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1.
High arsenic levels in groundwater of the aquifers, belonging to the Pliocene terrestrial layers and Quaternary alluvial sediments, have become a significant problem for the inhabitants living in Sarkisla (Turkey). The main objective of this study was to determine the origin and arsenic contamination mechanisms of the Sarkisla drinking water aquifer systems. The highest arsenic concentrations were found in Pliocene layers and alluvial sediments with concentrations ranging from 2.1 to 155 mg/kg. These rocks are the main aquifers in the study area, and most of the drinking groundwater demand is met by these aquifers. Groundwater from the Pliocene aquifer is mainly Ca-HCO3 and Ca-SO4 water type with high EC values reaching up to 3,270 μS/cm, which is due to the sulfate dissolution in some parts of the alluvial aquifer. Stable isotope values showed that the groundwater was of meteoric origin. Tritium values for the groundwater were between 8.31 and 14.06 TU, representing a fast circulation in the aquifer. Arsenic concentrations in the aquifers were between 0.5 and 345 μg/L. The highest arsenic concentrations detected in the Pliocene aquifer system reached up to 345 μg/L with an average value of 60.38 μg/L. The arsenic concentrations of the wells were high, while the springs had lower arsenic concentrations. These springs are located in the upper parts of the study area where the rocks are less weathered. The hydrogeochemical properties demonstrated that the water–rock interaction processes in sulfide-bearing rocks were responsible for the remarkably high groundwater arsenic contamination in the study area. In the study area, the arsenic levels determined in groundwater exceeded the levels recommended by the WHO. Therefore, it is suggested that this water should not be used for drinking purposes and new water sources should be investigated.  相似文献   

2.
The Andean region is characterized by important intramontane alluvial and glacial valleys; a typical example is the Tarqui alluvial plain, Ecuador. Such valley plains are densely populated and/or very attractive for urban and infrastructural development. Their aquifers offer opportunities for the required water resources. Groundwater/surface-water (GW–SW) interaction generally entails recharge to or discharge from the aquifer, dependent on the hydraulic connection between surface water and groundwater. Since GW–SW interaction in Andean catchments has hardly been addressed, the objectives of this study are to investigate GW–SW interaction in the Tarqui alluvial plain and to understand the role of the morphology of the alluvial valley in the hydrological response and in the hydrological connection between hillslopes and the aquifers in the valley floor. This study is based on extensive field measurements, groundwater-flow modelling and the application of temperature as a groundwater tracer. Results show that the morphological conditions of a valley influence GW–SW interaction. Gaining and losing river sections are observed in narrow and wide alluvial valley sections, respectively. Modelling shows a strong hydrological connectivity between the hillslopes and the alluvial valley; up to 92 % of recharge of the alluvial deposits originates from lateral flow from the hillslopes. The alluvial plain forms a buffer or transition zone for the river as it sustains a gradual flow from the hills to the river. Future land-use planning and development should include concepts discussed in this study, such as hydrological connectivity, in order to better evaluate impact assessments on water resources and aquatic ecosystems.  相似文献   

3.
Anthropogenic pressure influences the two-way interactions between shallow aquifers and coastal lagoons. Aquifer overexploitation may lead to seawater intrusion, and aquifer recharge from rainfall plus irrigation may, in turn, increase the groundwater discharge into the lagoon. We analyse the evolution, since the 1950s up to the present, of the interactions between the Campo de Cartagena Quaternary aquifer and the Mar Menor coastal lagoon (SE Spain). This is a very heterogeneous and anisotropic detrital aquifer, where aquifer–lagoon interface has a very irregular geometry. Using electrical resistivity tomography, we clearly identified the freshwater–saltwater transition zone and detected areas affected by seawater intrusion. Severity of the intrusion was spatially variable and significantly related to the density of irrigation wells in 1950s–1960s, suggesting the role of groundwater overexploitation. We distinguish two different mechanisms by which water from the sea invades the land: (a) horizontal advance of the interface due to a wide exploitation area and (b) vertical rise (upconing) caused by local intensive pumping. In general, shallow parts of the geophysical profiles show higher electrical resistivity associated with freshwater mainly coming from irrigation return flows, with water resources mostly from deep confined aquifers and imported from Tagus river, 400 km north. This indicates a likely reversal of the former seawater intrusion process.  相似文献   

4.
A multicriteria approach in studying hydrodynamics of a multilayer aquifer system has been used in the Lomellina region (Northern Italy). It involves the reconstruction of the hydrogeological framework coupled to the definition of the hydrochemical and isotopic features of the aquifers. A shallow phreatic aquifer, reaching depths of about 60–80 m from the surface, and deeper aquifers containing confined groundwater, were distinguished. Groundwater generally shows mineralisation decreasing with depth; dissolved ions depict calcium-bicarbonate hydrochemical facies and stable isotopes define the recharge mechanisms, the origin of groundwater, and the hydraulic confinement of deep aquifers. The phreatic aquifer is fed by local infiltration and by streams and irrigation channels. Tritium and Carbon-14 groundwater dating indicate long residence times (on the order of thousands of years) for confined aquifers. The confined aquifers show essentially passive hydrodynamic conditions and maintain a higher piezometric level than the phreatic aquifer. This inhibits the possibility of recent water penetrating far below the surface. The hydrogeological setting of the Lomellina region displays features which are common to other sectors of the Po plain. As a consequence, the results of this study, although conducted on a restricted area, are highly illustrative of groundwater hydrodynamics in large sedimentary aquifers.  相似文献   

5.
In the Apalachicola-Chattahoochee-Flint (ACF) river basin in Alabama, Georgia, and Florida (USA), population growth in the city of Atlanta and increased groundwater withdrawal for irrigation in southwest Georgia are greatly affecting the supply of freshwater to downstream regions. This study was conducted to understand and quantify the effect of irrigation pumpage on the karst Upper Floridan Aquifer and river–aquifer interactions in the lower ACF river basin in southwest Georgia. The groundwater MODular Finite-Element model (MODFE) was used for this study. The effect of two drought years, a moderate and a severe drought year, were simulated. Comparison of the results of the irrigated and non-irrigated scenarios showed that groundwater discharge to streams is a major outflow from the aquifer, and irrigation can cause as much as 10 % change in river–aquifer flux. The results also show that during months with high irrigation (e.g., June 2011), storage loss (34 %), the recharge and discharge from the upper semi-confining unit (30 %), and the river–aquifer flux (31 %) are the major water components contributing towards the impact of irrigation pumpage in the study area. A similar scenario plays out in many river basins throughout the world, especially in basins in which underlying karst aquifers are directly connected to a nearby stream. The study suggests that improved groundwater withdrawal strategies using climate forecasts needs to be developed in such a way that excessive withdrawals during droughts can be reduced to protect streams and river flows.  相似文献   

6.
A groundwater flow model of the Alpine valley aquifer in the Aosta Plain (NW Italy) showed that well pumping can induce river streamflow depletions as a function of well location. Analysis of the water budget showed that ～80% of the water pumped during 2 years by a selected well in the downstream area comes from the baseflow of the main river discharge. Alluvial aquifers hosted in Alpine valleys fall within a particular hydrogeological context where groundwater/surface-water relationships change from upstream to downstream as well as seasonally. A transient groundwater model using MODFLOW2005 and the Streamflow-Routing (SFR2) Package is here presented, aimed at investigating water exchanges between the main regional river (Dora Baltea River, a left-hand tributary of the Po River), its tributaries and the underlying shallow aquifer, which is affected by seasonal oscillations. The three-dimensional distribution of the hydraulic conductivity of the aquifer was obtained by means of a specific coding system within the database TANGRAM. Both head and flux targets were used to perform the model calibration using PEST. Results showed that the fluctuations of the water table play an important role in groundwater/surface-water interconnections. In upstream areas, groundwater is recharged by water leaking through the riverbed and the well abstraction component of the water budget changes as a function of the hydraulic conditions of the aquifer. In downstream areas, groundwater is drained by the river and most of the water pumped by wells comes from the base flow component of the river discharge.  相似文献   

7.
Al-Madinah City is located in the western part of Saudi Arabia on the Arabian Shield. The area underwent several tectonic events that developed its structural and geomorphic features, such as the Infracambrian Najd strike-slip faults, development of the Cenozoic basaltic flows of Northern Harrat Rahat, and Cenozoic N–S and E–W transtensional faults, related to the Red Sea rifting. These successive events formed a deltaic-shaped basin of Al-Madinah. The Al-Madinah basin is part of a 400?×?150-km2 Wadi Qanah–Al-Hamd watershed, which exhibits mainly parallel drainage pattern. Sub-basins, within the main basin, exhibit trellised and radial drainage patterns. The trellised drainage pattern reflects control of the Cenozoic faults, whereas the radial drainage pattern reflects volcanic-related system. Rotation of the Arabian Plate after several extensional events that lead to the opening of the Red Sea influenced the drainage flow to be going from east to west. This geological history that include eruption, normal faulting, and erosion prior to and during the Red Sea rifting formed relief inversion geomorphology of Tertiary basalts that cap Precambrian rocks of the Ayr and Jammah Mountains in western Al-Madinah. The groundwater in the central area is part of the northern Harrat Rahat basaltic aquifer in which the groundwater level rises up in the central area due to the blocking of groundwater flow by constructions below the central area and due to reduced groundwater abstraction. Building a dam 60 km northwest of Al-Madinah would preserve more surface water than the Al-Bayda dam, in which all main valleys join in at the suggested location.  相似文献   

8.
Groundwater depletion and seawater intrusion constitute major challenges along coastal aquifers in arid areas. This paper assesses the role of groundwater recharge dams constructed to replenish aquifers and fight seawater intrusion with reference to AlKhod dam, Oman, sited 7 km from the coast on a gravely unconfined aquifer. Water table rise in piezometers located downstream from the dam shows regular patterns correlating with magnitude of wadi flow, whereas upstream piezometers show irregular patterns. Controlled release of water captured by the dam optimizes water percolation and enhances artificial recharge which was estimated in the wet years 1997, 2003 and 2005 as 15, 22 and 27 Mm3, respectively, using water table fluctuation method. Recharge contributed 40–60 % of the total annual abstraction. Groundwater salinity increased in the 1980s and 1990s and the saline/freshwater interface advanced inland, but has receded partially after 1997 (highest rainfall) and completely after 2005 indicated by reduction in electrical conductivity and thickening of freshwater lens. The recession is attributed to the dam’s induced recharge and reduction of pumping in 2004 following the commissioning of Barka desalination plant. Integrating artificial recharge with groundwater resources management is therefore an effective measure to replenish aquifers in arid areas and mitigate seawater intrusion along the coasts.  相似文献   

9.
Groundwater is the main source of irrigation within south Al Madinah Al Munawarah region. It is also an important source of drinking water in many areas including Madinah city. The wells installed in the aquifer of the study area (south Madinah city) are not currently regulated by the local authorities although they are a key component of water supply. The aquifers in the study area range from unconfined to semi-confined and confined. The main aim of this study is to assess the groundwater in the region for drinking and agricultural uses. For this purpose, hydrochemical analyses of major, minor and trace constituents and nutrients were performed on 29 groundwater samples from the aquifer located about 20 km south of Madinah. The recharge rate of the aquifer of the study area was estimated to be 6.58 % of the annual precipitation using the chloride mass-balance method. Chloride was positively correlated with major ions, which suggests that agricultural activities have some effect on groundwater chemistry through leaching of readily soluble salts from the soil zone. Groundwater of the study area is characterized by dominance of Na over Ca. Chloride was found to be the most dominant anion and replaced by HCO3, thus reflecting geochemical evolution in the study area. The groundwater of the study area is not safe for drinking but can be safely used for salt-tolerant crops.  相似文献   

10.
This work investigated the freshening time and hydrochemical evolution of coastal groundwater in two brackish aquifers in Shenzhen, China. One was the brackish aquifer that resulted from heavy pumping, and the other was the aquifer reclaimed from the coastal sea. Freshening time and hydrochemical evolution of brackish aquifers were quantitatively evaluated using PHREEQC 2.0, a one-dimensional reactive-transport model. Freshening time was shown to mainly depend on pore water velocity, while the chemical composition of groundwater was determined by the cation exchange capacity of the aquifer. It was shown that after heavy pumping ceased, the freshening time for the original coastal aquifer ranged from 20 to over 80 years. While for the coastal reclaimed aquifer, the freshening time was from 85 to 140 years, which depended on the hydraulic conductivity of the fill materials in the reclaimed site. During aquifer freshening, groundwater evolved from Na–Cl type to Ca–Mg–HCO3 or Na–HCO3 type. A sensitivity analysis showed that the freshening time was most sensitive to the pore water velocity in the aquifer, while the groundwater chemical composition was most sensitive to the values of cation exchange capacity of the aquifer. As for the dispersivity, it had almost no effect on the freshening time and the chemical composition of groundwater.  相似文献   

11.
Groundwater pollution by arsenic is a major health threat in suburban areas of Hanoi, Vietnam. The present study evaluates the effect of the sedimentary environments of the Pleistocene and Holocene deposits, and the recharge systems, on the groundwater arsenic pollution in Hanoi suburbs distant from the Red River. At two study sites (Linh Dam and Tai Mo communes), undisturbed soil cores identified a Pleistocene confined aquifer (PCA) and Holocene unconfined aquifer (HUA) as major aquifers, and Holocene estuarine and deltaic sediments as an aquitard layer between the two aquifers. The Holocene estuarine sediments (approximately 25–40 m depth, 9.6–4.8 cal ka BP) contained notably high concentrations of arsenic and organic matter, both likely to have been accumulated by mangroves during the Holocene sea-level highstand. The pore waters in these particular sediments exhibited elevated levels of arsenic and dissolved organic carbon. Arsenic in groundwater was higher in the PCA (25–94 μg/L) than in the HUA (5.2–42 μg/L), in both the monitoring wells and neighboring household tubewells. Elevated arsenic concentration in the PCA groundwater was likely due to vertical infiltration through the arsenic-rich and organic-matter-rich overlying Holocene estuarine sediments, caused by massive groundwater abstraction from the PCA. Countermeasures to prevent arsenic pollution of the PCA groundwater may include seeking alternative water resources, reducing water consumption, and/or appropriate choice of aquifers for groundwater supply.  相似文献   

12.
In many arid and semi-arid areas, intensive cultivation is practiced despite water commonly being a limiting factor. Often, irrigation water is from local aquifers or imported from out-of-area aquifers and surface reservoirs. Irrigation return flows become a significant local recharge source, but they may deteriorate aquifer water quality. La Aldea valley, located in the western sector of Gran Canaria Island (Atlantic Ocean), is a coastal, half-closed depression in altered, low-permeability volcanics with alluvium in the gullies and scree deposits over a large part of the area. This area is intensively cultivated. Irrigation water comes from reservoirs upstream and is supplemented (average 30 %) by local groundwater; supplementation goes up to 70 % in dry years, in which groundwater reserves are used up to exhaustion if the dry period persists. Thus, La Aldea aquifer is key to the water-supply system, whose recharge is mostly from return irrigation flows and the scarce local rainfall recharge on the scree formations, conveyed to the gully deposits. To quantify the hydrogeological conceptual model and check data coherence, a simplified numerical model has been constructed, which can be used as a tool to help in water management.  相似文献   

13.
The purpose of this study is to evaluate the groundwater-withdrawal potential of the Fraser River watershed, a mountainous drainage system in north-central Colorado. Laboratory tests, field investigations, and numerical modeling are conducted to present a quantitative understanding of the watershed’s groundwater-flow system. Aquifer hydraulic conductivity values obtained from aquifer tests range from 1E?5 to 1E?3 m/s. Groundwater withdrawal is concentrated in channel-fill deposits of the Troublesome Formation within the Fraser basin. A steady state groundwater-flow model of the Fraser River watershed is developed and calibrated using 24 observation wells in the Fraser River valley and estimated baseflow of the Fraser River. Modeling results suggest that surface recharge is the major source of groundwater in the watershed. Groundwater exits the watershed through evapotranspiration and discharge to rivers. Transient groundwater-flow modeling evaluates future withdrawal scenarios using the hydraulic head distribution from the steady state model as the initial condition. Drawdown within Troublesome Formation aquifers from the current pumping schedule approaches 2 m. When the daily pumping rate is doubled, drawdown approaches 4 m. The radius of influence is hundreds of meters to 1 km. Pumping wells withdraw approximately 2 and 15 % of groundwater flowing through the well field for hydraulic conductivity of 1E?3 and 1E?5 m/s, respectively. This study suggests that the groundwater system at the Fraser Valley could sustain current and future withdrawals, given that the current recharge condition is maintained.  相似文献   

14.
The Bet She’an and Harod Valleys are regional recipients and mixing zones for groundwater draining to these valleys from a multiple aquifer system. This aquifer system includes two different carbonate aquifers, several groundwater-bearing basalt flows and deep-seated pressurized brine, the upflow of which causes salinization of fresh groundwater bodies. These aquifers drain through two groups of springs. Due to lack of information on the subsurface structure of the valley the flow-paths of groundwater feeding the springs, the initial distribution of salinities along the valley and particularly, the inflow-paths of the brines, have never been understood but were assumed to be fault-controlled. The interpretation of seismic profiles and analysis of gravity anomalies revealed the subsurface structure of the valley and namely the occurrence of a dense network of faults which branch out from those delineating the Jordan-Dead Sea Rift. The faults formed a series of uplifted and down-warped horst-and-graben structures. By joint analysis of structural, hydrological and geochemical evidence, it occurs that groundwater flow-paths leading to the springs emerging in the middle of the Bet She’an Valley are determined by structural elements such as major faults and fault-controlled structures. The penetration of the pressurized Ca-chloride Rift brines and their inflow into fresh groundwater bodies occurs prevalently along the faults outlining the western margins of the Dead Sea Rift Valley and at their intersection with outbranching NW–SE-striking faults.  相似文献   

15.
The combined effects of low rainfall, groundwater withdrawal in excess of 300 GL/year and reduced recharge in areas covered by pine plantations has caused the water table in a sandy unconfined aquifer on the Gnangara Mound in Western Australia to drop by up to 5 m and aquifer storage to decline by about 500 GL over the last 20 years. Groundwater has become acidic in areas of high drawdown, with pH values typically being less than 5.0 at the water table, and elevated concentrations of SO4 2?, Al, Fe, Zn, Cu, Ni and Pb. Trends of increasing acidity and base cation concentrations in deep water supply wells in the Mirrabooka wellfield indicate that about 0.7 keq/ha/year of base cations are being leached from soil within cones of depression of pumping wells. These results indicate that the assessment of the sustainable yields of aquifers under conditions of low rainfall needs to consider geochemical interactions between groundwater, aquifer sediments, soils and vegetation, and not be just based on aquifer hydraulics and water-balance changes.  相似文献   

16.
Groundwater plays a key role in arid regions as the majority of water is supplied by it. Groundwater pollution is a major issue, because it is susceptible to contamination from land use and other anthropogenic impacts. A study was carried out to build a vulnerability map for the Ordos Plateau using the DRASTIC model in a GIS environment. The map was designed to show the areas of the highest potential for groundwater pollution based on hydrogeological conditions. Seven environmental parameters, such as depth to water table, net recharge, aquifer media, soil media, topography, impact of the vadose zone media, and hydraulic conductivity of the aquifer, were incorporated into the DRASTIC model and GIS was used to create a groundwater vulnerability map by overlaying the available data. The results of this study show that 24.8 % of the study area has high pollution potential, 24.2 % has moderate pollution potential, 19.7 % has low pollution potential, and the remaining 31.3 % of the area has no risk of groundwater pollution. The regional distribution of nitrate is well correlated with the DRASTIC vulnerability index. In contrast to this, although the DRASTIC model indicated that the western part had no risk, nitrate concentrations were higher in some of these areas. In particular, higher nitrate concentrations were recorded along river valleys and around lakes, such as the Mulin River valley. This is mainly caused by the intensive agricultural development and favorable conditions for recharge along river valleys.  相似文献   

17.
Groundwater is of a paramount importance in arid areas, as it represents the main water resource to satisfy the different needs of the various sectors. Nevertheless, coastal aquifers are generally subjected to seawater intrusion and groundwater quality degradation. In this study, the groundwater quality of the coastal Jeffara aquifer (southeastern Tunisia) is evaluated to check its suitability for irrigation purposes. A total of 74 groundwater samples were collected and analyzed for various physical and chemical parameters, such as, electrical conductivity, pH, dissolved solids (TDS), Na, K, Ca, Mg, Cl, HCO3, and SO4. Sodium adsorption ratio, magnesium adsorption ratio, Sodium percentage, and permeability index were calculated based on the analytical results. The analytical results obtained show a strong mineralization of the water in the studied aquifer. TDS concentrations range from 3.40 to 18.84 g?L?1. Groundwater salinity was shown to be mainly controlled by sodium and chloride. The dominant hydrochemical facieses are Na–Cl–Ca–SO4, mainly as a result of mineral dissolution (halite and gypsum), infiltration of saline surface water, and seawater intrusion. Assessment of the groundwater quality of the different samples by various methods indicated that only 7% of the water, in the northwest of the study area, is considered suitable for irrigation purposes while 93% are characterized by fair to poor quality, and are therefore just suitable or unsuitable for irrigation purposes.  相似文献   

18.
The rapid expansion of agriculture, industries and urbanization has triggered unplanned groundwater development leading to severe stress on groundwater resources in crystalline rocks of India. With depleting resources from shallow aquifers, end users have developed resources from deeper aquifers, which have proved to be counterproductive economically and ecologically. An integrated hydrogeological study has been undertaken in the semi-arid Madharam watershed (95 km2) in Telangana State, which is underlain by granites. The results reveal two aquifer systems: a weathered zone (maximum 30 m depth) and a fractured zone (30–85 m depth). The weathered zone is unsaturated to its maximum extent, forcing users to tap groundwater from deeper aquifers. Higher orders of transmissivity, specific yield and infiltration rates are observed in the recharge zone, while moderate orders are observed in an intermediate zone, and lower orders in the discharge zone. This is due to the large weathering-zone thickness and a higher sand content in the recharge zone than in the discharge zone, where the weathered residuum contains more clay. The NO3 ? concentration is high in shallow irrigation wells, and F? is high in deeper wells. Positive correlation is observed between F? and depth in the recharge zone and its proximity. Nearly 50 % of groundwater samples are unfit for human consumption and the majority of irrigation-well samples are classed as medium to high risk for plant growth. Both supply-side and demand-side measures are recommended for sustainable development and management of this groundwater resource. The findings can be up-scaled to other similar environments.  相似文献   

19.
The Gravity Recovery and Climate Experiment (GRACE) satellite mission is aimed at assessment of groundwater storage under different terrestrial conditions. The main objective of the presented study is to highlight the significance of aquifer complexity to improve the performance of GRACE in monitoring groundwater. Vidarbha region of Maharashtra, central India, was selected as the study area for analysis, since the region comprises a simple aquifer system in the western region and a complex aquifer system in the eastern region. Groundwater-level-trend analyses of the different aquifer systems and spatial and temporal variation of the terrestrial water storage anomaly were studied to understand the groundwater scenario. GRACE and its field application involve selecting four pixels from the GRACE output with different aquifer systems, where each GRACE pixel encompasses 50–90 monitoring wells. Groundwater storage anomalies (GWSA) are derived for each pixel for the period 2002 to 2015 using the Release 05 (RL05) monthly GRACE gravity models and the Global Land Data Assimilation System (GLDAS) land-surface models (GWSAGRACE) as well as the actual field data (GWSAActual). Correlation analysis between GWSAGRACE and GWSAActual was performed using linear regression. The Pearson and Spearman methods show that the performance of GRACE is good in the region with simple aquifers; however, performance is poorer in the region with multiple aquifer systems. The study highlights the importance of incorporating the sensitivity of GRACE in estimation of groundwater storage in complex aquifer systems in future studies.  相似文献   

20.
Pollution of groundwater in the Bengal Basin (Bangladesh and West Bengal, India) by arsenic (As) puts at risk the health of more than 100 million consumers. Using 1,580 borehole lithological logs and published hydrochemistry on 2,387 wells, it was predicted that low-As (<10 μg/L) groundwater exists, in palaeo-interfluvial aquifers of brown sand capped by a protective palaeosol, beneath at least 45,000 km2 of the Bengal Basin. The aquifers were predicted to be at a depth of as little as 25 m below ground level (mbgl), and typically no more than 50 mbgl. The predictions were confirmed along an east–west traverse 115 km in length (i.e. across half of Bangladesh) by drilling 28 new boreholes to 91-m depth to reveal subsurface sedimentology, and by mapping As distribution in groundwater. The aquifers identified occur at typically <40 mbgl and so are accessible with local drilling methods. A protective palaeosol that caps the palaeo-interfluvial aquifers prevents downward movement into them of As-polluted groundwater present in shallower palaeo-channel aquifers and ensures that the palaeo-interfluvial aquifers will yield low-As groundwater for the foreseeable future. Their use, in place of the shallower As-polluted palaeo-channel aquifers, would rapidly mitigate the health risks from consumption of As-polluted groundwater.  相似文献   

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