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1.
Among several salt lakes in the Thar Desert of western India, the Sambhar is the largest lake producing about 2 × 105 tons of salt (NaCl) annually. The “lake system” (lake waters, inflowing river waters, and sub-surface brines) provides a
unique setting to study the geo-chemical behavior of uranium isotopes (238U, 234U) in conjunction with the evolution of brines over the annual wetting and evaporation cycles. The concentration of 238U and the total dissolved solids (TDS) in lake water increase from ~8 μg L−1 and ~8 g L−1 in monsoon to ~1,400 μg L−1 and 370 g L−1, respectively, during summer time. The U/TDS ratio (~1 μg g−1 salt) and the 234U/238U activity ratio (1.65 ± 0.05), however, remain almost unchanged throughout the year, except when U/TDS ratio approaches to
3.8 at/or beyond halite crystallization. These observations suggest that uranium behaves conservatively in the lake waters
during the annual cycle of evaporation. Also, uranium and salt content (TDS) are intimately coupled, which has been used to
infer the origin and source of salt in the lake basin. Furthermore, near uniform ratios in evaporating lake waters, when compared
to the ratio in seawater (~0.1 μg g−1 salt and 1.14 ± 0.02, respectively), imply that aeolian transport of marine salts is unlikely to be significant source of
salt to the lake in the present-day hydrologic conditions. This inference is further consistent with the chemical composition
of wet-precipitation occurring in and around the Sambhar lake. The seasonal streams feeding the lake and groundwaters (within
the lake’s periphery) have distinctly different ratios of U/TDS (2–69 μg g−1 salt) and 234U/238U (1.15–2.26) compared to those in the lake. The average U/TDS ratio of ~1 μg g−1 salt in lake waters and ~19 μg g−1 salt in river waters suggest dilution of the uranium content by the recycled salt and/or removal processes presently operating
in the lake during the extraction of salt for commercial use. Based on mass-balance calculations, a conservative estimate
of "uranium sink" (in the form of bittern crust) accounts for ~5 tons year−1 from the lake basin, an estimate similar to its input flux from rivers, i.e., 4.4 tons year−1. 相似文献
2.
National scale evaluation of groundwater chemistry in Korea coastal aquifers: evidences of seawater intrusion 总被引:3,自引:2,他引:1
Youngyun Park Jin-Yong Lee Jeong-Hee Kim Sung-Ho Song 《Environmental Earth Sciences》2012,66(3):707-718
Pollution of groundwater by seawater intrusion poses a threat to sustainable agriculture in the coastal areas of Korea. Therefore, seawater intrusion monitoring stations were installed in eastern, western, and southern coastal areas and have been operated since 1998. In this study, groundwater chemistry data obtained from the seawater intrusion monitoring stations during the period from 2007 to 2009 were analyzed and evaluated. Groundwater was classified into fresh (<1,500 μS/cm), brackish (1,500–3,000 μS/cm), and saline (>3,000 μS/cm) according to EC levels. Among groundwater samples (n = 233), 56, 7, and 37% were classified as the fresh, brackish, and saline, respectively. The major dissolved components of the brackish and saline groundwaters were enriched compared with those of the fresh groundwater. The enrichment of Na+ and Cl− was especially noticeable due to seawater intrusion. Thus, the brackish and saline groundwaters were classified as Ca–Cl and Na–Cl types, while the fresh groundwater was classified as Na–HCO3 and Ca–HCO3 types. The groundwater included in the Na–Cl types indicated the effects of seawater mixing. Ca2+, Mg2+, Na+, K+, SO4 2−, and Br− showed good correlations with Cl− of over r = 0.624. Of these components, the strong correlations of Mg2+, SO4 2−, and Br− with Cl− (r ≥ 0.823) indicated a distinct mixing between fresh groundwater and seawater. The Ca/Cl and HCO3/Cl ratios of the groundwaters gradually decreased and approached those of seawater. The Mg/Cl, Na/Cl, K/Cl, SO4/Cl, and Br/Cl ratios of the groundwaters gradually decreased, and were similar to or lower than those of seawater, indicating that Mg2+, Na+, K+, SO4 2−, and Br−, as well as Cl− in the saline groundwater can be enriched by seawater mixing, while Ca2+ and HCO3 − are mainly released by weathering processes. The influence of seawater intrusion was evaluated using threshold values of Cl− and Br−, which were estimated as 80.5 and 0.54 mg/L, respectively. According to these criteria, 41–50% of the groundwaters were affected by seawater mixing. 相似文献
3.
J. P. Richards C. J. Bray D. M. DeR. Channer E. T. C. Spooner 《Mineralium Deposita》1997,32(2):119-132
The Porgera gold deposit in Papua New Guinea is a world-class example of an alkalic-type epithermal gold system (stage II),
which overprints a precursor stage of magmatic-hydrothermal gold mineralization (stage I). Gas and ion chromatographic analyses
of fluid inclusions contained in vein minerals from both mineralization stages have been carried out in order to constrain
the compositions of the fluids involved in, and the processes attending, ore deposition. These data indicate the presence
of three end-member liquids, the most dilute of which was present throughout the mineralization history and is interpreted
to represent evolved groundwater of meteoric origin. Its composition is estimated to have been approximately 500 mM Na+, 10 mM K+, 5 mM Li+, 250 mM Cl−, 0.15 mM Br−, and 0.01 mM I−, plus significant concentrations of dissolved gases. More saline liquids were also present during the two main stages of
ore formation, and although their compositions differ, both are interpreted to have been derived at least in part from magmatic
fluids, and to have been the media by which gold was introduced into the system. Stage I minerals contain fluid inclusions
which decrease in salinity towards this dilute end-member composition through the vein paragenesis, reflecting progressive
dilution at depth of the magmatic fluid source by groundwaters. Ore deposition is thought to have been caused largely by simple
cooling and/or wallrock reactions, although limited in situ fluid mixing may also have occurred. The most saline fluids, present
in early quartz and pyrite, contain at least 810 mM Na+, 530 mM Ca2+, 130 mM K+, 12 mM Li+, 87 mM SO4
2−, 960 mM Cl−, 1.1 mM Br−, and 0.05 mM I−, plus significant but variable concentrations of dissolved gases. Fluid inclusions from stage II hydraulic breccia veins
reveal the presence of two distinct liquids with contrasting salinities, which were present at different times during vein
formation. A higher salinity liquid appears to have predominated during mineralization, whereas lower salinity groundwaters
filled the structures during intervening periods. The ore-forming fluid may have been forcibly injected into the veins from
depth during fracturing and depressurization events, displacing the resident groundwaters in the process. The original composition
of this fluid is estimated to have been at least 1770 mM Na+, 59 mM K+, 180 mM Li+, 210 mM SO4
2−, 680 mM Cl−, 1.4 mM Br−, and 0.09 mM I−, plus 1.5 mol% CO2, 0.19 mol% CH4, and 0.04 mol% N2. Gas chromatographic analyses of fluid inclusions from stage II samples show a decrease in total gas content between early
unmineralized veins and post-mineralization vuggy quartz (suitable samples could not be obtained from the ore stage itself).
Post-mineralization samples plot along an experimental gas-saturation curve in the CO2-CH4-H2O-NaCl system, obtained at conditions similar to those attending stage II ore deposition at Porgera (200–300 bar, ˜165 °C).
These results are interpreted to indicate a period of depressurization-induced phase separation during hydraulic fracturing,
which resulted in rich ore deposition. Volatile gases such as CH4 and N2, in addition to CO2 in solution, are shown to have a significant negative effect on total gas solubility. This effect may be of critical importance
in lowering the temperature and increasing the depth (pressure) at which phase separation can occur in epithermal systems.
Received: 28 November 1995 / Accepted: 17 July 1996 相似文献
4.
Nitrate pollution of groundwater in Toyserkan,western Iran 总被引:5,自引:2,他引:3
Mohsen Jalali 《Environmental Earth Sciences》2011,62(5):907-913
A total of 95 groundwater samples were collected from Toyserkan, western Iran to assess the chemical composition and nitrate
(NO3
−) status of groundwater. The most prevalent water type is Ca–HCO3 followed by water types Ca–Mg–HCO3. In comparison with the World Health Organization (WHO) drinking water guideline of 50 mg l−1 for NO3
−, a total of nine wells (9.5%) showed higher concentrations. In 36% of samples (34) NO3
− concentration was low (<20 mg l−1), and in 53.7% of samples (51), in the range of 20–50 mg l−1. The samples were classified into four groups based on NO3
− and chloride (Cl−) concentrations. Of the samples, 40% were classified as group 4 and were relatively high in Cl− and NO3
− (Cl− > 47 mg l−1, NO3
− > 27 mg l−1). The high correlation between NO3
− and Cl− (r = 0.86, p < 0.01) is consistent with a manure source, resulting from the practice of adding salt to animal feed. Pollution of groundwaters
appeared to be affected by the application of inorganic fertilizer at greater than agronomic rates, Cl-salt inputs, and irrigation
practice. 相似文献
5.
María del Carmen Blanco Juan Darío Paoloni Hector Morrás Carmen Fiorentino Mario Eduardo Sequeira Nilda N. Amiotti Oscar Bravo Silvana Diaz Martín Espósito 《Environmental Earth Sciences》2012,66(7):2075-2084
Excessive arsenic concentrations above the Argentinean and WHO guidelines for drinking water (10 μg L−1) affects shallow aquifers of the southern Pampean Plain (Argentina) hosted in the Pampean and the Post Pampean formations
(loess and reworked loess; Plio-Pleistocene–Holocene). Health problems related to high As concentrations in drinking waters
are known as Endemic Regional Chronic Hydroarsenicism. Hydrochemistry of shallow groundwaters and soil geochemistry were investigated
aiming to (1) understand the partition of As in the solid phase and its relationship with unacceptable As concentrations in
waters, (2) identify the provision source of As to groundwaters. Only 5% of the samples had As concentrations <10 μg L−1; in 27% As concentrations ranged from 10 to 50 μg L−1 and in 58% it reached 60–500 μg L−1. The coarse fraction (50–2,000 μm) hosts about 27% of the total As in the solid phase, being positively correlated to Ba
(p < 0.01; r
2 = 0.93). About 70% is included in the <2 μm fraction and had positive correlations of As–Fe (p < 0.05; r
2 = 0.85) and As–Cr (p < 0.05; r
2 = 0.68). Soils and sediment sand fractions of vadose zones are the primary sources of As in shallow groundwater while adsorption–desorption
processes, codisolution–coprecipitation, and evaporation during the dry seasons raise As concentrations in waters exceeding
the guideline value for drinking water. 相似文献
6.
In Lake Cuicocha watershed, a young caldera lake, soils consist of volcanic deposits with a high SiO2 and Al2O3 content; these andisols are in an early stage of development; and in drainage water from the watershed, aluminium concentrations
reach 15.0 μmol L−1. Total aluminium concentrations in Lake Cuicocha water raises up to 7.2 μmol L−1, with nearly 70% occurring as filterable Al at neutral to weak alkaline conditions. Al polymerization to gelatinous aggregates
of a few hundred micrometres in diameter as well as the occurrence of Al microcrystals like gibbsite as an ageing product
of gelatinous Al polymers was noted in the lake water. The gelatinous Al leads to the formation of larger aggregates resulting
in flocs of bacteria, algae, microorganisms and detritus. 相似文献
7.
Impact of Alkaline Earth Metals on Aqueous Speciation of Uranium(VI) and Sorption on Quartz 总被引:2,自引:0,他引:2
The effect of Mg-, Ca-, and Sr–Uranyl-Carbonato complexes with respect to sorption on quartz was studied by means of batch
experiments with U(VI) concentration of 0.126 × 10−6 M in the presence and absence of Mg, Ca, and Sr (each 1 mM) at pH from 6.5 to 9. In the absence of alkaline earth elements,
90% of the U(VI) sorbed on the quartz surface at all pH. In the presence of Mg, Ca, and Sr, the sorption of U(VI) on quartz
decreased to 50, 10, and 30%, respectively. Sorption kinetics of U(VI) on quartz is faster in the absence of alkaline earth
elements and reached equilibrium after 12 h, whereas in the presence of Mg, Ca and Sr, the kinetics of U(VI) sorption on quartz
is pH dependent and attained equilibrium after 24 h. Aqueous speciation calculations for alkaline earth uranyl carbonates
were carried out by using PHREEQC with the Nuclear Energy Agency thermodynamic database (NEA_2007) by adding constants for
MUO2(CO3)32− and M2UO2(CO3)30 (M = Ca, Mg, Sr). This study reveals that alkaline earth elements can have a significant effect on the aqueous speciation
of U(VI) under neutral to alkaline pH conditions and subsequently sorption behavior and mobility of U(VI) in aqueous environments. 相似文献
8.
Hydrochemical characteristics of groundwater in the Zhangye Basin, Northwestern China 总被引:3,自引:0,他引:3
The Zhangye Basin, located in arid northwest China, is an important agricultural and industrial center. In recent years rapid
development has created an increased demand for water, which is increasingly being fulfilled by groundwater abstraction. Detailed
knowledge of the geochemical evolution of groundwater and water quality can enhance understanding of the hydrochemical system,
promoting sustainable development and effective management of groundwater resources. To this end, a hydrochemical investigation
was conducted in the Zhangye Basin. Types of shallow groundwater in the Zhangye Basin were found to be HCO3
−, HCO3
−–SO4
2−, SO4
2−–HCO3
−, SO4
2−–Cl−, Cl−–SO4
2− and Cl− . The deep aquifer groundwater type was found to be HCO3−–SO42− throughout the entire area. Ionic ratio and saturation index calculations suggest that silicate rock weathering and evaporation
deposition are the main processes that determine the ionic composition in the study area. The suitability of the groundwater
for irrigation was assessed based on the US Salinity Laboratory salinity classification and the Wilcox diagram. In the study
area, the compositions of the stable isotopes δ18O and δD in groundwater samples were found to range from −4.00 to −9.28‰ and from −34.0 to −65.0‰, respectively. These values
indicate that precipitation is the main recharge source for the groundwater system; some local values indicate high levels
of evaporation. Tritium analysis was used to estimate the ages of the different groundwaters; the tritium values of the groundwater
samples varied from 3.13 to 36.62 TU. The age of the groundwater at depths of less than 30 m is about 5–10 years. The age
of the groundwater at depths of 30–50 m is about 10–23 years. The age of the groundwater at depths of 50–100 m is about 12–29 years.
For groundwater samples at depths of greater than 100 m, the renewal time is about 40 years. 相似文献
9.
Influence of hydrogeochemical processes on temporal changes in groundwater quality in a part of Nalgonda district, Andhra Pradesh, India 总被引:4,自引:3,他引:1
Geochemical processes that take place in the aquifer have played a major role in spatial and temporal variations of groundwater
quality. This study was carried out with an objective of identifying the hydrogeochemical processes that controls the groundwater
quality in a weathered hard rock aquifer in a part of Nalgonda district, Andhra Pradesh, India. Groundwater samples were collected
from 45 wells once every 2 months from March 2008 to September 2009. Chemical parameters of groundwater such as groundwater
level, EC and pH were measured insitu. The major ion concentrations such as Ca2+, Mg2+, Na+, K+, Cl−, and SO4
2− were analyzed using ion chromatograph. CO3
− and HCO3
− concentration was determined by acid–base titration. The abundance of major cation concentration in groundwater is as Na+ > Ca2+ > Mg2+ > K+ while that of anions is HCO3
− > SO4
2− > Cl− > CO3
−. Ca–HCO3, Na–Cl, Ca–Na–HCO3 and Ca–Mg–Cl are the dominant groundwater types in this area. Relation between temporal variation in groundwater level and
saturation index of minerals reveals the evaporation process. The ion-exchange process controls the concentration of ions
such as calcium, magnesium and sodium. The ionic ratio of Ca/Mg explains the contribution of calcite and dolomite to groundwater.
In general, the geochemical processes and temporal variation of groundwater in this area are influenced by evaporation processes,
ion exchange and dissolution of minerals. 相似文献
10.
Evaporation and energy balance estimates over a large inland lake in the Tibet-Himalaya 总被引:2,自引:1,他引:1
The process of evaporation from the lake surface is one of the main mechanisms in the energy and water budgets of the lake
hydrologic cycle, and an essential component of the water balance especially for inland lakes. In this study, using routine
meteorological data as input, a one-layer potential evaporation model was employed to simulate evaporation and energy fluxes
over Lake Yamdrok Yumco, the largest high-elevation inland lake in the mountain area of the Tibet-Himalaya in China. Then,
the calculation results were compared with the measured values from a big pan evaporator of 20 m2 near the lake. The results show that the average annual input radiation flux R
↓ is 128.2 W m−2, the lake storage heat flux G is 19.4 W m−2, the sensible heat flux H is 20.4 W m−2 and the latent heat flux lE is 107.8 W m−2. The R
↓ and G exhibit similar seasonal variations. The lE reaches a maximum in October, lagging nearly 4 months behind the R
↓ and the G, which indicates the large heat capacity of the lake. The simulated annual evaporation ranges from 1,113.2 to 1,429.1 mm
and its mean value is 1,252.5 mm during 1961–2005. The simulated annual evaporation is in good agreement with the measured
value, and the measured average lake temperature is as expected when compared with the measured lake surface temperature. 相似文献
11.
Hydrochemical characteristics and quality assessment of shallow groundwater in a coastal area of Southwest Bangladesh 总被引:4,自引:3,他引:1
In this study, the hydrochemical characteristics of shallow groundwater in a coastal region (Khulna) of southwest Bangladesh
have been evaluated based on different indices for drinking and irrigation uses. Water samples were collected from 26 boreholes
and analyzed for major cations and anions. Other physico-chemical parameters like pH, electrical conductivity (EC), and total
dissolved solids were also measured. Most groundwater is slightly alkaline and largely varies in chemical composition, e.g.
EC ranges from 962 to 9,370 μs/cm. The abundance of the major ions is as follows: Na+ > Ca2+ > Mg2+ > K+ = Cl− > HCO3
− > SO4
2− > NO3
−. Interpretation of analytical data shows two major hydrochemical facies (Na+–K+–Cl−–SO4
2− and Na+–K+–HCO3
−) in the study area. Salinity, 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. Results suggest that the
brackish nature in most of the groundwaters is due to the seawater influence and hydrogeochemical processes. 相似文献
12.
Julien Nikiema Mario Schirmer Walter Gläßer Ronald Krieg 《Environmental Earth Sciences》2010,61(1):11-26
About 24 samples from hand-dug wells and boreholes were used to characterize concentrations of the main inorganic ions in
a laterite environment under semi-arid climatic conditions in Tikaré, northern Burkina Faso. It was found that the most represented
groundwater anion in groundwater was HCO3
− with average levels of 49.1 mg/L in the dry season and 33.5 mg/L in the rainy season. The most represented cation was Ca2+ with mean concentrations of 13.7 and 9.5 mg/L, respectively. The main processes, which influence the concentrations of these
ions, are evaporation (dry season), local enrichment of recharge water in some elements, ion exchange and fixation by clay
minerals (in case of K+). The best correlations were found between Ca2+ and Mg2+ (r = 0.95), Cl− and Na+ (r = 0.95), HCO3
− and Mg2+ (r = 0.89), HCO3
− and Ca2+ (r = 0.89), and between HCO3
− and Na+ (r = 0.80). In general, the quality of the groundwater from the different wells sampled for this study was good enough to serve
as drinking water. However, there were situations where the quality of water was polluted because of anthropogenic contaminants
(mainly NO3
−, K+, Cl−) from septic tanks and manure pits located in the vicinity of some sampled wells. In addition, application of fertilizers
also represents a potential anthropogenic contamination source with regard to SO4
2−, Ca2+, K+, Na+, and Mg2+. Considering the high concentrations of SO4
2−, Mg2+, Na+ and Ca2+ found in one borehole, the deeper, fractured aquifers were also likely to be enriched in these elements. In contrast, the
shallow aquifers are likely to be contaminated with Cl−, NO3
− and K+. Cl− and K+ seem to be locally present in recharge water as shown by their relative higher mean concentrations in the rainy season samples. 相似文献
13.
Water quality assessment of groundwater in some rock types in parts of the eastern region of Ghana 总被引:2,自引:2,他引:0
Samuel Y. Ganyaglo Bruce Banoeng-Yakubo Shiloh Osae Samuel B. Dampare Joseph R. Fianko 《Environmental Earth Sciences》2011,62(5):1055-1069
A baseline study involving analyses of subsurface water samples from the Cape Coast granitoid complex, Lower Birimian, Togo
Formation and the Voltaian Group, was carried out to assess their suitability for drinking, domestic and agricultural purposes.
Study results show that pH within the range (3.0 ≤ pH ≤ 6.5) constitutes 74% of the boreholes analysed, and 51% have hardness
values ranging from 7.89 to 73.24 mg/l as CaCO3 and are described as soft. Total dissolved solids are less than 1,000 mg/l and generally characterized by low conductivity
values, of which 95% are within the range (55 ≤ EC ≤ 1,500 μS/cm). The mean values of the major cations (Ca2+, Mg2+, Na+, K+) and anions (SO42−, Cl−, HCO3−) are all within the World Health Organisation (WHO) standards. Five (5) of the boreholes sampled have nitrate (NO3−) contamination. Even though NO3− contamination and acidic waters exist in some of the boreholes, the majority of the boreholes are excellent for drinking
and domestic purposes. Assessment of the groundwaters for agricultural irrigation revealed three main categories. These are
low salinity–low sodicity (C1–S1), medium salinity–low sodicity (C2–S1) and high salinity–low sodicity (C3–S1), using the
US Salinity Laboratory (USSL) classification scheme. As much as 95% of the samples plotted in the ‘excellent to good’ and
‘good to permissible’ categories on the Wilcox diagram. The groundwater in the study area may therefore be regarded as good
for irrigation activities. The major identifiable geochemical processes responsible for the evolution of the various ions
are mineral weathering and chemical reactions. 相似文献
14.
This study presents the data on the hydrochemical characteristics and isotope chemistry of Liwa aquifer, which could be useful
to clarify the hydrochemical facies and hydrogeological regime in the study area. Electric conductivity and total dissolved
solid values show that the investigated water is slightly brackish, due to the effect of evaporation and the occurrences of
evaporite rocks in the adjacent Sabkhas of Abu Dhabi. Major cations and anions arranged according to their decreasing concentrations
are: Na+ > Ca+2 > K+ > Mg+2 and Cl− > HCO3
− > SO4−2, respectively. As sodium is the dominate cation and chloride is the prevailing anion, hydrochemically the groundwater of
Liwa can be classified as Na–Cl rich, predominantly chloridic. Ion concentrations increase towards the northeast and presumably
coincide with the lithological sources of ions. Factors affecting the hydrochemistry of the groundwater of the investigated
area include the effect of weathering of soil and rocks, evaporation and agricultural activities. Stable isotopes of oxygen
and hydrogen show that the shallow aquifers contain a single water type that originated in a distinct climatic regime. This
water type deviates from the local meteoric water line, as well as from the Eastern Mediterranean Meteoric Water Line, suggesting
potential evaporation of recharged water prior to infiltration. The waters are poor in tritium, and thus can be considered
generally as indication for recharge prior to 1952. The degradation of groundwater quality can be attributed to evaporation
and agricultural practices in most cases. 相似文献
15.
Zdzisław M. Migaszewski Agnieszka Gałuszka Stanisław Hałas Józef Dąbek Sabina Dołęgowska Irena Budzyk Ewa Starnawska Artur Michalik 《Environmental Geology》2009,57(1):29-40
In 2005 and 2006, hydrogeochemical study was carried out in the bipartite Wiśniówka Mała pit lake of the Holy Cross Mountains
(south-central Poland). This is the largest acidic water body in Poland. This report presents the element concentrations in
the water and sediment, stable sulfur and oxygen isotope ratios in the soluble sulfates, and stable oxygen isotope ratio in
the water. The scope of the investigation also encompassed mineralogical examinations (scanning electron microscope, X-ray
diffraction) of the sediment. The results of this study show that there is a spatial and temporal variability in concentrations
of most elements and sulfur isotope ratios in the examined pit lake. The water of the western pond displayed a lower pH with
a mean of 3.73 and higher conductivity (390 μS cm−1) as well as higher concentrations of sulfates (156 mg L−1) and most of the cations and anions. The concentrations of Fe2+ and Fe3+ averaged 0.8 and 0.4 mg·L−1. In contrast, the eastern pond water revealed a higher pH (mean of 4.36), lower conductivity (293 μS cm−1) and lower sulfate (90 mg L−1) and trace metal levels. Similar variations were recorded in the stable sulfur isotope ratios. The δ34SV-CDT(SO4
2−) values in the water of the western pit pond were in the range of −6.7 to −4.6‰ (mean of −5.6‰), whereas that in the eastern
pit pond ranged from −2.2 to −0.9‰ (−1.6‰). The alkalinity of the entire lake water was below 0.1 mg·L−1 CaCO3. No distinct difference in the δ18OV-SMOW(SO4
2−) was noted between the western and eastern pit ponds. Compared to the Purple Pond in the Sudetes (Poland) and similar sites
throughout the world, the examined pit lake is highlighted by distinctly low concentrations of sulfates, iron and other trace
metals. Based on this and other studies performed in the Holy Cross Mountains, a conclusion can be drawn that the SO4
2− in the Wiśniówka Mała pit lake water is a mixture of SO4
2− derived from the following sources: (1) pyrite oxidation (especially in the western pond water), (2) leaching of soluble
sulfates from soils and waste material, as well as (3) subordinate deposition of airborne sulfate precipitation. 相似文献
16.
Zongqiang Chang Qi Feng Jianhua Si Yonghong Su Haiyang Xi Jianlin Li 《Environmental Geology》2009,58(3):483-490
Field experiments on the CO2 flux of alpine meadow soil in the Qilian Mountain were conducted along the elevation gradient during the growing season of
2004 and 2005. The soil CO2 flux was measured using the Li-6400-09 soil respiration chamber attached to the Li-6400 portable photosynthesis system. The
effects of water and heat and roots on the soil CO2 flux were statistically analyzed. The results show that soil CO2 flux along the elevation gradient gradually decreases. The soil CO2 flux was low at night, with lowest value occurring between 0200 and 0600 hours, started to rise rapidly during 0700–0830
hours, and then descend during 1600–1830 hours. The peak CO2 efflux appears during 1100–1600 hours. The diurnal average of soil CO2 efflux was between 0.56 ± 0.32 and 2.53 ± 0.76 μmol m−2 s−1. Seasonally, soil CO2 fluxes are relatively high in summer and autumn and low in spring and winter. The soil CO2 efflux, from the highest to the lowest in the ranking order, occurred in July and August (4.736 μmol m−2 s−1), June and September, and May and October, respectively. The soil CO2 efflux during the growing season is positively correlated with soil temperature, root biomass and soil water content. 相似文献
17.
The applicability of the natural abundance of nitrogen gas isotope ratios was used to indicate the spatial distribution of
nitrogen transformations in the water column and sediment pore waters of Lake Ngapouri, a small (area 0.19 km2), monomictic, eutrophic lake in the Taupo Volcanic Zone, North Island, New Zealand. Samples were collected from the epilimnion,
hypolimnion, benthic boundary layer and at 5-cm intervals from the sediment pore waters at monthly intervals for 1 year. Values
of δ15N [N2] ranged from −1 to 0.28‰ in the epilimnion, −1.5 to 1.25‰ in the hypolimnion, −1.8 to 12.2‰ in the benthic boundary layer
and −0.7 to 3.5‰ in sediment pore waters. Values of δ15N [N2] showed a strong seasonal pattern that was related to the loss of dissolved oxygen in the hypolimnion during seasonal stratification.
Increases in 15N-enriched dinitrogen take place in the benthic boundary layer during the periods of anoxia (taken to be dissolved oxygen
concentrations <6.3 μM) and may be related to abundant ammonium substrate (up to 275 μM) to support denitrification. Nitrate
concentrations increased up to 36 μM with increasing duration of anoxia. We hypothesise that an alternative electron acceptor
besides oxygen is required to support the nitrification needed for the production of nitrate. Iron and manganese hydroxides
and oxides from material sedimenting out of the water column may have induced chemo-nitrification sufficient to oxidise ammonium
in the anoxic benthic boundary layer. The nitrate formed would mostly be rapidly denitrified so that the δ15N [N2] would continue to become enriched during the presence of anoxia, as observed in hypolimnion and benthic boundary layer of
Lake Ngapouri. The changes in δ15N [N2] values indicate the potential use of isotope ratios to identify and quantify potential chemo-nitrification/denitrification
in the water column and sediment pore waters of lakes. 相似文献
18.
The groundwaters from Zhongxiang City, Hubei Province of central China, have high fluoride concentration up to 3.67 mg/L,
and cases of dental fluorosis have been found in this region. To delineate the nature and extent of high fluoride groundwaters
and to assess the major geochemical factors controlling the fluoride enrichment in groundwater, 14 groundwater samples and
5 Quaternary sediment samples were collected and their chemistry were determined in this study. Some water samples from fissured
hard rock aquifers and Quaternary aquifers have high fluoride concentrations, whereas all karst water samples contain fluoride
less than 1.5 mg/L due to their high Ca/Na ratios. For the high fluoride groundwaters in the fissured hard rocks, high HCO3
− concentration and alkaline condition favor dissolution of fluorite and anion exchange between OH− in groundwater and exchangeable F− in some fluoride-bearing minerals. For fluoride enrichment in groundwaters of Quaternary aquifers, high contents of fluoride
in the aquifer sediments and evapotranspiration are important controls. 相似文献
19.
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
20.
Brijraj K. Das 《Environmental Geology》2005,49(2):230-239
A study of the water and sediment chemistry of the Nainital, Bhimtal, Naukuchiyatal and Sattal Lakes of Kumaun, has shown that the water of these lakes are alkaline and that electrical conductivity, total dissolved solid and bicarbonate HCO
3
−
are much higher in Nainital than in the other three lakes. The weathering of limestone lithology and anthropogenic pollution, the latter due to the very high density of population in the Nainital valley, are the primary sources of enhanced parameters. The low pH of Nainital Lake water is due to low photosynthesis and enhanced respiration, increasing CO2 in the water and the consequent enhancement of Ca2+ and HCO
3
−
. The dissolved oxygen in Nainital Lake is less compared to other lakes, indicating anoxic conditions developing at the mud–water interface at depth. The PO
4
3−
content in Nainital is higher (124 μg/l), showing an increasing trend over time leading to eutrophic conditions. The trace metals (Cu, Co, Zn, Ni, Mn, and Sr) are present in greater amounts in the water of Nainital Lake than in the other three lakes, though Fe and Cr are high in Bhimtal and Fe in Naukuchiyatal. The higher abundance is derived from the leaching of Fe–Mg from metavolcanic and metabasic rocks. Most of the heavy metals (Cr, Ni, Cu, Mn, Fe, Sr, and Zn) significantly enrich the suspended sediments of the lakes compared to the bed sediments which due to their adsorption on finer particles and owing to multiple hydroxide coating and organic content, except for Fe, which is enriched in the bed sediments. The high rate of sedimentation, 11.5 mm/year in Nainital, compared to Bhimtal with 4.70 mm/year, Naukuchiyatal with 3.72 mm/year, and Sattal with 2.99 mm/year, has resulted in shorter residence time, poor sorting of grains, and lesser adsorption of heavy metals, leading consequently, their depletion in the bed sediments of Nainital Lake. 相似文献