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1.
Documenting whether surface water catchments are in net chemical mass balance is important to understanding hydrological systems. Catchments that export significantly greater volumes of solutes than are delivered via rainfall are not in hydrologic equilibrium and indicate a changing hydrological system. Here an assessment is made of whether a saline catchment in southeast Australia is in chemical mass balance based on Cl. The upper reaches of the Barwon River, southeast Australia, has total dissolved solids, TDS, concentrations of up to 5860 mg/L and Cl concentrations of up to 3370 mg/L. The high river TDS concentrations are due to the influxes of groundwater with TDS concentrations of up to 68,000 mg/L. Between 1989 and 2011, the median annual Cl flux from the upper Barwon catchment was 17.8 × 106 kg (∼140 kg/a/ha). This represents 340–2230% of the annual Cl input by rainfall to the catchment. Major ion and stable isotope geochemistry indicate that the dominant source of solutes in the catchment is evapotranspiration of rainfall, precluding mineral dissolution as a source of excess Cl. The upper Barwon catchment is not in chemical mass balance and is a net exporter of solutes. The chemical imbalance may reflect the transition within the last 100 ka from an endorheic lake system where solutes were recycled producing shallow groundwater with high TDS concentrations to a better drained catchment. Alternatively, a rise in the regional water table following land clearing may have increased the input of groundwater with high TDS concentrations to the river system.  相似文献   

2.
Transient Electromagnetic (TEM), known also as Time Domain Electromagnetic (TDEM) and Magnetic Resonance Sounding (MRS) methods were applied jointly to investigate variations in lithology and groundwater salinity in the Nahal Hever South area (Dead Sea coast of Israel). The subsurface in this area is highly heterogeneous and composed of intercalated sand and clay layers over a salt formation, which is partly karstified. Groundwater is very saline, with a chloride concentration of 100–225 g/l. TEM is known as an efficient tool for investigating electrically conductive targets like saline water, but it is sensitive to both the salinity of groundwater and the porosity of rocks. MRS, however, is sensitive primarily to groundwater volume, but it also allows delineating of lithological variations in water-saturated formations. MRS is much less sensitive to variations in groundwater salinity in comparison with TEM. We show that MRS enables us to resolve the fundamental uncertainty in TEM interpretation caused by the equivalence between groundwater resistivity and lithology. Combining TEM and MRS, we found that the sandy Dead Sea aquifer filled with Dead Sea brine is characterized by a bulk resistivity of ρx > 0.4 Ωm, whereas zones with silt and clay in the subsurface are characterized by a bulk resistivity of ρx < 0.4 Ωm. These observations are confirmed by calibration of the TEM method performed near 18 boreholes.  相似文献   

3.
The chemical and isotopic (87Sr/86Sr, δ11B, δ34Ssulfate, δ18Owater, δ15Nnitrate) compositions of water from the Lower Jordan River and its major tributaries between the Sea of Galilee and the Dead Sea were determined in order to reveal the origin of the salinity of the Jordan River. We identified three separate hydrological zones along the flow of the river:
(1)
A northern section (20 km downstream of its source) where the base flow composed of diverted saline and wastewaters is modified due to discharge of shallow sulfate-rich groundwater, characterized by low 87Sr/86Sr (0.7072), δ34Ssulfate (−2‰), high δ11B (∼36‰), δ15Nnitrate (∼15‰) and high δ18Owater (−2 to-3‰) values. The shallow groundwater is derived from agricultural drainage water mixed with natural saline groundwater and discharges to both the Jordan and Yarmouk rivers. The contribution of the groundwater component in the Jordan River flow, deduced from mixing relationships of solutes and strontium isotopes, varies from 20 to 50% of the total flow.
(2)
A central zone (20-50 km downstream from its source) where salt variations are minimal and the rise of 87Sr/86Sr and SO4/Cl ratios reflects predominance of eastern surface water flows.
(3)
A southern section (50-100 km downstream of its source) where the total dissolved solids of the Jordan River increase, particularly during the spring (70-80 km) and summer (80-100 km) to values as high as 11.1 g/L. Variations in the chemical and isotopic compositions of river water along the southern section suggest that the Zarqa River (87Sr/86Sr∼0.70865; δ11B∼25‰) has a negligible affect on the Jordan River. Instead, the river quality is influenced primarily by groundwater discharge composed of sulfate-rich saline groundwater (Cl-=31-180 mM; SO4/Cl∼0.2-0.5; Br/Cl∼2-3×10-3; 87Sr/86Sr∼0.70805; δ11B∼30‰; δ15Nnitrate ∼17‰, δ34Ssulfate=4-10‰), and Ca-chloride Rift valley brines (Cl-=846-1500 mM; Br/Cl∼6-8×10-3; 87Sr/86Sr∼0.7080; δ11B>40‰; δ34Ssulfate=4-10‰). Mixing calculations indicate that the groundwater discharged to the river is composed of varying proportions of brines and sulfate-rich saline groundwater. Solute mass balance calculations point to a ∼10% contribution of saline groundwater (Cl−=282 to 564 mM) to the river. A high nitrate level (up to 2.5 mM) in the groundwater suggests that drainage of wastewater derived irrigation water is an important source for the groundwater. This irrigation water appears to leach Pleistocene sediments of the Jordan Valley resulting in elevated sulfate contents and altered strontium and boron isotopic compositions of the groundwater that in turn impacts the water quality of the lower Jordan River.
  相似文献   

4.
Evaporite karst has intensively developed recently along the Dead Sea (DS) coastal area in Israel and Jordan. It takes place in very saline groundwater dissolving buried salt layers, causing collapse of the surface. In this paper, groundwater salinity throughout the DS coastal area is investigated using the Transient Electromagnetic (TEM) method. Twenty-eight TEM soundings along the DS coastal area were carried out close to observation boreholes to calibrate resistivity–salinity relationships. Groundwater electrical conductivity was measured in these boreholes, and its salinity was analyzed at the laboratory by the Geological Survey of Israel (GSI). Quantitative relationships between bulk resistivity (ρx), water resistivity (ρw) and chloride concentration (Ccl) were derived in the resistivity range less than 1.0 Ω·m that enabled to evaluate the salinity of the aquifer in in situ conditions. Average values of the effective porosity of sandy sediments, φe = 0.32, and of silty ones, φe = 0.44, were used to generate the corresponding Archie equations. The study has shown that a DS aquifer with bulk resistivity in the range of 0.55–1.0 Ω·m contains in pores brine with 50–110 gchloride/l of (22–50% of that in saturated conditions, respectively), i.e. it keeps the potential to dissolve up to 114–174 g/l of salt.  相似文献   

5.
A detail investigation was carried out to improve the current knowledge of groundwater salinisation processes in coastal aquifers using hydrochemical and isotopic parameters. Data of major ions for 40 wells located in the Salalah plain aquifer, Sultanate of Oman, were collected during pre-monsoon 2004 and analysed. The groundwater changes along the general flow path towards the coast from fresh (EC < 1500 μS/cm), brackish (EC: 1500–3000 μS/cm) and saline (EC > 3000 μS/cm). Results of inverse modeling simulations using PHREEQC show that dissolution of halite may be the main source of Cl and Na in the study area. Ionic delta calculation indicates that the depletion of Na and K and enrichment of Ca and Mg in groundwater were probably attributed to reverse ion exchange reactions. During a sampling campaign conducted in October 2015, 11 groundwater samples were collected for Cl, Br and isotopic analysis (2H/18O). Molar Cl/Br ratios in fresh groundwater were higher than those of seawater, indicating the impact of halite dissolution on the groundwater quality. For saline groundwater, these ratios were less than those of seawater, showing the influence of anthropogenic input from agriculture on the same. Relatively depleted isotopic signature of all groundwater samples show that the monsoon precipitation is the main source of groundwater recharge in the study area.  相似文献   

6.
River water infiltration into an unconfined porous aquifer (∼73% gravels, ∼12% sands, ∼15% silts and clays) in the Petrignano d’Assisi plain, central Italy, was traced combining isotopic techniques (222Rn) with hydrochemical and hydrogeologic techniques in order to characterize the system under study. The 222Rn gave information about the river water residence times within the aquifer and hydrochemical data, in a two-component mixing model, which allowed estimating the extent of mixing between surface waters and groundwater in wells at increasing distances from the river. The mixing measured in the well closer to the riverbank indicated a higher contribution of river water (up to 99%) during the groundwater recession phase and a moderate contribution (up to 64%) during the recharge phase. A model describing 222Rn concentrations in groundwater as the result of both parent/daughter nuclide equilibrium and mixing process (222Rn mixing/saturation model) was used to describe observed Rn concentrations and mixing index trends with the aim of evaluating water mean infiltration velocities along the transect. The stream bank infiltration velocities obtained by the model ranged from 1 m day−1 during groundwater recharge periods, when river water infiltration is lower, to 39 m day−1 during recession phases, when river water infiltration is larger.  相似文献   

7.
In the arid sub-Saharan of southern Morocco, groundwater salinization poses a direct threat for agricultural production in six oases’ basins that are irrigated by water imported from the High Atlas Mountains. Here the geospatial distribution of salinity is evaluated in shallow groundwater, springs and surface waters in the Drâa Basin, integrating major and trace element geochemistry and isotopic tracers (O, H, Sr and B). The data show that water discharge from the High Atlas Mountains to the Upper section of the Drâa Basin is characterized by both low and high salinity, a distinctive low δ18O and δ2H composition (as low as −9‰ and −66‰, respectively), typical for meteoric water from high elevation, a 87Sr/86Sr range of 0.7078–0.7094, and δ11B of 12–17‰. The Ca–Mg–HCO3, Na–Cl–SO4, and Ca–SO4 compositions as well as the Br/Cl, 87Sr/86Sr, and δ11B values of the saline water suggest dissolution of Lower Jurassic carbonates and evaporite rocks in the High Atlas Mountain catchment. Storage and evaporation of the imported water in a man-made open reservoir causes an enrichment of the stable isotope ratios with a δ18O/δ2H slope of <8 but no change in the Sr and B isotope fingerprints. Downstream from the reservoir, large salinity variations were documented in the shallow groundwater from the six Drâa oases, with systematically higher salinity in the three southern oases, up to 12,000 mg/L. The increase of the salinity is systematically associated with a decrease of the Br/Cl ratio, indicating that the main mechanism of groundwater salinization in the shallow aquifers in the Drâa oases is via salt dissolution (gypsum, halite) in the unsaturated zone. Investigation of shallow groundwater that flows to the northern Drâa oases revealed lower salinity (TDS of 500–4225) water that is characterized by depleted 18O and 2H (as low as −9‰ and −66‰, respectively) and higher 87Sr/86Sr ratios (∼0.7107–0.7115) relative to irrigation water and groundwater flow from the Upper Drâa Basin. This newly-discovered low-saline groundwater with a different isotopic imprint flows from the northeastern Anti-Atlas Jabel Saghro Mountains to the northern oases of the Lower Drâa Basin. This adjacent subsurface flow results in a wide range of Sr isotope ratios in the shallow oases groundwater (0.7084–0.7131) and appears to mitigate salinization in the three northern Drâa oases. In contrast, in the southern oases, the higher salinity suggests that this mitigation is not as affective and increasing salinization through cycles of water irrigation and salt dissolution appears inevitable.  相似文献   

8.
The Aral Sea has been shrinking since 1963 due to extensive irrigation and the corresponding decline in the river water inflow. Understanding of the current hydrological situation demands an improved understanding of the surface water/groundwater dynamics in the region. 222Rn and 226Ra measurements can be used to trace groundwater discharge into surface waters. Data of these radiometric parameters were not previously available for the study region. We determined 222Rn activities after liquid phase extraction using Liquid Scintillation Counting (LSC) with peak-length discrimination and analyzed 226Ra concentrations in different water compartments of the Amu Darya Delta (surface waters, unconfined groundwater, artesian water, and water profiles from the closed Large Aral Sea (western basin).The water samples comprise a salinity range between 1 and 263 g/l. The seasonal dynamics of solid/water interaction under an arid climate regime force the hydrochemical evolution of the unconfined groundwater in the Amu Darya Delta to high-salinity Na(Mg)Cl(SO4) water types. The dissolved radium concentrations in the waters were mostly very low due to mineral over-saturation, extensive co-precipitation of radium and adsorption of radium on coexisting solid substrates.The analysis of very low 226Ra concentrations (<10 ppq) at remote study sites is a challenge. We used the water samples to test and improve different analytical methods. In particular, we modified a procedure developed for the α-spectrometric determination of 226Ra after solid phase extraction of radium using 3M Empore™ High Performance Extraction Disks (Purkl, 2002) for the analysis of the radionuclide using an ICP sector field mass spectrometer. The 226Ra concentration of 17 unconfined groundwater samples ranged between 0.2 and 5 ppq, and that of 28 artesian waters between <0.2 and 13 ppq. The ICP-MS results conformed satisfactorily to analytical results based on γ-measurements of the 222Rn ingrowth after purging and trapping on super-cooled charcoal. The 226Ra concentrations were positively correlated with the salinity and the dissolved NaCl concentrations. The occurrence of unusually high 226Ra activities is explained by radium release from adsorption sites with increasing salinity. The inferred spatial variability of 222Rn in the Aral Sea and of 222Rn and 226Ra in the groundwater of the Amu Darya Delta is discussed in the context of our own previous hydrochemical studies in the study sites. Relatively low 222Rn activities in the unconfined GW (1–9.5 Bq/l) indicate the alluvial sediments hosting the GW to be a low-238U(226Ra) substrate. Positive correlations between U and 226Ra, and U and 222Rn are likely related to locally deposited Fe(Mn)OOH precipitates. The 222Rn activity of the GW, however, distinctly exceeds the 222Rn concentration in the Aral Sea (10 mBq/l), in principle, making 222Rn a sensitive tracer for the inflow of GW. The high water volume of the Large Aral Sea and wind induced mixing of its water body, however, hamper the detection of local groundwater inflow.  相似文献   

9.
In Saudi Arabia, coastal sabkhas cover extensive areas along the coasts of the Red Sea and Arabian Gulf in addition to the continental sabkhas scattered in many places inland. Al-Lith sabkha is one of the typical coastal sabkhas located along the Red Sea coast. Sabkhas, in general, pose a number of geotechnical problems and need to be carefully investigated before being urbanized.A generalized geologic section in Al-Lith sabkha indicates a salty crust at the surface followed by yellowish brown silt and silty sand, olive gray silt and sandy silt and bottomed by coralline reefal limestone. Within this succession, there are several isolated lenticular bodies of sandy silt, silty sand and shelly silty sand. The clay minerals constituting the fine-grained portion of the soil are, in decreasing order, kaolinite, illite and montmorillonite in addition to minor chlorite.The depth to groundwater in 17 observation wells ranged from 0.18 to 1.81 m with a maximum fluctuation of 0.60 m between summer and winter. The permeability of the top silt layer was found to be very low with an average of 5.4×10−4 m/day. A pumping test was performed in a deep well penetrating the coralline limestone. The measured permeability is 1.1×102 m/day and the estimated storage coefficient is 4×10−5.Soil water evaporation was measured using a lysimeter constructed with undisturbed soil samples having different depths to the water level. The rate of evaporation ranges from 2.8 to 27.8 ml/day decreasing with an increase in depth to the water level.Groundwater samples were analyzed for their major anions and cations. Salt concentrations show a general increase toward the sea except for the calcium and carbonates that show a landward increase. The groundwater could be classified as a Cl+SO4 brine. The salinity of the groundwater was determined at different depths in the pumping well and was found to be low in the top 4 m. It sharply increases until it reaches a value approximately 10 times the salinity of the top layer indicating groundwater intermixing with freshwater and salt-water intrusion. The change in the salinity during pumping was erratic but within a range of 2%.  相似文献   

10.
The pollution and deterioration of most important vital rivers in the Katanga region, Democratic Republic of Congo (DRC) are mainly due to the discharge of untreated industrial effluents as well as to the mining and artisanal mineral exploitation activities. In this study, the concentrations of metals (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, and Pb) and major elements (Na, Mg, and K) in mining effluents, water and sediment samples of two main rivers of the district of Kolwezi (Katanga, DRC) were subjected to analysis by Inductive Coupled Plasma-Mass Spectroscopy (ICP-MS). The results showed that, in general, the metal concentrations in the sampling sites from the mining effluent and river waters exceed largely the World Health Organization and the Aquatic Quality Guidelines for the Protection of Aquatic Life recommendation limits. The highest metal concentrations in water and sediment samples were detected surrounding the mining effluents discharge. In the surface sediments of Luilu River, the values of 47,468 and 13,199 mg kg−1 were observed for Cu and Co, respectively. For the sediment samples from Musonoie River, the maximum values of 370.8 and 240.6 mg kg−1 for Cu and Co, respectively were observed. The results of this study suggest that the mining effluents being discharged into the rivers and the accumulation of pollutants in sediments might represent a source of toxicity for aquatic living organisms and could pose significant human health risks. The measures to establish a monitoring program and the application of wastewater treatment techniques to the mining effluents prior to discharge are recommended to reduce the load of contaminants into the receiving systems.  相似文献   

11.
Exploration of unconventional natural gas reservoirs such as impermeable shale basins through the use of horizontal drilling and hydraulic fracturing has changed the energy landscape in the USA providing a vast new energy source. The accelerated production of natural gas has triggered a debate concerning the safety and possible environmental impacts of these operations. This study investigates one of the critical aspects of the environmental effects; the possible degradation of water quality in shallow aquifers overlying producing shale formations. The geochemistry of domestic groundwater wells was investigated in aquifers overlying the Fayetteville Shale in north-central Arkansas, where approximately 4000 wells have been drilled since 2004 to extract unconventional natural gas. Monitoring was performed on 127 drinking water wells and the geochemistry of major ions, trace metals, CH4 gas content and its C isotopes (δ13CCH4), and select isotope tracers (δ11B, 87Sr/86Sr, δ2H, δ18O, δ13CDIC) compared to the composition of flowback-water samples directly from Fayetteville Shale gas wells. Dissolved CH4 was detected in 63% of the drinking-water wells (32 of 51 samples), but only six wells exceeded concentrations of 0.5 mg CH4/L. The δ13CCH4 of dissolved CH4 ranged from −42.3‰ to −74.7‰, with the most negative values characteristic of a biogenic source also associated with the highest observed CH4 concentrations, with a possible minor contribution of trace amounts of thermogenic CH4. The majority of these values are distinct from the reported thermogenic composition of the Fayetteville Shale gas (δ13CCH4 = −35.4‰ to −41.9‰). Based on major element chemistry, four shallow groundwater types were identified: (1) low (<100 mg/L) total dissolved solids (TDS), (2) TDS > 100 mg/L and Ca–HCO3 dominated, (3) TDS > 100 mg/L and Na–HCO3 dominated, and (4) slightly saline groundwater with TDS > 100 mg/L and Cl > 20 mg/L with elevated Br/Cl ratios (>0.001). The Sr (87Sr/86Sr = 0.7097–0.7166), C (δ13CDIC = −21.3‰ to −4.7‰), and B (δ11B = 3.9–32.9‰) isotopes clearly reflect water–rock interactions within the aquifer rocks, while the stable O and H isotopic composition mimics the local meteoric water composition. Overall, there was a geochemical gradient from low-mineralized recharge water to more evolved Ca–HCO3, and higher-mineralized Na–HCO3 composition generated by a combination of carbonate dissolution, silicate weathering, and reverse base-exchange reactions. The chemical and isotopic compositions of the bulk shallow groundwater samples were distinct from the Na–Cl type Fayetteville flowback/produced waters (TDS ∼10,000–20,000 mg/L). Yet, the high Br/Cl variations in a small subset of saline shallow groundwater suggest that they were derived from dilution of saline water similar to the brine in the Fayetteville Shale. Nonetheless, no spatial relationship was found between CH4 and salinity occurrences in shallow drinking water wells with proximity to shale-gas drilling sites. The integration of multiple geochemical and isotopic proxies shows no direct evidence of contamination in shallow drinking-water aquifers associated with natural gas extraction from the Fayetteville Shale.  相似文献   

12.
In recent years, voices in Jordan became lauder to exploit the fresh to brackish deep groundwater overlain by fresh groundwater bodies. In this article the implications of such a policy on the existing fresh water bodies are worked out through studying the sources of salinity in the different aquifer systems and the potentials of salinity mobilization by artificial changes in the hydrodynamic regimes. It is concluded that extracting the groundwater of deep aquifers overlain by fresh water bodies, whether the deep groundwater is fresh to brackish, brackish or salty, is equivalent to extracting groundwater from the overlying fresh groundwater bodies because of the hydraulic connections of the deep and the shallow aquifers’ groundwaters. The consequences are even more complicated and severe because exploiting the deep groundwater containing brackish or salty water will lead to refilling by fresh groundwater leaking from the overlying aquifers. The leaking water becomes salinized as soon as it enters the pore spaces of the emptied deep aquifer matrix and by mixing with the deep aquifer brackish or saline groundwater. Therefore, the move to exploit the deep groundwater is misleading and damaging the aquifers and is unjust to future generation's rights in the natural wealth of Jordan or any other country with similar aquifers’ set-up. In addition, desalination produces brines with high salinity which cannot easily be discharged in the highlands of Jordan (with only very limited access to the open sea) because they will on the long term percolate down into fresh water aquifers.  相似文献   

13.
The Ca–Mg relationship in groundwaters strongly points to the overall dolomitization and local albitization. The Mg/Ca ratios reveal two trends by which saline waters develop: increase of Mg/Ca ratio by evaporation and decreasing Mg/Ca ratios due to dolomitization and albitization. Br/Cl vs. Na/Cl ratios demonstrate that albitization does not play a major role which leaves dolomitization to be the main source for decreasing Mg/Ca ratios in saline waters. In the eastern and southern Region of Lake Kinneret, salinization occurs by mixing with a Ca/Mg molar ratio <1 brine (Ha’On type). Along the western shoreline of the Lake, a Ca/Mg > 1 dominates, which developed by the albitization of plagioclase in abundant mafic volcanics and the dolomitization of limestones. The most saline groundwater of the Tabgha-, Fuliya-, and Tiberias clusters could be regional derivatives of at least two mother brines: in diluted form one is represented by Ha’On water, the other is a Na-rich brine of the Zemah type. Additionally, a deep-seated Ca-dominant brine may ascend along the fractures on the western side of Lake Kinneret, which is absent on the eastern side. Groundwaters of the Lower Jordan Valley are chemically different on both sides of the Jordan River, indicating that the exchange of water is insignificant. All saline waters from the Dead Sea and its surroundings represent a complex mixture of brines, and precipitation and local dissolution of halite and gypsum. Many wells of the Arava/Araba Valley pump groundwater from the Upper Cretaceous limestone aquifer, the origin of the water is actually from the Lower Cretaceous Kurnub Group sandstones. Groundwater drawn from the Quaternary alluvial fill either originates from Kurnub Group sandstones (Eilat 108, Yaalon 117) or from altered limestones of the Judea Group. The origin of these waters is from floods flowing through wadis incised into calcareous formations of the Judea Group. On the other hand, as a result of step-faulting, hydraulic contact is locally established between the Kurnub- and the Judea Groups aquifers facilitating the inter-aquifer flow of the confined Kurnub paleowater into the karstic formations of the Judea Group. Two periods of Neogene brine formation are considered: the post-Messinan inland lagoon resulting in drying up of the Sdom Sea and the evaporation of the Pleistocene Samra Lake, which went further through the stage of Lake Lisan to the present Dead Sea. For the first period, major element hydrochemistry suggests that the saline waters and brines in the Jordan-Dead Sea–Arava Valley transform evolved from the gradual evaporation of an accumulating mixture of sea-, ground-, and surface water. Due to the precipitation of carbonates, gypsum, and halite, such an evaporating primary water body was strongly enriched in Mg, Br, and B and shows high molar ratios of Br/Cl, B/Cl, and Mg/Ca but low Na/Cl ratios. The development of the Br/Cl ratio is chemically modelled, showing that indeed brine development is explicable that way. Along with the evaporation brine, evaporites formed which are leached by infiltrating fresh water yielding secondary brines with Na/Cl ratios of 1. When primary brines infiltrated the sub-surface, they were subjected to Mg–Ca exchange in limestones (dolomitization) and to chloritization and albitization in basic igneous rocks turning them into Ca-Cl brines. These tertiary brines are omnipresent in the Rift. The brines of the late Lisan and Dead Sea were generated by evaporating drainage waters, which leached halite, gypsum, and carbonates from the soil and from the sub-surface. All these brines are still being flushed out by meteoric water, resulting in saline groundwaters. This flushing is regionally enhanced by intensive groundwater exploitation. In variable proportions, the Neogene and late Lisan Lake and Recent Dead Sea brines have to be considered as the most serious sources of salinization of groundwaters in the Rift. Deep-seated pre-Sdom brines cannot strictly be excluded, but if active they play a negligible role only. An erratum to this article can be found at  相似文献   

14.
In this study, we report for the first time lanthanum and gadolinium anomalies at the catchment scale (Rhine-Meuse River system) together with the partitioning of their anthropogenic contents between the dissolved and the particulate phases. We compare the dissolved and total REE patterns of samples taken at 9 locations in the Rhine Branches including Lobith (situated at the German–Dutch border where the Rhine is not yet divided in three Branches), in surface water fed by the Rhine Branches (canals and lake IJsselmeer and Ketelmeer) and 3 locations where the water is derived from the river Meuse (originating from Belgium and France).We demonstrate that the anthropogenic input of lanthanum in the German part of the Rhine River identified by Kulaksiz and Bau (2011) can be traced in the complex Rhine-Meuse Delta up to the North Sea. In the Dutch Branches of the Rhine River, in contrast to the German part of the Rhine River, the anthropogenic lanthanum (LaANTHRO) is mainly present in the particulate phase (SPM) and not in the dissolved phase (defined as the <0.45 μm fraction). In the Meuse River no anthropogenic lanthanum was found. The amount of LaANTHRO transported by the Rhine River at the Lobith station (German–Dutch border) varies from 2008 to 2010 between 3.7 and 5.2 tons/y in the dissolved phase, and between 28.8 and 37.4 tons/y in the particulate phase. However, a big discrepancy is evidenced when we compare the LaANTHRO load calculated on bases of the total water samples with the LaANTHRO load calculated as the sum of the particulate and dissolved load: the total LaANTHRO load is roughly 2 times larger than the LaANTHRO load calculated as the sum of the dissolved and particulate LaANTHRO load. The difference between the two calculated fluxes is most likely caused by not sampling the finest fraction of the particulate pool in the SPM samples with an overflow centrifuge.The anthropogenic gadolinium identified by high gadolinium anomalies in the REE patterns originates from numerous point sources (waste water treatment plant effluents) and can thus be considered as diffuse pollution when compared to anthropogenic lanthanum clearly resulting from a single source. The amount of anthropogenic gadolinium measured in the dissolved phase (main carrier of Gd) increases or decreases along the Rhine and Meuse Rivers depending whether or not the mixing water contains anthropogenic gadolinium, i.e. receives waste water effluents.  相似文献   

15.
A conceptual groundwater flow model was developed for the crystalline aquifers in southeastern part of the Eastern region, Ghana. The objective was to determine approximate levels of groundwater recharge, estimate aquifer hydraulic parameters, and then test various scenarios of groundwater extraction under the current conditions of recharge. A steady state groundwater flow model has been calibrated against measured water levels of 19 wells in the area. The resulting recharge is estimated to range from 8.97 × 10?5 m/d to 7.14 × 10?4 m/d resulting in a basin wide average recharge of about 9.6% of total annual precipitation, which results in a basin wide quantitative recharge of about 2.4 million m3/d in the area. This compares to recharge estimated from the chloride mass balance of 7.6% of precipitation determined in this study. The general groundwater flow in the area has also been determined to conform to the general northeast–southwest structural grain of the country. The implication is that the general hydrogeology is controlled by post genetic structural entities imposed on the rocks to create ingresses for sufficient groundwater storage and transport. Calibrated aquifer hydraulic conductivities range between 0.99 m/d and over 19.4 m/d. There is a significant contribution of groundwater discharge to stream flow in the study area. Increasing groundwater extraction will have an effect on stream flow. This study finds that the current groundwater extraction levels represent only 0.17% of the annual recharge from precipitation, and that groundwater can sustain future increased groundwater demands from population growth and industrialization.  相似文献   

16.
《Applied Geochemistry》1999,14(7):917-925
The origin of salinity within the Äspö groundwater system is investigated by combining interpretations of conservative dissolved ions and of stable isotope ratios in water. The interpretation concludes that the groundwater salinity results from a mixing between Baltic Sea water intrusion and a deep seated saline groundwater of marine origin. This conclusion supports the geochemical model developed for the Äspö site. The residence time of the deep salinity is assessed by comparing the 36Cl content of dissolved salt at different depths and the secular equilibrium value of the host rock. The 36Cl of deepest levels corresponding to the highest salinity, is in equilibrium with rock, suggesting a penetration of the deep salinity into the host rock more than 1.5 Ma ago.  相似文献   

17.
《Quaternary Science Reviews》2007,26(19-21):2586-2597
Recent paleoclimatic work on terrestrial and marine deposits from Asia and the Indian Ocean has indicated abrupt changes in the strength of the Asian monsoon during the last deglaciation. Comparison of marine paleoclimate records that track salinity changes from Asian rivers can help evaluate the coherence of the Indian Ocean monsoon (IOM) with the larger Asian monsoon. Here we present paired Mg/Ca and δ18O data on the planktic foraminifer Globigerinoides ruber (white) from Andaman Sea core RC12-344 that provide records of sea-surface temperature (SST) and δ18O of seawater (δ18Osw) over the past 25,000 years (ka) before present (BP). Age control is based on nine accelerator mass spectrometry (AMS) dates on mixed planktic foraminifera. Mg/Ca-SST data indicate that SST was ∼3 °C cooler during the last glacial maximum (LGM) than the late Holocene. Andaman Sea δ18Osw exhibited higher than present values during the Lateglacial interval ca 19–15 ka BP and briefly during the Younger Dryas ca 12 ka BP. Lower than present δ18Osw values during the BØlling/AllerØd ca 14.5–12.6 ka BP and during the early Holocene ca 10.8–5.5 ka BP are interpreted to indicate lower salinity, reflect some combination of decreased evaporation–precipitation (E–P) over the Andaman Sea and increased Irrawaddy River outflow. Our results are consistent with the suggestion that IOM intensity was stronger than present during the BØlling/AllerØd and early Holocene, and weaker during the late glaciation, Younger Dryas, and the late Holocene. These findings support the hypothesis that rapid climate change during the last deglaciation and Holocene included substantial hydrologic changes in the IOM system that were coherent with the larger Asian monsoon.  相似文献   

18.
The Yellow, Yangtze and Pearl Rivers supply over 90% of the sediment flux from China to the western Pacific Ocean. Trends and abrupt changes in the water discharge and sediment load of the three rivers were examined and compared based on data updated to the year 2011 at the seasonal and annual scales. The total water discharge from the three rivers shows a statistically insignificant decreasing trend with a rate of 0.62 × 109 m3/a, and the total sediment load shows a statistically significant decreasing trend at a rate of 31.12 × 106 t/a from the 1950s to 2011. The water discharge of the entire Yellow River and the upstream portion of the Yangtze River shows significant decreasing trends, and that of the mid-lower stream of Yangtze River and the entire Pearl River shows insignificant trends. The sediment loads in the three river basins all show significant decreasing trends at the annual and seasonal scales, and a dramatic decrease in the 2000s resulted in a more obvious decreasing trend over the studied period. From the 1950s to the 2000s, the contribution of sediment flux from the Yellow River to the ocean decreased from 71.8% to 37.0%, and the contributions of the Yangtze and Pearl Rivers increased from 24.2% and 4.0% to 53.0% and 10.0%, respectively. Inter-annual variations in water discharge and sediment load were affected by climate oscillations, such as the El Niño/Southern Oscillation, and the long-term decreasing trend in sediment load was primarily caused by human activities. Dam constructions and soil conservation projects were the major causes of sediment reduction. From the 1970s to the 2000s, the decrease in total sediment load from the three rivers caused by climate change and human activities was 2.24 × 108 t/a (23.0%) and 7.5 × 108 t/a (77.0%), respectively. In the coming decades, the sediment flux from the three rivers into the sea will decrease further with intensifying human activities, resulting in many challenges for the management of river basins and river deltas.  相似文献   

19.
《Applied Geochemistry》2006,21(7):1184-1203
This paper examines the seasonal cycling of temperature and salinity in Dexter pit lake in arid northern Nevada, and describes an approach for modeling the physical processes that operate in such systems. The pit lake contains about 596,200 m3 of dilute, near neutral (pHs 6.7–9) water. Profiles of temperature, conductivity, and selected element concentrations were measured almost monthly during 1999 and 2000. In winter (January–March), the pit lake was covered with ice and bottom water was warmer (5.3 °C) with higher total dissolved solids (0.298 g/L) than overlying water (3.96 °C and 0.241 g/L), suggesting inflow of warm (11.7 °C) groundwater with a higher conductivity than the lake (657 versus 126–383 μS/cm). Seasonal surface inflow due to spring snowmelt resulted in lower conductivity in the surface water (232–247 μS/cm) relative to deeper water (315–318 μS/cm). The pit lake was thermally stratified from late spring through early fall, and the water column turned over in late November (2000) or early December (1999). The pit lake is a mixture of inflowing surface water and groundwater that has subsequently been evapoconcentrated in the arid environment. Linear relationships between conductivity and major and some minor (B, Li, Sr, and U) ions indicate conservative mixing for these elements.Similar changes in the elevations of the pit lake surface and nearby groundwater wells during the year suggest that the pit lake is a flow-through system. This observation and geochemical information were used to configure an one-dimensional hydrodynamics model (Dynamic Reservoir Simulation Model or DYRESM) that predicts seasonal changes in temperature and salinity based on the interplay of physical processes, including heating and cooling (solar insolation, long and short wave radiation, latent, and sensible heat), hydrologic flow (inflow and outflow by surface and ground water, pumping, evaporation, and precipitation), and transfers of momentum (wind stirring, convective overturn, shear, and eddy diffusion). Inputs to the model include the size and shape of the lake, daily meteorological data (short wave radiation, long wave radiation or cloud cover, air temperature, vapor pressure, wind speed, and rainfall), rates for water inputs and outputs, the composition of inflowing water, and initial profiles of temperature and salinity. Predicted temperature profiles, which are influenced by seasonal changes in the magnitude of solar radiation, are in good agreement with observations and show the development of a strong thermocline in the summer, erosion of the thermocline during early fall, and turnover in late fall. Predicted salinity profiles are in reasonable agreement with observations and are affected by the hydrologic balance, particularly inflow of surface and groundwater and, to a lesser degree, evaporation. Defining the hydrodynamics model for Dexter pit lake is the first step in using a coupled physical – biogeochemical model (Dynamic Reservoir Simulation Model-Computational Aquatic Ecosystem Dynamics Model or DYRESM-CAEDYM) to predict the behavior of non-conservative elements (e.g., dissolved O2, Mn, and Fe) and their effect on water quality in this system.  相似文献   

20.
《Applied Geochemistry》2005,20(10):1907-1919
Soil from an infiltration trench for highway runoff was leached in columns alternately with NaCl and de-ionised water to simulate the runoff of de-icing salt into the trench followed by snowmelt or rainwater. Simultaneously, two columns with the same soil were leached with de-ionised water throughout the experiment. In addition, the groundwater below the infiltration trench was sampled on some occasions. The column leachate and groundwater were split into two sub samples, one was filtered though a 0.45 μm filter; both were analysed for Pb, Cd, Zn, Fe and total organic carbon (TOC). The column experiment showed clearly that an extensive mobilisation of Pb occurred in low electrolyte water leaching following NaCl leaching. The high Pb concentration coincided with peaks in Fe and TOC concentrations and implied colloid-assisted transport. Conversely, Cd and Zn concentrations were raised in the NaCl leachate and a high correlation with Cl showed that Cl complexes are important for the mobilisation, although a pH effect and ionic exchange cannot be excluded. Only 0.15% and 0.06% of the total amount of Pb was leached from the columns leached with alternating NaCl and deionised water confirming the usual hypotheses about the high immobility of Pb in soils. However, on one occasion when the ionic strength and pH was the lowest measured the concentration of Pb in groundwater sampled from 2.5 m depth was 27 μg L−1 in the dissolved phase (<0.45 μm) and 77 μg L−1 in the particle phase (>0.45 μm). These Pb concentrations are almost 3 and 8 times above the Swedish limit for drinking water quality. Accordingly, in spite of the immobility of Pb the accumulation in roadside soils is so large that groundwater quality is threatened. In conclusion, the study suggests that roadside soils impacted by NaCl from de-icing operations contribute Pb to groundwater by colloid-assisted transport.  相似文献   

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