共查询到20条相似文献,搜索用时 31 毫秒
1.
Groundwater origins and mixing pattern in the multilayer aquifer system of the Gafsa-south mining district: a chemical and isotopic approach 总被引:3,自引:2,他引:1
Younes Hamed Lassaad Dassi Meriem Tarki Riadh Ahmadi Khalid Mehdi Hamed Ben Dhia 《Environmental Earth Sciences》2011,63(6):1355-1368
Major ion geochemistry and environmental isotopes were used to identify the origins and the mineralisation processes of groundwater
flowing within the three aquifer levels of the multilayer system of the Gafsa-south mining district (Southwestern Tunisia).
It has been demonstrated that groundwaters are characterised by a Ca–Mg–SO4 water type. Geochemical pattern is mainly controlled by the dissolution of halite, gypsum and/or anhydrite as well as by
the incongruent dissolution of dolomite. δ18O and δ2H values are much lower than the isotopic signature of regional precipitation and fall close to the meteoric water lines,
indicating that groundwaters have not been significantly affected by evaporation or mineral–water reactions. The distribution
of stable and radiogenic isotopes (δ18O, δ2H, δ13C and 14C) within the aquifer levels suggests that the deep confined aquifer receives a significant modern recharge at higher altitudes,
while, the shallow unconfined aquifer has been mainly recharged under cooler paleoclimatic condition, likely during Late Pleistocene
and Early Holocene humid periods. However, waters from the intermediate confined/unconfined aquifer have composite isotopic
signatures, highlighting that they are derived from a mixture of the two first end-members. 相似文献
2.
Yu. K. Vasil’chuk A. C. Vasil’chuk N. A. Budantseva Ju. N. Chizhova W. Papesh Ye. Ye. Podborny L. D. Sulerzhitsky 《Doklady Earth Sciences》2009,429(1):1326-1332
The conditions and forming time of massive ice were specified (Bovanenkovo gas condensate field, Central Yamal). Here, massive
ice lies as stratums, laccoliths, stocks, and lenses. Three thousand boreholes 10–100 m in depth were analyzed. In 260 of
them massive ice was broached. The ice foot is situated from 1 to 57 m deep. The maximal thickness of ice broached with boreholes
came to 28.5 m; on average, it was about 8 m. The extension of massive ice is sometimes more than 2000 m, and its area is
quite often more than 10 km2. According to the radiocarbon method, loams of the third terrace, containing and overlapping ice deposits, were formed from
25 000 to 20 000 years ago or somewhat later. These strongly peat loams containing massive ice formed either in shallow sea
conditions or during periodical draining conditions of beaches or low laida, where organic matter appeared due to erosion
and deposition and accumulated during draining and overgrowing of drains. In more inclement conditions than at present, loam
deposits were frozen immediately, forming massive ice, which occupied the barely water-saturated layers. The oxygen isotope
composition (δ18O) of massive ice samples varied from −12.49‰ (here and further, relative to SMOW) to −22.95‰. The deuterium
concentration (δD) varied from −91.7 to −177.1‰. Deuterium kurtosis (d
exc) varied from 3.4 to 10.6‰. In one seam outcrop, the content of stable isotopes varied significantly. Here, at a depth of
0.2–0.8 m, the δ18O content varied by more than 10‰ (from −12.49 to −22.75), and the δD content, from −91.7 to −171.9‰. Such variations testify
about ice extraction upon freezing of water-saturated grounds in a closed system. According to palynological analysis of ice
stratums, numerous remains of unicellular green algae and diatoms were revealed. It is possible that this is evidence of the
existence of a fresh well, which was a source of water, feeding the layer. Most probably these were near-bottom silt waters
of a large lake or desalted bay, which were frozen syngenetically. This accentuates the new type of massive ice, syncriogenic
segregative ice, which probably formed 25 000–20 000 yr BP. 相似文献
3.
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
4.
Geochemistry of heavily exploited aquifers in the Emilia-Romagna region (Po Valley, northern Italy) 总被引:1,自引:0,他引:1
More than 5 800 chemical analyses on water samples collected during 1987–1995 from 528 monitoring wells located in the southernmost
part of the Po Valley (Emilia-Romagna region, northern Italy), one of the most urbanized, industrialized and agriculturally
developed areas of Italy, have been processed. The analysis of data showed that: (1) waters are discharging from both confined
and unconfined aquifers; (2) the water in the unconfined aquifer(s) is Ca(Mg)-HCO3 in composition while confined ones are Na-Cl and/or Na-(HCO3); (3) both confined and unconfined aquifer samples have δ18O and δD isotopic values of meteoric signature; (4) waters from both the aquifers are at least 40 years old; (5) the pumping
rate has caused subsidence, particularly where the aquifer(s) is (are) unconfined; (6) the unconfined aquifer(s) is exposed
to the risk of NO3 pollution; (7) considering the present "pressure" (i.e. pumping rate) on this natural environment by human activity, care
must be taken in the future to preserve this "strategic" resource.
Received: 27 October 1997 · Accepted: 12 March 1998 相似文献
5.
Recent sedimentary records from the Arabian Sea 总被引:1,自引:0,他引:1
An attempt is made to understand the redox conditions that prevailed in the north eastern continental margins of the Arabian
Sea and in the nearby deep water regions during the past few centuries using short undisturbed sediment cores. The geochronology
is accomplished using210Pb excess method and the proxy indicators chosen for productivity and associated redox changes are CaCO3, organic matter (OM), Mn and U along with major elements Fe and Al. Such changes in principle are related to high productivity
in the overlying waters which in turn depend on monsoonal intensity that causes upwelling responsible for increase in productivity.
Alongwith the published data on gravity cores from the same region, our measurements suggest the following:
At ∼ 300 m water depth, south of 21°N, the sediment-water interface at depths of ∼ 300 m had been anoxic during the time span
represented by the presently studied cores for approximately ∼ 700y as evidenced by low Mn/Al (< 0.7 × 10−2) and high U/Al (> 10−4) weight ratios. In some adjacent deeper regions, however, the environment turned oxic around ∼ 200 y BP. Whereas both Mn
and Ra were lost to the overlying waters in the anoxic regions (depth ∼340m), the Mn that diffused from deeper sections appears
to have mineralized at the sediment-water-interface. Studies of this type on long undisturbed cores from the margins of the
Arabian Sea and the Bay of Bengal, involving several proxies and geochronology by more than one method are needed to understand
short term environmental (and monsoonal intensity) changes of the recent past with high resolution. 相似文献
6.
P. Möller S. M. Weise M. Tesmer P. Dulski A. Pekdeger U. Bayer F. Magri 《International Journal of Earth Sciences》2008,97(5):1057-1073
Conjoint consideration of distribution of major, rare earth elements (REE) and Y (combined to REY) and of H, O, C, S, Sr isotopes
reveals that four types of groundwater are distinguishable by their chemical composition presented by spider patterns. REY
patterns indicate thermo-saline deep water and two types of shallow saline groundwaters. Presence of connate waters is not
detectable. Sr isotope ratios distinguish three sources of Sr: fast and slow weathering of biotite and K-feldspar in Pleistocene
sediments, respectively, and dissolution of limestones. δ13C(DIC) indicate dissolution of limestone under closed and open system conditions. Numerous samples show δ13C(DIC) > 13‰ which is probably caused by incongruent dissolution of calcite and dolomite. The brines from below 1,000 m represent
mixtures of pre-Pleistocene seawater or its evaporation brines and infiltrated post-Pleistocene precipitation. The shallow
waters represent mixtures of Pleistocene and Recent precipitation salinized by dissolution of evaporites or by mixing with
ascending brines. The distribution of water types is independent on geologic units and lithologies. Even the Tertiary Rupelian
aquiclude does not prevent salinization of the upper aquifer. 相似文献
7.
Groundwater is often the only water source in semi-arid regions of Turkey. Günyüzü Basin, located in the Sakarya River basin,
SW of Eskişehir, exhibits semi-arid conditions. The study area is composed of Paleozoic metamorphic rocks, Eocene granitic
rocks, Neogene sedimentary rocks, and Quaternary alluvium. In the basin, Paleozoic Marbles are the main reservoir rocks for
hot and cold water, bordered by impermeable diabases dykes at the sides and by impermeable granites and schists. Neogene-aged
limestones, conglomerates and alluvium represent the other significant aquifers. Water samples chosen to exemplify the aquifer
characteristics, were collected from springs and wells in both the dry and the wet seasons. The cation and anion permutation
of the samples show that carbonates are the dominant lithology in the formation of chemical composition. δ18O (−11.2 to −8.9‰) and δ2H (−79 to −60‰) isotopic values show that all waters (thermal and cold) are meteoric in origin. The hydrological, hydrochemical,
and isotopic properties of the waters reveal that there exist two main groups of groundwater systems; one of these is deep
circulating, while the other one is shallow. Tritium values, 0–4 TU (Tritium Unit) indicate the presence of old, static water
in these aquifer systems. 相似文献
8.
Foresighted and determined local authorities, purposeful exploration (i.e. by seismic reflection) and extensive testing led
to the discovery of a substantial groundwater resource near the community of Seon (Switzerland) at a depth of 268–305 m. Production
tests revealed a hydraulic conductivity of ∼5.10–5 m/s, transmissivity of ∼5.10–4 m2/s and a storage coefficient of ∼2% in the aquifer. Pumping up to 1500 l/min is sustainable; the water quality complies chemically
and bacteriologically with drinking-water requirements. The residence time of several 103 years, determined by isotope techniques, guarantees protection from surface contamination. The elevated temperature of 19.5 °C
of the produced water enables combined use for drinking water and space heating. The environmental benefits are substantial:
the emission reduction amounts up to 780 tons/year CO2 and 1 ton/year SO2.
Received: 21 September 1998 · Accepted: 10 February 1999 相似文献
9.
Hydrogeochemical and isotopic investigation of the Bursa-Oylat thermal waters, Turkey 总被引:1,自引:1,他引:0
Suzan Pasvano?lu 《Environmental Earth Sciences》2011,64(4):1157-1167
The Oylat spa is located 80 km southeast of Bursa and 30 km south of Ineg?l in the Marmara region. With temperature of 40°C
and discharge of 45 l/s, the Oylat main spring is the most important hot water spring of the area. Southeast of the spa the
Forest Management spring has a temperature of 39.4°C and discharge of 2 l/s. The G?z spring 2 km north of the spa, which is
used for therapy of eye disease, and cold waters of the Saadet village springs with an acidic character are the further important
water sources of the area. EC values of Main spring and Forest Management hot spring (750–780 μS/cm) are lower than those
of Saadet and G?z spring waters (2,070–1,280 μS/cm) and ionic abundances are Ca > Na + K > Mg and SO4 > HCO3 > Cl. The Oylat and Sızı springs have low Na and K contents but high Ca and HCO3 concentrations. According to AIH classification, these are Ca–SO4–HCO3 waters. Based on the results of δ18O, 2H and 3H isotope analyses, the thermal waters have a meteoric origin. The meteoric water infiltrates along fractures and faults,
gets heated, and then returns to surface through hydrothermal conduits. Oylat waters do not have high reservoir temperatures.
They are deep, circulating recharge waters from higher enhanced elevations. δ13CDIC values of the Main spring and Forest Management hot spring are −6.31 and −4.45‰, respectively, indicating that δ13C is derived from dissolution of limestones. The neutral pH thermal waters are about +18.7‰ in δ34S while the sulfate in the cold waters is about +17‰ (practically identical to the value for the neutral pH thermal waters).
However, the G?z and Saadet springs (acid sulfate waters) have much lower δ34S values (~+4‰). 相似文献
10.
Amor Ben Moussa Sarra Bel Haj Salem Kamel Zouari Vincent Marc Fayçal Jlassi 《Environmental Earth Sciences》2011,62(6):1287-1300
Detailed hydrogeochemical and isotopic data of groundwaters from the Hammamet–Nabeul unconfined aquifer are used to provide
a better understanding of the natural and anthropogenic processes that control the groundwater mineralization as well as the
sources of different groundwater bodies. It has been demonstrated that groundwaters, which show Na–Cl and Ca–SO4–Cl water facies, are mainly influenced by the dissolution of evaporates, the dedolomitization and the cation-exchange process;
and supplementary by anthropogenic process in relation with return flow of irrigation waters. The isotopic signatures permit
to classify the studied groundwaters into two different groups. Non-evaporated groundwaters that are characterized by depleted
δ
18O and δ
2H contents highlighting the importance of modern recharge at higher altitude. Evaporated groundwaters with enriched contents
reflecting the significance infiltration of return flow irrigation waters. Tritium data in the studied groundwaters lend support
to the existence of pre-1950 and post-1960 recharge. Carbon-14 activities in shallow wells that provide evidence to the large
contamination by organic 14C corroborate the recent origin of the groundwaters in the study area. 相似文献
11.
Palaeoclimate and palaeoecological study was carried out using palynological and thecamoebian evidences buried in ∼4 m vertically
exposed sediment section (12 km inland from the present shoreline) of Late Holocene age along the banks of Gautami-Godavari
River and from three shallow cores from its Nilarevu tributary, Andhra Pradesh. Inferred climatic periods include (1) a basal
cold/arid period (∼3000-2000 yrs BP) with dominance of Botryococcus and other fresh water algal remains coupled with abundance of 25 species of thecamoebians indicating shallow and lentic ecosystem
during most of the period and (2) a relatively warm/wet conditions (since ∼2000 yrs BP) reveal lotic fresh water ecosystem
characterized by the evidences of tree palynotaxa and low percentage of thecamoebians. The three shallow cores (0.5–1 m) near
the mouth (∼8 km stretch) of the Nilarevu tributary reveal fluvio-marine deposition in the top 50–80 cm sediment unlike the
deeper fresh water depositional environment suggesting sea water ingression in the recent decades. The study illustrates that
the Gautami-Godavari River delta gradually prograded since ∼3000 yrs BP until 100–150 yrs unlike the intermittent relative
sea level rise and fall recorded during the same period in the contemporary south-east deltaic areas. 相似文献
12.
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
13.
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
14.
Hydrogen sulfide occurs in high concentration (10–200 mg/l) in different parts of Kuwait City and its suburbs at relatively
shallow depths (15–40 m from the surface). This was revealed by drilling through the aquifer system underlying the city and
sampling and analyzing the ground water at the drilled locations. The near-absence of coliform bacteria in the sulfide-rich
zones, the presence of sulfur-reducing bacteria in the deep (>80 m) Dammam Formation aquifer and a linear positive relation
between the concentration of hydrogen sulfide and the total dissolved solids content suggested non-anthropogenic origin of
the sulfide in the ground water of Kuwait. The upward movement of sulfide-rich water from depth and its differential flushing
by surface recharge through outcrops of the aquifers appear to have given rise to the present distribution of hydrogen sulfide
in the aquifers underlying the Kuwait City. 相似文献
15.
We present a comparative analysis of lower depth limits for growth of eelgrass, large brown algae and other macroalgae measured by SCUBA-diving along 162 transects in 27 Danish fjords and coastal waters, coupled to 1,400 data series of water chemistry (especially nitrogen) and Secchi depth transparency collected between March and October. Danish coastal waters are heavily eutrophied and characterized by high particle concentrations, turbid water and lack of macrophyte growth in deep water. Median values are 3.6 m for Secchi depth and median lower-depth limits are 4.0 m for eelgrass, 5.3 m for brown algae and 5.0 m for other macroalgae. Depth limits for growth of eelgrass and macroalgae increase linearly with transparency in the coastal waters. The relationships are highly significant (p<10−6) and transparency accounts for about 60% of the variability of depth limits. Eelgrass extends approximately to half the maximum depth of macroalgae, presumably because of greater respiratory costs to maintain the below-ground rhizomes and roots of eelgrass, which often constitutes half the plant weight. As a reflection of the importance of total nitrogen (TN) in controlling phytoplankton biomass and thus Secchi depth in coastal marine waters, we found that TN could explain 48–73% of the variation in depth limits of eelgrass and macroalgae, according to a multiplicative model (Y=aXb). As with Secchi depth, the relationship to eelgrass showed a lower slope, reflecting the higher respiratory costs of eelgrass. The models show great sensitivity and a profound quantitative response with proportional effects on Secchi depth and depth limits when total-N concentrations are reduced. 相似文献
16.
B. Gertsch G. Keller T. Adatte Z. Berner A. S. Kassab A. A. A. Tantawy A. M. El-Sabbagh D. Stueben 《International Journal of Earth Sciences》2010,99(1):165-182
Environmental and depositional changes across the Late Cenomanian oceanic anoxic event (OAE2) in the Sinai, Egypt, are examined
based on biostratigraphy, mineralogy, δ13C values and phosphorus analyses. Comparison with the Pueblo, Colorado, stratotype section reveals the Whadi El Ghaib section
as stratigraphically complete across the late Cenomanian–early Turonian. Foraminifera are dominated by high-stress planktic
and benthic assemblages characterized by low diversity, low-oxygen and low-salinity tolerant species, which mark shallow-water
oceanic dysoxic conditions during OAE2. Oyster biostromes suggest deposition occurred in less than 50 m depths in low-oxygen,
brackish, and nutrient-rich waters. Their demise prior to the peak δ13C excursion is likely due to a rising sea-level. Characteristic OAE2 anoxic conditions reached this coastal region only at
the end of the δ13C plateau in deeper waters near the end of the Cenomanian. Increased phosphorus accumulations before and after the δ13C excursion suggest higher oxic conditions and increased detrital input. Bulk-rock and clay mineralogy indicate humid climate
conditions, increased continental runoff and a rising sea up to the first δ13C peak. Above this interval, a dryer and seasonally well-contrasted climate with intermittently dry conditions prevailed.
These results reveal the globally synchronous δ13C shift, but delayed effects of OAE2 dependent on water depth. 相似文献
17.
Hydrogeochemical study of the thermal and mineralized waters of the Banaz (Hamamboğazi) area,western Anatolia,Turkey 总被引:1,自引:1,他引:0
The Hamamboğazi spa in western Turkey was built around natural hot springs with discharge temperatures in the range of 30–54°C;
the waters have near neutral pH values of 6.50–7.10 and a TDS content between 2,694 and 2,982 mg/l. Thermal water with a temperature
of 47.5–73°C has been produced at 325 l/s from five wells since 1994, causing some springs to go dry. A management plan is
required in the study area to maximize the benefits of this resource, for which currently proposed direct uses include heating
in the district and greenhouses, as well as balneology in new spas in the area. The best use for the water from each spring
or well will depend on its temperature, chemistry and location. The thermal waters are mixed Na–Mg–HCO3–SO4 fluids that contain a significant amount of CO2 gas. The chemical geothermometers applied to the Hamamboğazi thermal waters yield a maximum reservoir temperature of 130°C.
Isotope results (18O, 2H, 3H) indicate that the thermal waters have a meteoric origin: rainwater percolates downward along fractures and faults, is heated
at depth, and then rises to the surface along fractures and faults that act as a hydrothermal conduit. The basement around
the Banaz Hamamboğazi resort is comprised of Paleozoic metamorphic schist and marbles exposed 8 km south and 15 km north of
Banaz. Mesozoic marble, limestone and ophiolitic complex are observed a few km west and in the northern part of Banaz. These
units were cut at a depth of 350–480 m in boreholes drilled in the area. Overlying lacustrine deposits are composed of fine
clastic units that alternate with gypsum, tuff and tuffites of 200–350 m thickness. The marble and limestones form the thermal
water aquifer, while lacustrine deposits form the impermeable cap. 相似文献
18.
Tunisian Chott’s region is one of the most productive artesian basins in Tunisia. It is located in the southwestern part of
the country, and its groundwater resources are developed for water supply and irrigation. The chemical composition of the
water is strongly influenced by the interaction with the basinal sediments and by hydrologic characteristics such as the flow
pattern and time of residence. The system is composed of an upper unconfined “Plio-Quaternary” aquifer with a varying thickness
of 20–200 m, an intermediate confined/unconfined “Complex Terminal” aquifer about 100 m in thickness and a deeper “Continental
Intercalaire” aquifer about 150 m in thickness separated by thick clay and marl layers. The dissolution of evaporites and
carbonates explains part of the contained Na+, Ca2+, Mg2+, K+, SO42− and Cl-, but other processes, such carbonate precipitation, also contributes to the water composition. The stable isotope composition
of waters establishes that the deep groundwater (depleted as compared to present corresponding local rainfall) is ancient
water recharged probably during the late Pleistocene and the early Holocene periods. The relatively recent water in the Plio-Quaternary
aquifer is composed of mixed waters resulting presumably from upward leakage from the deeper groundwater. 相似文献
19.
Large karstic springs in east-central Florida, USA were studied using multi-tracer and geochemical modeling techniques to better understand groundwater flow paths and mixing of shallow and deep groundwater. Spring water types included Ca–HCO3 (six), Na–Cl (four), and mixed (one). The evolution of water chemistry for Ca–HCO3 spring waters was modeled by reactions of rainwater with soil organic matter, calcite, and dolomite under oxic conditions. The Na–Cl and mixed-type springs were modeled by reactions of either rainwater or Upper Floridan aquifer water with soil organic matter, calcite, and dolomite under oxic conditions and mixed with varying proportions of saline Lower Floridan aquifer water, which represented 4–53% of the total spring discharge. Multiple-tracer data—chlorofluorocarbon CFC-113, tritium (3H), helium-3 (3Hetrit), sulfur hexafluoride (SF6)—for four Ca–HCO3 spring waters were consistent with binary mixing curves representing water recharged during 1980 or 1990 mixing with an older (recharged before 1940) tracer-free component. Young-water mixing fractions ranged from 0.3 to 0.7. Tracer concentration data for two Na–Cl spring waters appear to be consistent with binary mixtures of 1990 water with older water recharged in 1965 or 1975. Nitrate-N concentrations are inversely related to apparent ages of spring waters, which indicated that elevated nitrate-N concentrations were likely contributed from recent recharge.The online version of the original article can be found at 相似文献
20.
Mixing of shallow and deep groundwater as indicated by the chemistry and age of karstic springs 总被引:1,自引:0,他引:1
Large karstic springs in east-central Florida, USA were studied using multi-tracer and geochemical modeling techniques to better understand groundwater flow paths and mixing of shallow and deep groundwater. Spring water types included Ca–HCO3 (six), Na–Cl (four), and mixed (one). The evolution of water chemistry for Ca–HCO3 spring waters was modeled by reactions of rainwater with soil organic matter, calcite, and dolomite under oxic conditions. The Na–Cl and mixed-type springs were modeled by reactions of either rainwater or Upper Floridan aquifer water with soil organic matter, calcite, and dolomite under oxic conditions and mixed with varying proportions of saline Lower Floridan aquifer water, which represented 4–53% of the total spring discharge. Multiple-tracer data—chlorofluorocarbon CFC-113, tritium (3H), helium-3 (3Hetrit), sulfur hexafluoride (SF6)—for four Ca–HCO3 spring waters were consistent with binary mixing curves representing water recharged during 1980 or 1990 mixing with an older (recharged before 1940) tracer-free component. Young-water mixing fractions ranged from 0.3 to 0.7. Tracer concentration data for two Na–Cl spring waters appear to be consistent with binary mixtures of 1990 water with older water recharged in 1965 or 1975. Nitrate-N concentrations are inversely related to apparent ages of spring waters, which indicated that elevated nitrate-N concentrations were likely contributed from recent recharge.An erratum to this article can be found at 相似文献