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1.
The Ganges River water and riverbank shallow groundwater were studied during a single wet season using the hydrochemical and isotopic composition of its dissolved load. The dissolved concentrations of major ions (Cl?, SO4 2?, NO3 ?, HCO3 ?, Ca2+, Na+, Mg2+, and K+), trace elements (barium (Ba) and strontium (Sr)) and stable isotopes (O and D) were determined on samples collected from the Ganges River and its riverbank shallow aquifers. In the present study, the shallow groundwater differs significantly from the Ganges River water; it shows distinct high concentrations of Ca2+, Mg2+, HCO3 ?, Ba, and Sr due to water–rock interaction and this in particular suggests that the Ganges River may not contribute significantly to the riverbank shallow aquifers during wet season. Besides, the sum of the total cationic charge (∑+, in milliequivalents per liter) in the groundwater shows high values (2.48 to 13.91 meq/L, average 9.12 meq/L), which is much higher than the sum of the cations observed in the Ganges water (1.36 to 3.10 meq/L, average 1.94 meq/L). Finally, the more depleted stable isotopic (δ 18O and δ 2H) compositions of the Ganges River water are in contrast to those of the riverbank aquifer having enriched stable isotopic values during the wet season and the riverbank groundwater thus has a purely local origin from precipitation.  相似文献   

2.
The study was done to assess the effect of the river Sutlej on arsenic (As) contamination. Sampling was done from the alluvial plain with increasing distance from the river Sutlej in district Vehari and compared with the study done in the proximity of River Sutlej. Sixty (60) groundwater samples mostly from shallow depths were collected and analyzed for As concentrations. Multivariate statistical tools (PCA and CA), saturation index, piper plots and Gibbs diagrams were used to detect evidence about the interrelationship and sources of As and other water quality variables responsible for groundwater contamination. Results revealed that As concentration ranged from below detection limit to 156 µg/L indicating that 50% samples exceeding the WHO guidelines (10 µg/L) and 17% exceeding the Pakistan National Environmental Quality Standards (NEQS) limits (50 µg/L) Sutlej. The piper plot revealed that water chemistry of the study area was Ca–HCO3?, Ca–Mg–Cl, type. Correlations between As and HCO3? (r2?=?0.433) was positive, while negative correlations were observed between As–Mn2+ and As–Fe2+ (r2?=???0.102), (r2?=?0.107) respectively. Geochemical signatures of the groundwater in the study area showed that the As could be released by oxidative dissolution to some extent and elevated evaporation in the arid environment of the study area under the stimulus of alkaline water and high pH (range 7.1–8.4). Although the concentrations are exceeding the WHO limit in 50% of the water samples but, are less than the previous study done in Mailsi near River Sutlej. Further, the concentrations decreased as the distance from the River increased which shows the probable role of sediments deposited by the River Sutlej.  相似文献   

3.
A total of 194 groundwater samples were collected from wells in hard rock aquifers of the Medak district, South India, to assess the distribution of fluoride in groundwater and to determine whether this chemical constituent was likely to be causing adverse health effects on groundwater user in the region. The study revealed that the fluoride concentration in groundwater ranged between 0.2 and 7.4 mg/L with an average concentration of 2.7 mg/L. About 57% of groundwater tested has fluoride concentrations more than the maximum permissible limit of 1.5 mg/L. The highest concentrations of fluoride were measured in groundwater in the north-eastern part of the Medak region especially in the Siddipeta, Chinnakodur, Nanganoor and Dubhaka regions. The areas are underlain by granites which contain fluoride-bearing minerals like apatite and biotite. Due to water–rock interactions, the fluoride has become enriched in groundwater due to the weathering and leaching of fluoride-bearing minerals. The pH and bicarbonate concentrations of the groundwater are varied from 6.6 to 8.8 and 18 to 527 mg/L, respectively. High fluoride concentration in the groundwater of the study area is observed when pH and the bicarbonate concentration are high. Data plotted in Gibbs diagram show that all groundwater samples fall under rock weathering dominance group with a trend towards the evaporation dominance category. An assessment of the chemical composition of groundwater reveals that most of the groundwater samples have compositions of Ca2+–Mg2+–Cl? > Ca2+–Na+–HCO3 ? > Ca2+–HCO3 ? > Na+–HCO3 ?. This suggests that the characteristics of the groundwater flow regime, long residence time and the extent of groundwater interaction with rocks are the major factors that influence the concentration of fluoride. It is advised not to utilize the groundwater for drinking purpose in the areas delineated, and they should depend on alternate safe source.  相似文献   

4.
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   

5.
Hydrochemical studies were conducted in Chinnaeru river basin of Nalgonda district, Andhra Pradesh, India, to explore the causes of high fluorides in groundwater and surface water causing a widespread incidence of fluorosis in local population. The concentration of fluoride in groundwater ranges from 0.4 to 2.9 and 0.6 to 3.6 mg/l, stream water ranges from 0.9 to 3.5 and 1.4 to 3.2 mg/l, tank water ranges from 0.4 to 2.8 and 0.9 to 2.3 mg/l, for pre- and post-monsoon periods, respectively. The modified Piper diagram reflects that the water belongs to Ca2+–Mg2+–HCO3 ? to Na+–HCO3 ? facies. Negative chloroalkali indices in both the seasons prove that ion exchange between Na+ and K+ in aquatic solution took place with Ca2+ and Mg2+ of host rock. The interpretation of plots for different major ions and molar ratios suggest that weathering of silicate rocks and water–rock interaction is responsible for major ion chemistry of groundwater/surface water. High fluoride content in groundwater was attributed to continuous water–rock interaction during the process of percolation with fluorite bearing country rocks under arid, low precipitation, and high evaporation conditions. The low calcium content in rocks and soils, and the presence of high levels of sodium bicarbonate are important factors favouring high levels of fluoride in waters. The basement rocks provide abundant mineral sources of fluoride in the form of amphibole, biotite, fluorite, mica and apatite.  相似文献   

6.
The bank infiltration (BI) technique may be a viable option if the local climate, hydrological, and geological conditions are conducive. This study was specifically conducted to explore the possibility of using BI to source the polluted surface water in conjunction with groundwater. Three major factors were considered for evaluation: (1) investigation on the contribution of surface water through BI, (2) input of local groundwater, and (3) water quality characteristics of water supply. Initially, the geophysical method was employed to define the subsurface geology and hydrogeology, and isotope techniques were performed to identify the source of groundwater recharge and interaction between surface water and groundwater. The physicochemical and microbiological parameters of the local surface water bodies and groundwater were analyzed before and during water abstraction. Extracted water revealed a 5 %–98 % decrease in turbidity, as well as HCO3 +, SO4 ?, NO3 ?, Al, As, and Ca concentration reduction compared with those of Langat river water. However, water samples from test wells during pumping show high concentrations of Fe2+ and Mn2+. In addition, amounts of Escherichia coli, total coliform, and Giardia were significantly reduced (99.9 %). Pumping test results indicate that the two wells (DW1 and DW2) were able to sustain yields.  相似文献   

7.
Bank infiltration (BI) is one of the solutions to providing raw water for public supply in tropical countries. This study in Malaysia explores the use of BI to supplement a polluted surface-water resource with groundwater. Three major factors were investigated: (1) contribution of surface water through BI to the resulting abstraction, (2) input of local groundwater, and (3) water-quality characteristics of the resulting water supply. A geophysical method was employed to define the subsurface geology and hydrogeology, and isotope techniques were performed to identify the source of groundwater recharge and the interaction between surface water and groundwater. The physicochemical and microbiological parameters of the local surface-water bodies and groundwater were analyzed before and during water abstraction. Extracted water revealed a 5–98 % decrease in turbidity, as well as reductions in HCO3 ?, Cl?, SO4 2?, NO3 ?, Ca2+, Al3+ and As concentrations compared with those of Langat River water. In addition, amounts of E. coli, total coliform and Giardia were significantly reduced (99.9 %). However, water samples from test wells during pumping showed high concentrations of Fe2+ and Mn2+. Pumping test results indicate that the two wells used in the study were able to sustain yields.  相似文献   

8.
Hydrogeochemical controlling factors for high rate of groundwater contamination in stressed aquifer of fractured, consolidated rocks belonging to semi-arid watershed are examined. The groundwater in mid-eastern part of Prakasam district confining to Musi-Gundlakamma sub-basins is heavily contaminated with nitrate and fluoride. Distinct water chemistry is noticed among each group of samples segregated based on concentration of these contaminants. The nitrate is as high as 594 mg/l and 57 % of the samples have it in toxic level as per BIS drinking water standards, so also the fluoride which has reached a maximum of 8.96 mq/l and 43 % of samples are not fit for human consumption. Nitrate contamination is high in shallow aquifers and granitic terrains, whereas fluoride is in excess concentration in deeper zones and meta-sediments among the tested wells, and 25 % of samples suffer from both NO3 ? and F? contamination. Na+ among cations and HCO3 ? among anions are the dominant species followed by Mg2+ and Cl?. The NO3 ?-rich groundwater is of Ca2+–Mg2+–HCO3 ?, Ca2+–Mg2+–Cl? and Na+–HCO3 ? type. The F?-rich groundwater is dominantly of Na+–HCO3 ? type and few are of Na+–SO4 2? type, whereas the safe waters (without any contaminants) are of Ca2+–Mg2+–HCO3 ?– and Na+–HCO3 ? types. High molecular percentage of Na+, Cl?, SO4 2? and K? in NO3 ? rich groundwater indicates simultaneous contribution of many elements through domestic sewerage and agriculture activity. It is further confirmed by analogous ratios of commonly associated ions viz NO3 ?:Cl?:SO4 2? and NO3 ?:K+:Cl? which are 22:56:22 and 42:10:48, respectively. The F? rich groundwater is unique by having higher content of Na+ (183 %) and HCO3 ? (28 %) than safe waters. The K+:F?:Ca2+ ratio of 10:5:85 and K+:F?: SO4 2? of 16:7:77 support lithological origin of F? facilitated by precipitation of CaCO3 which removes Ca2+ from solution. The high concentrations of Na+, CO3 ? and HCO3 ? in these waters act as catalyst allowing more fluorite to dissolve into the groundwater. The indices, ratios and scatter plots indicate that the NO3 ? rich groundwater has evolved through silicate weathering-anthropogenic activity-evapotranspiration processes, whereas F? rich groundwater attained its unique chemistry from mineral dissolution-water–rock interaction-ion exchange. Both the waters are subjected to external infusion of certain elements such as Na+, Cl?, NO3 ? which are further aggravated by evaporation processes leading to heavy accumulation of contaminants by raising the water density. Presence of NO3 ? rich samples within F? rich groundwater Group and vice versa authenticates the proposed evolution processes.  相似文献   

9.
This study investigates the origin and chemical composition of the thermal waters of Platystomo and Smokovo areas in Central Greece as well as any possible relationships of them to the neighboring geothermal fields located in the south-eastern part of Sperchios basin. The correlations between different dissolved salts and the temperature indicate that the chemical composition of thermal waters are controlled by, the mineral dissolution and the temperature, the reactions due to CO2 that originates possibly by diffusion from the geothermal fields of Sperchios basin and the mixing of thermal waters with fresh groundwater from karst or shallow aquifers. Two major groups of waters are recognized on the basis of their chemistry: thermal waters of Na–HCO3–Cl type and thermal waters mixed with fresh groundwater of Ca–Mg–Na–HCO3 type. All thermal waters of the study area are considered as modified by water–rock interaction rainwater, heated in depth and mixed in some cases with fresh groundwater when arriving to the surface. Trace elements present low concentrations. Lithium content suggests discrimination between the above two groups of waters. Boron geochemistry confirms all the above remarks. Boron concentration ranges from 60 μg L?1 to 10 mg L?1, while all samples’ constant isotopic composition (δ11B ≈ 10 ‰) indicates leaching from rocks. The positive correlation between the chemical elements and the temperature clearly indicates that much of the dissolved salts are derived from water–rock interactions. The application of geothermometers suggests that the reservoir temperature is around 100–110 °C. Chalcedony temperatures are similar to the emergent temperatures and this is typical of convective waters in fault systems in normal thermal gradient areas.  相似文献   

10.
Caldas de Moledo thermal (27–46 °C) spring and borehole waters issue in the region of the famous Port Wine vineyards, in the Douro River valley (Northern Portugal). The most abundant lithotypes are lower Cambrian metasedimentary rocks, Variscan granitoids and aplite-pegmatitic veins. The thermal waters are characterised by pH ≈ 9.0, TDS ranging from 200 to 350 mg/L, and belong to the HCO3–Na facies indicating that the reservoir rock should be mainly granite. Since the local Spa is strongly dependent on water quality, the effects of mixing between local shallow cold groundwaters and deep thermal waters have been properly investigated. In the SO4 2? (mg/L) versus δ18O (‰ vs. V-SMOW) diagram we can observe that some of the thermal springs show evidences of mixing (higher SO4 2? concentrations) with local meteoric waters infiltrated at lower altitude sites (enriched δ18O signatures), showing the “altitude effect” in the isotopic composition of the recharge waters. Similar trends can be found in the K+, NO3 ?, Ca2+ and Na+ (mg/L) versus δ18O (‰ vs. V-SMOW) diagrams. It should be stated that SO4 2?, K+ and Ca2+ are present in the fertilizers and fungicides used in the vineyards in the northern part of the country. Up to now, the thermal waters from boreholes used in the local Spa do not show evidences of mixing with shallow groundwaters contaminated with agrochemicals. The results obtained so far indicate that in the near future, special attention should be put on the possible occurrence of diffuse agricultural contamination (related to the Port Wine vineyards) in the thermal spring waters.  相似文献   

11.
Groundwater of the unconfined aquifer (1,100 sq. km) of a two-tier coastal aquifer located in the Amol–Ghaemshahr plain, Mazandaran Province, Northern Iran, is classified into fresh and brackish water types. Fresh groundwater (FGW) samples (n = 36) are characterized by Ca2+ > Na+ > Mg2+ > K+ and HCO3 ? > Cl? > SO4 2? > NO3 ?. Spearman’s rank correlation coefficient matrices, factor analysis data, values of the C-ratio (av. = 0.89) and CAI and values of the molar ratios of Ca2+/HCO3 ?, Ca2+/SO4 2?, Mg2+/HCO3 ? and Mg2+/SO4 2? indicate that the ionic load in the FGW is derived essentially from carbonic acid-aided weathering of carbonates and aluminosilicates, saline/sea water trapped in the aquifer sediments (now admixed with the groundwater) and ion exchange reactions. Values of the CAI and Na+/Cl? molar ratio suggest that the part of the Ca2+ (±Mg2+) content in 23 FGW samples is derived from clay minerals of the aquifer matrix, and part of the Na+ content in 20, 12, and 3 FGW samples is derived, respectively, from alkali feldspar weathering, clay minerals of the aquifer matrix and rain water and/or halite. Brackish groundwater (BGW) samples (n = 4) contain Cl? as the dominant anion and their average total ionic concentration (38.65 meq/L) is 1.79 times higher than that of the FGW samples (21.50 meq/L). BGW pockets were generated by non-conservative mixing of FGW with the upconed saline water from the underlying saline groundwater zone of the semi-confined aquifer along bore wells involved in excessive extraction of groundwater from the unconfined aquifer. Groundwater belongs essentially to “high salinity, low sodium” irrigation water class.  相似文献   

12.
This paper summarizes a new outlook on the conceptual model of Melgaço–Messegães CO2-rich cold (≈18 °C) mineral water systems, issuing in N of Portugal, based on their isotopic (2H, 3H, 13C, 14C and 18O) and geochemical features. Stable isotopes indicate the meteoric origin of these CO2-rich mineral waters. Based on the isotopic fractionation with the altitude, a recharge altitude between 513 up to 740 m a.s.l. was estimated, corroborating the tritium results. The lowest 3H content (0 TU) is found in the groundwater samples with the highest mineralization. The mineral waters circulation are mainly related to a granitic and granodioritic environment inducing two different groundwater types (Ca/Na–HCO3 and Na/Ca–HCO3), indicating different underground flow paths. Calcium dissolution is controlled by hydrolysis of rock-matrix silicate minerals (e.g. Ca-plagioclases) and not associated to anthropogenic sources. The shallow dilute groundwaters exhibit signatures of anthropogenic origins (e.g. NO3) and higher Na/Ca ratios. The stable isotopes together with the geochemistry provided no indication of mixing between the regional shallow cold dilute groundwater and mineral water systems. The heavy isotopic signatures identified in the δ13C data (δ13C = 4.7 ‰, performed on the total dissolved inorganic carbon (TDIC) of CO2-rich mineral waters) could be derived from a deep-seated (upper mantle) source or associated to methanogenesis (CH4 source). The negligible 14C content (≈2 pmC) determined in the TDIC of the mineral waters, corroborates the hypothesis of a mantle-derived carbon source to the mineral groundwater systems or dissolution of carbonate layers at depth.  相似文献   

13.
Agricultural activities act as dominant polluter of groundwater due to increased fertilizers and pesticides usage. Bist-Doab region, Punjab, India, is one such region facing deterioration of groundwater quality due to usage of fertilizers. This study aims in delineating and evaluating the groundwater quality in the region. Water samples are collected from canals, reservoir, and shallow and deep groundwater. Water types in canal and reservoir in Kandi region are Mg2+HCO3 ? and Mg2+Ca2+Na+HCO3 ?, respectively. While water types of shallow and deep groundwaters are found to be of two types: Na+Mg2+Ca2+HCO3 ? and Ca2+Mg2+Na+HCO3 ?. Presence of Mg2+ in groundwater at locations adjoining canals indicates recharge due to canal. The major ion (Na+, Mg2+, Ca2+, HCO3 ?) chemistry of the region is due to weathering of rocks that are rich in sodic minerals and kankar. Deep groundwater quality in the region meets BIS and WHO standards for drinking purpose, unlike shallow groundwater which is of poor quality at many locations. Both shallow and deep groundwater with high sodium concentration (>1.5 meq/l) affect cropping yield and permeability of soil matrix. High concentration of SO4 2? and NO3 2? (>1 meq/l) in shallow groundwater at few locations indicates influence of anthropogenic (fertilizer) activity. Factor analysis indicates that the major cations, bicarbonate and chloride are derived from weathering/dissolution of source rocks. Higher concentration of nitrate and presence of sulphate in shallow groundwater at few locations is due to usage of fertilizers and pesticides.  相似文献   

14.
Hydrochemical and stable isotopes (18O and 2H) analyses of groundwater samples were employed to establish the origin of major dissolved ions in groundwater within the Lower Pra Basin. Results showed that, the major processes responsible for chemical evolution of groundwater include: silicate (SiO4)4? dissolutions, ion exchange reactions, sea aerosol spray and pyrite (FeS2) and arsenopyrite (FeAsS) oxidations. The groundwater is strongly acidic to neutral, with pH generally range from 3.5 to 7.0 pH units and mean 5.9 (±0.5). Approximately 89 % of boreholes had pH values outside the World Heath Organization (WHO, Guidelines for drinking water quality, 2004) guideline value for drinking water due principally to natural biogeochemical processes and therefore, not suitable for potable purposes. Electrical conductivity (EC) range from 57.6 to 1,201 μS/cm with mean 279.3 (±198.8) μS/cm. Total dissolved solids (TDS) range from 32 to 661 mg/L with mean 151.7 (±106.8) mg/L, with 98.6 % of groundwater as fresh (TDS < 500 mg/L). The chemical constituents generally have low concentrations and are within the WHO (Guidelines for drinking water quality, 2004) guideline value for drinking water. The relative abundance of cations and anions is in the order: Na+ > Ca2+> Mg2+ > K+ and HCO3 ? > Cl? > SO4 2?, respectively. A plot of ?18O ‰ against 2H ‰ showed that, ground and surface waters clustered on or closely along the Global Meteoric Water Line, suggesting that, the waters emanated principally from meteoric source with evaporation playing an insignificant role on the infiltrating water.  相似文献   

15.
The physicochemical properties and major ion chemistry of the groundwater sources from alluvial aquifers along the stretch (60 km) of Jhelum River in Kashmir Himalaya were determined in order to identify hydro-geochemical processes and their suitability for drinking purposes. The data depicted that calcium and bicarbonates were dominating among the cations and anions. The results indicate the trend of cation dominance as Ca2+ > Na+ > Mg2+ > K+, whereas anion dominance was in the order of HCO3 ? > Cl? > SO4 2?. Ratio of calcium to magnesium indicated the dissolution of Ca2+ from CaCO3, which results in an increased levels of Ca2+ in the groundwater. Interpretation of Piper Trilinear plot understands the various geochemical processes affecting the groundwater quality and shows groundwater was dominated by Ca–HCO3 type. The pH was recorded in the slightly alkalinity range 7.2–7.8 and was showing positive correlation with HCO3 ?. The chloro-alkaline indices revealed 86% of the sources exchange by a type of base-exchange reactions, rest by cation–anion exchange. Gibbs diagram revealed groundwater sources fall in the category of rock dominance. The concentration of the nitrogen compounds was in the progression of NO3–N > NH4–N > NO2–N, and the PO4 ? fluctuated from 0.12 to 0.22 mg/L. Moreover, corrosivity ratio indicated that water from the majority of sources (71%) is safe to supply using pipes without any corrosive effects, while 29% of sources are corrosive in nature and need non-corrosive pipes for transporting and lifting of groundwater. The results revealed, groundwater samples were within permissible limits as prescribed by International and National standards, for drinking purposes. The State government and NGO’s can show their interest in utilizing such water resources to overcome the shortage of drinking water in a sustainable way for the daily consumption of the people living in the vicinity of Jhelum River.  相似文献   

16.
Groundwater of an aquifer located in the vicinity of a large coal washery near Zarand City, Iran consists of two hydrochemically differing facies, which have been informally designated as groundwater (A) and groundwater (B). Groundwater (A) is native, brackish in composition and is characterized by Na+ > Mg2+ > Ca2+ > K+ and SO4 2? > HCO3 ? > Cl? > NO3 ?. Spearman’s rank correlation coefficient matrices, factor analysis data, and values of chloro-alkaline indices, C ratio and Na+/Cl? molar ratio indicate that in the groundwater (A), the ionic load of Ca2+, Mg2+, Na+, K+, SO4 2? and HCO3 ? is derived essentially from weathering of both carbonates and aluminosilicates and direct cation and reverse cation–anion exchange reactions. Groundwater (B) is the polluted variant of the groundwater (A), brackish to saline in composition, and unlike the groundwater (A), consists of HCO3 ? as the dominant anion. In comparison with the groundwater (A), the groundwater (B) contains higher concentrations of all ions, and its average ionic load (av. = 59.74 me/L) is 1.43 times higher than that of the groundwater (A) (av. = 41.54 me/L). Additional concentrations of Ca2+, Mg2+, K+, SO4 2?, Cl? and HCO3 ? in the groundwater (B) are provided mainly by downward infiltrating water from the coal washery tailings pond and reverse cation–anion exchange reaction between tailings pond water and exchanger of the aquifer matrix during non-conservative mixing process of groundwater (A) and tailings pond water. Certain additional concentrations of Na+, K+ and NO3 ? in the groundwater (B) are provided by other anthropogenic sources. Quality wise, both groundwaters are marginally suitable for cultivation of salt-tolerant crops only.  相似文献   

17.
The Cuatrociénegas area is useful for the investigation of the effect of groundwater extraction in the Chihuahuan freshwater xeric ecoregion. It has been investigated at this time using a selection of geochemical indicators (major, minor and trace elements) and δ34S data, to characterize the origin of groundwater, the main geochemical processes and the mineral/groundwater interactions controlling the baseline geochemistry. The area is composed of limestones of Mesozoic age, with a composite thickness of about 500 m, overlaid by basin fill (poorly consolidated young sediments). Substantial water extraction and modification of natural discharges from the area along the last century have produced a detrimental impact on ecosystem structure and function. Water–rock interactions, mixing and evaporative processes dominate the baseline groundwater quality. Natural recharge is HCO3–Ca type in equilibrium with calcite, low salinity (TDS?<?500 mg/L), Cl? lower than 11 mg/L and average Li+ concentration of 0.005 mg/L. Along the groundwater flow systems, δ34S evidence and mass transfer calculations indicate that Cretaceous gypsum dissolution and dedolomitization reactions adjust water composition to the SO4–Ca type. The increase of water–rock interaction is reflected by Cl? values increase (average 68 mg/L), TDS up to about 1500 mg/L and an average Li+ concentration of 0.063 mg/L. Calculations with chemical geothermometers indicate that temperature at depth could be at maximum of 15–20 °C higher than field-measured temperature for pozas. After groundwater is discharged to the surface, chemical evolution continues; water evaporation, CO2 degassing and precipitation of minerals such as gypsum, calcite and kaolinite represent the final processes and reactions controlling water chemical composition.  相似文献   

18.
Quality assessment as well as hydrogeochemical characterization of 45 representative groundwater samples around Umrer coal mine area was undertaken. The pH of the water lies in the normal range i.e. from 7.5 to 8.5, the electrical conductivity varies from 826 to 1,741, the total hardness varies from 289 to 1,302 and the TDS values range from 528.6 to 1,114.2 mg/l which reflects variation in lithology and thus, the distinction in hydrogeological regime. The cation chemistry is dominated by Ca2+ and Mg2+ while anion chemistry is dominated by Cl? and HCO3 ?. Out of total ten hydrochemical facies, the two dominant facies are Mg–Ca–HCO3 (37.7 %) and Ca–Mg–SO4–HCO3 (17.7 %). The groundwater in the study area, in general, is useful for drinking and domestic use; however, it has marginal utility for irrigation purpose. Standard US Salinity Laboratory classification shows that water of the study area belongs to C2–S1 and C3–S1 classes. The concentration of 9 trace elements analysed from 18 samples did not exceed the desirable limit.  相似文献   

19.
李状  苏晶文  董长春  叶永红  杨洋 《中国地质》2022,49(5):1509-1526
【研究目的】 了解长江中下游平原地区地下水流系统并深入分析其地下水水化学特征及其演化机制。【研究方法】 综合马鞍山市当涂地区的水文地质条件、水动力场等,基于研究区水化学基本特征,运用多元统计分析、水化学图件、离子比值和反向水文地球化学模拟等方法对该地区浅层地下水水化学演化进行分析。【研究结果】 结果表明：（1）研究区地下水主要为低矿化度偏碱性水,地下水组分中阳离子以Ca2+和Mg2+为主,阴离子以HCO3-和SO42-为主。（2）研究区地下水水化学类型主要可分为7类,其中松散岩类孔隙含水岩组和碎屑岩类孔隙裂隙含水岩组的水化学类型主要为HCO3-Ca型、HCO3-Ca·Na型、HCO3·Cl-Ca·Na型以及HCO3-Ca·Mg型;基岩类裂隙含水岩组的化学类型主要为HCO3·SO4-Ca·Mg型和SO4·HCO3-Ca·Mg型。（3）研究区浅层地下水水样超标率为46%,总体水质较差,超标率较高的组分依次为Mn、高锰酸盐指数（CODMn）、硝酸盐（以N计）、Fe、As、氨氮（以N计）等。（4）研究区地下水的化学组分主要受到岩石风化作用的控制;此外,还存在Na-Ca的正向阳离子交替吸附作用。反向水文地球化学模拟结果进一步定量论证了水岩相互作用对本区浅层地下水组分的形成和演化起着主导作用。【结论】 研究区地下水主要为低矿化度偏碱性,主要可分为松散岩类孔隙水、碎屑岩类孔隙裂隙水和基岩类裂隙水。主要离子比例和反向水文地球化学模拟揭示了本区浅层地下水化学组分主要是地下水溶滤方解石、白云石等碳酸盐矿物、石英、长石等硅酸盐矿物,高岭土等黏土矿物以及岩盐、石膏等达到过饱和之后形成的。  相似文献   

20.
The Vea catchment, mainly underlain by crystalline basement rocks, is located in Northern Ghana. Hydrogeochemical studies were carried out in this area with the objective of identifying the geochemical processes influencing water quality and suitability of surface and groundwater for agricultural and domestic uses. Sixty-one groundwater and four surface water samples were collected from boreholes, dams and rivers and analysed for Ca2+, Mg2+, Na+, K+, HCO3 ?, Cl?, and SO4 2?, Fetot, PO4 3?, Mntot, NH4 +, NO3 ?, NO2 ?. In addition, pH, total dissolved solids, electrical conductivity, total hardness, turbidity, colour, salinity and dissolved oxygen were analysed. Chloro-alkaline indices 1 and 2, and characterization of weathering processes suggest that the chemistry of groundwater is dominated by the interaction between water and rocks. Cation exchange and silicate weathering are the dominant processes controlling the chemical composition of the groundwater in the area studied. Mineral saturation indices indicate the presence of at least three groups of groundwater in the Vea catchment with respect to residence time. The meteoric genesis index suggests that 86% of the water samples belong to the shallow meteoric water percolation type. The findings further suggest that the groundwater and surface water in the basin studied are mainly Ca–Mg–HCO3 water type, regardless of the geology. Compared to the water quality guidelines of WHO, the study results on sodium absorption ratio, sodium percentage, magnesium hazard, permeability index and residual sodium carbonate indicate that groundwater and surface water in the Vea catchment are generally suitable for drinking and irrigation purposes.  相似文献   

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