Application of electromagnetic techniques in survey of contaminated groundwater at an abandoned mine complex in southwestern Indiana,U.S.A.

In part of a large abandoned mining complex, electromagnetic geophysical surveys were used along with data derived from cores and monitoring wells to infer sources of contamination and subsurface hydrologic connections between acidic refuse deposits and adjacent undisturbed geologic materials.Electrical resistivity increases sharply along the boundary of an elevated deposit of pyritic coarse refuse, which is highly contaminated and electrically conductive, indicating poor subsurface hydrologic connections with surrounding deposits of fine refuse and undisturbed glacial material. Groundwater chemistry, as reflected in values of specific conductance, also differs markedly across the deposit's boundary, indicating that a widespread contaminant plume has not developed around the coarse refuse in more than 40 yr since the deposit was created. Most acidic drainage from the coarse refuse is by surface runoff and is concentrated around stream channels.Although most of the contaminated groundwater within the study area is concentrated within the surficial refuse deposits, transects of apparent resistivity and phase angle indicate the existence of an anomalous conductive layer at depth (>4 m) in thick alluvial sediments along the northern boundary of the mining complex. Based on knowledge of local geology, the anomaly is interpreted to represent a subsurface connection between the alluvium and a flooded abandoned underground mine.     

Fluids’ dynamics in transient air sparging of a heterogeneous unconfined aquifer

Water table dynamics, dissolved oxygen (DO) content, electrical resistivity (ER) in monitoring wells and air pressure in the vadose zone are monitored in air sparging (AS) accompanied by soil vapor extraction (SVE) at a hydrocarbon-contaminated groundwater site in Oman, where a diesel spillover affected a heterogeneous unconfined aquifer. The formation of a groundwater mound at the early stage of air injection and potential lateral migration of contaminants from the mound apex called for an additional hydrodynamic barrier constructed as a pair of pump-and-treat (P&T) wells whose recirculation zone encompassed the AS and SVE wells. In all monitored piezometers the phreatic surface showed a rapid and distinct peak, which is attributed to the time of air breakthrough from the injection point to the vadose zone and a relatively mild recession limb interpreted as a decay of the mound. Tracer tests showed a layer of a relatively low hydraulic conductivity at an intermediate depth of the screened interval of the wells. Increased levels of DO and borehole air pressure that have been observed (as far as 50 m away) are likely mitigated by SVE and P&T. Radius of influence can be indirectly inferred from ER and DO changes in the AS operation zone. Salt tracer tests have shown that groundwater velocity within the AS zone decreases with the increase of air injection rate.     

Hydrochemical characteristics of groundwater in the Kingston Basin,Kingston, Jamaica

The Kingston Basin in Jamaica is an important hydrologic basin in terms of both domestic and industrial sector. The Kingston hydrologic basin covers an area of approximately 258 km² of which 111 km² underlain by an alluvium aquifer, 34 km² by a limestone aquifer and the remainder underlain by low permeability rocks with insignificant groundwater resources. Rapid development in recent years has led to an increased demand for water, which is increasingly being fulfilled by groundwater abstraction. A detailed knowledge of the water quality can enhance understanding of the hydrochemical system, promoting sustainable development and effective management of groundwater resources. To achieve this, a hydrochemical investigation was carried out in the Kingston Basin. Results showed that the water is Na–Ca–Cl–HCO₃ and Na–Ca–HCO₃ type with higher concentrations of nitrate, sodium and chloride as the leading causes of contamination in most of the wells. High concentrations of nitrate correlate with wells from areas of high population density and could be attributed to anthropogenic causes, mainly involving improper sewage treatment methodologies or leaking sewer lines. Jamaica, owing to its island nature, has the continuous problem of saline water intrusion, and this is reflected in the higher levels of chloride, sodium and conductivity in the water samples collected from the wells. The wells studied show higher concentrations of chloride ranging from around 10.2 mg/l in wells located approximately (4931.45 m) from the coast to around 234 mg/l in the well located near to the coast. The conductivity values also closely correlate with the chloride levels found in the wells.     

Using saline tracers to evaluate preferential recharge in fractured rocks,Floyd County,Virginia, USA

Potassium chloride (KCl) and potassium bromide (KBr) tracers were used to explore the role of geologic structure on groundwater recharge and flow at the Fractured Rock Research Site in Floyd County, Virginia, USA. Tracer migration was monitored through soil, saprolite, and fractured crystalline bedrock for a period of 3 months with chemical, physical, and geophysical techniques. The tracers were applied at specific locations on the ground surface to directly test flow pathways in a shallow saprolite and deep fractured-rock aquifer. Tracer monitoring was accomplished with differential electrical resistivity, chemical sampling, and physical monitoring of water levels and spring discharge. KCl, applied at a concentration of 10,000 mg/L, traveled 160 m downgradient through the thrust fault aquifer to a spring outlet in 24 days. KBr, applied at a concentration of 5,000 mg/L, traveled 90 m downgradient through the saprolite aquifer in 19 days. Tracer breakthrough curves indicate diffuse flow through the saprolite aquifer and fracture flow through the crystalline thrust fault aquifer. Monitoring saline tracer migration through soil, saprolite, and fractured rock provided data on groundwater recharge that would not have been available using other traditional hydrologic methods. Travel times and flowpaths observed during this study support preferential groundwater recharge controlled by geologic structure.     

集束式监测井成井工艺研究

随着人类经济社会活动的加剧,地下水遭受污染的范围和强度不断加大,尤其是浅层地下水面临污染的风险更大。如何及时发现并科学评价浅层地下水污染程度和治理的效果,迫切需要简单易行、有效可靠的浅层地下水分层监测井。传统的浅层地下水分层监测井存在占地多,监测层位少等问题,巢式监测井监测5层,连续多通道监测井口径小,因此有必要研究即占地少,又能监测多层,而且监测井井管口径能满足不同种类监测仪器的安装要求。通过室内和野外试验,研究了集束式浅层地下水分层监测井建设过程中止水方法、止水材料、粒径、止水层厚度及止水效果检验、下管方式等关键技术,实现同一孔内监测100 m以内的多层含水层或多个含水段的分层监测,施工口径小,占用土地少,建设成本经济。集束式监测井可以应用到地下水监测、环境污染调查研究等多个领域,该研究将为集束式浅层地下水分层监测井建设施工提供理论依据和技术支撑,使未来的监测更加精细化、准确化,为今后监测井的发展提供新的思路和研究方向。     

A temporary sampling technique for investigating groundwater quality near the ground surface

Improved knowledge of processes determining groundwater quality is an important precondition for the solution of various ecological and water management problems. In areas with highly fluctuating groundwater levels, time-limited access, local pollution sources or temporary interactions between surface water and groundwater, a temporary groundwater sampling technique could be of advantage. Furthermore, depth-specific sampling is of high value for investigating groundwater pollution related to seepage or surface water infiltration. A stainless steel core probe has been developed to obtain groundwater samples and to measure the hydraulic head distribution at various defined depths. The sampling technique is applicable only for non-volatile water constituents. An advantage of the core probe is that it can be driven into soil or sediments using ordinary low cost percussion equipment. The probe enables hydraulic head measurements and water sampling over vertical intervals of 0.3 m. Results from field experiments using the stainless steel core probe were in good correspondence with results from groundwater sampling at nearby observation wells. In the upper layer of the aquifer, the intrinsic spatial change in concentrations of sulphate, chloride and other water constituents is a function of distance between observation points and groundwater surface. Results indicate strong effects of a fluctuating groundwater level on groundwater quality at certain depths.     

Groundwater quality degradation as a result of overpumping in the delta Wadi El-Arish area,Sinai Peninsula,Egypt

The delta Wadi El-Arish area of the Sinai Peninsula is one of the most important parts of Egypt for industrial and agricultural expansion projects because of its relatively abundant supply of groundwater. This study focuses on the hydrogeology and hydrochemistry of the Quaternary aquifer in the delta Wadi El-Arish area and on the impacts pumping has had on groundwater quality. The objectives were to determine the relationships between groundwater pumping and water levels and water quality, to estimate the hydraulic parameters of the Quaternary aquifer, and to determine the hydrochemistry of groundwater in the Quaternary aquifer and its suitability for irrigation. The conclusions are: (1) potentiometric surface elevations have declined by an average of about 0.5 m since 1981 in response to an increase in pumping, (2) the transmissivity of the lower Pleistocene calcareous sandstone (kurkar) unit is higher than the transmissivity of the upper Pleistocene alluvium, (3) groundwater in the Pleistocene aquifer is augmented with groundwater leaking from the overlying Holocene sand dune deposits through the intervening sandy clay aquitard, (4) groundwater in the kurkar is of lower quality than groundwater in the alluvium, (5) total dissolved solids (TDS) concentrations have increased by an average of about 1500 ppm since 1962, (6) an increase in saltwater intrusion has occurred in the northern part of the study area, and (7) the irrigation suitability of groundwater pumped from wells in much of the area is limited to salt tolerant crops. Our recommendations are: (1) no new pumping wells should be drilled and no increase in pumping rates should be allowed in the delta Wadi El-Arish area, (2) reliable estimates of the quantity of groundwater recharge should be made, (3) flood irrigation systems should be replaced by either drip or sprinkler     

北京平原地下水水位监测网优化

文章在北京市地下水水位监测现状基础上,分潜水和承压水对北京平原地下水监测网的监测密度和监测频率进行了优化设计。主要采用编制地下水动态类型图的方法进行了地下水水位监测网的优化,克里金插值法能定量评价依据监测网观测值绘制的地下水水位等高线的精度,因而可以用来评价监测优化结果。并根据时间序列分析和统计检验提供的定量标准优化了地下水水位监测频率。优化后,北京平原共有监测孔400眼,其中利用原有监测孔300眼,新设计监测孔100眼,手工监测频率由原来的每月6次优化为每月1次,专项高频率监测可以由地下水自动监测仪实现。文中还对地下水自动监测仪(DIVER)的监测结果和手工监测结果进行了对比评价,提出了地下水水位监测网的维护、管理措施和信息发布方式。     

屋顶雨水回灌裂隙岩溶含水层连通示踪试验

雨水回灌后对岩溶水的影响分析和效果需要对回灌井和下游的观测井监测数据说明。由于岩溶含水层中岩溶发育极不均匀,在测定地下水位并判定出地下水流向的基础上,连通示踪试验是选择与回灌井相对应的观测井的有效办法。用氯化钠作为示踪剂,监测不同测井不同埋深地下水电导率随时间变化的方法确定了岩溶水观测井选址、岩溶含水层的结构及水文地质条件。示踪试验结果表明,3#观测井(西院井)可用来监测雨水回灌效果,并计算出该地区的地下水势流速在9 m/h～20 m/h之间。该成果对北方地区岩溶含水层回灌和环境评价具有重要的参考价值。     

Aquifer parameter estimation using tide-induced water-table fluctuations in the Biscayne Aquifer,Miami-Dade County,Florida (USA)

The Biscayne Aquifer (Florida, USA) is a coastal, shallow, unconfined, and heterogeneous aquifer with high water tables, composed of less-permeable sand to highly permeable karstic limestone. These properties make the Biscayne Aquifer one of the world’s most productive groundwater resources. The aquifer’s high yield and non-Darcian flow cause challenges for estimating aquifer parameters, which are essential for understanding groundwater processes and managing and protecting the groundwater resources. Water-table fluctuations in the Biscayne Aquifer are associated with astronomical tidal forces and gate operations on canal water-control structures. Analysis of observed groundwater level fluctuations can provide an understanding of the connectivity between the aquifer, Biscayne Bay, and the water level in the canals. Further, groundwater level fluctuations can be used for aquifer parameter estimation. In this research, observed ocean water levels measured at tidal stations and groundwater levels are fitted to Jacob’s analytical solution, where the amplitude of the groundwater head fluctuation decreases exponentially, and the time lag increases with distance from the shore. Observed groundwater levels were obtained from monitoring wells along the Miami-Dade shore and the barrier island of Miami Beach. Results indicate that Jacob’s solution is effective for aquifer parameter estimation in Miami Beach, where monitoring wells are closer to the shore. Estimated hydraulic conductivity appears to increase by four orders of magnitude to approximately 1 m s^–1 as the distance from shore increases. Constructing monitoring wells closer to the shore in Miami-Dade County and elsewhere would permit improved aquifer parameter estimation and support enhanced groundwater modeling efforts.

     

Impact of liquid waste disposal on potable groundwater resources near Perth,Western Australia

 Drilling of 15 boreholes at a disused liquid waste disposal site near Perth, Western Australia, has indicated that a contamination plume extends about 1000 m in a southerly direction from the site in the direction of groundwater flow. The plume is up to 600 m wide and 5–40 m thick. Chemical and microbiological analyses have indicated that contaminated groundwater contains high concentrations of ammonia, iron, and bacteria at levels that commonly exceed national drinking water guidelines. It is likely that a proposed water supply production well in the path of the contamination plume will have to be abandoned, and additional wells may have to be abandoned if the plume continues to extend in the direction of groundwater flow. There is currently insufficient information to indicate whether the plume is continuing to expand, but studies on similar plumes in the Perth metropolitan area have indicated that contaminated groundwater can move at rates up to 100 m yr^–1. Several other liquid waste disposal sites are now located in residential areas of Perth where wells are used for garden irrigation. Further work is required to ensure that there is no potential impact of groundwater contamination on public health in these areas. Received: 31 July 1995 · Accepted: 18 September 1995     

Water resources development and management in the Cuddapah district, India

 Intensive application of surface water in command areas of irrigation projects is creating water logging problems, and the increase of groundwater usage in agriculture, industry and domestic purposes (through indiscriminate sinking of wells) is causing continuous depletion of water levels, drying up of wells and quality problems. Thus the protect aquifers to yield water continuously at economical cost, the management of water resources is essential. Integrated geological, hydrological (surface and groundwater) and geochemical aspects have been studied for the development and management of water resources in drought-prone Cuddapah district. The main lithological units are crystallines, quartzites, shales and limestones. About 91 000 ha of land in the Cuddapah district is irrigated by canal water. A registered ayacut of about 47 000 ha is irrigated by 1368 minor irrigation tanks. A total of 503 spring channels are identified in the entire district originating from the rivers/streams, which has the capacity of irrigating about 8700 ha. The average seasonal rise in groundwater level is 7.32 m in quartzites, 5.35 m in crystallines, 3.82 m in shales, 2.50 m in limestones and 2.11 m in alluvium. Large quantities of groundwater are available in the mining areas which can be utilised and managed properly by the irrigation department/cultivators for the irrigation practices. Groundwater assessment studies revealed that 584 million m³ of groundwater is available for future irrigation in the district. From the chemical analysis, the quality of groundwater in various rock units is within the permissible limits for irrigation and domestic purposes, but at a few places the specific conductance, chloride and fluoride contents are high. This may be due to untreated effluents, improper drainage system and/or the application of fertilisers. Received: 10 June 1998 · Accepted: 15 November 1998     

Groundwater nitrate pollution in an alluvium aquifer, Eskişehir urban area and its vicinity, Turkey

 A large amount of the water requirement (municipal, industrial, etc.) of Eskişehir city, Turkey, is supplied from groundwater via wells in the urban area. The groundwater in the Eskişehir Plain alluvium has been polluted by municipal and industrial wastewater, and agricultural activities. The nitrate concentrations at nine sampling points on Porsuk River, the main water course in the plain, ranged from 1.5 to 63.3 mg/l during the period from July 1986 to August 1988. In the same period, the nitrate concentrations measured in water from 51 wells ranged between 2.2–257.0 mg/l. The nitrate content of the groundwater samples was 34.2% above 45 mg/l, the upper limit for nitrate in drinking water standards. High nitrate levels were observed in water from wells in the central and eastern parts of the urban area. The nitrate content of the well water is subject to seasonal fluctuation. In general, low nitrate concentrations were observed in wet seasons, and high ones in dry seasons. Received: 16 April 1996 · Accepted: 2 October 1996     

Groundwater flow,nutrient, and stable isotope dynamics in the parafluvial-hyporheic zone of the regulated Lower Colorado River (Texas,USA) over the course of a small flood

Periodic releases from an upstream dam cause rapid stage fluctuations in the Lower Colorado River near Austin, Texas, USA. These daily pulses modulate fluid exchange and residence times in the hyporheic zone where biogeochemical reactions are typically pronounced. The effects of a small flood pulse under low-flow conditions on surface-water/groundwater exchange and biogeochemical processes were studied by monitoring and sampling from two dense transects of wells perpendicular to the river. The first transect recorded water levels and the second transect was used for water sample collection at three depths. Samples were collected from 12 wells every 2 h over a 24-h period which had a 16-cm flood pulse. Analyses included nutrients, carbon, major ions, and stable isotopes of water. The relatively small flood pulse did not cause significant mixing in the parafluvial zone. Under these conditions, the river and groundwater were decoupled, showed potentially minimal mixing at the interface, and did not exhibit any discernible denitrification of river-borne nitrate. The chemical patterns observed in the parafluvial zone can be explained by evaporation of groundwater with little mixing with river water. Thus, large pulses may be necessary in order for substantial hyporheic mixing and exchange to occur. The large regulated river under a low-flow and small flood pulse regime functioned mainly as a gaining river with little hydrologic connectivity beyond a narrow hyporheic zone.     

Testing the 14C ages and conservative behavior of dissolved 14C in a carbonate aquifer in Yucca Flat,Nevada (USA), using 36Cl from groundwater and packrat middens

Corrected groundwater ¹⁴C ages from the carbonate aquifer in Yucca Flat at the former Nevada Test Site (now the Nevada National Security Site), USA, were evaluated by comparing temporal variations of groundwater ³⁶Cl/Cl estimated with these ¹⁴C ages with published records of meteoric ³⁶Cl/Cl variations preserved in packrat middens (piles of plant fragments, fecal matter and urine). Good agreement between these records indicates that the groundwater ¹⁴C ages are reasonable and that ¹⁴C is moving with chloride without sorbing to the carbonate rock matrix or fracture coatings, despite opposing evidence from laboratory experiments. The groundwater ¹⁴C ages are consistent with other hydrologic evidence that indicates significant basin infiltration ceased 8,000 to 10,000 years ago, and that recharge to the carbonate aquifer is from paleowater draining through overlying tuff confining units along major faults. This interpretation is supported by the relative age differences as well as hydraulic head differences between the alluvial and volcanic aquifers and the carbonate aquifer. The carbonate aquifer ¹⁴C ages suggest that groundwater velocities throughout much of Yucca Flat are about 2 m/yr, consistent with the long-held conceptual model that blocking ridges of low-permeability rock hydrologically isolate the carbonate aquifer in Yucca Flat from the outlying regional carbonate flow system.     

Temporal trends in concentrations of DBCP and nitrate in groundwater in the eastern San Joaquin Valley,California, USA

Temporal monitoring of the pesticide 1,2-dibromo-3-chloropropane (DBCP) and nitrate and indicators of mean groundwater age were used to evaluate the transport and fate of agricultural chemicals in groundwater and to predict the long-term effects in the regional aquifer system in the eastern San Joaquin Valley, California. Twenty monitoring wells were installed on a transect along an approximate groundwater flow path. Concentrations of DBCP and nitrate in the wells were compared to concentrations in regional areal monitoring networks. DBCP persists at concentrations above the US Environmental Protection Agency’s maximum contaminant level (MCL) at depths of nearly 40 m below the water table, more than 25 years after it was banned. Nitrate concentrations above the MCL reached depths of more than 20 m below the water table. Because of the intensive pumping and irrigation recharge, vertical flow paths are dominant. High concentrations (above MCLs) in the shallow part of the regional aquifer system will likely move deeper in the system, affecting both domestic and public-supply wells. The large fraction of old water (unaffected by agricultural chemicals) in deep monitoring wells suggests that it could take decades for concentrations to reach MCLs in deep, long-screened public-supply wells, however.     

淮北平原浅层地下水多年动态变化及监测统测评估

【研究目的】变化环境下地下水时空规律的研究有助于水资源精细化管理和区域水资源安全保障。【研究方法】本文基于淮北平原区典型气象站1953—2019年月降雨数据,采用小波分析及M-K检验法,研究多年尺度降雨周期性变化及趋势规律;结合395个国家级监测井及地下水统测数据,采用主成分分析法进行监测井优化评价。【研究结果】淮北平原多年降雨量呈现多时空尺度变化特征,南部地区主周期较北部地区偏小,但周期尺度较多,变化更为复杂;西北部的浅层地下水位持续下降,其余区域水位处于有升有降的波动状态;南部区域浅层地下水水位在1970年、2003年及2019年3个时段呈现出先降低再恢复,北部部分区域地下水水位则呈现先升高再降低的特征,研究区水位总体存在下降趋势,但2000年以来水位总体有所回升;经主成分分析优化后的277个监测井（221个水利井和56个自然资源井）能代表395个原国家监测井的总体水位变化情况。【结论】国家地下水监测工程长序列监测数据能够很好地服务于流域尺度水资源评价及管理,但省市级尺度或重点区域还需要进行优化和加密,地下水位统测可有效填补,该工作应在重要河湖两侧、淮河北岸一带、东北部山前平原等高水力梯度区域进行加密。     

Interaction between groundwater, the hyporheic zone and a Chalk stream: a case study from the River Lambourn, UK

Understanding the processes controlling groundwater/surface-water interaction is essential for effective resource management and for protecting sensitive ecosystems. Through intensive monitoring of Chalk groundwater, shallow gravel groundwater and surface water in the River Lambourn, UK, using a combination of hydrochemical and hydrophysical techniques, a complex pattern of interactions has been elucidated. The river is broadly in hydraulic contact with the streambed sediments and adjacent gravels and sands, but these deposits are mainly hydraulically separate from the underlying Chalk at the site. The hydraulic relationship between the river and underlying alluvium is variable, involving components of groundwater flow both parallel and transverse to the river and with both effluent and influent behaviour seen. While the gravel aquifer is significant in controlling groundwater/surface-water interaction, its importance as a route for flow down the catchment is likely to be modest compared with river discharge. The hydrological complexity revealed in a geological setting typical of lowland UK Chalk streams has implications both for investigation methods and for management such as in the setting of environmental objectives in the European Water Framework Directive.     

济南岩溶泉域地下水位监测

文章采用编制济南岩溶泉域地下水动态类型图的方法优化设计了地下水水位监测密度。通过对地下水水位多年变化趋势的分析确定了手测监测频率。选取质量好的观测孔安装了水位自计仪,提出了地下水水位监测维护措施。将对相关政府部门和每个水用户提供所需的地下水信息,以便达到水管理者与水用户共同参与泉水保护的目的。     

Sources of dissolved oxygen in monitoring and pumping wells

Groundwater monitoring and pumping wells set in anoxic aquifers require attention to keep the groundwater free of dissolved oxygen (DO). In properly constructed monitoring or pumping wells, two processes can however still introduce oxygen to anoxic groundwater: (1) permeation of oxygen through polymer materials such as silicone, PVC, HDPE or Teflon, and (2) thermally driven convection, which can occur in all types of piezometers or wells, regardless of construction material, when the water table or pressure head is close (<10 m) to the land surface. Here, field measurements (temperature and DO well loggings) from a monitoring well in Bilthoven, the Netherlands, are combined with analytical and numerical modelling to investigate the role of both processes on oxygenation of anoxic groundwater in wells. The results of numerical and analytical modeling show that both permeation and convection can introduce oxygen into anoxic wells to near saturation concentrations. In the field data gathered, convection is primarily responsible for oxygen intrusion up to a depth of around 12 m. Oxygen intrusion through convection and permeation in monitoring and pumping wells may influence groundwater sampling and analyses, and may contribute to well clogging, depending on site conditions. The combination of field and modelling provides new insights into these processes, which can be used for both groundwater sampling and pumping well design.