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1.
Groundwater in Farashband plain, Southern Iran, is the main source of water for domestic and agricultural uses. This study was carried out to assess the overall water quality and identify major variables affecting the groundwater quality in Farashband plain. The hydrochemical study was undertaken by randomly collecting 84 groundwater samples from observation wells located in 13 different stations covering the entire plain in order to assess the quality of the groundwater through analysis of major ions. The water samples were analyzed for various physicochemical attributes. Groundwater is slightly alkaline and largely varies in chemical composition; e.g., electrical conductivity (EC) ranges from 2314 to 12,678 μS/cm. All the samples have total dissolved solid values above the desirable limit and belong to a very hard type. The abundance of the major ions is as follows: Na+ > Ca2+ > Ma2+ > K+ and Cl? > SO4 2– > HCO3 ?. Interpretation of analytical data shows three major hydrochemical facies (Ca–Cl, Na–Cl, and mixed Ca–Mg–Cl) in the study area. Salinity, total dissolved solids, total hardness, and sodium percentage (Na%) indicate that most of the groundwater samples are not suitable for irrigation as well as for domestic purposes and far from drinking water standard. A comparison of groundwater quality in relation to drinking water standards showed that most of the water samples are not suitable for drinking purposes. Based on the US salinity diagram, most of samples belong to high salinity and low to very high sodium type.  相似文献   

2.
The valley plain of Lhasa City is located on the Qinghai-Tibetan Plateau, which is one of the most developed and densely populated areas in Tibet. Groundwater is an important water supply source and plays an irreplaceable role in the social and economic development of Lhasa City. This study has investigated the dynamic characteristics of groundwater in the valley plain of Lhasa City through the methods of mathematical statistics and hydrochemical analysis. The results showed that local topography, climate, and urbanization substantially influenced the groundwater dynamics. Under the combined influences from urbanization and climate, the groundwater level decreased over three time periods, but the groundwater-level configuration has not shown significant changes in over 15 years. From 1997 to 2015, the hydrochemical type of groundwater has changed from HCO3–Ca to HCO3·SO4–Ca·Mg and HCO3·SO4–Ca. The concentrations of Cl?, Mg2+, and SO42? in groundwater increased, but the concentrations of other ions were relatively stable. Water–rock interaction was the main mechanism controlling the groundwater chemistry in the study area, and it was mainly associated with the dissolution of silicate, carbonate, and halite.  相似文献   

3.
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   

4.
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   

5.
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   

6.
Groundwater hydrochemistry could reveal the interaction mechanism between groundwater and the environment, which provides a scientific basis for environmental resources management. In this study, Shukaliefu’s classification method and Piper diagram were adopted to determine the hydrochemical types of groundwater in the Tarim Basin of Xinjiang, China. The method of “one-vote veto” was applied to evaluate the quality of groundwater. Phreeqc software was used to calculate the saturation indices of calcite and fluorite in groundwater. By comparing groundwater quality data of 2003 and 2011, we characterized the variations in hydrochemical types and water quality types, salinization of groundwater and fluoride geochemistry of the plain area of the Tarim Basin. Results show that the primary anion in phreatic water in the plain area of the Tarim Basin changed from HCO3 ? to SO4 2? or Cl?. On the contrary, the primary anion in confined water changed from SO4 2? or Cl? to HCO3 ?. In 2003, 63.1 % of the sampling points in the study area exceeded the Class III water quality standard of China. In 2011, the proportion increased to 82.5 %. In addition, severe groundwater salinization was found at 19.7 % of the sampling points. Some of the deep groundwater samples were salinized as well. In the Aksu area at the north-west part of the Tarim Basin, F? concentration exceeding the standard limit (1 mg/L) was found to be 55.0 % of the groundwater samples tested. Based on these findings, it is concluded that the phreatic water in the study area was severely influenced by the industrial wastewater and domestic sewage related to human activities, while the confined water was less affected. The general quality of groundwater was in an aggravation trend, and the groundwater salinization was in a severe condition in this area. The Ca2+–Na+ ionic exchange, the unsaturated fluorite and oversaturated calcite in the aquifer of the Aksu area are proposed to cause F? enrichment in groundwater of this area.  相似文献   

7.
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   

8.
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9.
Groundwater is the most important source of water supply in Iran and understanding the geochemical evolution of groundwater is important for sustainable development of the water resources in Tabas area. A total of 29 samples of groundwater in Tabas area have been analyzed for ions and major elements. Groundwater of the study area is characterized by the dominance of Na–Cl water type. Groundwater was generally acidic to high alkaline with pH ranging from 5.42 to 10.75. The TDS as a function of mineralization characteristics of the groundwater ranged from 479 to 10,957 mg/l, with a mean value of 2,759 mg/l. The Ca2+, Mg2+, SO4 2? and HCO3 ? were mainly derived from the dissolution of calcite, dolomite and gypsum. The Cu, Pb and Zn ions are not mobile in recent pH–Eh, but these conditions controlled dissolved Se, V and Mo in groundwater. The As is released in groundwater as a result of the weathering of sulfide minerals like arsenopyrite.  相似文献   

10.
Groundwater is crucial for multiple uses over the world, especially in arid and semiarid regions. However, human activities significantly decreased groundwater quality. In this study, the spatiotemporal variation of groundwater quality was evaluated in an arid area where long-term paper wastewater irrigation has been implemented. For this study, seven wells were regularly monitored for physicochemical parameters over a period of 1 year. Statistical and graphical approaches were applied to interpret the spatiotemporal variation of groundwater quality parameters in the wastewater irrigation zone. Correlation analysis was also carried out to reveal the sources of some major ions. The results indicate that the groundwater type in the study area is dominated by the Cl–Na, followed by the HCO3–Na, the HCO3–Ca·Mg, and the SO4·Cl–Ca·Mg types. Groundwater in the area is significantly contaminated locally with fluoride, nitrite and ammonia, and the chemical oxygen demand levels were increased in some groundwater monitoring wells. Most contaminants showed an increasing trend from the Yellow River water irrigation zone toward the wastewater irrigation zone. Rock weathering, mineral dissolution, and cation exchange are important processes controlling groundwater quality, but human activities, such as wastewater irrigation, play an undeniable role in affecting groundwater quality in this area. The results of this study contribute to the understanding of the formation and circulation of groundwater under human activities and provide a scientific basis for regional water quality evaluation, water quality improvement, and protection.  相似文献   

11.
The demand for water is rapidly increasing in Egypt, because of high population and agriculture production growth rate, which makes research of water resources necessary. The regional multi-aquifer system of the Miocene–Pleistocene age is discharged in Wadi El Natrun area. Intensive aquifer overexploitation and agricultural development in the area are related to groundwater quality deterioration. Hydrochemical and hydrogeological data was evaluated to determine the groundwater origin and quality in the south-eastern part of wadi, which appears to be more significant for water supply owing to lower groundwater salinity. The dominance of the high mineralised Cl groundwater type was found; however, also less mineralised SO4 and HCO3 types were identified there. Based on the ion relations, halite and gypsum dissolution and ion exchange are the most important hydrochemical processes forming the groundwater chemical composition. The Cl dominated groundwater matches the discharge part of the regional hydrogeological system. Contrary, the presence of HCO3 and SO4 hydrochemical types corresponds to the infiltration and transferring parts of the hydrogeological system indicating the presence of zones conducting low mineralised groundwater. The discharge area of the over-pumped aquifer in Wadi El-Natrun lies 23 m beneath the sea level with the shoreline being at the distance of 100 km, thus there is a real risk of seawater intrusion. Using the hydrochemical facies evolution diagram, four samples in the centre of the discharge area indicate advanced seawater intrusion. The zones of the highest demand for groundwater quality protection were indicated based on a spatial pattern of hydrogeochemical composition.  相似文献   

12.
The present work was carried out in Nalbari district of Assam (India) with an objective to assess the quality of groundwater and to check its suitability for drinking and irrigation purposes. Groundwater samples were collected from 50 different locations during pre- and post-monsoon seasons of 2016. Results of chemical analysis revealed that mean concentration of cations varied in the order Ca2+?>?Na+?>?Mg2+?>?K+, while for anions the order was HCO3 ??>?Cl??>?SO42??>?NO32??>?F? during both pre- and post-monsoon seasons. The suitability of groundwater samples for drinking purpose was assessed by comparing the results of physico-chemical analysis of groundwater with Indian Standards. Further, its suitability for irrigation purpose was assessed by evaluating several parameters like sodium adsorption ratio (SAR), sodium percentage (Na%), magnesium ratio, Kelly’s ratio and residual sodium carbonate (RSC). The SAR values obtained for all the samples were plotted against EC values in the US Salinity Laboratory diagram, and it was revealed that the most of the samples fall under water type C2-S1 indicating medium salinity and low SAR. Further, it was found that the majority of the samples belong to Ca–Mg–HCO3 hydrochemical facies followed by Ca–Mg–Cl–SO4, whereas only a few samples belong to Na–K–HCO3 hydrochemical facies.  相似文献   

13.
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   

14.
Correct identification of water inrush sources is particularly important to prevent and control mine water disasters. Hydrochemical analysis, Fisher discriminant analysis, and geothermal verification analysis were used to identify and verify the water sources of the multi‐aquifer groundwater system in Gubei coal mine, Anhui Province, North China. Results show that hydrochemical water types of the Cenozoic top aquifer included HCO3–Na+K–Ca, HCO3–Na+K–Mg and HCO3–Na+K, and this aquifer was easily distinguishable from other aquifers because of its low concentration of Na++K+ and Cl–. The Cenozoic middle and bottom aquifers, the Permian fissure aquifer, and the Taiyuan and Ordovician limestone aquifers were mainly characterized by the Cl–Na+K and SO4–Cl‐Na+K or HCO3–Cl–Na+K water types, and their hydrogeochemistries were similar. Therefore, water sources could not be identified via hydrochemical analysis. Fisher model was established based on the hydrogeochemical characteristics, and its discrimination rate was 89.19%. Fisher discrimination results were improved by combining them with the geothermal analysis results, and this combination increased the identification rate to 97.3 % and reasonably explained the reasons behind two water samples misjudgments. The methods described herein are also applicable to other mines with similar geological and hydrogeological conditions in North China.  相似文献   

15.
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   

16.
The study area, the Fasa Plain, is situated in the semiarid region of Fars Province in the south of Iran. The Salloo diapir is a salt dome that crops out in the northwest of the study area. Isotopic and hydrochemical analyses were used to examine the water and how the origin of salinity and the diapir affect the quality of the groundwater quality in the study area. Groundwater was sampled from 31 representative pumping wells in alluvial aquifer and five springs in order to measure their stable isotope compositions, bromide ion concentration, and physical and chemical parameters. The alluvial aquifer was organized into two main groups based on the chemistry, with Group 1 consisting of low-salinity well samples (544–1744 µS/cm) with water type Ca–Mg–HCO3–SO4 which were taken in the center and north of the area, and Group 2 consisting of high-salinity samples (2550–4620 µS/cm) with water type Ca–Mg–Cl–SO4 which were taken from the wells in the south and southwest of the area. A saline spring near the salt dome with an EC of 10,280 µS/cm has water type Na–Cl, while the compositions of the water in the other karstic springs is comparable to the fresh groundwater samples. All groundwater samples are undersaturated with respect to gypsum, anhydrite, and halite and are supersaturated with respect to calcite and dolomite. Stable isotopes (δ18O and δ2H) differentiated four water types: saline springs, freshwater spring, fresh groundwater, and saline groundwater. The results indicate that meteoric water is the main origin of these water resources. Halite dissolution from the salt dome was identified as the origin of salinity. The Na/Cl and Cl/Br ratios confirmed the results. Groundwater compositions in the southwestern part of the area are affected by the intrusion of saltwater from the salt dome. The average saltwater fraction in the some water wells is about 0.2%. In the south and southwestern part of the area, the saltwater fraction is positive in mixed freshwater/saltwater (Group 2). Different processes interact together to change the hydrochemical properties of Fasa’s alluvial aquifer. The main processes that occur in the aquifer are mixing, gypsum dissolution, and calcite precipitation.  相似文献   

17.
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   

18.
Hydrogeochemical investigation of groundwater has been carried out in the coastal aquifers of southern Tamil Nadu, India. Seventy-nine dug well samples were collected and analyzed for various physicochemical parameters. The result of the geochemical analysis indicates the groundwater in the study area is slightly alkaline with moderate saline water. The cation and anion concentrations confirm most of the groundwater samples belong to the order of Na+ > Mg2+ > Ca2+ > K+ and Cl? > SO4 2? > HCO3 ?. Thereby three major hydrochemical facies (Ca–Cl, mixed Ca–Mg–Cl and Na–Cl) were identified. Based on the US Salinity diagram, majority of the samples fall under medium to very high salinity with low to high sodium hazard. The cross plot of Ca2+ + Mg2+ versus chloride shows 61 % of the samples fall under saline water category. Higher EC, TDS and Cl concentrations were observed from Tiruchendur to Koodankulam coastal zone. It indicates that these regions are significantly affected by saltwater contamination due to seawater intrusion, saltpan deposits, and beach placer mining activities.  相似文献   

19.
In this study, hydrochemical and isotope investigations were conducted in the Yanqi Basin to determine the chemical composition, and to gain insight into the groundwater recharge process in the Yanqi Basin. It mainly used hydrochemistry, environmental isotopes, and a series of comprehensive data interpretation, e.g., statistics, ionic ratios, and Piper diagram to obtain a better understanding of the functioning of the system. The following hydrochemical processes were identified as the main factors controlling the water quality of the groundwater system: weathering of silicate minerals, dissolution, ion exchange, and to a lesser extent, evaporation, which seemed to be more pronounced down gradient of the flow system. As groundwater flows from the recharge to discharge areas, chemical patterns evolve in the order of Ca2+–HCO3 ?, Ca2+/Mg2+–HCO3 ? to Ca2+–Mg2+–Cl?–SO4 2?, Na+–K+–Cl?–SO4 2? and Na+–Cl? according to lithology. The environmental isotope (δ 18O, δ 2H, 3H) measurements further revealed that precipitation was the main recharge source for the groundwater system; some local values indicated high levels of evaporation. Tritium and CFC analysis were used to estimate the ages of the different groundwater; the tritium values of the groundwater samples varied from 2.82 to 29.7 TU. The age of the groundwater at depths of <120 m is about 30–50 years. CFC values obtained for six samples to determine groundwater age; the age of the groundwater is about 20–50 years.  相似文献   

20.
Groundwater from karst subterranean streams is among the world’s most important sources of drinking water supplies, and the hydrochemical characteristics of karst water are impacted by both natural environment and people. Therefore, the study of hydrochemistry and its solutes’ sources is very important to ensure the normal function of life support systems. In this paper, thirty?five representative karst groundwater samples were collected from different aquifers (limestone and dolomite) and various land use types in Chongqing to trace the sources of solutes and relative hydrochemical processes. Hydrogeochemical types of karst groundwater in Chongqing were mainly of the Ca?HCO3 type or Ca (Mg)?HCO3 type. However, some hydrochemical types of karst groundwater were the K+Na+Ca?SO4 type (G25 site) or Ca?HCO3+SO4 type (G26 and G14 site), indicating that the hydrochemistry of these sites might be strongly influenced by anthropogenic activities or unique geological characteristics. The dissolved Sr concentrations of the studied groundwater ranged from 0.57 to 15.06 μmmol/L, and the 87Sr/86Sr varied from 0.70751 to 0.71627. The δ34S?SO42? fell into a range of ?6.8‰?21.5‰, with a mean value of 5.6‰. The variations of both 87Sr/86Sr and Sr values of the groundwater samples indicated that the Sr element was controlled by the weathering of limestone, dolomite and silicate rock. However, the figure of 87Sr/86Sr vs. Sr2+/[K++Na+] showed that the anthropogenic inputs also obviously contributed to the Sr contents. For tracing the detailed anthropogenic effects, we traced the sources of solutes collected karst groundwater samples in Chongqing according to the δ34S value of potential sulfate sources. The variations of both δ34S and 1/SO42? values of the groundwater samples indicated that the atmospheric acid deposition (AAD), dissolution of gypsum (GD), oxidation of sul?de mineral (OS) or anthropogenic inputs (SF: sewage or fertilizer) have contributed to solutes in karst groundwater. The influence of oxidation of sul?de mineral, atmospheric acid deposit and anthropogenic inputs to groundwater in Chongqing karst areas was much widespread.  相似文献   

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