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1.
Samir Kamel 《Environmental Earth Sciences》2011,63(1):189-199
The hydrodynamic groundwater data and stable isotopes of water have been used jointly for better understanding of upward leakage
and mixing processes in the Djerid aquifer system (southwestern Tunisia). The aquifer system is composed of the upper unconfined
Plio-Quaternary (PQ) aquifer, the intermediate (semi-)confined Complex Terminal (CT) aquifer and the deeper confined Continental
Intercalaire (CI) aquifer. A total of 41 groundwater samples from the CT and PQ aquifers were collected during June 2001.
The stable isotope composition of waters establishes that the CT deep groundwater (depleted as compared to present Nefta local
rainfall) is ancient water recharged during late Quaternary time. The relatively recent water in the shallow PQ aquifer is
composed of mixed water resulting from upward leakage and sporadic meteoric recharge. In order to characterize the meteoric
input signal for PQ in the study area, rainfall water samples were collected during 4 years (2000–2003) at the Nefta meteorological
station. Weighted mean values of isotopic contents with respect to rainfall amounts have been computed. Despite the short
collection period in the study area, results agree with those found in Beni Abbes (southwestern Algerian Sahara) by Fontes
on 9 years of rainfall surveillance. Stable isotopic relationships provide clear evidence of shallow PQ aquifer replenishment
by deep CT groundwater. The 18O/upward leakage rate allowed the identification of distinctive PQ waters related to CT aquifer configuration (confined in
the western part of the study area, semi-permeable in the eastern part). These trends were confirmed by the relation 18O/TDS. The isotope balance model indicated a contribution of up to 75% of the deep CT groundwater to the upper PQ aquifer
in the western study area, between Nefta and Hazoua. 相似文献
2.
Geochemical and isotopic characterization of groundwater from shallow and deep limestone aquifers system of Aleppo basin (north Syria) 总被引:2,自引:2,他引:0
A. Al-Charideh 《Environmental Earth Sciences》2012,65(4):1157-1168
Stable isotopes (δ18O, δ2H and 13C) and radioactivity (3H, 14C) have been used in conjunction with chemical data to evaluate the processes generating the chemical composition, reconstruct
the origin of the water and groundwater residence time. The Aleppo basin is comprised of two main limestone aquifers: the
first one is unconfined of Paleogene age and the second is confined of Upper Cretaceous age. The chemical data indicate that
the dissolution of minerals and evaporation are the main processes controlling groundwater mineralization. The groundwater
from the two aquifers is characterized by distinctive stable isotope signatures. This difference in water isotopes is interpreted
in terms of difference origin and recharge period. Fresh and brackish shallow groundwater were mostly recharged during the
Holocene period. The presence of 3H in several groundwater samples of this aquifer gives evidence that groundwater recharge is going on. Brackish water of the
deep confined aquifer has depleted stable isotope composition and very low 14C activity that indicates recharge during the late Pleistocene cold period. 相似文献
3.
The integrated impacts of natural processes and human activities on groundwater salinization in the coastal aquifers of Beihai,southern China 总被引:1,自引:0,他引:1
Salinization in coastal aquifers is usually related to both seawater intrusion and water–rock interaction. The results of chemical and isotopic methods were combined to identify the origin and processes of groundwater salinization in Daguansha area of Beihai, southern China. The concentrations of the major ions that dominate in seawater (Cl?, Na+, Ca2+, Mg2+ and SO 4 2– ), as well as the isotopic content and ratios (2H, 18O, 87Sr/86Sr and 13C), suggest that the salinization occurring in the aquifer of the coastal plain is related to seawater and that the prevailing hydrochemical processes are evaporation, mixing, dissolution and ion exchange. For the unconfined aquifer, groundwater salinization has occurred in an area that is significantly influenced by land-based sea farming. The integrated impacts of seawater intrusion from the Beibuwan Gulf and infiltration of seawater from the culture ponds are identified in the shallowest confined aquifer (I) in the middle of the area (site BBW2). Leakage from this polluted confined aquifer causes the salinization of groundwater in the underlying confined aquifer (II). At the coastal monitoring site (BBW3), confined aquifer I and lower confined aquifer II are heavily contaminated by seawater intrusion. The weak connectivity between the upper aquifers, and the seaward movement of freshwater, prevents saltwater from encroaching the deepest confined aquifer (III). A conceptual model is presented. Above all, understanding of the origin and processes of groundwater salinization will provide essential information for the planning and sustainable management of groundwater resources in this region. 相似文献
4.
Total dissolved inorganic carbon (TDIC) and its stable isotope ratio δ13CTDIC are used to trace the evolution of the carbon system of groundwater in three UK Permo-Triassic sandstone aquifers. Samples
were collected from multilevel piezometers, open boreholes and sewer sampling points in the British Midlands (Nottingham,
Birmingham and Doncaster) to evaluate both local and regional variations in δ13CTDIC. δ13C samples of matrix and pore water have also been analysed in each aquifer to further constrain the interpretations. Combining
δ13CTDIC ratios with measurements of TDIC and pH clearly distinguishes the principal processes underlying the geochemical evolution
of groundwater in Triassic sandstone aquifers, where processes can be both natural (e.g. carbonate dissolution) and anthropogenic
(sewer-derived recharge). The paper shows that δ13CTDIC resolves ambiguities that arise from the interpretation of TDIC and pH measurements in isolation. Field measurements demonstrate
that, under natural conditions, the carbonate system evolves similarly in each aquifer. An open-system evolution during recharge
largely saturates the groundwater with carbonate depending upon its availability in the sandstone matrix. The contribution
of sewer exfiltration to urban recharge is readily distinguished by lower pH and higher TDIC values without significant changes
in δ13CTDIC. 相似文献
5.
Galip Yuce 《Environmental Geology》2007,51(5):857-868
The aim of this study was to determine geochemical properties of groundwater and thermal water in the Misli Basin and to assess
thermal water intrusion into shallow groundwater due to over-extraction. According to isotope and hydrochemical analyses results,
sampled waters can be divided into three groups: cold, thermal, and mixed waters. Only a few waters reach water–rock chemical
equilibrium. Thermal waters in the area are characterized by Na+–Cl−–HCO3−, while the cold waters by CaHCO3 facies. On the basis of isotope results, thermal waters in the Misli basin are meteoric origin. In particular, δ18O and δ2H values of shallow groundwater vary from −10.2 to −12.2‰ and −71.2 to −82‰, while those of thermal waters range from −7.8
to −10.1‰ and from −67 to −74‰, respectively. The tritium values of shallow groundwater having short circulation as young
waters coming from wells that range from 30 to 70 m in depth vary from 10 to 14 TU. The average tritium activity of groundwater
in depths more than 100 m is 1.59 ± 1.16, which indicates long circulation. The rapid infiltration of the precipitation, the
recycling of the evaporated irrigation water, the influence of thermal fluids and the heterogeneity of the aquifer make it
difficult to determine groundwater quality changes in the Misli Basin. Obtained results show that further lowering of the
groundwater table by over-consumption will cause further intrusion of thermal water which resulted in high mineral content
into the fresh groundwater aquifer. Because of this phenomenon, the concentrations of some chemical components which impairs
water quality in terms of irrigation purposes in shallow groundwaters, such as Na+, B, and Cl−, are highy probably expected to increase in time. 相似文献
6.
Recharge rate estimation in the Mountain karst aquifer system of Figeh spring, Syria 总被引:3,自引:1,他引:2
A. Al-Charideh 《Environmental Earth Sciences》2012,65(4):1169-1178
Figeh watershed spring is one of the important groundwater aquifer, which is considered a major source for drinking waters
of Damascus city and countryside. The origin identification and recharge estimates of groundwater are significant components
of sustainable groundwater development in this Mountain karst aquifer of Figeh spring. During the period 2001–2009, monthly
groundwater and precipitation samples were taken and the isotopic compositions of δ18O, δ2H, and chloride contents were analyzed to identify groundwater origins and to estimate recharge rates. The δ18O, δ2H of the groundwater show that the groundwater recharge is of meteoric origin. The chloride mass balance (CMB) method was
used to quantify recharge rates of groundwater in the Mountain karst aquifer of Figeh spring. The recharge rate varies from
192 to 826 mm/year, which corresponds to 43 and 67% of the total annual rainfall. Recharge rates estimated by CMB were compared
with values obtained from other methods and were found to be in good agreement. This study can be used to develop effective
programs for groundwater management and development. 相似文献
7.
Marco Petitta Paolo Primavera Paola Tuccimei Ramon Aravena 《Environmental Earth Sciences》2011,63(1):11-30
Hydro- and isotope geochemistry are used to refine groundwater conceptual models in two areas of central Italy (Acque Albule
Basin and Velino River Valley) affected by extensional Quaternary tectonics, where deep and shallow groundwater flow systems
are interacting. The role of geology, of recent deposits filling the plains and of main tectonic features controlling groundwater
flowpaths and deep-seated fluids emergences are investigated and discussed. Environmental isotopes (2H and 18O) confirm recharge in the surrounding carbonate aquifers, and meteoric origin of both shallow and deep groundwater. Major
ion chemistry indicates a mixing between shallow Ca-HCO3 groundwater from carbonate aquifers and deep Ca-HCO3-SO4 groundwater, characterised by higher salinity and temperature and high concentration in sulphates. Isotopic composition of
dissolved sulphates (δ
34S and δ
18O) and dissolved inorganic carbon (δ
13C), henceforth indicated as DIC, are used to verify the presence of different sources of groundwater, and to validate the
mixing model suggested by the major ion analyses. Sulphate isotope composition suggests a marine origin for the groundwater
characterised by elevated sulphate concentration, whose source is present in the deep buried sequences. Carbon isotope composition
confirms the role of a DIC source associated to CO2 degassing of a deep reservoir. Groundwater conceptual models are improved underlining the importance of Plio-Pleistocene
sequences filling the tectonic depression. In the Acque Albule area, the travertine plateau represents a mixing stratified
aquifer, where deep groundwater contribution is spread into the shallow aquifer. The alluvial–clastic–lacustrine leaky aquifer
of Velino Valley enables a complete mixing of shallow and deep groundwater allowing spot-located discharge of deep groundwater
along tectonic patterns and facilitating sulphate reduction in the lacustrine sediments, explaining locally the presence of
H2S. 相似文献
8.
Hydrochemical characteristics and salinity of groundwater in the Ejina Basin, Northwestern China 总被引:8,自引:0,他引:8
A hydrochemical investigation was conducted in the Ejina Basin to identify the hydrochemical characteristics and the salinity
of groundwater. The results indicate that groundwater in the area is brackish and are significantly zonation in salinity and
water types from the recharge area to the discharge area. The ionic ration plot and saturation index (SI) calculation suggest
that the silicate rock weathering and evaporation deposition are the dominant processes that determine the major ionic composition
in the study area. Most of the stable isotope δ18O and δD compositions in the groundwater is a meteoric water feature, indicating that the groundwater mainly sources from
meteoric water and most groundwater undergoes a long history of evaporation. Based on radioactive isotope tritium (3H) analysis, the groundwater ages were approximately estimated in different aquifers. The groundwater age ranges from less
than 5 years, between 5 years and 50 years, and more than 50 years. Within 1 km of the river water influence zone, the groundwater
recharges from recent Heihe river water and the groundwater age is about less than 5 years in shallow aquifer. From 1 km to
10 km of the river water influence zone, the groundwater sources from the mixture waters and the groundwater age is between
5 years and 50 years in shallow aquifer. The groundwater age is more than 50 years in deep confined aquifer. 相似文献
9.
Evaluation of groundwater dynamics and quality in the Najd aquifers located in the Sultanate of Oman
K. Al-Mashaikhi S. Oswald S. Attinger G. Büchel K. Knöller G. Strauch 《Environmental Earth Sciences》2012,66(4):1195-1211
The Najd, Oman, is located in one of the most arid environments in the world. The groundwater in this region is occurring in four different aquifers A to D of the Hadhramaut Group consisting mainly of different types of limestone and dolomite. The quality of the groundwater is dominated by the major ions sodium, calcium, magnesium, sulphate, and chloride, but the hydrochemical character is varying among the four aquifers. Mineralization within the separate aquifers increases along the groundwater flow direction from south to north-northeast up to high saline sodium-chloride water in aquifer D in the northeast area of the Najd. Environmental isotope analyses of hydrogen and oxygen were conducted to monitor the groundwater dynamics and to evaluate the recharge conditions of groundwater into the Najd aquifers. Results suggest an earlier recharge into these aquifers as well as ongoing recharge takes place in the region down to present day. Mixing of modern and submodern waters was detected by water isotopes in aquifer D in the mountain chain (Jabal) area and along the northern side of the mountain range. In addition, δ2H and δ18O variations suggest that aquifers A, B, and C are assumed to be connected by faults and fractures, and interaction between the aquifers may occur. Low tritium concentrations support the mixing assumption in the recharge area. The knowledge about the groundwater development is an important factor for the sustainable use of water resources in the Dhofar region. 相似文献
10.
Samir Kamel 《Arabian Journal of Geosciences》2013,6(6):2103-2117
The shallow Plio-Quaternary (PQ) water table, present over almost the whole Djerid and Chott El Gharsa basins (southern Tunisia), is used as a complement of oases irrigation, especially in summer season. The simplicity of the Plio-Quaternary lithology is confronted to the complexity of the mineralisation mechanisms and the water origin in this aquifer. An approach combining the use of water-dissolved chemical species and isotopic contents has been used to better understand the PQ behaviour under severe increasing exploitation and to determinate the origin of its different water bodies. In southern Tunisia, the aquifer system is composed of the upper unconfined PQ aquifer, the intermediate semi-confined/confined Complexe Terminal (CT) and the deeper confined Continental Intercalaire (CI). Chemical analyses highlighted an origin of mineralisation in close relationship to the dissolution of both sulphated salts (MgSO4 and Na2SO4) and chlorinated salts (NaCl and MgCl) abundant in the surface and subsurface gypsum crust. Positive correlations between gypsum anhydrite, mirabilite, thenardite and halite saturation indexes with respective mineral species, confirm evaporites dissolutions. Isotopic data showed that in addition of sporadic rainfall events, there is a contribution from the CI and the CT Saharan groundwaters, recharging the PQ aquifer in the study area. Return flow irrigation is partly affected by evaporation, before recharging the shallow aquifer, in oases limits. 相似文献
11.
An approach combining the use of water dissolved chemical species and isotopic fingerprints has been used to understand the behavior of a phreatic aquifer and to determine the origin of its different water components. This aquifer is located in the large sedimentary basin of the Great Oriental Erg (Algeria) and overlies two deeper aquifers: the Complexe Terminal (CT) and the Continental Intercalaire (CI). Besides the deterioration of its groundwater quality, its water table has risen during the last 20 years. A water budget surplus between 950 and 2500 l s?1 was estimated. Down-gradient groundwater evolution (south-north) has shown that the mineralisation increases from 1.23 to 5.20 g l?1 due to evaporite minerals dissolution. Chemical and isotopic data demonstrated that in addition to rainfall there is a contribution from the CT and CI aquifers. The latter are tritium-free and less mineralized than the phreatic aquifer. Their radiocarbon contents are very low (<10 pmC, percent modern Carbon) (Pleistocene recharge) whereas quite the contrary is observed for the superficial aquifer which exhibits fairly high and variable C-14 activities (50–100 pmC), evidence of recent recharge. On the basis of tritium contents, two groundwater groups were identified for the phreatic aquifer. 相似文献
12.
Mohamed Fethi Ben Hamouda Jamila Tarhouni Christian Leduc Kamel Zouari 《Environmental Earth Sciences》2011,63(5):889-901
As in many other semi-arid regions, the Plio-quaternary aquifer of the eastern coast of Cap Bon peninsula (NE Tunisia) shows
a parallel increase in overexploitation and mineralization of groundwater resources and so the water quality is deteriorating.
Different methods using geochemistry (ions Na+, Cl−, Ca2+, Mg2+, Br−) and stable isotopes (18O, 2H) are compared with the hydrodynamic information for identifying the main processes involved in the increase of salinization.
Along the coast, intrusion of seawater resulting from groundwater overexploitation is identified, but is not the only cause
of qualitative degradation: the development of irrigation that induces soil leaching and transfer of fertilizers to groundwater
over the whole aquifer extent is another major reason for the increase in salinization. A total of 48 groundwater wells were
sampled to obtain additional information on the hydrochemical characteristics of the groundwater defined in previous studies. 相似文献
13.
Study of shallow groundwater quality evolution under saline intrusion with environmental isotopes and geochemistry 总被引:2,自引:0,他引:2
Evolution of the shallow groundwater quality under saline intrusion in porous aquifer system has been studied with environmental
isotopes and geochemistry in the Laizhou Bay area, China. Two campaigns of water sampling from various sources were carried
out in spring and winter for environmental isotopic and chemical analyses. The origin of groundwater salinity from intrusion
of both modern seawater and deep brine water was identified by analysing the correlations between 18O, D, T, Cl−, SO42− and electrical conductivity. The results indicate that the brine is originated from evaporating and concentrating of intruded
seawater and its δD and δ18O are different from modern seawater but similar to those of mixture of seawater with fresh groundwater. It is hard to distinguish
the salinity origin in this area by the δD–δ18O relationship alone. The relations between δ18O and conductivity, Cl− and SO42− have been used to identify the salinity origin due to the distinct difference in salinity between the brine and seawater,
conjunctively with use of T. A threshold of T = 12 TU was adopted to identify the origin of saline groundwater. 相似文献
14.
Groundwater salinization processes in shallow coastal aquifer of Djeffara plain of Medenine, Southeastern Tunisia 总被引:3,自引:3,他引:0
Rim Trabelsi Kamel Abid Kamel Zouari Houcine Yahyaoui 《Environmental Earth Sciences》2012,66(2):641-653
Urban and industrial development and the expansion of irrigated agriculture have led to a drastic increase in the exploitation
of groundwater resources. The over-exploitation of coastal aquifers has caused a seawater intrusion and has seriously degraded
groundwater quality. The shallow coastal aquifer of the Djeffara plain, southeastern Tunisia constitutes an example of water
resource suffering an intensive and uncontrolled pumping for irrigation. Intensive exploitation of the aquifer and climate
aridity caused a decrease in piezometric level and an increase in salinity. According to the hydrochemical data (Cl−, SO4
2−, NO3
−, HCO3
−, Br−, Ca2+, Mg2+, Na+, K+) and the stable isotope composition (oxygen-18 and deuterium content), groundwater salinization in the investigated system
is caused by three main processes: (i) salts dissolution especially in the central part of Jerba and around Medenine plain;
(ii) evaporation process; and (iii) seawater intrusion which caused the increase in salinity in the peninsula of El Jorf,
in Jerba and in the North of Ben Gardane. 相似文献
15.
Rouaida Trabelsi Moncef Zaïri Habib Smida Hamed Ben Dhia 《Comptes Rendus Geoscience》2005,337(5):515-524
The intensive agricultural and economic activities induce the increase of the risk of groundwater quality degradation through high groundwater pumping rates. The salinization and contamination are the main sources of this pollution, especially in coastal aquifers. The explanation of the origin of salinity for the shallow aquifer of Northern Sahel of Sfax was analysed by a chemical study of the groundwater main compounds. The partitioning of groundwaters into homogenous groups is undertaken by graphical techniques, including a Stiff pattern diagram, an expanded Durov diagram and several binary diagrams. The study indicates the presence of various salinization processes. In the recharge area, salinization is the result of dissolution/precipitation of the aquifer formation material (group I). The irrigation water return and the intensive pumping have been identified as major sources of salinization in the south by direct cation exchange and mixing reactions (groups II and III). The anomaly of high groundwater salinity observed near the Hazeg zone was explained by the presence of a seawater intrusion in this area. This hypothesis is related to the high chloride concentration, to the presence of inverse cation exchange reactions (group IV), and to the piezometric level inferior to sea level. To cite this article: R. Trabelsi et al., C. R. Geoscience 337 (2005). 相似文献
16.
Wilson Yetoh Fantong Hiroshi Satake Festus T. Aka Samuel N. Ayonghe Kazuyoshi Asai Ajit K. Mandal Andrew A. Ako 《Environmental Earth Sciences》2010,60(1):107-120
Unplanned exploitation of groundwater constitutes emerging water-related threats to MayoTsanaga River Basin. Shallow groundwater
from crystalline and detrital sediment aquifers, together with rain, dams, springs, and rivers were chemically and isotopically
investigated to appraise its evolution, recharge source and mechanisms, flow direction, and age which were used to evaluate
the groundwater susceptibility to contamination and the basin’s stage of salinization. The groundwater which is Ca–Na–HCO3 type is a chemically evolved equivalent of surface waters and rain water with Ca–Mg–Cl–SO4 chemistry. The monsoon rain recharged the groundwater preferentially at an average rate of 74 mm/year, while surface waters
recharge upon evaporation. Altitude effect of rain and springs show a similar variation of −0.4‰ for δ18O/100 m, but the springs which were recharged at 452, 679, and 773 m asl show enrichment of δ18O through evaporation by 0.8‰ corresponding to 3% of water loss during recharge. The groundwater which shows both local and
regional flow regimes gets older towards the basins` margin with coeval enrichment in F− and depletion in NO3
−. Incidentally, younger groundwaters are susceptible to anthropogenic contamination and older groundwaters are sinks of lithologenic
fluoride. The basins salinization is still at an early stage. 相似文献
17.
Contributions of boron isotopes to understanding the hydrogeochemistry of the coastal detritic aquifer of Castellón Plain,Spain 总被引:1,自引:0,他引:1
The Castellón Plain alluvial aquifer, Spain, is intensively exploited to meet the demand for agricultural irrigation and industrial water supply. The geochemistry of its groundwater shows complex salinization in the northern and southern parts of the aquifer, with significant pollution from human origin in the central portion. Boron content and B isotope geochemistry are useful for distinguishing between various sources of pollution and their relative importance in different parts of this aquifer. Boron concentrations in the groundwater vary between 0.01 and 0.85 mg/L. In the more saline groundwaters, found at the northern and southern ends of the study area, the presence of B is linked to inputs from seawater and water with a calcium-magnesium sulphate facies, which feed the aquifer and clearly influence the chemistry of its waters. Evidence of B adsorption processes in some samples is shown by the low B/Cl ratios and the high values of δ11B. In the central portion of the aquifer, the high B/Cl ratios and the strongly negative δ11B are related to pollution of human origin. 相似文献
18.
A Triassic carbonate unit has been intensively drained by zinc and lead ore mines and numerous borehole fields since the nineteenth
century. Its groundwater recharge has increased due to: pumping of water from boreholes, mining activity, and urbanization.
An approach to determine the amounts of the recharge at a variety of spatial scales is presented in the paper. Different methods
were used to identify and quantify recharge components on a regional and local scale: mathematical modelling was performed
for four aquifers included in an aquifer system, an analytical estimation based on the assumption that an average recharge
is equal to the average discharge of the hydrogeological system—for six man-made drainage centres, and the method of water
level fluctuation (WLF) was applied in one observation borehole. Results of modelling have been supplemented by observation
of environmental tracers (δ18O, δ2H, 3H), noble gases temperatures, and 4Heexc in groundwater. The regional aquifer’s current recharge according to estimations performed by means of modelling varies from
39 to 101 mm/year on average. Depending on the aquifer site the average precipitation ranges from 779 to 864 mm/year. In the
confined part of the aquifer average recharge ranges from 26 to 61 mm/year. Within outcrops average recharge varies from 96
to 370 mm/year. Current recharge estimated by the analytical method for man-made drainage centres varies from 158 up to 440 mm/year.
High values are caused by different recharge sources like precipitation, induced leakage from shallow aquifers, and water
losses from streams, water mains and sewer systems. Pumping of water, mining and municipal activities constitute additional
factors accounting for the intensified recharge. 相似文献
19.
Paula M. Carreira Mohamed Bahir Ouhamdouch Salah Paula Galego Fernandes Dina Nunes 《Hydrogeology Journal》2018,26(8):2595-2615
Environmental stable and radioactive isotopes (δ2H, δ13C, δ18O; 3H and 14C), together with physical and geochemical data, were used in the determination of the origins of groundwater salinization and geochemical evolution processes in coastal regions. Two case studies on the Atlantic Coast are discussed, one located in the Essaouira sedimentary basin, western Morocco, and the second, in the Lower Tagus–Sado sedimentary basin, southwest Portugal. In both regions, groundwater degradation occurs by salinization increase to different concentrations and in relation to different origins. The main quality issues for the groundwater resources are related to seawater intrusion, dissolution of diapiric structures intruding the aquifer layers, brine dissolution at depth, and/or evaporation of irrigation water. Anthropogenic pollution ascribed to agricultural activities is another source for groundwater degradation, affecting mainly the shallow aquifers. The apparent 14C age of the analysed samples ranges from 2.9?±?0.3 up to 45.6?±?0.6 pmC in the Miocene groundwater samples from the basin in Portugal; at the Essaouira basin in Morocco, the 14C content varies from 60 to 86 pmC. In most of the water samples, the 3H concentration is below the detection limit. In both basins, the isotopic results together with the geochemical data provided an effective label for tracing the mineralization origin and groundwater degradation processes. Further, the isotopic signatures were used in the identification of a paleoclimate (colder period), recorded in the stable isotopic composition and corroborated with the 14C data. 相似文献
20.
The alluvial aquifer of the Alto Guadalquivir River is one of the most important shallow aquifers in Jaén, Spain. It is located
in the central-eastern part of the province, and its groundwater resources are used mainly for crop irrigation in an agriculture-dominated
area. Hydrochemical and water-quality data obtained through a 2-year sampling (2004–2006) and analysis program indicate that
nitrate pollution is a serious problem affecting groundwater due to the use of nitrogen (N)-fertilizers in agriculture. During
the study, 231 water samples were collected from wells and springs to determine water chemistry and the extent of nitrate
pollution. The concentration of nitrate in groundwater ranged from 1.25 to 320.88 mg/l. Considerable seasonal fluctuations
in groundwater quality were observed as a consequence of agricultural practices and other factors such as annual rainfall
distribution and the Guadalquivir River flow regime. The chemical composition of the water is not only influenced by agricultural
practices, but also by interaction with the alluvial sediments. The dissolution of evaporites accounts for part of the Na+, K+, Cl−, SO4
2−, Mg2+, and Ca2+, but other processes, such as calcite precipitation and dedolomitization, also contribute to groundwater chemistry. 相似文献