamäe–Kunda aquifers of the Ordovician system in the area of closed and working mines. Using the method of inverse mixing, sulphate ion distribution is a possibility to study the movement of groundwater in lateral and transversal directions.     

水化学综合识别模式在矿井水源判别中的应用

 随着煤炭资源开采逐步向下延伸,面临的矿井充水条件逐渐复杂。下组煤开采面临的突水水源有上部老空水、第四系松散层水、地表水、顶板砂岩裂隙水和深部奥灰水;在复杂构造条件的影响下,井下涌水出现异常,但目标充水水源水位监测数据未发生明显变化,此时准确判别井下涌水的主要充水水源对矿井防治水至关重要。通过应用实例的分析,证明以常规水化学聚类分析和环境同位素分析构成的水化学综合识别模式对复杂条件下矿井充水水源的判别成效明显,为预防矿井突水事故、保障安全生产提供重要依据。     

基于煤炭采空影响的多含水层水文地质响应——以新桥煤矿为例

为研究受煤炭采空影响的多含水层的水文地质响应，以新桥煤矿为例，通过对其采空区分布和地表塌陷的调查，结合煤矿地质构造、含水层水文地质特征等的分析，探讨采空影响下煤层顶底板工程地质条件的改变而产生的导水通道，造成采空区地下水的补给和径流，并通过计算和PHREEQC模拟软件分别对采空区水量、水质进行预测，从而为煤矿安全生产和采空区地下水开发利用提供依据。     

杨柳煤矿主采10煤层充水条件分析及充水水源识别

在研究杨柳煤矿地质条件水文地质特征的基础上,对矿井的充水水源及充水通道进行了分析,并利用地下水化学法做出Piper三线图来识别突水水源。结果表明:杨柳煤矿充水水源主要是二叠系主采煤层间含水层和底板的灰岩裂隙水,为矿井水害防治提供一定的参考依据。     

Chemometrics in Ascertaining Hydrogeochemical Characteristics of Coal Mine Discharge vis-à-vis Behaviour of Surface and Groundwater Resources of the Mahan River Catchment Area,Central India

We investigated the hydrogeochemical regime of an AMD-affected coal mining province. 98 water samples were collected over two seasons and analysed for 14 parameters. We attempted to discriminate the sources of variation of water quality using select multivariate techniques: display methods (principal component analysis) and unsupervised pattern recognition (cluster analysis). Most of the groundwater and river water were characterised by shallow freshwater facies (Ca–Mg–HCO₃ type), whereas the samples representative of mine water were of the Ca–Mg–SO₄ type. The mines of the area annually discharge 2901 t of solute loads, ranging from 91 to 1030 t/year. Various molar ratios suggest that dissolution of the silicates associated with the mixing process is the predominant solute acquisition processes that govern the water chemistry of the region besides AMD. The chemometric results indicated that only a few groundwater and river water samples had low pH and elevated total dissolved solids, and these were near the three mines that were affected by AMD. These results substantiate the effectiveness of the mine water treatment measures implemented at the mine sites.

     

Laboratory Simulation of Groundwater Along Uranium-Mining-Affected Flow Paths Near the Grand Canyon,Arizona, USA

Mining of volumetrically small, but relatively enriched (average 0.6% U₃O₈) breccia pipe uranium (BPU) deposits near the Grand Canyon, Arizona, USA has the potential to affect groundwater and springs in the area. Such deposits also contain base metal sulfides that can oxidize to generate acid mine drainage and release trace metals. In this study, sequential batch experiments were conducted to simulate the geochemistry of local shallow groundwater that contacts BPU ore and then moves downgradient through sedimentary strata. The experiments simulated shallow groundwater in a carbonate aquifer followed by contact with BPU ore. The experiments subsequently simulated contact with sedimentary rocks and changing oxygen availability. Concentrations of several contaminants of potential concern became substantially elevated in the waters exposed to BPU ore, including As, Co, Ni, U, and Zn, and to a lesser extent, Mo. Of these, Co, Mo, Ni, and U were minimally attenuated by downgradient processes, whereas Zn was partially attenuated. Sb and Tl concentrations were more moderately elevated but also generally minimally attenuated. Although the mixture of elements is particular to these BPU ore deposits, sulfide oxidation in the ore and carbonate buffering of pH by sedimentary rocks generates patterns of water chemistry common in acid mine drainage settings. Ultimately, downgradient concentrations of elements sourced from BPU ore will also be strongly influenced by non-geochemical factors such as the quantities of water contacting BPU materials, heterogeneity of materials along flow paths, and mixing with waters that have not contacted BPU materials.

     

Major Ion Chemistry of Shallow Groundwater in the Dongsheng Coalfield, Ordos Basin, China

A hydrogeochemical study was conducted in the Dongsheng Coalfield, Ordos Basin, China, to identify the mechanisms responsible for the chemical compositions of the shallow groundwater and to document water quality with respect to agricultural and drinking supply standards, prior to mining. Tri-linear diagrams, principal component analysis, and correlation analysis were used to reveal the hydrogeochemical characteristics of the shallow groundwater, and the potential water–rock interactions. In general, the major cations and anions were present at low concentrations, but were relatively higher around Jiushenggong than elsewhere in the study area. Groundwater around Jiushenggong has a long residence time and is also subject to extensive evapotranspiration. The dominant hydrochemical facies are HCO₃-Ca, HCO₃-Na, and mixed HCO₃-Ca·Na·Mg types. Increases in major ion concentrations along the flow path, including Na, Cl, and SO₄, coincide with increases in total dissolved solids. The predominant mechanism controlling groundwater chemistry proved to be the dissolution of carbonates, gypsum, and halite. Cation exchange and mixing with local recharge water are also important factors. The shallow groundwater quality in the study area is suitable for agricultural and drinking purposes.     

Numerical Simulation of Mine Water Inflow with an Embedded Discrete Fracture Model: Application to the 16112 Working Face in the Binhu Coal Mine,China

Properly accounting for the effect of heterogeneity of aquifers and accurately predicting mine water inflow during the mining process is still a challenging problem in China. We developed a stochastic modelling methodology that considers a large range of possible multi-scale fracture configurations and heterogeneous porous rock to predict mine water inflow close to the observed data. The coupled discrete fracture–rock matrix models were built for the Binhu coal mine 16,112 working face with the Monte Carlo method. The models were solved using the embedded discrete fracture model to calculate groundwater inflow from the aquifer beneath the coal seam floor. The calculated results and the observed groundwater inflows in the field agreed well. Sensitivity analysis indicates that groundwater inflow increases with increased fracture length and fracture density. The effect of natural fractures introduces a large uncertainty for the models, due to the existence of long fractures that could act as conduits between the Ordovician limestone and no. 14 aquifers. The results highlight the importance of multi-scale fractures on modeling and simulating flow in the mine area.

     

Groundwater Hydrogeochemical Processes and the Connectivity of Multilayer Aquifers in a Coal Mine with Karst Collapse Columns

Mine Water and the Environment - Understanding groundwater hydrogeochemical processes and the connectivity of multilayer aquifers in a coal mine with karst collapse columns (KCCs) is very important...