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1.
An attempt has been made to study the groundwater geochemistry in part of the NOIDA metropolitan city and assessing the hydrogeochemical processes controlling the water composition and its suitability for drinking and irrigation uses. The analytical results show that Na and Ca are the major cations and HCO3 and Cl are the major anions in this water. The higher ratios of Na+K/TZ+ (0.2–0.7), Ca+Mg/HCO3 (0.8–6.1); good correlation between Ca-Mg (0.75), Ca-Na (0.77), Mg-Na (0.96); low ratio of Ca+Mg/Na+K (1.6), Ca/Na (1.03), Mg/Na (0.64), HCO3/Na (1.05) along with negative correlation of HCO3 with Ca and Mg signify silicate weathering with limited contribution from carbonate dissolution. The hydro-geochemical study of the area reveals that many parameters are exceeding the desirable limits and quality of the potable water has deteriorated to a large extent at many sites. High concentrations of TDS, Na, Cl, SO4, Fe, Mn, Pb and Ni indicate anthropogenic impact on groundwater quality and demand regional water quality investigation and integrated water management strategy. SAR, %Na, PI and Mg-hazard values show that water is of good to permissible quality and can be used for irrigation. However, higher salinity and boron concentration restrict its suitability for irrigation uses at many sites.  相似文献   

2.
The present study investigates the hydrogeochemistry and contamination of Varamin deep aquifer located in the southeast of Tehran province, Iran. The study also evaluates groundwater suitability for irrigation uses. The hydrogeochemical study was conducted by collecting and analyzing 154 groundwater samples seasonally during 2014. Based on evolutionary sequence of Chebotarev, the aquifer is in the stage of SO4 + HCO3 in the north half of the plain and it has evolved into SO4 + Cl in the south half. The unusual increase in TDS and Cl? toward the western boundaries of the aquifer indicates some anomalies. These anomalies have originated from discharge of untreated wastewater of Tehran city in these areas. The studied aquifer contains four dominant groundwater types including Na–Ca–SO4 (55%), Na–Ca–HCO3 (22%), Na–Cl (13%) and Ca–Cl (10%). The spatial distributions of Na–Cl and Ca–Cl water types coincide with observed anomalies. Ionic relationships of SO4 2? versus Cl? and Na+ versus Cl? confirm that water–rock interaction and anthropogenic contribution are main sources of these ions in the groundwater. The main processes governing the chemistry of the groundwater are the dissolution of calcite, dolomite and gypsum along the flow path, and direct ion exchange. Reverse ion exchange controls the groundwater chemistry in the areas contaminated with untreated wastewater. Based on Na% and SAR, 10.3 and 27% of water samples are unsuitable for irrigation purposes, respectively. Regarding residual sodium carbonate, there is no treat for crop yields. Only 6% of water samples represent magnesium adsorption ratios more than 50% which are harmful and unsuitable for irrigation.  相似文献   

3.
Aquifer-based groundwater quality assessment offers critical insight into the major hydrochemical processes, and aids in making groundwater resources management decisions. The Texas Rolling Plains (TRP), spanning over 22 counties, is a major agro-ecological region in Texas from where highest groundwater nitrate (NO3 ?) levels in the state have been reported. In this study, we present a comparative assessment of major hydrochemical facies pertaining to NO3 ? contamination and a host of species such as sulfate (SO4 2?), chloride (Cl?), and total dissolved solids (TDS) in different water use classes in the Seymour and Blaine aquifers, underlying the TRP. Aquifer-stratified groundwater quality information from 1990 to 2010 was obtained from the Texas Water Development Board and aggregated over decadal scale. High groundwater salinization was found in the municipal water use class in the Blaine aquifer with about 100, 87 and 50 % of observations exceeding the secondary maximum contaminant level for TDS, SO4 2?, and Cl?, respectively in the 2000s (2000–2010). The NO3-contamination was more alarming in the Seymour aquifer with 82 and 61 % of observations, respectively, exceeding the maximum contaminant level (MCL) in the irrigation and municipal water use classes in the 2000s. Salinization was more influenced by SO4 2? and Cl? in the Blaine aquifer and by NO3 ? in the Seymour aquifer. High NO3 ? (>MCL) observations in the Seymour aquifer occurred in the Ca–HCO3 and Ca–Mg–HCO3 facies, the domains of fresh water recharge and anthropogenic influences (e.g., agricultural activities, waste disposal). High SO4 2?, Cl? and TDS observations in the Blaine aquifer dominated the Ca–Cl, Na–Cl, and mixed Ca(Mg)–SO4(Cl) facies indicating evaporite dissolution, mixing and solute exchange, and lack of fresh recharge.  相似文献   

4.
In the light of progressive depletion of groundwater reservoir and water quality deterioration of the Neyveli basin, an investigation on dissolved major constituents in 25 groundwater samples was performed. The main objective was detection of processes for the geochemical assessment throughout the area. Neyveli aquifer is intensively inhabited during the last decenniums, leading to expansion of the residential and agricultural area. Besides semi-aridity, rapid social and economic development stimulates greater demand for water, which is gradually fulfilled by groundwater extraction. Groundwaters of the study area are characterized by the dominance of Na?+?K over Ca?+?Mg. HCO3 was found to be the dominant anion followed by Cl and SO4. High positive correlation was obtained among the following ions: Ca–Mg, Cl–Ca,Mg, Na–K, HCO3–H4SiO4, and F–K. The hydrochemical types in the area can be divided into two major groups: the first group includes mixed Ca–Mg–Cl and Ca–Cl types. The second group comprises mixed Ca–Na–HCO3 and Ca–HCO3 types. Most of the groundwater samples are within the permissible limit of WHO standard. Interpretation of data suggests that weathering, ion exchange reactions, and evaporation to some extent are the dominant factors that determine the major ionic composition in the study area.  相似文献   

5.
The present research aims to identify sources of ions and factors controlling the geochemical evolution of groundwater in an intermountain basin, comprising hill and valley fill region, of Outer Himalaya in Himachal Pradesh, India. The groundwater samples collected from 81 tubewells and handpumps are analyzed for major ions, trace metals and stable isotopes (δ18O and δD). Geochemically the dominant hydrochemical facies in the Una basin are Ca–HCO3, Ca–Mg–HCO3 and Na–Cl types at few locations. A relatively lower ionic concentration in the valley fills indicates dilution and low residence time of water to interact with the aquifer mass due to high porosity and permeability. The ionic ratios of 0.9, 0.8 and 3.8 to 5.7, respectively, for (Ca?+?Mg): HCO3, (Ca?+?Mg): (HCO3?+?SO4) and Na: Cl, suggests that ionic composition of groundwater is mainly controlled by rock weathering of, particularly by dissolution/precipitation of calcrete and calcite hosted in rock veins and Ca–Na feldspar hosted in conglomerate deposits derived from the Higher and Lesser Himalaya during the formation of Siwalik rocks. Although Na, K, NO3 and SO4 are introduced in the groundwater through agricultural practices, Na has also been introduced through ion exchange processes that have occurred during water–rock interaction, as indicated by negative CAI values. Factor analysis further suggests three major factors affecting the water chemistry of the area. The first two factors are associated with rock weathering while the third is anthropogenic processes associated with high nitrate and iron concentration. High concentrations of Fe and Mn ions that are exceeded that of WHO and BIS standards are also present at few locations. The recharge of groundwater in the Outer Himalaya is entirely through Indian Southwest Monsoon (ISM) and depleted ratios of δ18O/δD in valley region indicate infiltration from irrigation in recharging the groundwater and fractionation of isotopes of precipitation due to evaporation before infiltration. High d-excess values and inverse relation with δ18O are indicative of secondary evaporation of precipitation during recharge of groundwater.  相似文献   

6.
Insufficient knowledge of the hydrogeochemistry of aquifers in the Central Region of Ghana has necessitated a preliminary water quality assessment in some parts of the region. Major and minor ions, and trace metal compositions of groundwater have been studied with the aim of evaluating hydrogeochemical processes that are likely to impair the quality of water in the study area. The results show that groundwater in the area is weakly acidic with mean acidity being 5.83 pH units. The dominant cation in the area is Na, followed by K, Ca, and Mg, and the dominant anion is Cl?, followed by HCO3 ? and SO4 2?. Two major hydrochemical facies have been identified as Na–Cl and Na–HCO3, water types. Multivariate statistical techniques such as cluster analysis (CA) and factor analysis/principal component analysis (PCA), in R mode, were employed to examine the chemical compositions of groundwater and to identify factors that influenced each. Q-mode CA analysis resulted in two distinct water types as established by the hydrochemical facies. Cluster 1 waters contain predominantly Na–Cl. Cluster 2 waters contain Na–HCO3 and Na–Cl. Cluster 2 waters are fresher and of good quality than cluster 1. Factor analysis yielded five significant factors, explaining 86.56% of the total variance. PC1 explains 41.95% of the variance and is contributed by temperature, electrical conductivity, TDS, turbidity, SO4 2?, Cl?, Na, K, Ca, Mg, and Mn and influenced by geochemical processes such as weathering, mineral dissolution, cation exchange, and oxidation–reduction reactions. PC2 explains 16.43% of the total variance and is characterized by high positive loadings of pH and HCO3 ?. This results from biogenic activities taking place to generate gaseous carbon dioxide that reacts with infiltrating water to generate HCO3 ?, which intend affect the pH. PC3 explains 11.17% of the total variance and is negatively loaded on PO4 3? and NO3 ? indicating anthropogenic influence. The R-mode PCA, supported by R-mode CA, have revealed hydrogeochemical processes as the major sources of ions in the groundwater. Factor score plot revealed a possible flow direction from the northern sections of the study area, marked by higher topography, to the south. Compositional relations confirmed the predominant geochemical process responsible for the various ions in the groundwater as mineral dissolution and thus agree with the multivariate analysis.  相似文献   

7.
Assessment of chemistry of groundwater infiltrated by pit-toilet leachate and contaminant removal by vadose zone form the focus of this study. The study area is Mulbagal Town in Karnataka State, India. Groundwater level measurements and estimation of unsaturated permeability indicated that the leachate recharged the groundwater inside the town at the rate of 1 m/day. The average nitrate concentration of groundwater inside the town (148 mg/L) was three times larger than the permissible limit (45 mg/L), while the average nitrate concentration of groundwater outside the town (30 mg/L) was below the permissible limit. The groundwater inside the town exhibited E. coli contamination, while groundwater outside the town was free of pathogen contamination. Infiltration of alkalis (Na+, K+) and strong acids (Cl?, SO4 2?) caused the mixed Ca–Mg–Cl type (60 %) and Na–Cl type (28 %) facies to predominate groundwater inside the town, while, Ca–HCO3 (35 %), mixed Ca–Mg–Cl type (35 %) and mixed Ca–Na–HCO3 type (28 %) facies predominated groundwater outside/periphery of town. Reductions in E. coli and nitrate concentrations with vadose zone thickness indicated its participation in contaminant removal. A 4-m thickness of unsaturated sand + soft, disintegrated weathered rock deposit facilitates the removal of 1 log of E. coli pathogen. The anoxic conditions prevailing in the deeper layers of the vadose zone (>19 m thickness) favor denitrification resulting in lower nitrate concentrations (28–96 mg/L) in deeper water tables (located at depths of ?29 to ?39 m).  相似文献   

8.
Dar es Salaam Quaternary coastal aquifer is a major source of water supply in Dar es Salaam City used for domestic, agricultural, and industrial uses. However, groundwater overdraft and contamination are the major problems affecting the aquifer system. This study aims to define the principal hydrogeochemical processes controlling groundwater quality in the coastal strip of Dar es Salaam and to investigate whether the threats of seawater intrusion and pollution are influencing groundwater quality. Major cations and anions analysed in 134 groundwater samples reveal that groundwater is mainly affected by four factors: dissolution of calcite and dolomite, weathering of silicate minerals, seawater intrusion due to aquifer overexploitation, and nitrate pollution mainly caused by the use of pit latrines and septic tanks. High enrichment of Na+ and Cl? near the coast gives an indication of seawater intrusion into the aquifer as also supported from the Na–Cl signature on the Piper diagram. The boreholes close to the coast have much higher Na/Cl molar ratios than the boreholes located further inland. The dissolution of calcite and dolomite in recharge areas results in Ca–HCO3 and Ca–Mg–HCO3 groundwater types. Further along flow paths, Ca2+ and Na+ ion exchange causes groundwater evolution to Na–HCO3 type. From the PHREEQC simulation model, it appears that groundwater is undersaturated to slightly oversaturated with respect to the calcite and dolomite minerals. The results of this study provide important information required for the protection of the aquifer system.  相似文献   

9.
There are 59 springs at the Gevas–Gurp?nar–Güzelsu basins, 38 of these springs emerge from the fractured karst aquifers (recrystallized limestone and travertine) and 21 emerge from the Yuksekova ophiolites, K?rkgeçit formation and alluvium. The groundwater samples collected from 38 out of the total of 59 springs, two streams, one lake and 12 wells were analyzed physico-chemically in the year 2002. EC and TDS values of groundwater increased from the marble (high altitude) to the ophiolites and alluvium (toward Lake Van) as a result of carbonate dissolution and connate seawater. Five chemical types of groundwater are identified: Ca–Mg–HCO3, Mg–Ca–HCO3, Mg–Na–HCO3, Na–Ca–HCO3 and Mg–Ca–Na–HCO3. The calculations and hydrochemical interpretations show that the high concentrations of Ca2+, Mg2+ and HCO3 ? as predominant ions in the waters are mainly attributed to carbonate rocks and high pCO2 in soil. Most of the karst springs are oversaturated in calcite, aragonite and dolomite and undersaturated in gypsum, halite and anhydrite. The water–rock interaction processes that singly or in combination influence the chemical composition of each water type include dissolution of carbonate (calcite and dolomite), calcite precipitation, cation exchange and freshening of connate seawater. These processes contribute considerably to the concentration of major ions in the groundwater. Stable isotope contents of the groundwater suggest mainly direct integrative recharge.  相似文献   

10.
The study area Mettur forms an important industrial town situated NW of Salem district. The geology of the area is mainly composed of Archean crystalline metamorphic complexes. To identify the major process activated for controlling the groundwater chemistry an attempt has been made by collecting a total of 46 groundwater samples for two different seasons, viz., pre-monsoon and post-monsoon. The groundwater chemistry is dominated by silicate weathering and (Na + Mg) and (Cl + SO4) accounts of about 90% of cations and anions. The contribution of (Ca + Mg) and (Na + K) to total cations and HCO3 indicates the domination of silicate weathering as major sources for cations. The plot for Na to Cl indicates higher Cl in both seasons, derived from Anthropogenic (human) sources from fertilizer, road salt, human and animal waste, and industrial applications, minor representations of Na also indicates source from weathering of silicate-bearing minerals. The plot for Na/Cl to EC indicates Na released from silicate weathering process which is also supported by higher HCO3 values in both the seasons. Ion exchange process is also activated in the study area which is indicated by shifting to right in plot for Ca + Mg to SO4 + HCO3. The plot of Na-Cl to Ca + Mg-HCO3-SO4 confirms that Ca, Mg and Na concentrations in groundwater are derived from aquifer materials. Thermodynamic plot indicates that groundwater is in equilibrium with kaolinite, muscovite and chlorite minerals. Saturation index of silicate and carbonate minerals indicate oversaturation during pre-monsoon and undersaturation during post-monsoon, conforming dissolution and dilution process. In general, water chemistry is guided by complex weathering process, ion exchange along with influence of Cl ions from anthropogenic impact.  相似文献   

11.
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   

12.
To reveal the geochemical characters of water coproduced with coalbed gas and shallow groundwater,water samples were collected from 12 wells of coalbed methane and 7 wells of shallow groundwater.The pH,CODMn,fCO2,total dissolved solids （TDS）,total hardness,and concentrations of metasilicic acid,sodium and kalium,calcium ion,magnesium ion,ammonium iron,bicarbonate ion,carbonate,chloride,sulfate ion,nitrate ion,fluoride,lithium,zinc,nickel,manganese,iron,boron,barium,etc.of the samples were measured.Research results showed the following：（1） Concentrations of TDS,chloride,fluoride,sodium and kalium,ammonium,iron,and barium in the water coproduced with coalbed gas exceeded the national standards of China; however,physical,chemical,and biological properties of shallow groundwater could meet the national standard.（2） The water produced from coalbed contained mainly Na-Cl·HCO3,with average TDS of 4588.5 ppm,whereas shallow groundwater contained a mixture of chemicals including Na.Mg.Ca-HCO3·SO4 and Na.Mg-HCO3·SO4,with average TDS of 663.8 ppm.（3） In general,it was observed that bicarbonate and sodium accumulated in a reducing environment and deeper system,while depletion of hydrogen ions and dissolution of sulfate,calcium,and magnesium occurred in a redox environment and shallow system.（4） Sodium and kalium,ammonium,chloride,and bicarbonate ions were the main ions found in the study area.  相似文献   

13.
The chemical characteristics of surface, groundwater and mine water of the upper catchment of the Damodar River basin were studied to evaluate the major ion chemistry, geochemical processes controlling water composition and suitability of water for domestic, industrial and irrigation uses. Water samples from ponds, lakes, rivers, reservoirs and groundwater were collected and analysed for pH, EC, TDS, F, Cl, HCO3, SO4, NO3, Ca, Mg, Na and K. In general, Ca, Na, Mg, HCO3 and Cl dominate, except in samples from mining areas which have higher concentration of SO4. Water chemistry of the area reflects continental weathering, aided by mining and other anthropogenic impacts. Limiting groundwater use for domestic purposes are contents of TDS, F, Cl, SO4, NO3 and TH that exceed the desirable limits in water collected from mining and urban areas. The calculated values of SAR, RSC and %Na indicate good to permissible use of water for irrigation. High salinity, %Na, Mg-hazard and RSC values at some sites limit use for agricultural purposes.  相似文献   

14.
The Vaal River Basin is an economically significant area situated in the interior of South Africa (SA), where mining, industrial, domestic and agricultural activities are very intense. The purpose of the study was to assess the influence of geology and anthropogenic activities on groundwater chemistry, and identify the predominant hydrochemical processes in the basin. Data from seventy groundwater sites were retrieved from the national database, and attention was paid to fifteen water quality parameters. Groundwater samples were clustered into seven hydrochemically distinct groups using Hierarchical Cluster Analysis (HCA), and three samples treated independently. A Piper plot revealed two major water types, Ca–Mg–HCO3 and Ca–Mg–SO4-Cl, which were linked to dissolution of the underlying geology and mine pollution. The Ca?+?Mg vs HCO3?+?SO4 plot indicated that reverse ion exchange is an active process than cation exchange in the area. Principal component analysis (PCA) was used to identify the main natural and anthropogenic processes causing variation in groundwater chemistry. Four principal components were extracted using PCA that explains 82% of the total variance in the chemical parameters. The PCA results can be categorized by four components: (1) evaporites and silicates weathering enrichment of Na, K, Cl, SO4 and F, and anthropogenic Cl; (2) dissolution of dolomite, limestone and gypsum; (3) agricultural fertilizers (4) wastewater treatment. This study reveals that both natural and anthropogenic activities are the cause of groundwater variation in the basin.  相似文献   

15.
The leaching processes along the flow path and over abstraction of the alluvial aquifer, the principal aquifer in delta Tokar, by the agricultural and domestic sectors and natural factors, have led to its salinization which may be due to interaction between geological formations and adjacent brackish and saline water bodies as well as seawater transgression. The main objectives of this study are to assess the hydrochemical characteristics of the groundwater and to delineate the locations and the sources of aquifer salinization. Water samples in the project area were chemically analyzed for major cations and anions at the laboratory by the standard analytical procedures. Chemical data and water level measurements were manipulated using GIS techniques for hydro chemical and flow direction maps and piper diagram for chemical facies and SPSS software for statistical analyses such as basic statistics (mean and standard deviation) and Spearman’s correlation matrix. The general flow direction of the groundwater is from Southwest towards East and Northeast. The hydraulic gradient is relatively steeper at the apex of the delta (0.06) and amounts to 0.005 at the distal part of the delta. The average transmissivity value of the water bearing formations was found to be about 4.5?×?103 m2/s, whereas, the storage coefficient was about 0.28. A hydrochemical study identified the locations and the sources of aquifer salinization and delineated their areas of influence. The investigation indicates that the aquifer water quality is significantly modified as groundwater flows from the southwestern parts of the study area, where the aquifer receives its water by lateral underflow from Khor Baraka flood plain, to the central and northeastern parts, with few exceptions of scattered anomalous concentration pockets in the deltaic plain. Significant correlation between TDS and/or EC with the major components of Na+, Cl?, and SO 4 ?2 ions is an indication of seawater influence on the groundwater salinity. Moreover, Cl?, SO 4 2? , and Na+ are predominant ions followed by Ca2+ and HCO 3 ? . Hence, four types of groundwater can be chemically distinguished: Na–Ca–SO4–Cl– facies, Na–Cl–SO4–HCO3– facies, Na–Ca–Mg–SO4–Cl–HCO3 facies, and Na–Ca–Mg–Cl–SO4 facies. The processes that govern changes in groundwater composition as revealed by chemical and statistical analyses are mainly associated with over-abstraction, biodegradation, marine intrusions, and carbonate saturation.  相似文献   

16.
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17.
Water samples for chemical analyses were collected in January 2012. A total of 72 samples of groundwater were collected from 72 boreholes in the Midyan Basin, northwestern Saudi Arabia. Samples were collected in polyethylene bottles and preserved and the used analytical techniques were in accordance with the standard methods from American public health association. Geochemical analyses of the groundwater samples from Midyan Basin reveal the concentration of fluoride (F) between 0.98 and 2.1 mg/l. Other parameters, e.g, pH, EC, TDS, HCO3, SO4, NO3, Cl, K, Na, Mg, and Ca have been found in a variable proportion. Among them, the concentration of EC, HCO3, K, Na and Mg is higher than the permissible limits. According to thermodynamical considerations, most of the analysed samples are graded under-saturated with respect to calcite and fluoride, while saturation has been observed in some samples. The under-saturation could probably be attributed to low concentration of calcite and fluoride in the studied wells. Fluoride concentration shows weak positive correlation with EC, TDS, Na, Cl, and SO4. Factors controlling the concentration of fluoride (F) in the studied samples are the area climate, water chemistry and the presence of accessory minerals in the rocks through which groundwater is circulating, besides the anthropogenic activities in the area.  相似文献   

18.
The Imphal valley is an intramontane basin confined within an anticlinorium of several anticlines and synclines in the Disang Group of rocks of Tertiary age. This valley of more than 2 million people is occupied by fluvio-lacustrine deposits of Quaternary age and is located in the central part of the Indo-Myanmar range of Northeast India. The hydrogeochemical parameters of temperature, pH, ORP, TDS, Na, Cl, Br, Ba, B, Sr, Li, δ18O, HCO3, K, Mg, Ca, NO3, PO4, SO4 in 173 samples using ion-chromatograph, ICP (AES), ICP (OES), ICP (MS) and 37 dugwells were studied to understand the occurrence and origin of salinization process for the first time. The order of abundance of ions is identified as HCO3 > Na > Cl > Ca > Mg > K > NO3 > PO4 > Sr > Br > B>Ba > Li > SO4. Five hydrochemical facies (Na–Cl, Ca–Mg–HCO3, Na–HCO3, Ca–Mg–HCO3–Cl and Ca–Mg–Cl) represent the types of waters. The saline-dominated water types (Na–Cl and Na–HCO3) represent piedmont and the rest of the facies represent alluvial plain and flood plain groundwaters. Durov’s diagram reveales initial and intermediate stages of groundwater evolution. Isotope δ18O, Gibbs diagram and ions scatter plots suggest evaporation and crystallization processes leading to halite encrustation in the Disang shales. Negative Eh, low NO3 and the absence of SO4 indicates reduced condition coupled with rich dissolve organic matters leading to elevation of salts in soils around piedmont where the rock type is exclusively of the Disang shales. Trilinear plot, correlation matrix and water table flow analysis suggest salinization of groundwater originates in piedmont groundwater and disseminates towards alluvial plain and flood plain along the flow path.  相似文献   

19.
The Barwon Downs Graben lies on the northern flanks of the Otway Ranges and is situated approximately 70 km southwest of Geelong, Victoria, Australia. The major lower Tertiary Barwon Downs Graben aquifer comprises highly permeable sands and gravels interbedded with clays and silts of the hydraulically interconnected Pebble Point, Dilwyn and Mepunga Formations. Groundwater flows east into the Barwon Downs Graben from the Barongarook High, and yields 14C ages up to ～20 ka implying that recharge rates are low and, consequently, that the resource could be impacted by overabstraction. The presence of three different lithological units has led to the development of localized flow systems that has resulted in a lack of regular spatial variations in groundwater chemistry. Stable isotopic data suggests that groundwater was recharged under similar climatic conditions as of today. The major ion chemistry of the freshest groundwater is dominated by Na and HCO3 while higher TDS groundwater, from the confining Narrawaturk Marl, is dominated by Na and Cl. Cl/Br ratios are close to rainfall suggesting that halite dissolution is not the principle source of salts. An excess of Na relative to Cl in fresher groundwater suggests that feldspar dissolution has occurred, however, water–rock interaction is limited. The concentrations of Ca, Mg, and SO4 are controlled by silicate dissolution and ion-exchange reactions with clays.  相似文献   

20.
Groundwater is the most important source of water supply in the Yeniceoba Plain in Central Anatolia,Turkey.An understanding of the geochemical evolution of groundwater is important for the sustainable development of water resources in this region.A hydrogeochemical investigation was conducted in the Plio-Quaternary aquifer system using stable isotopes(δ~(18)O andδD),tritium(~3H),major and minor elements(Ca,Na,K,Mg,Cl,SO_4,NO_3,HCO_3 and Br)in order to identify groundwater chemistry patterns and the processes affecting groundwater mineralization in this system.The chemical data reveal that the chemical composition of groundwater in this aquifer system is mainly controlled by rock/water interactions including dissolution of evaporitic minerals,weathering of silicates,precipitation/dissolution of carbonates,ion exchange,and evaporation.Based on the values of Cl/Br ratio(300 mg/l)in the Plio-Quaternary groundwater,dissolution of evaporitic minerals in aquifer contributes significantly to the high mineralization.The stable isotope analyses indicate that the groundwater in the system was influenced by evaporation of rainfall during infiltration.Low tritium values(generally1 tritium units)of groundwater reflect a minor contribution of recent recharge and groundwater residence times of more than three or four decades.  相似文献   

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