煤矿矿井水水质形成及演化的水动力场-水化学场-微生物场耦合作用与数值模拟

煤矿矿井水的水质形成与演化过程机理复杂,受水动力场、水化学场和微生物场等多场作用影响显著。深入研究并揭示煤矿矿井水水质形成机理与演化趋势、阐明采空区封闭后矿井水的多场耦合作用机制是矿井水污染防控与修复的理论基础。以鄂尔多斯盆地某煤矿采空区为水文地质原型,在前期研究的基础上,进一步建立了煤矿采空区积水水位回升、蓄满后水动力-水化学-微生物场(HCB)多场耦合室内相似模拟和数值模型。采空区水动力场研究结果表明基质-裂隙双孔隙模型能有效模拟采空区水位回升过程,模拟误差为9.9%,其模拟精度远高于理论预测和单孔隙模型。水化学场模拟结果与试验较为吻合,SO_(4)^(2-)、HCO_(3)-和p H模拟相对误差分别为3.0%、21.0%和6.2%,模拟结果较为可靠。模拟结果显示采空区蓄水过程中水岩反应和微生物作用不明显;而蓄满后水动力几乎停滞,但水化学场和微生物场较为活跃,2号煤和3号煤层中黄铁矿的氧化反应使得SO_(4)^(2-)质量浓度提升约24.6%;后期采空区水环境演化为弱酸性、厌氧还原条件,微生物降解作用凸显,将SO_(4)^(2-)有一定的“自净”能力。通过调整微生物代谢速率常数,可将SO_(4)^(2-)降解比例提高到61.6%。实际工程场景中可通过补充碳源、人工建立密闭厌氧环境等强化手段实现这一目标。将多场耦合室内试验和数值模拟技术拓展到煤矿采空区积水水质形成与演化规律研究,研究结论可为煤矿区矿井水污染防治提供指导。

A mathematical model of gas flow during coal outburst initiation

A proposed concept of outburst initiation examines the release of a large amount of gas from coal seams resulted from disintegrating thermodynamically unstable coal organic matter(COM).A coal microstructure is assumed to getting unstable due to shear component appearance triggered by mining operations and tectonic activities considered as the primary factor while COM disintegration under the impact of weak electric fields can be defined as a secondary one.The energy of elastic deformations stored in the coal microstructure activates chemical reactions to tilt the energy balance in a“coal–gas”system.Based on this concept a mathematical model of a gas flow in the coal where porosity and permeability are changed due to chemical reactions has been developed.Using this model we calculated gas pressure changes in the pores initiated by gas release near the working face till satisfying force and energy criteria of outburst.The simulation results demonstrated forming overpressure zone in the area of intensive gas release with enhanced porosity and permeability.The calculated outburst parameters are well combined with those evaluated by field measurements.

Prediction of land subsidence caused by groundwater exploitation in Hanoi, Vietnam, using multifactorial correlation analysis

Multifactorial correlation analysis is a new method used to predict the land subsidence caused by groundwater exploitation This article introduces and applies the method to establish the function of the surface settlement rate （Vs） and the function of the time-dependent surface settlement （St） caused by groundwater exploitation, based on data acquired at three land subsidence monitoring stations in the Hanoi area of Vietnam. Comparison with actual monitoring data indicates that the prediction results are relatively close to the monitoring data. From this, we conclude that multifactorial correlation analysis is a reliable method and can be used to predict future land subsidence caused by groundwater exploitation in Hanoi.

The first power generation test of hot dry rock resources exploration and production demonstration project in the Gonghe Basin,Qinghai Province,China

Hot dry rock(HDR)is a kind of clean energy with significant potential.Since the 1970s,the United States,Japan,France,Australia,and other countries have attempted to conduct several HDR development research projects to extract thermal energy by breaking through key technologies.However,up to now,the development of HDR is still in the research,development,and demonstration stage.An HDR exploration borehole(with 236℃ at a depth of 3705 m)was drilled into Triassic granite in the Gonghe Basin in northwest China in 2017.Subsequently,China Geological Survey(CGS)launched the HDR resources exploration and production demonstration project in 2019.After three years of efforts,a sequence of significant technological breakthroughs have been made,including the genetic model of deep heat sources,directional drilling and well completion in high-temperature hard rock,large-scale reservoir stimulation,reservoir characterization,and productivity evaluation,reservoir connectivity and flow circulation,efficient thermoelectric conversion,monitoring,and geological risk assessment,etc.Then the whole-process technological system for HDR exploration and production has been preliminarily established accordingly.The first power generation test was completed in November 2021.The results of this project will provide scientific support for HDR development and utilization in the future.

Fluoride ions in groundwater of the Turkana County, Kenya, East Africa

Groundwater samples were evaluated throughout Turkana County(Kenya,East Africa)while looking for drinking water sources.Some samples showed high concentrations of fluoride with values in the range of 0.15–5.87 mg/L.Almost 50%of the samples exceeded the WHO and Kenyan potable water standard guideline value of 1.5 mg/L for drinking water quality.The hydrogeochemical studies revealed that the dominant cation in water is Na^(+)and the dominant anion is HCO_(3)^(-)resulting in Na-HCO_(3) type of groundwater,followed by Ca/Mg-HCO_(3) or Na-SO_(4) and Na-Cl in a few cases.Speciation modelling revealed that the groundwater is undersaturated with respect to gypsum and anhydrite,mostly undersaturated with respect to fluorite(6 samples are at equilibrium),and supersaturated or at equilibrium with respect to calcite(CaCO_(3)).Precipitation of calcite favours the dissolution of F-rich minerals in the alkaline medium.Simultaneously,groundwater is enriched with sodium and bicarbonate,probably as a result of chemical weathering of Na-feldspar.Investigated groundwater can be presumably used for drinking purposes from 17 wells,but a detailed investigation of other trace element concentrations is necessary.

Interpretation for technical requirements of mapping regional groundwater resources

Under the organization of China Geological Survey,relevant departments have made industry specifications and technical requirements based on hydrogeological survey data collection at the scale of 1:50 000.Among them,groundwater resource map is a must.According to nationally unified technical requirements of mapping groundwater resources put forward in 2018,this paper mainly interprets relevant principles,content,methods,diagrams as well as legend,and further to point out future directions:Higher precision will equal to higher demand of application,so that is there any more effective way to further interpret application aspect rather than only rules?

Assessment of Groundwater Quality in the Dogger Aquifer of Poitiers, Poitou-Charentes Region, France

The Poitou-Charentes, located in the Center-West of France, is a region where economy is based mainly on agriculture. This region, made up of 4 Departments (Vienne, Charente, Charente Maritime, Deux-Sèvres), is supplied largely by groundwater exploitation, both for consumption and for irrigation. This resource is thus vital to the region and its preservation is a major issue. The objective of this study is the determination of the groundwater quality in the Dogger aquifer of Poitiers (Vienne Department), which is the main water resource for this area and to achieve a better understanding of the factors influencing groundwater mineralization. Sixty-six wells, distributed over the study area, were sampled and analyzed for major ions (Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, SO42-, NO3-). Data were interpreted using graphical (Piper diagram, binary diagrams) and statistical methods (correlation matrix, principal components analysis). Saturation and chloro-alkaline indices were also computed. It is shown that the groundwater mineralization is mainly associated with Ca2+, K+, HCO3-, Cl-, SO42-, and NO3-. Hydrochemistry of groundwater is determined by both natural processes, and anthropogenic factors. Natural factors are dissolution of carbonate and dolomitic minerals, and cation exchanges with clays, while anthropogenic factors are contaminant infiltration with waste waters and agricultural fertilizers. Nitrate is the main contaminant found in the groundwater and makes this resource unsuitable for consumption at some places.

Nitrate contamination in groundwater of Kabul Province,Afghanistan:Reasons behind and conceptual management framework discourse

Groundwater contamination has been on the rise in Afghanistan.It has become a major concern among the policy makers.This paper aims to propose practical options for the management of nitrate contamination in one of Afghanistan’s groundwater polluted provinces,Kabul.The management framework utilized Mann-Kendall and Sen Slope tests to detect nitrate trend and geostatistical analysis option in Arc GIS 10.5 to assess the nitrate change.To explore the impact of various management options,a number of legislative documents were reviewed.The results indicate a decline in the nitrate storage of Kabul aquifers from 108 mg/L in 2005 to 0.044 mg/L in 2010.Considering the whole period of the study,the results show that the nitrate volumes remain lower than the nitrate concentration range proposed by World Health Organization(50 mg/L).Groundwater dynamics in Kabul aquifers were influenced by nitrate derived from precipitation and nitrate input from root zones in agricultural areas.Finally,different management options for groundwater pollution from nitrate and corresponding authorities,incorporated urban,rural and agriculture,were proposed.It is expected that this study will help policy makers to better manage the nitrate storage of Kabul aquifers by implementing the proposed management options.

Process of Salinisation of a Lagoon and a Coastal Aquifer in Annaba Area （East Algerian）

The study area is located in a Mediterranean region, so the effects of the climate variations are very important. The authors contribution to this subject is based on the compilation of many results obtained from dissertations and theses that are carried out under their supervision. The main tool used, in addition to other methods, is the water hydrochemistry as it is proved very useful in obtaining good results and helpful in getting objective interpretations regarding the presence and absence of salinity. Several factors are undertaken to show the presence of salts in waters in the plain, the lithology of the geological formations shows that they are composed of alluvium sediments where the permeability is quite high, and this enables hydraulic communication between the fresh water of the aquifer and saline water of the sea. The study of climate shows a decrease of precipitation which favors an important decrease of recharge rate to the aquifer, and hence a decrease of water resource. The strontium which is a good indicator for the origin of salinity shows a variation that indicates a variation in the distribution of the salinity, and therefore diverse origins of salinity all over the studied area. This can infer the presence of marine invasion in the down-stream part of the aquifer, whereas elsewhere salinity is caused by the presence of evaporitic formation, mainly by the argillaceous matrix in the bottom of the lake. in the up-stream part of the aquifer. In the lake, salinity is explained

Seasonal Temperature Variations of Lake Vrana on the Island of Cres and Possible Influence of Global Climate Changes

Lake Vrana on the island of Cres is one of the largest fresh water features on Mediterranean islands. The maximum depth of the lake is 72 m and it stores 220 million m3 of fresh water. The paper provides an overview of lake and groundwater temperature measurements to date and recent activities within the EU project ＂CC-WaterS （Climate Change and Impacts on Water Supply）＂. Groundwater temperatures in the lake surrounding are almost constant throughout the year, in the range from 14.6 ℃ to 13.1 ℃, while thermodynamic cycle of the lake conforms to the characteristics of a monomictic, medium depth lake in the moderate climate belt. Present and future climate simulations using three limited area models were analyzed （Aladin, Promes and RegCM3）, they pointed out further air temperature increase in range of 0.27 ℃/10 yrs to 0.32 ℃/10 yrs. The significant changes of precipitation rates were not indicated. Considering increasing water consumption from the lake, already asserted negative trends, indicated climate changes and possible effects on the lake recharge, it is necessary to establish continual monitoring of parameters that describe lake system behaviour and periodically analyze lake conditions, especially with respect to the extraction for the public water supply.

Numerical Simulation of Groundwater Flow and Solute Transport for the Northern Batinah Area, Oman

The northern Batinah occupies approximately 12,150 km2 in the north of Oman Quaternary deposits and Neogene＇s upper Fats form the aquifer units. MODFLOW compatible MT3D was used for simulation development of the area. It can be concluded that： （1） The groundwater in the Batinah area generally flows from the south-west to the gulf of Oman in the north-east; （2） Recharge takes place through direct recharge from rainfall and wadi flow by about 902 ×10^3 ma/day; （3） The hydraulic conductivity attains a relatively wide range between 0.02 m/day and 78 m/day and 0.02 m/day and 60 m/day for the Quaternary and Fars respectively; （4） There is probably less potential for groundwater abstraction in the northern part of the area; （5） The water level decreased by about 6 m over 24 years and （6） The increase of salinity most likely due to a contribution of sea water intrusion from the gulf along the coast. It is recommended that： （1） automatic well control system should be installed to accurate measurements of abstraction; （2） further analysis under different future scenarios should be made and （3） formulate an integrated management plan for the basin.

Hydrogeochemical Assessment of Groundwater in the Precambrian Rocks, South Eastern Desert, Egypt

This work refers to the characterization of the hydrochemistry of the southern part of the Eastern Desert in Egypt, on the basis of physico-chemical properties of groundwater occurring in the fractured Precambrian rocks inland and in sedimentary formations on the coastline of the Red Sea. Thirty-five groundwater samples have been collected from the study area for hydrochemical investigations to understand the sources of dissolved ions and assess the chemical quality of the groundwater. Several methods were used to interpret the hydrochemical data, i.e. graphical methods, principal components analysis, ions exchanges indices and saturation indices of various minerals. The results show that the major ionic relationships are Na+ > Ca2+ > Mg2+ and Cl- > > HCO3- and that groundwater chemical characteristics are controlled by natural geochemical processes but also, to a lesser extent, by anthropogenic activities. Natural minerals dissolution, ion exchanges and evaporation play a prominent role in the ion enrichment of groundwater. A comparison of groundwater quality in relation to WHO water quality standards proved that most of the water samples are not totally suitable for drinking water purpose.

Study on standards of 1:50000 hydrogeological maps in China

In compilation of 1: 50 000 hydrogeological map, Some principles which are suitable for hydrogeological characteristics in China have been defined. Groundwater development and protection have been regarded as equally important. Some key problems such as classification of water-bearing formation, water yield property, color system and color scale of water yield property of water-bearing formation, expression of groundwater system, expression of hydrogeological parameters have been solved. This standardizing work can lay solid foundation for integration of 1: 50 000 synthetic hydrogeological map achievement and data, so as to broaden the service areas of hydrogeological survey.

Isotopic Composition of Waters in the Dem?novská dolina Valley and Its Underground Hydrologic System During Winter and Spring of 2010/2011

In the Dem?novská dolina Cave system（Slovakia） and its vicinity,32 sampling places for regular observation（in 2-months interval） of δ18O and δ2H in water were established.This monitoring included precipitation waters,waters in the surface streams,waters of the underground hydrological system as well as the dripping seepage waters of the cave system.Altitudinal extent of the area was from 800 m a.s.l.（lowermost cave entrance） to 2024 m a.s.l.（Chopok Mt.on the top of the crystalline range）.Initial results show some similarities but also differences within the analyzed water types.For precipitation,a high variability of isotopic composition was confirmed,from quite depleted up to more enriched waters(δ18O from-16.8‰ up to-5.7‰;δ2H from-121.6‰ to-32.7‰).During the recharge process and groundwater/surface water formation,precipitation water is homogenized,what is reflected in much more stable isotope content.The most depleted(δ18O ≈-11.7‰ to-10.8‰;δ2H ≈-78.9‰ to-73.4‰) were the waters of surface streams,running from the northern slopes of the Nízke Tatry Mts.,formed by crystalline rocks,alochtonous to the underground hydrological system.Smaller autochtonous surface water streams（formed in the side valleys of the main karstic canyon） are slightly enriched(heavier,as δ18O ≈-11.4‰ to-10.6‰;δ2H ≈-78.3‰ to-71.5‰),what reflects lower altitudes of their watersheds.Interesting is the distribution of the isotope content of the underground streams in the cave system.The most depleted are the underground streams directly（visibly） communicating with surface waters(δ18O≈-11.33±0.13‰;δ2H≈-76.88±1.68‰).Extent of the relationship of underground streams to the autochtonous seepage waters（slow circulation through the fissures） is manifested by respective portion of isotopically enriched waters–as the underground streams show different isotope composition.The combination of the alochtonous water components（from surface streams reaching the karstic area from the adjacent crystalline via swallow holes） and autochtonous water components（recharged directly in karstified limestones） is visible especially on the subsurface stream of Dem?novka.The most isotopically enriched（heaviest） of all water types are dripping seepage waters(δ18O ≈-10.4‰ to-9.4‰;δ2H ≈-71.6‰ to-65.0‰).

确定复杂蓄水层中水文地球化学过程的地球统计分析:案例研究(西班牙东南部阿尔梅里亚省阿古阿都斯单元)

位于西班牙东南部的阿古阿都斯蓄水层单元是一个复杂的水文地质系统,因为蓄水地层的岩性变化大,单元内部发生的过程可变性大。数据的因子分析使变量数目削减到3个因子,这3个因子与诸如海水侵入和含盐沉积物淋溶等物理化学过程有关。对这些因子应用了变量统计分析,以采用普通克里金方法进行的空间布局研究为终结。这些因子的制图不需要使用纯粹的水文地球化学技术,就可以显示出一些过程的快速分化,这些过程影响着阿古阿都斯单元内加多尔(Gador)碳酸盐蓄水层的水。结果表明存在着一些与盐分有关的因子:海水侵入、古水、和/或泥灰土和蒸发盐沉积的淋溶。所使用的技术是有效的,研究结果与使用水文地球化学方法(传导率和温度的垂直记录、离子比率及其它)所得到的结果一致。本次研究的结果证明,这种分析方法的应用能够对影响地下水成分的因子进行有效的评估。

Seepage laws in aquifer near a partially penetrating river with an intensive extraction of ground water

The intensive extraction of ground water from aquifers near a river is an efficient way to exploit ground water resources. A lot of problems, however, have arisen because the mechanism of ground water flow in this way has not been clear. A sand-box model and a numerical model are respectively used to simulate the extraction of ground water near a partially penetrating river physically and theoretically. The results show that the ground water will lose saturated hydraulic connection with the river water as the pumping intensity increases. The broken point of hydraulic connection is located in the interior of aquifers rather than on the riverbed. After hydraulic disconnection occurs, two saturated zones, a suspended saturated zone linked with river and an unconfined aquifer, are formed.

Vulnerability of groundwater resources under climate change in the Pannonian basin

The impact of climate change on groundwater vulnerability has been assessed in the Pannonian basin over 1961–2070.High-resolution climatemodels,aquifers composition,land cover,and digital elevation model were the main factors which served to perform the spatial analysis using Geographical Information Systems.The analysis reported here is focused on the long-term period,including three temporal time sets:the past period of 1961–1990(1990s),the present period of 2011–2040(2020s),and the future period of 2041–2070(2050s).During the 1990s,the high and very high areas of groundwater vulnerability were identified in all the central,western,eastern,southeastern,and northern sides of the Pannonian basin.In these areas,the water availability is lower and the pollution load index is high,due to the agricultural activities.The low and very low vulnerability classwas depicted in the South-West part of the basin and in few locations from the peripheral areas,mainly in the North and West.The medium groundwater vulnerability spreads over the Pannonian basin,but it ismore concentrated in the central,South,and South-West.The most affected territory is Hungary,while the territories of Slovenia,Croatia,and Bosnia and Herzegovina are less affected.In the present and future periods,the very high groundwater vulnerability increased in areas by 0.74%and 0.87%,respectively.The low class area decreased between the 1990s and the 2020s by 2.33%and it is expected to decrease up to 2.97%in the 2050s.Based on this analysis and the groundwater vulnerabilitymaps,the Pannonian basin appears more vulnerable to climate change in the present and future.These findings demonstrate that the aquifers from Pannonian basin experience high negative effect under climate conditions.In addition,the land cover contributes to this negative status of groundwater resources.The original maps of groundwater vulnerability represent an instrument for water management planning and for research.

Synthesis of zeolites using fly ash and their application in removing heavy metals from waters

Three types of zeolite (NaP1 zeolite, analcime and chabazite) were hydrothermally synthesized by reacting fly ash with NaOH solution. The maximum conversion rate from fly ash to single zeolite is about 40%—75%, and the total conversion rate 60%—80%. The synthesis experimental results indicate that factors including vortex, viscosity, temperature, reaction time, and NaOH concentration in the reaction system strongly affect the type and conversion rate of zeolites. The batch experiments of removing Cu2+, Pb2+ and Cd2+ from wastewaters show that the adsorption capacity of zeolites synthesized is higher than that of fly ash.

Drought adaptability of phreatophytes:insight from vertical root distribution in drylands of China

Aims The vertical distribution of plant roots is a comprehensive result of plant adaptation to the environment.Limited knowledge on fine vertical root distributions and complex interactions between roots and environmental variables hinders our ability to reliably predict climatic impacts on vegetation dynamics.This study attempts to understand the drought adaptability of plants in arid areas from the perspective of the relationship between vertical root distribution and surroundings.Methods By analyzing root profiles compiled from published studies,the root vertical profiles of two typical phreatophytes,Tamarix ramosissima and Populus euphratica,and their relationships with environmental factors were investigated.A conceptual model was adopted to link the parameter distribution frequency with plant drought adaptability.Important Findings The strong hydrotropism(groundwater-dependent)and flexible water-use strategy of T.ramosissima and P.euphratica help both species survive in hyperarid climates.The differences in the developmental environments between T.ramosissima and P.euphratica can be explained well by the different distribution characteristics of root profiles.That is,higher root plasticity helps T.ramosissima develop a more efficient water-use strategy and therefore survive in more diverse climatic and soil conditions than P.euphratica.We conclude that the higher variation in root profile characteristics of phreatophytes can have greater root adaptability to the surroundings and thus wider hydrological niches and stronger ecological resilience.The inadequacy of models in describing root plasticity limits the accuracy of predicting the future response of vegetation to climate change,which calls for developing process-based dynamic root schemes in Earth system models.