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1.
Yvonne S. Anku Bruce Banoeng-Yakubo Daniel K. Asiedu Sandow M. Yidana 《Environmental Geology》2009,58(5):989-997
Hydrochemical data are presented for groundwater samples, collected from fractured aquifers in parts of northern Ghana. The
data was collected to assess the groundwater suitability for domestic and agricultural use. Results of the study reveal that
the pH of the groundwater in the area is slightly acidic to slightly alkaline. The electrical conductivity values, total dissolved
solids (TDS) values and calcium, magnesium and sodium concentrations in the groundwater are generally below the limit set
by the WHO for potable water supply. On the basis of activity diagrams, groundwater from the fractured aquifers appears to
be stable within the montmorillonite field, suggesting weathering of silicate minerals. An inverse distance weighting interpolator
with a power of 2 was applied to the data points to produce prediction maps for nitrate and fluoride. The distribution maps
show the presence of high nitrate concentrations (50–194 mg/l) in some of the boreholes in the western part of the study area
indicating anthropogenic impact on the groundwater. Elevated fluoride level (1.5–4 mg/l), higher than the WHO allowable fluoride
concentration of 1.5, is recorded in the groundwater underlying the northeastern part of the study area, more specifically
Bongo and its surrounding communities of the Upper East region. Results of this study suggest that groundwater from the fractured
aquifers in the area exhibit low sodicity–low salinity (S1–C1), low sodicity–medium salinity (S1–C2) characteristics [United
States Salinity Laboratory (USSL) classification scheme]. All data points from this study plot within the ‘Excellent to good’
category on a Wilcox diagram. Groundwater in this area thus appears to provide irrigation water of excellent quality. The
hydrochemical results indicate that, although nitrate and fluoride concentrations in some boreholes are high, the groundwater
in the study area, based on the parameters analyzed, is chemically potable and suitable for domestic and agricultural purposes. 相似文献
2.
The San Antonio-El Triunfo mining district, located at a mountainous region 45 km south-east of La Paz, Baja California,
has been worked since the late 1700s. Mine waste material produced during 200 years of mineral extraction area poses a risk
of local groundwater pollution and eventually, regional pollution to the Carrizal (west basin) and the Los Planes (east basin)
aquifers. There are different types of deposits in the mining area. These are dominated by epithermal veins, in which arsenopyrite
is an important component. Carrillo and Drever (1998a) concluded that, even though the amount of mine waste is relatively
small in comparison to the large scale area, significant As in groundwater derived from the mine waste piles is found locally
in the groundwater. This paper shows the results of geochemical analyses of groundwater samples from the San Antonio-El Triunfo
area and the Carrizal and Los Planes aquifers during several years of monitoring (1993–1997). The highest values of total
dissolved solids (TDS) and As are in the mineralized area where the mining operations occurred (∼1500 ppm TDS and 0.41 ppm
As). The lowest concentrations of TDS and As are, in general, away from the mineralized area (∼500 ppm TDS and 0.01 ppm As).
Sulfate and bicarbonate (alkalinity) are, in general, high near the mineralized area and low away from it. The arsenic concentrations
vary seasonally, especially after the heavy summer thunderstorms. Geochemical modeling (MINTEQA2 and NETPATH) and analysis
of the regional geochemical evolution of the groundwater from the mining area towards the aquifer of Los Planes shows that
the most likely hydrochemical processes include: dilution, precipitation of calcite, and adsorption of As onto surfaces of
iron oxyhydroxides (ferrihydrite). These processes act as natural controls to the extent and amount of As pollution in the
Carrizal and Los Planes aquifers.
Received: 4 May 1999 · Accepted: 22 February 2000 相似文献
3.
A detailed water quality analysis was carried out in the quaternary aquifer system of the marginal alluvial plain (Ganga Plain)
in Bah Tahsil, Agra district, India. The electrical conductivity of 50 samples each from dug wells, hand pumps and tube wells
was analysed for the study of salinity levels in shallow, intermediate and deep aquifers. Out of 50, 20 samples of each were
also analysed for other chemical constituents such as Na+, K+, Cl−, F− and TDS. The analyses show drastic changes in the salinity levels of shallow, intermediate and deep aquifers. The deep aquifers
are more saline compared to the shallow and intermediate aquifers. On the contrary, the concentration of chemical constituents
such as Na+, K+, Cl− and F− was more in the shallow aquifers compared to the deep aquifers. Moreover, there is an indication that the salinity and concentration
of the above chemical constituents also escalate with time in each aquifer. The chemical constituents such as Na+, K+, Cl−, F− and TDS range from 51 to 165 mg/l, 1 to 14 mg/l, 224 to 1,459 mg/l, 0 to 1.5 mg/l and 750 to 2,650 mg/l, respectively. Over
a 3-year period, the salinity levels have sharply increased and the average F level has increased by 0.1–0.3 mg/l. An attempt
has been made here to discuss the factors causing the variation and escalation of chemical constituents and salinity in the
water of the three aquifers. 相似文献
4.
An assessment of the origin and variation of groundwater salinity in southeastern Ghana 总被引:1,自引:1,他引:0
Groundwater from the major aquifers in southeastern part of Ghana was sampled to determine the main controls on groundwater
salinity in the area. This paper uses multivariate statistical methods, conventional graphical methods and stable isotope
data to determine spatial relationships among groundwaters from the different hydrogeologic units in the area on the basis
of salinity. Q-mode hierarchical cluster analysis (HCA) was used to spatially classify the samples, whilst R-mode factor analysis
was used to reduce the dataset into two major principal components representing the sources of variation in the hydrochemistry.
Analysis of the major chemical parameters suggests that the principal component responsible for salinity increment in the
area is the weathering of minerals in the aquifers. This factor is especially more significant in the upland areas away from
the coast. The second factor responsible for salinity in the area is the combined effects of seawater intrusion, and anthropogenic
activities. This study finds that four major spatial groundwater groups exist in the area: low salinity, acidic groundwaters
which are mainly derived from the Birimian and Togo Series aquifers; low salinity, moderate to neutral pH groundwaters which
are mainly from the Voltaian, Buem and Cape Coast granitoids; very high salinity waters which are not suitable for most domestic
and irrigation purposes and are mainly from the Keta aquifers; and intermediate salinity groundwaters comprising groundwater
from the Keta basin aquifers with minor contributions from the other major terrains. The major water type identified in this
study is the Ca–Mg–HCO3 type, which degrades into predominantly Na–Cl–SO4 more saline groundwaters toward the coast. Stable isotope data analyses suggest that groundwater in the Voltaian aquifers
is largely of recent meteoric origin. The Birimian and Togo aquifers receive a component of recharge from the tributaries
of the Densu and Volta Rivers, after the waters have undergone evaporative enrichment of the heavier isotopes. In the Keta
basin, recharge is mainly from precipitation but an observed enrichment of 2H and 18O isotopes is probably due to seawater and evaporative effects since the water table there is very shallow. An analysis of
the irrigation quality of groundwater from the six aquifers in the study area using sodium adsorption ratio and electrical
conductivity suggests that most of the aquifers supply groundwater of acceptable quality for irrigation. The only exception
is the Keta Basin area, where extremely high salinities and SAR values render groundwater from this basin unsuitable for irrigation
purposes. 相似文献
5.
The degradation of groundwater quality, which has been noted in the recent years, is closely connected to the intensification
of agriculture, the unreasonable use of chemical fertilizers and the excess consumption of large volumes of irrigation water.
In the hilly region of central Thessaly in Greece, which suffers the consequences of intense agricultural use, a hydrogeological
study is carried out, taking groundwater samples from springs and boreholes in the Neogene aquifers. The aim of this study
is the investigation of irrigation management, water quality and suitability for various uses (water supply, irrigation),
the degradation degree and the spatial distribution of pollutants using GIS. The following hydrochemical types prevail in
the groundwater of the study area: Ca–Mg–HCO3, Mg–Ca–Na–HCO3 and Na–HCO3. In the above shallow aquifers, especially high values of NO3
− (31.7–299.0), NH4
+ (0.12–1.11), NO2
− (0.018–0.109), PO4
3− (0.07–0.55), SO4
2− (47.5–146.5) and Cl− (24.8–146.5) are found, particularly near inhabited areas (values are in mg L−1). The water of shallow aquifers is considered unsuitable for human use due to their high polluting load, while the water
of the deeper aquifers is suitable for human consumption. Regarding water suitability for irrigation, the evaluation of SAR
(0.153–7.397) and EC (481–1,680 μS cm−1) resulted in classification category ‘C3S1’, indicating high salinity and low sodium water which can be used for irrigation
in most soils and crops with little to medium danger of development of exchangeable sodium and salinity. The statistical data
analysis, the factor analysis and the GIS application have brought out the vulnerable-problematic zones in chemical compounds
of nitrogen and phosphates. The groundwater quality degradation is localized and related exclusively to human activities.
Based on 2005 and 2008 estimates, the annual safe yield of the region’s aquifers were nearly 41.95 MCM. However, the existing
situation is that 6.37 MCM of water is over extracted from these aquifers. 相似文献
6.
Influence of contaminated Vistula River water on the groundwater entering the Zakrzówek limestone quarry, Cracow region, Poland 总被引:1,自引:0,他引:1
Chemical composition of water inflows in the Zakrzówek quarry, developed in fractured and karstified Upper Jurassic limestones,
is controlled by infiltration of polluted water from the Vistula River and by infiltrating meteoric water. The river water
TDS value is 2.5 g/dm3. The quarry waters have 0.6–2.0 g/dm3 TDS. Highly mineralised waters belong to Cl-Na type. With decreasing TDS the percentage of sulphates, calcium, magnesium
and hydrocarbonates increases. This seems to result from various processes including dilution of polluted river water, leaching
of aquifer rocks, and ion exchange. The transfer time of river water to the quarry is about 100–120 days. Concentration of
contaminants contained in the river water declines during the migration through limestones to the quarry.
Received: 7 March 1997 · Accepted: 7 December 1998 相似文献
7.
L. A. Shevenell 《Environmental Geology》2000,39(7):807-815
Within the next 10–15 years, over 35 mines in Nevada will have a lake in their open pit mines after dewatering and cessation
of mining. Of the ten past or existing pit lakes at eight different gold mines for which temporal data are available, most
had near neutral pH, yet most had at least one constituent (e.g., As, SO4, TDS) that exceeded drinking water standards for at least one sampling event. Most samples from pit lakes had TDS exceeding
drinking water standards, but lower than that in the natural Pyramid (TDS≈5,500 mg/l) and Walker (TDS≈14,000 mg/l) Lakes.
In the past century, salinity increased in both natural, terminal lakes, in part due to irrigation withdrawals and evapoconcentration.
The salinity in the pit lakes may also increase through time via evapoconcentration. However, water balance models indicate
that up to 132% (Walker Lake) of the total yearly inflow evaporates from the terminal lakes, whereas steady-state may be reached
in the pit lakes modelled, where evaporative losses account for only ≈6% of the total pit lake volume annually and ≈100% of
the net inflow (groundwater inflow minus outflow, precipitation and runoff into the lake). The effects of evapoconcentration
are expected to be less significant at most pit lakes than at the natural, terminal lakes because (1) evaporation rates are
lower at many pit lakes because they are located at higher elevations than the terminal lakes, and (2) the surface area to
depth ratio of the pit lakes is >1000 times smaller than that of the terminal lakes.
Received: 1 March 1999 · Accepted: 13 April 1999 相似文献
8.
The sea level rise has its own-bearing on the coastal recession and hydro-environmental degradation of the River Nile Delta.
Attempts are made here to use remote sensing to detect the coastal recession in some selected parts and delineating the chemistry
of groundwater aquifers and surface water, which lie along south-mid-northern and coastal zone of the Nile Delta. Eight water
samples from groundwater monitoring wells and 13 water samples from surface water were collected and analyzed for various
hydrochemical parameters. The groundwater samples are classified into five hydrochemical facies on Hill-Piper trilinear diagram
based on the dominance of different cations and anions: facies 1: Ca–Mg–Na–HCO3–Cl–SO4 type I; facies 2: Na–Cl–HCO3 type II; facies 3: Na–Ca–Mg–Cl type III, facies 4: Ca–Na–Mg–Cl–HCO3 type IV and facies 5: Na–Mg–Cl type V. The hydrochemical facies showed that the majority of samples were enriched in sodium,
bicarbonate and chloride types and, which reflected that the sea water and tidal channel play a major role in controlling
the groundwater chemical composition in the Quaternary shallow aquifers, with a severe degradation going north of Nile Delta.
Also, the relationship between the dissolved chloride (Cl, mmol/l), as a variable, and other major ion combinations (in mmol/l)
were considered as another criterion for chemical classification system. The low and medium chloride groundwater occurs in
southern and mid Nile Delta (Classes A and B), whereas the high and very high chloride (classes D and C) almost covers the
northern parts of the Nile Delta indicating the severe effect of sea water intrusion. Other facets of hydro-environmental
degradation are reflected through monitoring the soil degradation process within the last two decades in the northern part
of Nile Delta. Land degradation was assessed by adopting new approach through the integration of GLASOD/FAO approach and Remote
Sensing/GIS techniques. The main types of human induced soil degradation observed in the studied area are salinity, alkalinity
(sodicity), compaction and water logging. On the other hand, water erosion because of sea rise is assessed. Multi-dates satellite
data from Landsat TM and ETM+ images dated 1983 and 2003 were used to detect the changes of shoreline during the last two
decades. The obtained results showed that, the eroded areas were determined as 568.20 acre; meanwhile the accreted areas were
detected as 494.61 acre during the 20-year period. 相似文献
9.
Relationship Between Surface Water and Groundwater in the Liujiang Basin—Hydrochemical Constrains 总被引:2,自引:0,他引:2
The interaction between surface water and groundwater is not only an important part of the water cycle, but also the foundation of the study on regional water resources quantity. The field hydrogeological investigation and sampling in the Liujiang basin were conducted in the dry season, in April, 2015. The isotopic ratios of hydrogen and oxygen and ion compositions as well as the hydrogeochemical characteristics indicated that the groundwater in the basin was mainly HCO3-Ca and HCO3-Ca·Mg type low salinity water. The groundwater of each region had a unified connection, experiencing the same or similar hydrochemical formation, and the surface water had the same hydrochemical type and source of hydrochemical composition as groundwater. The hydrogen and oxygen isotopic compositions of surface water and groundwater were close to each other, which were mainly from the atmospheric precipitation. In the runoff process, the river water was affected by the evaporation concentration so that the heavy isotopes were slightly enriched. Under the influence of topographical, geological and hydrogeological conditions, the interaction between groundwater and surface water in the basin had obvious segmentation and mutual transformation. The river was recharged by both sides of groundwater in upstream region of Dashi River and Donggong River basin while river water supplied groundwater on both sides of it in downstream region of Dashi River. 相似文献
10.
Thermal and mineral waters in north-eastern Slovenia 总被引:2,自引:0,他引:2
The Mura basin in north-eastern Slovenia is made up of two depressions, developed during the Late Neogene and Early Pliocene
all within a widespread system of Pannonian basins. Both depressions are characterized by the occurrence of thermal waters
of somewhat different hydrogeochemical character. Radgona depression is in the northern part of the basin and reaches depths
of about 2 km. Thermal waters are generally dominated by sodium-bicarbonate, not related to the age of an aquifer, its wallrock
composition, the type of porosity or total concentration of dissolved solids. Locally, sulphate-rich waters are encountered,
and they are related to the presence of gypsum in the rocks of pre-Tertiary basement. The adjacent Ljutomer depression is
over 4 km deep and comprises compartments with stagnant or semi-stagnant aquifers. Herein saline waters predominate, even
in the aquifers of carbonate composition and abundant CO2 gas. In shallower, unconsolidated, intergranular aquifers sodium-bicarbonate waters predominate. Thermal aquifers of this
type are very important to the economy of the region, but they are also subjected to overexploitation which is reflected in
time-dependent changes of dynamic pressures, temperature, conductance, salinity, pH and concentration of major ions, trace
elements, dissolved gasses, and total organic carbon. Mineral waters occur in shallow aquifers or springs in marginal areas
of the Radgona depression. Bicarbonate waters are dominated by calcium, or both calcium and sodium. Some mineral waters are
formed mainly by penetration of CO2 gas into shallow aquifers and consequent water–rock interaction. Composition of some mineral waters indicate their possible
evolution from thermal waters which have risen from central parts of the Radgona depression along deep-seated faults, and
have been modified by cooling and mixing processes.
Received: 30 November 1998 · Accepted: 22 March 1999 相似文献
11.
The total amount of groundwater resources in the middle and upper Odra River basin is 5200×103 m3/d, or about 7.7% of the disposable groundwater resources of Poland. The average modulus of groundwater resources is about
1.4 L/s/km2. Of the 180 'Major Groundwater Basins' (MGWB) in Poland, 43 are partly or totally located within the study area. The MGWB
in southwestern Poland have an average modulus of groundwater resources about 2.28 L/s/km2 and thus have abundant water resources in comparison to MGWB from other parts of the country.
Several types of mineral waters occur in the middle and upper Odra River basin. These waters are concentrated especially in
the Sudety Mountains. Carbon-dioxide waters, with yields of 414 m3/h, are the most widespread of Sudetic mineral waters.
The fresh waters of the crystalline basement have a low mineralization, commonly less than 100 mg/L; they are a HCO3–Ca–Mg or SO4–Ca–Mg type of water. Various hydrochemical compositions characterize the groundwater in sedimentary rocks. The shallow aquifers
are under risk of atmospheric pollution and anthropogenic effects. To prevent the degradation of groundwater resources in
the middle and upper Odra River basin, Critical Protection Areas have been designated within the MGWB.
Received, January 1995 Revised, May 1996, August 1997 Accepted, August 1997 相似文献
12.
运用水化学方法,通过对祖厉河这一黄河上游重要支流的多次实地考察和采样,结合区域水文地质条件,对祖厉河流域水体盐分的空间变化特征进行分析,并揭示流域水体的演化过程。结果表明,流域水体TDS普遍较高,总体以咸水为主。水中阳离子以Na~+为主,阴离子则以Cl-、SO_4~(2-)为主。水化学类型方面,源区地下水以Mg-Ca-Na-HCO_3型水为主,河水则以Na-Mg-Cl-SO_4型水为主。流域内水体盐分主要来源于阳离子交替吸附作用、上游地下水淋滤地层盐分后以泉的形式向河流排泄以及河流径流过程中侵蚀两岸高盐分土壤或含盐地层。径流过程中,当地干旱的气候环境使水体进一步蒸发浓缩,这是流域内水体TDS进一步增高的外在水化学演化过程。总之,由于多种来源的盐分,特别是源区高TDS地下水排泄、流域内强烈的土壤侵蚀以及干旱的气候条件等多重作用过程,是祖厉河TDS显著增高失去水资源功能的主要机制。 相似文献
13.
Assessing hydrochemical evolution of groundwater in limestone terrain via principal component analysis 总被引:2,自引:2,他引:0
Zargham Mohammadi 《Environmental Earth Sciences》2009,59(2):429-439
This paper describes the use of multivariate statistical analysis to trace hydrochemical evolution in a limestone terrain
at Zagros region, Iran. The study area includes a deep confined aquifer, overlaid by an unconfined aquifer. The method involves
the use of principal component analysis (PCA) to assess and evaluate the hydrochemical evolution based on chemical and isotope
variables of 12 piezometers drilled in both the unconfined and confined aquifers. First PCA on all variables shows that water–rock
interaction under different conditions with respect to the atmospheric CO2 is the main process responsible for chemical constituents. As a result, combinations of several ratios such as Ca/TDS, SO4/TDS and Mg/TDS with physico-chemical and isotope variables reveal different hydrochemical evolution trend in the aquifers.
Second PCA on the selective samples and variables reveals that displacement of the unconfined samples from dry to wet season
follows a refreshing trend towards river samples that is characterized by reducing electrical conductivity and increasing
sulphate and tritium contents. However, the refreshing trend cannot be traced in the confined aquifer samples suggesting no
recharge from river to the confined aquifer. Third PCA reveals that, chemical composition of water samples in the unconfined
aquifer tends to have considerable difference from each other in the end of recharge period. In contrast, the confined aquifer
samples have a tendency to show similar chemical composition during recharge period in comparison to end of dry period. This
difference is caused by different mechanism of recharge in the unconfined aquifer (through the whole aquifer surface) and
the confined aquifer (through the limited recharge area). 相似文献
14.
In this case study, silica concentration, oxygen and strontium isotopes of water samples were used to study surface water–groundwater
interaction at the Xin’an karst water system. The silica concentration in rain water is commonly less than 1 mg/l. In the
areas around the south tributary of the Zhuozhang River, silica concentrations in the groundwater in Quaternary aquifers range
between 4.04 and 7.66 mg/l while that of the surface water varies from 1.49 to 6.9 mg/l. Silica concentrations of most surface
water samples increase with TDS, indicating the effect of groundwater recharge on river water chemistry. On the contour map
of silica concentration of groundwater in Quaternary aquifers, samples located close to surface water often have lower silica
concentrations as a result of surface water recharge. Both overland flow and surface water have impact on karst water according
to our hydrogeochemical study of stable oxygen isotope, Sr isotope and strontium contents. Calculation results of three end
member mixing model show that the contribution of karst water, surface water and overland flow water is 45, 28 and 27%, respectively. 相似文献
15.
Hydrochemical characteristics and salinity of groundwater in the Ejina Basin, Northwestern China 总被引:8,自引:0,他引:8
A hydrochemical investigation was conducted in the Ejina Basin to identify the hydrochemical characteristics and the salinity
of groundwater. The results indicate that groundwater in the area is brackish and are significantly zonation in salinity and
water types from the recharge area to the discharge area. The ionic ration plot and saturation index (SI) calculation suggest
that the silicate rock weathering and evaporation deposition are the dominant processes that determine the major ionic composition
in the study area. Most of the stable isotope δ18O and δD compositions in the groundwater is a meteoric water feature, indicating that the groundwater mainly sources from
meteoric water and most groundwater undergoes a long history of evaporation. Based on radioactive isotope tritium (3H) analysis, the groundwater ages were approximately estimated in different aquifers. The groundwater age ranges from less
than 5 years, between 5 years and 50 years, and more than 50 years. Within 1 km of the river water influence zone, the groundwater
recharges from recent Heihe river water and the groundwater age is about less than 5 years in shallow aquifer. From 1 km to
10 km of the river water influence zone, the groundwater sources from the mixture waters and the groundwater age is between
5 years and 50 years in shallow aquifer. The groundwater age is more than 50 years in deep confined aquifer. 相似文献
16.
Pioneer information about the chemical composition of river water in Wrangel Island has been obtained. It is shown that the
water composition reflects the lithogeochemical specifics of primary rocks and ore mineralization. In contrast to many areas
of the Russian Far North, river waters of the island are characterized by an elevated background value of total mineralization
(i.e., total dissolved solids, TDS) (0.3–2 g/l) and specific chemical type (SO4-Ca-Mg). This is related to abundance of Late Carboniferous gypsiferous and dolomitic sequences in the mountainous area of
the island. It has also been established that the salt composition of some streams is appreciably governed by supergene alterations
of the sulfide mineralization associated with the quartz-carbonate vein systems. They make up natural centers of surface water
contamination. Waters in such streams are characterized by low pH values (2.4–5.5), high TDS (up to 6–23 g/l) and the SO4-Mg composition. These waters are also marked by anomalously high concentrations of heavy and nonferrous metals, as well as
REE, U, and Th. 相似文献
17.
Sandow Mark Yidana 《Environmental Geology》2009,57(4):789-796
Surface water resources play a crucial role in the domestic water delivery system in Ghana. In addition, sustainable food
production is based on the quality and quantity of water resources available for irrigation purposes to supplement rain-fed
agricultural activities in the country. The objective of this research was to determine the main controls on the hydrochemistry
of surface water resources in the southern part of Ghana and assess the quality of water from these basins for irrigation
activities in the area. R-mode factor and cluster analyses were applied to 625 data points from 6 river basins in southern Ghana after the data had
been log transformed and standardized for homogeneity. This study finds that surface water chemistry in the south is controlled
by the chemistry of silicate mineral weathering, chemistry of rainfall, fertilizers from agricultural activities in the area,
as well as the weathering of carbonate minerals. A Gibb’s diagram plotted with total dissolved solids (TDS) on the vertical
axis against (Na+ + K+)/(Ca2+ + K+ + Na+) on the horizontal axis indicates that rock weathering plays a significant role in the hydrochemistry. Activity diagrams
for the CaO–Na2O–Al2O–SiO2–H2O and CaO–MgO–Al2O3–SiO2–H2O systems suggest that kaolinite is the most stable clay mineral phase in the system. In addition, an assessment of the irrigation
quality of water from these basins suggests that the basins are largely low sodium—low to medium salinity basins, delivering
water of acceptable quality for irrigation purposes. 相似文献
18.
Hydrogeologic and hydrochemical framework of the shallow groundwater system in the southern Voltaian Sedimentary Basin, Ghana 总被引:4,自引:0,他引:4
The southern Voltaian Sedimentary Basin underlies an area of about 5000 km2 in east-central Ghana. Groundwater in the basin occurs in fractures in highly consolidated siliciclastic aquifers overlain
by a thin unsaturated zone. Aquifer parameters were evaluated from available aquifer-test data on 28 shallow wells in the
basin. Hydraulic-conductivity values range from 0.04–3.6 m/d and are about two orders of magnitude greater than the hydraulic
conductivity calculated using Darcy's Law and the average groundwater velocity estimated from carbon-14 dating. Linear-regression
analysis of the transmissivity and specific-capacity data allowed the establishment of an empirical relationship between log
transmissivity and log specific capacity for the underlying aquifers.
Groundwater chemistry in the basin is controlled by the weathering of albitic plagioclase feldspar. The weathering rates of
various minerals were estimated using 14C-derived average velocity in the basin. The weathering rate of albite was calculated to be 2.16 μmol L–1 yr–1 with the resulting formation of 3.3 μmol L–1 yr–1 of kaolinite and 0.047 μmol L–1 yr–1 of calcite. The low porosity and permeability of the aquifers in the basin are attributed to the precipitation of secondary
minerals on fracture surfaces and interlayer pore spaces.
Received, September 1997 Revised, July 1998, August 1998 Accepted, August 1998 相似文献
19.
Hydrogeochemical analysis and evaluation of groundwater quality in the Gadilam river basin,Tamil Nadu,India 总被引:2,自引:0,他引:2
M V PRASANNA S CHIDAMBARAM A SHAHUL HAMEED K SRINIVASAMOORTHY 《Journal of Earth System Science》2011,120(1):85-98
Water samples were collected from different formations of Gadilam river basin and analyzed to assess the major ion chemistry
and suitability of water for domestic and drinking purposes. Chemical parameters of groundwater such as pH, electrical conductivity
(EC), total dissolved solids (TDS), Sodium (Na + ), Potassium (K + ), Calcium (Ca + ), Magnesium (Mg + ), Bicarbonate (HCO3 -_{3}^{\ \,-}), Sulphate (SO4 -_{4}^{\ \,-}), Phosphate (PO4 -_{4}^{\ \,-}) and Silica (H4SiO4) were determined. The geochemical study of the aquatic systems of the Gadilam river basin show that the groundwater is near-acidic
to alkaline and mostly oxidizing in nature. Higher concentration of Sodium and Chloride indicates leaching of secondary salts
and anthropogenic impact by industry and salt water intrusion. Spatial distribution of EC indicates anthropogenic impact in
the downstream side of the basin. The concentration levels of trace metals such as Iron (Fe), Lead (Pb), Nickel (Ni), Bromide
(Br), Iodide (I) and Aluminium (Al) have been compared with the world standard. Interpretation of data shows that some trace
metals such as Al, Ni and Pb exceed the acceptable limit of world standard. Geophysical study was carried out to identify
the weathered zone in the hard rock and contaminated zone by anthropogenic impact in the downstream of river Gadilam. A few
of the groundwater samples in the study area were found to be unsuitable for domestic and drinking purposes. 相似文献
20.
The purpose of this study is to investigate the quality and usage possibility of groundwater in the Çavuşçayı basin and suggest the best water structure for the groundwater use. Results from hydrochemical analyses reveal that groundwater is mostly affected by salty (Na+–Cl−) waters of the Incik Formation and brackish (Ca2+, Mg2+–SO
4
2−
) waters of the Bayındır Formation. The Alibaba saltpan discharged (2 l/s) from the Incik Formation is used for salt production. In the basin, salinity risk increases with depth and along the groundwater flow direction. Therefore, shallow water and trenches opened in the alluvium aquifer at the east of the basin were determined to yield suitable water with no Na+ and Cl− contamination. Following the heavy rainy period, waters of less salinity and conductivity are possibly used for agriculture. 相似文献