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6 pages, 208 KiB

Open AccessEditorial

Isotopes in Hydrology and Hydrogeology

by Maurizio Barbieri

Water 2019, 11(2), 291; https://doi.org/10.3390/w11020291 - 7 Feb 2019

Cited by 64 | Viewed by 10081

Abstract

The structure, status, and processes of the groundwater system, which can only be acquired through scientific research efforts, are critical aspects of water resource management. Isotope hydrology and hydrogeology is a genuinely interdisciplinary science. It developed from the application of methods evolved in [...] Read more.

The structure, status, and processes of the groundwater system, which can only be acquired through scientific research efforts, are critical aspects of water resource management. Isotope hydrology and hydrogeology is a genuinely interdisciplinary science. It developed from the application of methods evolved in physics (analytical techniques) to problems of Earth and the environmental sciences since around the 1950s. In this regard, starting from hydrogeochemical data, stable and radioactive isotope data provide essential tools in support of water resource management. The inventory of stable isotopes, which has significant implications for water resources management, has grown in recent years. Methodologies based on the use of isotopes in a full spectrum of hydrological problems encountered in water resource assessment, development, and management activities are already scientifically established and are an integral part of many water resource investigations and environmental studies. The driving force behind this Special Issue was the need to point the hydrological and water resource management societies in the direction of up-to-date research and best practices. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

Research

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17 pages, 2042 KiB

Open AccessArticle

Classification of Stable Isotopes and Identification of Water Replenishment in the Naqu River Basin, Qinghai-Tibet Plateau

by Xi Chen, Guoli Wang and Fuqiang Wang

Water 2019, 11(1), 46; https://doi.org/10.3390/w11010046 - 28 Dec 2018

Cited by 14 | Viewed by 4061

Abstract

The stable isotopic study of the mechanism of runoff replenishment in the Qinghai-Tibet Plateau is a time-consuming and complicated process requiring complex monitoring data and scientific evaluation methods. Based on the data of water stable isotopes (¹⁸O and ²H) in [...] Read more.

The stable isotopic study of the mechanism of runoff replenishment in the Qinghai-Tibet Plateau is a time-consuming and complicated process requiring complex monitoring data and scientific evaluation methods. Based on the data of water stable isotopes (¹⁸O and ²H) in the Naqu River basin, the present paper developed a framework of the variable fuzzy evaluation model (VFEM) to provide a method to classify stable isotopes and generalize the source identification of water replenishment by rainfall or snowmelt in the Naqu River basin. The grade eigenvalues of tributaries were ranked from low to high as follows: 1, 1.005, 1.089, 1.151, 1.264, 1.455 and 2.624. Three sets of tributaries were distinguished. The grade eigenvalues of the Najinqu, Bazongqu, Mumuqu, Chengqu and Gongqu Rivers were small, indicating that these tributaries were strongly supplemented by precipitation and snowmelt; the grade eigenvalue of the Zongqingqu River was in the medium range (1.455); the third group included the Mugequ River with a high status value (2.624). This study mainly highlighted the combination of the classification of stable isotopes and plots of δ²H vs. δ¹⁸O in the source identification of water replenishment, which will be helpful for studying runoff replenishment and the evolution mechanism in the Qinghai-Tibet Plateau. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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12 pages, 1666 KiB

Open AccessArticle

Waters from the Djiboutian Afar: A Review of Strontium Isotopic Composition and a Comparison with Ethiopian Waters and Red Sea Brines

by Tiziano Boschetti, Mohamed Osman Awaleh and Maurizio Barbieri

Water 2018, 10(11), 1700; https://doi.org/10.3390/w10111700 - 21 Nov 2018

Cited by 28 | Viewed by 8224

Abstract

Drinking water is scarce in Djibouti because of the hot desert climate. Moreover, seawater intrusion or fossil saltwater contamination of the limited number of freshwater aquifers due to groundwater overexploitation affect those who live close to the coastline (~80% of the population). Despite [...] Read more.

Drinking water is scarce in Djibouti because of the hot desert climate. Moreover, seawater intrusion or fossil saltwater contamination of the limited number of freshwater aquifers due to groundwater overexploitation affect those who live close to the coastline (~80% of the population). Despite this, the geothermal potential of the country’s plentiful hot springs could resolve the increasing electricity demand. Strontium isotopes (⁸⁷Sr/⁸⁶Sr) are routinely used to determine sources and mixing relationships in geochemical studies. They have proven to be useful in determining weathering processes and quantifying endmember mixing processes. In this study, we summarise and reinterpret the ⁸⁷Sr/⁸⁶Sr ratio and Sr concentration data of the groundwater collected to date in the different regions of the Djibouti country, trying to discriminate between the different water sources, to evaluate the water/rock ratio and to compare the data with those coming from the groundwater in the neighbouring Main Ethiopian Rift and the Red Sea bottom brine. New preliminary data from the groundwater of the Hanlé-Gaggadé plains are also presented. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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24 pages, 11635 KiB

Open AccessArticle

High-Frequency Water Isotopic Analysis Using an Automatic Water Sampling System in Rice-Based Cropping Systems

by Amani Mahindawansha, Lutz Breuer, Alejandro Chamorro and Philipp Kraft

Water 2018, 10(10), 1327; https://doi.org/10.3390/w10101327 - 25 Sep 2018

Cited by 10 | Viewed by 4434

Abstract

High-resolution data on a field scale is very important for improving our understanding of hydrological processes. This is particularly the case for water-demanding agricultural production systems such as rice paddies, for which water-saving strategies need to be developed. Here we report on the [...] Read more.

High-resolution data on a field scale is very important for improving our understanding of hydrological processes. This is particularly the case for water-demanding agricultural production systems such as rice paddies, for which water-saving strategies need to be developed. Here we report on the application of an in situ, automatic sampling system for high-resolution data on stable isotopes of water (¹⁸O and ²H). We investigate multiple rice-based cropping systems consisting of wet rice, dry rice and maize, with a single, but distributed analytical system on a sub-hourly basis. Results show that under dry conditions, there is a clear and distinguishable crop effect on isotopic composition in groundwater. The least evaporative affected groundwater source is that of maize, followed by both rice varieties. Groundwater is primarily a mixture of irrigation and rainwater, where the main driver is irrigation water during the dry season and rainwater during the wet season. Stable isotopes of groundwater under dry season maize react rapidly on irrigation, indicating preferential flow processes via cracks and deep roots. The groundwater during the dry season under wet and dry rice fields is dominated at the beginning of the growing season mainly by the input of rainwater; later, the groundwater is more and more replenished by irrigation water. Overall, based on our data, we estimate significantly higher evaporation (63–77%) during the dry season as compared to the wet season (27–36%). We also find, for the first time, significant sub-daily isotopic variation in groundwater and surface ponded water, with an isotopic enrichment during the daytime. High correlations with relative humidity and temperature, explain part of this variability. Furthermore, the day-night isotopic difference in surface water is driven by the temperature and relative humidity; however, in groundwater, it is neither driven by these factors. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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11 pages, 2868 KiB

Open AccessArticle

Diurnal and Semidiurnal Cyclicity of Radon (²²²Rn) in Groundwater, Giardino Spring, Central Apennines, Italy

by Marino Domenico Barberio, Francesca Gori, Maurizio Barbieri, Andrea Billi, Roberto Devoti, Carlo Doglioni, Marco Petitta, Federica Riguzzi and Sergio Rusi

Water 2018, 10(9), 1276; https://doi.org/10.3390/w10091276 - 18 Sep 2018

Cited by 28 | Viewed by 6876

Abstract

Understanding natural variations of Rn (²²²Rn) concentrations is the fundamental prerequisite of using this radioactive gas as a tracer, or even precursor, of natural processes, including earthquakes. In this work, Rn concentrations in groundwater were continuously measured over a seven-month period, [...] Read more.

Understanding natural variations of Rn (²²²Rn) concentrations is the fundamental prerequisite of using this radioactive gas as a tracer, or even precursor, of natural processes, including earthquakes. In this work, Rn concentrations in groundwater were continuously measured over a seven-month period, during 2017, in the Giardino Spring, Italy, together with groundwater levels in a nearby well installed into a fractured regional aquifer. Data were processed to reduce noise, and then analyzed to produce the Fourier spectra of Rn concentrations and groundwater levels. These spectra were compared with the spectrum of tidal forces. Results showed that diurnal and semidiurnal cycles of Rn concentrations, and filtered oscillations of groundwater levels, in the nearby well, are correlated with solar and luni-solar components of tidal forces, and suggested no correlation with the principal lunar components. Therefore, influencing factors linked to solar cycles, such as daily oscillations of temperature and atmospheric pressure, and related rock deformations, may have played a role in Rn concentrations and groundwater levels. An open question remains regarding the correlation, which is documented elsewhere, of Rn concentrations and groundwater levels with the lunar components of the solid Earth tides. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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16 pages, 3206 KiB

Open AccessArticle

Evaluating Temporal and Spatial Variation in Nitrogen Sources along the Lower Reach of Fenhe River (Shanxi Province, China) Using Stable Isotope and Hydrochemical Tracers

by Zhilong Meng, Yonggang Yang, Zuodong Qin and Lei Huang

Water 2018, 10(2), 231; https://doi.org/10.3390/w10020231 - 24 Feb 2018

Cited by 37 | Viewed by 5755

Abstract

Nitrate is one of the most common pollutants in river systems. This study takes the lower reach of Fenhe River as a case study, combined with a multi-isotope and hydrochemical as the tracers to identify nitrate sources in river system. The results show [...] Read more.

Nitrate is one of the most common pollutants in river systems. This study takes the lower reach of Fenhe River as a case study, combined with a multi-isotope and hydrochemical as the tracers to identify nitrate sources in river system. The results show that all samples in the industrial region (IR) and urban region (UR) and 68.8% of the samples in the agriculture region (AR) suffer from nitrate pollution. NO₃⁻–N is the main existing form of dissolved inorganic nitrogen (DIN), followed by NH₄⁺–N, which account for 57.9% and 41.9% of the DIN, respectively. The temporal variation in nitrogenous species concentration is clear over the whole hydrological year. The spatial variation is smaller among different sampling sites in the same region but greater among different regions. The main source of nitrogenous species is from anthropogenic rather than natural effects. Multi-isotope analysis shows that denitrification is found in some water samples. Combined with the apportionment of nitrate sources by the IsoSource model and the analysis of the Cl⁻ content, the main source of nitrate in the IR, UR and AR are industrial sewage and manure, domestic sewage and manure, and chemical fertilizers, respectively. Atmospheric nitrogen deposition is also a source of nitrate in the study area. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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14 pages, 7184 KiB

Open AccessArticle

Simulation of Groundwater Flow and Migration of the Radioactive Cobalt-60 from LAMA Nuclear Facility-Iraq

by Thair Sharif Khayyun

Water 2018, 10(2), 176; https://doi.org/10.3390/w10020176 - 9 Feb 2018

Cited by 11 | Viewed by 5054

Abstract

This study provides a simulation of groundwater flow and advective-dispersive migration of radioactive Co-60 through an aquifer with three layers, which release or leak to groundwater from the Active Metallurgy Testing Laboratory (LAMA) Nuclear Facility-Iraq due to the nuclear accident scenario. Processing Modflow [...] Read more.

This study provides a simulation of groundwater flow and advective-dispersive migration of radioactive Co-60 through an aquifer with three layers, which release or leak to groundwater from the Active Metallurgy Testing Laboratory (LAMA) Nuclear Facility-Iraq due to the nuclear accident scenario. Processing Modflow for windows (PMWIN) and Modular Three-Dimensional Multispecies Transport (MT3DMS) Models were used for this purpose. The study area and the contaminated area were 12.7 km² and 0.005625 km², respectively. Water levels of the groundwater have been measured in six monitoring wells. The simulation time was assumed to have started in 2016. The PMWIN model simulated the flow for two scenarios of water level in Tigris River (average and minimum water levels). The MT3DMS model simulated 10 years of plume travel, beginning in 2016. The simulated Co-60 concentrations after five years of travel were 32.34 and 34.44 μg/m³ for the two scenarios. The maximum predicted Co-60 concentrations at the end of Year 10 were 34.86 and 37.31 μg/m³, respectively. The sensitivity analysis showed that the simulated hydraulic heads in the observation wells and the simulated plume of Co-60 were highly sensitive to changes in the effective porosity but less sensitive to changes in other parameters of the dispersion and chemical reaction processes. The time necessary to reach steady state condition was predicted to be approximately 16 years. The contaminated area was isolated by using remedial process which is represented by three fully penetrating pumping wells with a suitable flow rate (0.045 m³/s) for controlling the movement of Co-60 pollutant. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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21 pages, 7059 KiB

Open AccessArticle

Quantification of Groundwater Discharge in a Subalpine Stream Using Radon-222

by Elizabeth Avery, Richard Bibby, Ate Visser, Bradley Esser and Jean Moran

Water 2018, 10(2), 100; https://doi.org/10.3390/w10020100 - 25 Jan 2018

Cited by 24 | Viewed by 5801

Abstract

During the dry months of the water year in Mediterranean climates, groundwater influx is essential to perennial streams for sustaining ecosystem health and regulating water temperature. Predicted earlier peak flow due to climate change may result in decreased baseflow and the transformation of [...] Read more.

During the dry months of the water year in Mediterranean climates, groundwater influx is essential to perennial streams for sustaining ecosystem health and regulating water temperature. Predicted earlier peak flow due to climate change may result in decreased baseflow and the transformation of perennial streams to intermittent streams. In this study, naturally occurring radon-222 (²²²Rn) was used as a tracer of groundwater influx to Martis Creek, a subalpine stream near Lake Tahoe, CA. Groundwater ²²²Rn is estimated based on measurements of ²²²Rn activity in nearby deep wells and springs. To determine the degassing constant (needed for quantification of water and gas flux), an extrinsic tracer, xenon (Xe), was introduced to the stream and monitored at eight downstream locations. The degassing constant for ²²²Rn is based on the degassing constant for Xe, and was determined to be 1.9–9.0 m/day. Applying a simple model in which stream ²²²Rn activity is a balance between the main ²²²Rn source (groundwater) and sink (volatilization), the influx in reaches of the upstream portion of Martis Creek was calculated to be <1 to 15 m³/day/m, which cumulatively constitutes a significant portion of the stream discharge. Experiments constraining ²²²Rn emanation from hyporheic zone sediments suggest that this should be considered a maximum rate of influx. Groundwater influx is typically difficult to identify and quantify, and the method employed here is useful for identifying locations for focused stream flow measurements, for formulating a water budget, and for quantifying streamwater–groundwater interaction. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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22 pages, 7378 KiB

Open AccessArticle

Tracers Reveal Recharge Elevations, Groundwater Flow Paths and Travel Times on Mount Shasta, California

by Elizabeth Peters, Ate Visser, Bradley K. Esser and Jean E. Moran

Water 2018, 10(2), 97; https://doi.org/10.3390/w10020097 - 23 Jan 2018

Cited by 18 | Viewed by 8755

Abstract

Mount Shasta (4322 m) is famous for its spring water. Water for municipal, domestic and industrial use is obtained from local springs and wells, fed by annual snow melt and sustained perennially by the groundwater flow system. We examined geochemical and isotopic tracers [...] Read more.

Mount Shasta (4322 m) is famous for its spring water. Water for municipal, domestic and industrial use is obtained from local springs and wells, fed by annual snow melt and sustained perennially by the groundwater flow system. We examined geochemical and isotopic tracers in samples from wells and springs on Mount Shasta, at the headwaters of the Sacramento River, in order to better understand the hydrologic system. The topographic relief in the study area imparts robust signatures of recharge elevation to both stable isotopes of the water molecule (δ¹⁸O and δD) and to dissolved noble gases, offering tools to identify recharge areas and delineate groundwater flow paths. Recharge elevations determined using stable isotopes and noble gas recharge temperatures are in close agreement and indicate that most snowmelt infiltrates at elevations between 2000 m and 2900 m, which coincides with areas of thin soils and barren land cover. Large springs in Mt Shasta City discharge at an elevation more than 1600 m lower. High elevation springs (>2000 m) yield very young water (<2 years) while lower elevation wells (1000–1500 m) produce water with a residence time ranging from 6 years to over 60 years, based on observed tritium activities. Upslope movement of the tree line in the identified recharge elevation range due to a warming climate is likely to decrease infiltration and recharge, which will decrease spring discharge and production at wells, albeit with a time lag dependent upon the length of groundwater flow paths. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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12 pages, 1306 KiB

Open AccessArticle

Understanding the Burial and Migration Characteristics of Deep Geothermal Water Using Hydrogen, Oxygen, and Inorganic Carbon Isotopes

by Xinyi Wang, Weifang Qiao, Jing Chen, Xiaoman Liu and Fang Yang

Water 2018, 10(1), 7; https://doi.org/10.3390/w10010007 - 22 Dec 2017

Cited by 11 | Viewed by 4856

Abstract

Geothermal water samples taken from deep aquifers within the city of Kaifeng at depths between 800 and 1650 m were analyzed for conventional water chemical compositions and stable isotopes. These results were then combined with the deuterium excess parameter (d value), and the [...] Read more.

Geothermal water samples taken from deep aquifers within the city of Kaifeng at depths between 800 and 1650 m were analyzed for conventional water chemical compositions and stable isotopes. These results were then combined with the deuterium excess parameter (d value), and the contribution ratios of different carbon sources were calculated along with distributional characteristics and data on the migration and transformation of geothermal water. These results included the conventional water chemical group, hydrogen, and oxygen isotopes (δD-δ¹⁸O), dissolved inorganic carbon (DIC) and associated isotopes (δ¹³C_DIC). The results of this study show that geothermal water in the city of Kaifeng is weakly alkaline, water chemistry mostly comprises a HCO₃-Na type, and the range of variation of δD is between −76.12‰ and −70.48‰, (average: −74.25‰), while the range of variation of δ¹⁸O is between −11.08‰ and −9.41‰ (average: −10.15‰). Data show that values of d vary between 1.3‰ and 13.3‰ (average: 6.91‰), while DIC content is between 91.523 and 156.969 mg/L (average: 127.158 mg/L). The recorded range of δ¹³C_DIC was between −10.160‰ and −6.386‰ (average: −9.019‰). The results presented in this study show that as depth increases, so do δD and δ¹⁸O, while d values decrease and DIC content and δ¹³C_DIC gradually increase. Thus, δD, δ¹⁸O, d values, DIC, and δ¹³C_DIC can all be used as proxies for the burial characteristics of geothermal water. Because data show that the changes in d values and DIC content are larger along the direction of geothermal water flow, so these proxies can be used to indicate migration. This study also shows demonstrates that the main source of DIC in geothermal water is CO₂thathas a biological origin in soils, as well as the dissolution of carbonate minerals in surrounding rocks. Thus, as depth increases, the contribution of soil biogenic carbon sources to DIC decreases while the influence of carbonate dissolution on DIC increases. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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21 pages, 5530 KiB

Open AccessArticle

The Source, Flow Rates, and Hydrochemical Evolution of Groundwater in an Alluvial Fan of Qilian Mountain, Northwest China

by Qiaona Guo, Zhifang Zhou and Shan Wang

Water 2017, 9(12), 912; https://doi.org/10.3390/w9120912 - 23 Nov 2017

Cited by 10 | Viewed by 5651

Abstract

Major ions and selected environmental tracers (D, ¹⁸O, ³H and chlorofluorocarbons (CFCs)) were employed to determine the source, flow rates, and hydrochemical evolution of groundwater in an alluvial fan along the front of the Qilian Mountains, which serves as an important [...] Read more.

Major ions and selected environmental tracers (D, ¹⁸O, ³H and chlorofluorocarbons (CFCs)) were employed to determine the source, flow rates, and hydrochemical evolution of groundwater in an alluvial fan along the front of the Qilian Mountains, which serves as an important groundwater reservoir in northwest China. Temporal and spatial variations in ion concentrations were limited near the upper portion of the alluvial fan. However, groundwater quality deteriorated along the flow path as concentrations of Mg²⁺, Na⁺, SO₄²⁻, and Cl⁻ increased toward the fan toe and into the center of the valley. The relative abundance of the major cations and anions also changed down-fan from Ca²⁺ to Na⁺ and Mg²⁺, and from HCO₃⁻ to SO₄²⁻ and Cl⁻, respectively. Isotopic data suggests that precipitation within the Qilian Mountains, which recharged the alluvial deposits near the mountain front, was the primary source of groundwater. Apparent groundwater ages determined by CFCs varied from 23 to 40 years, and in general, increased in age from south to north (down-fan). It is concluded that groundwater in the study area was recharged by the Qilian Mountains, flowed through the alluvial fan from south to north, and was subsequently discharged several decades later from springs located along the toe of the fan, after which it re-entered the Shule River. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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10 pages, 3024 KiB

Open AccessFeature PaperArticle

Evolution of Uranium Isotopic Compositions of the Groundwater and Rock in a Sandy-Clayey Aquifer

by Alexander I. Malov

Water 2017, 9(12), 910; https://doi.org/10.3390/w9120910 - 23 Nov 2017

Cited by 9 | Viewed by 5480

Abstract

Uranium isotopes have been used as mechanistic or time scale tracers of natural processes. This paper describes the occurrence and redistribution of U in the Vendian aquifer of a paleo-valley in NW Russia. Forty-four rock samples were collected from nine boreholes with depths [...] Read more.

Uranium isotopes have been used as mechanistic or time scale tracers of natural processes. This paper describes the occurrence and redistribution of U in the Vendian aquifer of a paleo-valley in NW Russia. Forty-four rock samples were collected from nine boreholes with depths up to 160 m, and 25 groundwater samples were collected from 23 boreholes with depths up to 300 m. The U, Fe concentration, and ²³⁴U/²³⁸U activity ratio were determined in the samples. Estimations were made of the ¹⁴C and ²³⁴U-²³⁸U residence time of groundwater in the aquifer. It has been established that the processes of chemical weathering of Vendian deposits led to the formation of a strong oxidation zone, developed above 250 m.b.s.l. The inverse correlation between the concentrations of uranium and iron is a result of removal of U from paleo-valley slopes in oxidizing conditions, accumulation of U at the bottom of the paleo-valley in reducing conditions, and accumulation of Fe on the slopes and removal from the bottom of the paleo-valley. Almost all U on the slopes has been replaced by a newly formed hydrogenic U with a higher ²³⁴U/²³⁸U activity ratio. After, dissolution and desorption of hydrogenic U occurred from the slopes during periods with no glaciations and marine transgressions. Elevated concentrations of U are preserved in reduced lenses at the paleo-valley bottom. In these areas, the most dangerous aspect is the flow of groundwater from the underlying horizons, since during the operation of water supply wells it can lead to the creation of local zones of oxidizing conditions in the perforated screens zone and the transition of uranium into solution. For groundwater under oxidizing conditions, an increase in the concentration of uranium is characteristic of an increase in the residence time (age) of water in the aquifer. Also, the ²³⁴U/²³⁸U activity ratio increases with increasing radioactivity of groundwater. Therefore, the most rational approach is to use groundwater for drinking water supply from the slopes of the Northern Dvina basin. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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16 pages, 2762 KiB

Open AccessFeature PaperArticle

Compound-Specific Isotope Analysis (CSIA) Application for Source Apportionment and Natural Attenuation Assessment of Chlorinated Benzenes

by Luca Alberti, Massimo Marchesi, Patrizia Trefiletti and Ramon Aravena

Water 2017, 9(11), 872; https://doi.org/10.3390/w9110872 - 9 Nov 2017

Cited by 13 | Viewed by 5323

Abstract

In light of the complex management of chlorobenzene (CB) contaminated sites, at which a hydraulic barrier (HB) for plumes containment is emplaced, compound-specific stable isotope analysis (CSIA) has been applied for source apportionment, for investigating the relation between the upgradient and downgradient of [...] Read more.

In light of the complex management of chlorobenzene (CB) contaminated sites, at which a hydraulic barrier (HB) for plumes containment is emplaced, compound-specific stable isotope analysis (CSIA) has been applied for source apportionment, for investigating the relation between the upgradient and downgradient of the HB, and to target potential CB biodegradation processes. The isotope signature of all the components potentially involved in the degradation processes has been expressed using the concentration-weighted average δ¹³C of CBs + benzene (δ¹³C_sum). Upgradient of the HB, the average δ¹³C_sum of −25.6‰ and −29.4‰ were measured for plumes within the eastern and western sectors, respectively. Similar values were observed for the potential sources, with δ¹³C_sum values of −26.5‰ for contaminated soils and −29.8‰ for the processing water pipeline in the eastern and western sectors, respectively, allowing for apportioning of these potential sources to the respective contaminant plumes. For the downgradient of the HB, similar CB concentrations but enriched δ¹³C_sum values between −24.5‰ and −25.9‰ were measured. Moreover, contaminated soils showed a similar δ¹³C_sum signature of −24.5‰, thus suggesting that the plumes likely originate from past activities located in the downgradient of the HB. Within the industrial property, significant δ¹³C enrichments were measured for 1,2,4-trichlorobenzene (TCB), 1,2-dichlorobenzene (DCB), 1,3-DCB, and 1,4-DCBs, thus suggesting an important role for anaerobic biodegradation. Further degradation of monochlorobenzene (MCB) and benzene was also demonstrated. CSIA was confirmed to be an effective approach for site characterization, revealing the proper functioning of the HB and demonstrating the important role of natural attenuation processes in reducing the contamination upgradient of the HB. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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15 pages, 2440 KiB

Open AccessArticle

Variability of Stable Isotope in Lake Water and Its Hydrological Processes Identification in Mt. Yulong Region

by Xiaoyi Shi, Tao Pu, Yuanqing He, Cuishan Qi, Guotao Zhang and Dunsheng Xia

Water 2017, 9(9), 711; https://doi.org/10.3390/w9090711 - 16 Sep 2017

Cited by 10 | Viewed by 5965

Abstract

Lakes are regarded as important nodes in water resources, playing pivotal roles in the regional hydrological cycle. However, the systematic study on lake water balance is scarce in Mt. Yulong region. Here, we study the stable isotope compositions of precipitation, inflowing rivers and [...] Read more.

Lakes are regarded as important nodes in water resources, playing pivotal roles in the regional hydrological cycle. However, the systematic study on lake water balance is scarce in Mt. Yulong region. Here, we study the stable isotope compositions of precipitation, inflowing rivers and lake water to exploit the characteristics of hydrological supply and lake water balance. The results showed that there was a typical spatial distribution of surface isotope in August and April. Relatively high δ¹⁸O values with low d-excess were found on the east and west shores of the lake in August and in the middle part of the lake in April. The lowest δ¹⁸O with highest d-excess were found in the north and south shores in August and April, respectively. Meanwhile, slight isotopic stratification indicated that the lake water was vertically mixed-well. Subsequently, the evaporation-to-inflow ratios (E/Is) during the two periods were further derived based on the isotope mass balance model. Approximately 51% in August and 12% in April of the water flowing into Lashi Lake underwent evaporation. This study provides a reference for the long-term monitoring and modeling the hydrology processes of the basin, and is important for the regional water resource. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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11 pages, 2857 KiB

Open AccessArticle

Temporal and Spatial Variations of Hydrological Processes on the Landscape Zone Scale in an Alpine Cold Region (Mafengou River Basin, China): An Update

by Yonggang Yang and Bin Li

Water 2017, 9(8), 574; https://doi.org/10.3390/w9080574 - 12 Aug 2017

Cited by 5 | Viewed by 5536

Abstract

This study investigates precipitation, snow, groundwater, glaciers and frozen soil in different landscape zones using isotopic and hydrogeochemical tracers. The aim of this study is to identify temporal and spatial variations, as well as hydrological processes in the alpine cold region. The results [...] Read more.

This study investigates precipitation, snow, groundwater, glaciers and frozen soil in different landscape zones using isotopic and hydrogeochemical tracers. The aim of this study is to identify temporal and spatial variations, as well as hydrological processes in the alpine cold region. The results show that there was no significant difference in water chemical characteristics of various waterbodies, and no obvious temporal variation, but exhibited spatial variation. In the wet season, various waterbodies are enriched in oxygen δ¹⁸O and deuterium δD due to a temperature effect. Precipitation and the temperature decrease during the dry season, which cannot easily be affected by secondary evaporation. The d-excess (deuterium excess) of various waterbodies was greater than 10‰. There are no altitude effects during wet and dry seasons because the recharged water resources are different in the wet and dry seasons. It is influenced by the freezing-thawing process of glacier snow and frozen soil. The river water is recharged by thawed frozen soil water and precipitation in the wet season, but glacier snow meltwater with negative δ¹⁸O and δD is less (14–18%). In the dry season, glacier snow meltwater and groundwater are the dominant source of the river water, and thawed frozen soil water is less (10–15%). Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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21 pages, 4729 KiB

Open AccessArticle

Applications of Hydro-Chemical and Isotopic Tools to Improve Definitions of Groundwater Catchment Zones in a Karstic Aquifer: A Case Study

by Alberto Jiménez-Madrid, Silvino Castaño, Iñaki Vadillo, Carlos Martinez, Francisco Carrasco and Albert Soler

Water 2017, 9(8), 595; https://doi.org/10.3390/w9080595 - 10 Aug 2017

Cited by 10 | Viewed by 5204

Abstract

Some researchers have proposed the groundwater protection zone (GPZ) method as a methodological framework for defining safeguard zones of groundwater bodies. Its goal is to protect the quality of water intended for human consumption and to facilitate a common implementation of this method [...] Read more.

Some researchers have proposed the groundwater protection zone (GPZ) method as a methodological framework for defining safeguard zones of groundwater bodies. Its goal is to protect the quality of water intended for human consumption and to facilitate a common implementation of this method in all European Union member states. One of the criteria used to establish GPZs is to define contributing catchment areas (CCAs). This methodology has been applied to the Sierra de Cañete, a region comprising a carbonate aquifer in the province of Malaga, Spain. The tools used to define CCAs are hydro-chemical and isotopic characterizations, namely water isotopes (i.e., ²H, ¹⁸O and tritium) and the isotopes of dissolved sulfates (i.e., ³⁴S and ¹⁸O). Traditionally, the Sierra de Cañete aquifer has been divided into six sectors. Hydro-chemical and isotopic characterization differentiated between two large areas in the carbonate aquifer. The southern part presents younger water that is the result of faster recharge and that shows a high level of karstification, while the northern area has a slower flow, and recharge is produced over several years. In addition, the northern part is hydraulically connected to an alluvial aquifer (i.e., Llanos de Almargen) that borders the Sierra de Cañete to the north. This aquifer has high levels of pollution due to agricultural and livestock activities carried out in the Llanos de Almargen area. This pollution is transmitted to the carbonate aquifer when groundwater depletion occurs. Therefore, the Sierra de Cañete GPZ needs to be extended to include the Llanos de Almargen aquifer. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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12 pages, 9704 KiB

Open AccessArticle

Identifying Groundwater Recharge Sites through Environmental Stable Isotopes in an Alluvial Aquifer

by Julián González-Trinidad, Anuard Pacheco-Guerrero, Hugo Júnez-Ferreira, Carlos Bautista-Capetillo and Arturo Hernández-Antonio

Water 2017, 9(8), 569; https://doi.org/10.3390/w9080569 - 2 Aug 2017

Cited by 36 | Viewed by 7649

Abstract

Environmental isotope tracers have been a useful tool in providing new insights into hydrologic processes. In Mexico, there have been several studies reporting different values for

δ^{18} O

and

δ^{2} H

for certain geographical areas. The objective of this study is [...] Read more.

Environmental isotope tracers have been a useful tool in providing new insights into hydrologic processes. In Mexico, there have been several studies reporting different values for

δ^{18} O

and

δ^{2} H

for certain geographical areas. The objective of this study is to achieve the isotopic characterization of rainfall and groundwater and to report the comprehensive understanding of groundwater flow processes around and within the Calera aquifer and, consequently, its potential recharge sites. The samples used for the stable isotope analysis (

δ^{18} O, δ^{2} H

) were measured using a GV-Isoprime isotope-ratio mass spectrometer at the Isotopy Laboratory of the Water Center for Latin America and the Caribbean. The

δ D

of precipitation ranged between −110.20‰ and 10.11‰, with a mean of −55.67‰

\pm

27.81‰. The

δ^{18} O

ranged between −17.80‰ and 2.74‰, with a mean of −9.44‰

\pm

4.74‰. The

δ D

of groundwater ranged between −81.92‰ and −36.45‰, with a mean of −66.05‰

\pm

8.58‰. The

δ^{18} O

ranged between −18.26‰ and −8.84‰, with a mean of −12.35‰

\pm

2.12‰. The local meteoric water line of the Zacatecas state is

δ D = - 2.03 + 5.68 δ^{18} O

. The groundwater samples were clustered into four groups. The clustering of the samples led to the finding that streamflows play a significant role in the hydrological balance as a source of local recharge to the aquifer. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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15 pages, 1293 KiB

Open AccessArticle

Understanding the Role of Groundwater in a Remote Transboundary Lake (Hulun Lake, China)

by Hongbin Gao, M. Cathryn Ryan, Changyou Li and Biao Sun

Water 2017, 9(5), 363; https://doi.org/10.3390/w9050363 - 22 May 2017

Cited by 24 | Viewed by 6861

Abstract

Hulun Lake, located in a remote, semi-arid area in the northeast part of Inner Mongolia, China, shares a transboundary basin with Mongolia and supports a unique wetland ecosystem that includes many endangered species. Decadal scale decreases in the lake stage and increased salinity [...] Read more.

Hulun Lake, located in a remote, semi-arid area in the northeast part of Inner Mongolia, China, shares a transboundary basin with Mongolia and supports a unique wetland ecosystem that includes many endangered species. Decadal scale decreases in the lake stage and increased salinity make an understanding of the lake’s water and salt sources critical for appropriate design of strategies to protect and manage the lake. Multiple tracers (chloride, and δ¹⁸O and δ²H in water) in samples collected from lake water, rivers, and nearby water wells were used in conjunction with an annual water balance based on historic data to better understand the lake’s major water and salt sources. The average annual water balance was conducted for two time periods: 1981–2000 and 2001–2013. The contribution of river discharge to the annual lake input decreased by half (from 64% to 31%) between the two time periods, while the volumetric contribution of groundwater discharge increased four-fold (from about 11% to about 50% of the total lake input). Significant evaporation was apparent in the stable isotope composition of the present-day lake water, however, evaporation alone could not account for the high lake water chloride concentrations. Limited domestic well water sampling, a regional salinity survey, and saline soils suggest that high chloride groundwater concentrations exist in the region south of the lake. The chloride mass balance suggested that groundwater currently contributes more than 90% of the annual chloride loading to the lake, which is likely four times greater than the earlier period (1981–2000) with lower groundwater input. The use of water and chloride mass balances combined with water isotope analyses could be applied to other watersheds where hydrologic information is scarce. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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15 pages, 1739 KiB

Open AccessArticle

Using δ¹⁵N and δ¹⁸O Signatures to Evaluate Nitrate Sources and Transformations in Four Inflowing Rivers, North of Taihu Lake

by Da Li, Xia Jiang and Binghui Zheng

Water 2017, 9(5), 345; https://doi.org/10.3390/w9050345 - 17 May 2017

Cited by 14 | Viewed by 5887

Abstract

Taihu Lake is the third largest freshwater lake in China. Due to rapid economic development and excessive nutrient discharges, there is serious eutrophication in the northern part of the lake. Nitrogen (N) is one of the key factors for eutrophication in Taihu Lake, [...] Read more.

Taihu Lake is the third largest freshwater lake in China. Due to rapid economic development and excessive nutrient discharges, there is serious eutrophication in the northern part of the lake. Nitrogen (N) is one of the key factors for eutrophication in Taihu Lake, which mainly comes from the rivers around the lake. Samples from four inflowing rivers were analysed for δ¹⁵N and δ¹⁸O isotopes in December 2013 to identify the different sources of nitrogen in the northern part of Taihu Lake. The results indicated that the water quality in Taihu Lake was clearly influenced by the water quality of the inflowing rivers and nitrate (NO₃⁻-N) was the main component of the soluble inorganic nitrogen in water. The soil organic N represented more than 70% of the total NO₃⁻-N loads in the Zhihugang. Domestic sewage was the major NO₃⁻-N source in the Liangxi river, with a contribution of greater than 50%. Soil organic N and domestic sewage, with contributions of more than 30% and 35% respectively, were the major NO₃⁻-N sources in the Lihe river and Daxigang river. Denitrification might be responsible for the shifting δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻ values in the Daxigang river, and a mixing process may play a major role in N transformations in the Lihe river in winter. The results of this study will be useful as reference values for reducing NO₃⁻ pollution in the inflowing rivers in the north of Taihu Lake. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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15 pages, 6667 KiB

Open AccessArticle

Identification of Waters Incorporated in Laguna Lake, Republic of the Philippines, Based on Oxygen and Hydrogen Isotopic Ratios

by Seiji Maruyama and Hisaaki Kato

Water 2017, 9(5), 328; https://doi.org/10.3390/w9050328 - 6 May 2017

Cited by 7 | Viewed by 10502

Abstract

We examined the oxygen and hydrogen isotopic ratios of surface waters and groundwaters in the catchment of Laguna Lake, Republic of the Philippines, to identify the types of water that combine and control these ratios in the lake water. The oxygen and hydrogen [...] Read more.

We examined the oxygen and hydrogen isotopic ratios of surface waters and groundwaters in the catchment of Laguna Lake, Republic of the Philippines, to identify the types of water that combine and control these ratios in the lake water. The oxygen and hydrogen isotopic ratios of water samples collected from rivers, lakes, springs, and irrigation canals were determined using cavity ring-down spectroscopy. The lake water data deviated from the meteoric line of the Philippines by between −13.5‰ and −10‰, and between −11.5‰ and −1.5‰ in the dry and wet seasons, respectively. The values for the groundwaters and surface waters were mainly between −8‰ and 3‰ throughout the year. In addition to rainwater, evaporative concentration, which may have an almost constant effect throughout the year, was the main control on the oxygen and hydrogen isotopic properties of Laguna Lake. The contributions of the surface waters and groundwaters to the oxygen and hydrogen isotopic ratios of the lake were relatively constant. Based on their isotopic properties, the waters within the water catchment area of Laguna Lake can be roughly divided into lake water with heavier isotopic ratios, and groundwater and surface water with lighter isotopic ratios. Full article

(This article belongs to the Special Issue Isotopes in Hydrology and Hydrogeology)

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