Showing papers on "Environmental isotopes published in 2020"

Hydrochemical and environmental isotopes analysis for characterizing a complex karst hydrogeological system of Watuputih area, Rembang, Central Java, Indonesia

Abstract: The karst hydrogeology systems of the Watuputih Hills region of Central Java, Indonesia, have many springs with varying discharge and are composed of formations with complex geological structures. This work characterized the karst hydrogeology by studying 50 hydrogeological features (caves, springs and wells) and by analyzing the chemical-physical properties of groundwater in the field (pH, temperature, EC, HCO3−, 222Rn) and the major ions and stable isotopes of the groundwater samples in the laboratory, along with the stable isotope content of rainwater sampled over 1 year. Hierarchical cluster analysis of the water samples identified three hydrochemical groups: groundwater flowing through carbonate rocks (groups C2 and C3), through quartz sandstones and volcanic rocks (group C4), and through carbonate rocks and the siliciclastic rocks (quartz sandstones) underneath them (group C1). Springs with large discharge, typified as artesian fault-guided springs, were categorized into group C1. These springs are Sumbersemen, Brubulan Tahunan, and Brubulan Pesucen, with mean discharges of 1,516, 165, and 95 L/s, respectively. Based on the results of the stable isotope analysis, the d-excess calculation and the 222Rn concentrations, groups C2, C3, and C4 associate with shallow groundwater systems that dominantly flow through pores, whereas group C1 associates with a deep groundwater system controlled by geological structure. The geological structure also determines the groundwater flow in the cave streams. The shallow groundwater system is sourced by local rainwater, while the deep groundwater system displays a relationship with the groundwater in the northern hills at an elevation >375 m above sea level.

Hydrogeochemical characteristics of a closed karst groundwater basin in North China

Abstract: Understanding the hydrogeochemical processes of carbonate aquifers is essential for utilizing local karst groundwater resources sustainability. Integrating hydrochemistry, environmental isotopes and hydrogeological conditions was used to study hydrogeochemical characteristics of a closed karst groundwater basin located in Shandong Province, North China. The dominant hydrochemistry type was HCO3–SO4–Ca in the karst groundwater system. Carbonates dissolution (especially calcite dissolution) as the main rock chemical weathering dominated the chemical compositions of the carbonate aquifers. Hydrogeochemical evolution processes of the closed karst groundwater basin were mainly carbonates dissolution accompanied with weak influences of human activities and weak evaporation during the recharging of atmospheric precipitation.

Environmental isotopes as indicators of groundwater recharge, residence times and salinity in a coastal urban redevelopment precinct in Australia

Abstract: Fishermans Bend is an urban redevelopment precinct situated on the Yarra River estuary in Melbourne, Australia. Understanding the hydrogeological system is important for characterising the impacts from legacy contamination and for monitoring the effects of urbanisation on groundwater flow systems and quality. Stable isotopes of water (δ18O, δ2H) and carbon (δ13C), radioisotopes (3H, 14C) and other geochemical indicators were used to assess sources of water and salinity in the shallow groundwater. Groundwater in the upper aquifer was predominantly Ca-HCO3− dominant, with fresh to brackish salinity—189–3,680 mg/L total dissolved solids (TDS). Localised areas of Ca-SO42− and Na-HCO3− dominant groundwater were impacted by industrial activities and legacy landfills, respectively. Stable isotopes (e.g. δ18O −5.7 to −2.9‰) and tritium activities (1.75–2.45 TU) within the aquifer indicate meteoric water recharged by modern rainfall with short residence times. Carbonate dissolution from shell material, and decay of organic waste and methanogenesis in landfill-leachate-impacted bores were shown to enrich δ13C values up to −4.2‰. In contrast, groundwater in the adjacent/lower aquitard was Na-Cl dominant and saline (19,600–23,900 mg/L TDS), with molar ratios reflective of ocean water, indicating relict emplaced salts. This is consistent with 14C dating of shell material, indicating deposition in a Holocene marine environment. The presence of tritium above background levels (0.20–0.35 TU) in the groundwater, however, suggests a component of modern recharge. Salinity fluctuations within the aquitard at times of peak river level suggest the modern water source is ingress from the adjacent Yarra River.

Major ion, trace metal and environmental isotope characterization of groundwater in selected parts of Uddanam coastal region, Andhra Pradesh, India

Abstract: This paper elaborates the hydrochemical and environmental isotope (δ2H and δ18O) inferences obtained from Uddanam region, Andhra Pradesh, India. Groundwater samples collected during pre-monsoon (June 2019) showed that the quality is fresh (EC < 1539 µS/cm) and contaminants like fluoride (<1.6 mg/L) and nitrate (<49 mg/L) are present within permissible limits. The composite water quality indices for drinking (DWQI: 14.1–92.5) and irrigation (IWQI: 2.8–20.2) are found to be satisfactory. The major water types are found to be Ca–Na–HCO3, Na–Ca–HCO3, Na–Mg–HCO3–Cl, Ca–Mg–HCO3–Cl and Na–HCO3. Three geochemical pathways are found signifying evaporite dissolution, contribution of silicate mineral weathering and base-exchange process, which is supported by estimated chloro-alkaline indices (CAI-1: −4.3 to −0.2, CAI-2: −1.03 to −0.08). Trace metal data clearly suggest that groundwater is free from any metal pollution. Dissolved silica (SiO2) levels range from 34 to 131 mg/L and do not show any particular spatial trend. Isotope data infer that groundwater is recharged by rainwater after undergoing evaporation (δ18O: −6.0‰), which matches with that of the combined isotope signature (δ18O: −5.5‰) of SW and NE monsoon rainfall. δ18O–TDS correlations and hydrochemical facies evolution (HFE) diagram do not infer any seawater intrusion into these coastal aquifers.

Hydrogeological Characterization of the Thyspunt Area, Eastern Cape Province, South Africa

Abstract: This paper presents a comprehensive hydrogeological investigation that involves field work, aquifer test, hydrogeochemical analysis, environmental isotope analysis, and interpretations around a proposed nuclear power facility in South Africa. The study was undertaken to test the complementarity of the various methods in the coastal aquifer and to verify the hydrogeological conditions within and around the site. The study revealed the presence of two types of aquifers: an upper primary aquifer made up of the Cenozoic deposits of the Algoa Group, and a deeper fractured aquifer made of the Palaezoic Table Mountain Group (TMG) metasedimentary rocks. Owing to ductile deformation in the form of folding, the fractured quartzite and shale aquifers resulted in an artesian condition, often characterized by slightly acidic (pH ≤ 6) and iron-rich groundwater. The most important hydrogeochemical processes responsible for the observed changes in the hydrochemical composition and facies are mineral dissolution, ion exchange and mixing. The environmental isotope results suggest that all groundwater samples are characterized by a depleted δ18O and δ2H signal, indicating high latitude moisture source (southern polar region) and recharge from rainfall, with no or minimal evaporation before and during infiltration. Similarities in the stable isotope signatures between the deeper and shallow aquifer confirm the presence of a strong hydraulic link. The residence time of groundwater in the aquifers underlying the proposed nuclear power plant is estimated using tritium (3H) and 14C, and the results indicate that in the shallow aquifer it ranges from recent recharge to 50 years, and in the deeper aquifer, it ranges from 430 ± 5 years to 1000 ± 10 years, which exists in a quasi-pristine condition.

Baseline Groundwater Quality before Shale Gas Development in Xishui, Southwest China: Analyses of Hydrochemistry and Multiple Environmental Isotopes (2H, 18O, 13C, 87Sr/86Sr, 11B, and Noble Gas Isotopes)

Abstract: The baseline quality of pre-drilling shallow groundwater is essential for the evaluation of potential environmental impacts of shale gas development The Xishui region in the northern Guizhou Province of Southwest China has the potential for shale gas development but there is a lack of commercial production As for the future environmental concerns in this undeveloped area, this study presented the hydrochemical and isotopic characteristics of shallow groundwater and its dissolved gas before shale gas development and determined the sensitive monitoring indicators Results showed that shallow groundwater with an average pH of 773 had low total dissolved solids (TDS) ranging between 102 and 397 mg/L, with the main water chemistry types of HCO3-Ca and HCO3-Ca·Mg The quality of most groundwater samples satisfied the drinking water standards of China The mass concentration of dissolved methane in groundwater was below the detection limit (<001 mg/L), suggesting the low baseline value of hydrocarbon The shallow groundwater was mainly recharged by local precipitation based on water isotopes Water chemistry was modified by the dominant dissolution of carbonate rocks and partial dissolution of clastic rocks, as indicated by δ13C-DIC, 87Sr/86Sr, and δ11B Evidence from carbon isotopes of dissolved methane and CO2 (δ13C-CH4 and δ13C-CO2) and noble gas isotopes (3He/4He and 4He/20Ne) demonstrated that the biogenic methane mainly originated from acetate fermentation and the dissolved noble gas was a result of the dissolution of air Based on the geochemical and isotopic differences between shallow groundwater and flowback and produced water (including shale gas) from the Weiyuan and Fuling shale gas fields as well as shale gas from Xishui, this study has provided the sensitive monitoring indicators and methods for identifying potential pollution of regional shallow groundwater related to shale gas development in the future

Influence of regional climatic on the hydrogeochemistry of a tropical river basin—a study from the Walawe river basin of Sri Lanka

Abstract: The Walawe river basin is one of the important watersheds in Sri Lanka subjected to water scarcity due to intensive exploitation for irrigation and domestic purposes. The groundwater resource in the basin is under-explored for its capacity to sustain a continuous supply of water for future demand while facing the growing climate change challenges. The objective of this study was to identify the behavior of groundwater in the Walawe river basin that flows through two major climatic zones in Sri Lanka. The study approach includes hydrogeochemical and stable isotope analysis in order to differentiate the geochemical evolution of groundwater in the basin with respect to climatic factors. Water samples from thirty-eight (38) deep wells (> 20 m), 25 shallow wells, and 14 surface water bodies were collected and measured for their major ions, and isotope ratios of δ2H and δ18O. The results indicated a clear difference in the geochemistry of groundwater between the two climatic zones of the basin. The dry zone area was characterized by a higher content of dissolved minerals as compared to that in the wet zone area. Silicate weathering, calcite dissolution, and ion exchange processes were found to be the main control of groundwater geochemistry in the basin. The Ca-HCO3-type water was found to be the predominant water type. The isotope data suggested that the groundwater in the study area is recharged mainly from the northeast monsoon rain. Isotope characteristics also suggested that direct infiltration is prominent in the wet zone regions, whereas modifications of shallow groundwater by evaporation were dominated in the dry zone areas. The findings of the study suggest that water quality management in the dry zone areas of the basin is critical for the future sustainability of the water resource of the basin.

Groundwater Isotopes in the Sonoyta River Watershed, USA-Mexico: Implications for Recharge Sources and Management of the Quitobaquito Springs

Abstract: Groundwater resources in the southwestern United States are finite and riparian and wetland areas are vulnerable to aquifer overdraft and unregulated groundwater use. Environmental isotopes and water chemistry were used to distinguish water types, recharge mechanisms, and residence time along several reaches of the Sonoyta River and Quitobaquito Springs located near the U.S.-Mexico border. Areas located upgradient from the Sonoyta River, such as the Puerto Blanco Mountains and La Abra Plain, are supported by local recharge which corresponds to water from the largest 30% of rain events mainly occurring during winter. For Quitobaquito Springs, the δ18O and δ2H values are too low to be derived from local recharge. Stable isotope data and Cl/SO4 mass ratios indicate that the Sonoyta River supplied Quitobaquito Springs through flow along a suggested fault system. Based on these results, Quitobaquito Springs flow could be diminished by any activity resulting in increased groundwater extraction and lowering of water elevations in the Sonoyta River regional aquifer.

Stable isotope imprints during pyrite leaching: implications for acid rock drainage characterization

Abstract: The characterization of acid rock drainage (ARD) is traditionally based on mineralogical and geochemical techniques (e.g., Acid Base Accounting tests). The complexity of ARD processes warrants contribution of methods from various disciplines. In the past decade, the increasing role of environmental isotopes in pollution monitoring has enabled the successful application of isotope methods in ARD investigations. While isotopic compositions of different pollutants can refer to their parent mineral, the degree of isotope fractionations are indicative of the mechanisms taking place during the release and transportation of ARD-related contaminants. In natural environments, however, the measured isotope fractionations are predominantly the result of several coexisting or sequential processes. Therefore, the identification and quantification of the distinct contributions of these processes to isotope variations is difficult and requires well-defined laboratory conditions, where the influence of ARD generation on different isotope systems can be assessed with greater certainty. This review provides readers with a single source of information regarding isotopic variations generated by laboratory pyrite leaching.

Origin of groundwater in Hanoi, Vietnam, revealed by environmental isotopes.

Abstract: In 2015 and 2016, groundwater samples were collected in Hanoi to analyse the isotopic composition (δ2H, δ18O and 3H) and elucidate the relationship between groundwater and surface water, as well as the origin of the groundwater. The values for δ18O and δ2H indicate that the groundwater originated from evaporated meteoric water and the isotope enrichment is due to the evaporation of shallow groundwater. Evaporation is the primary process affecting stable isotope signatures. Water samples collected from both Holocene and Pleistocene aquifers are more depleted in the heavy isotopes 18O and 2H than the rainfall in the area. This indicates that part of the groundwater is paleo-groundwater or may be caused by the altitude effect due to recharge at a higher elevation. The results also show the close interaction between two granular aquifers and the Red River. Furthermore, the contribution of modern groundwater could be observed by the appearance of tritium in both aquifers. The presence of tritium indicates that originally tritium-free groundwater from the margins of the basin has been diluted by young water. The results of this study might help managers to evaluate the origin and reserves of groundwater more accurately.

Recharge Estimation Using CMB and Environmental Isotopes in the Verlorenvlei Estuarine System, South Africa and Implications for Groundwater Sustainability in a Semi-Arid Agricultural Region

Abstract: Groundwater recharge remains one of the most difficult hydrogeological variables to measure accurately, especially for semi-arid environments where the recharge flux is much smaller than in humid conditions. In this study, groundwater recharge was estimated using chloride mass balance (CMB) in the Verlorenvlei catchment, South Africa where the effects of recent severe drought conditions in an already semi-arid environment have impacted both agricultural activity as well as the RAMSAR-listed Verlorenvlei estuarine system. Chloride, 18O and 2H tracers were used to improve understanding of the groundwater flow patterns and allowed the fresh parts of the groundwater system, defined by Ca2+-HCO3− groundwater types, to be separated from those where additional salts were being introduced through groundwater mixing, and thus characterized as Na+-Cl− groundwater types. Recharge rates calculated from CMB in the fresh parts of the system were between 4.2–5.6% and 11.4–15.1% of mean annual precipitation for the headwater valley and mountains of the Krom Antonies and are largely consistent with previous studies. However, much lower recharge rates in the valleys where agriculture is dominant contrasts with previous results, which were higher, since groundwater-mixing zones were not recognised. Although the chloride concentration in precipitation is based on only one year of data between 2015 and 2016, where 2015 had on average 28% less precipitation than 2016, the results provide a snapshot of how the system will respond to increasing drought frequency in the future. The results suggest that low rates of groundwater recharge under dry spell conditions will impact on low flow generations which are required to sustain the Verlorenvlei estuarine lake system. Overall, the study highlights the importance of combining hydrochemical tracers such as bulk chloride and stable isotopes with numerical modelling in data-scarce catchments to fully understand the nature of hydrological resilience.

Use of environmental isotopes to assess groundwater pollution caused by agricultural activities

Abstract: This work applied environmental isotope techniques to validate the results of previous studies on recharge sources in a rural area in central Chile (34.3° S and 71.3° W) and discern the origin of n...

Environmental isotope applications in Latin America and the Caribbean region.

Abstract: This Special Issue illustrates the use of environmental isotopes in studying and assessing hydrogeological and ecohydrological issues in the Latin America and the Caribbean (LAC) region. The issue ...

Hydrochemical and isotopic characteristics of thermal groundwater at Farafra Oasis, Western Desert, Egypt

Abstract: Groundwater from the Nubian Sandstone aquifer at Farafra Oasis in the Western Desert of Egypt has been investigated using chemical tracers and environmental isotopes to clarify the hydrochemical features of this aquifer. The majority of the collected samples are characterized by Ca-Cl water type, which may be attributed to dissolution of the carbonate-rich sediments. Calculated saturation indices show that the main hydrogeochemical processes were the dissolution of carbonates and evaporites and the precipitation of Fe-rich minerals. Temperatures calculated using the K-Mg geothermometer show that the reservoir temperature ranges from 58°C to 121°C. The groundwater samples have δD and δ18O values similar to the isotopic content of the Nubian aquifer palaeowater in the Western Desert. Additionally, the isotopic composition suggests that there is no active potential current recharge from the local precipitation. Gamma spectrometry of 226Ra, 232Th and 40K activities indicates that the groundwater of the Nubian aquifer is safe with respect to radioactivity. Groundwater in Farafra Oasis is the main source of irrigation and drinking water for local residents. All the samples are excellent for irrigation uses for all types of crops. It is suggested that the water samples may require some treatment regarding the high iron content before usage as drinking water. Supplementary material:https://doi.org/10.6084/m9.figshare.c.4938252

Using environmental isotopes to investigate the groundwater recharge mechanisms and dynamics in the North-eastern Basin, Palestine

Abstract: This study aims to differentiate the potential recharge areas and flow mechanisms in the North-eastern Basin, Palestine. The results differentiate the recharge into three main groups. The first is ...

Salinization Processes in the Benichab Coastal Aquifer-Mauritania

Abstract: A comprehensive and detailed study was conducted for the first time in the Benichab Region (western part of Mauritania) unique groundwater resource to identify the main process driving groundwater salinization using major and minor ions together with environmental isotopes. One hundred and nineteen samples were collected from 45 points (dug-wells and boreholes) during the period 2015 to 2017, where physico-chemical, chemical and isotope parameters were analyzed. pH values indicate circumneutral to basic (6.8 to 8.6) values while Electric Conductivity (EC) values show an increasing gradient from fresh groundwater lense (EC

Surface -Groundwater Interaction in the Area between El-Timsah Lake and Ismailia Canal Using Hydrochemical and Isotopic Techniques

Abstract: The study aims to understand how surface-groundwater interacts and impact in both water quality in the area between El-Timsah Lake and Ismailia Canal. In order to achieve this aim, and integration of hydrochemistry, trace elements, and environmental stable isotopes investigations were done. Twenty-one surfaces and groundwater samples were collected from the study area. Salinity (TDS) of El-Timah lake differs from 16730- 34560 mg/l indicates the discharge of Ismailia Canal and drainage water into the lake in the eastern and middle parts of the lake. While salinity of groundwater ranged from 345.7 to 1099 mg/l. According to the drinking water quality index (DWQI), most of the groundwater is suitable for drinking purposes but some wells in the study area threatened due to increasing salinity. Stable isotopes δ18O and δ2H of groundwater samples ranged from (2.54-3.39‰) and (22.95-27.79 ‰) respectively. The isotopic content (δ18O and δD) of groundwater is similar to the isotopic content value of the Nile water and Ismailia canal. This confirms that the Ismailia canal and drainage water as a recharge source for the unconfined aquifer. The highest values of nitrate and phosphate concentration in groundwater were observed 53.4 and 1.8 mg/l respectively which are slightly above permissible limits. Also trace elements (Al, B, Fe, Si, and Sr) of some surface and groundwater samples exceeded the international standard limits. Increase nitrate, phosphate and trace elements concentration may be fed rapid pollution path to the underlying, shallow aquifers which may have an impact on groundwater quality.

Assessment of the groundwater at Ali Al-Garbi area, Iraq using geochemical modeling and environmental isotopes

Abstract: Geochemical modeling and environmental isotopes (deuterium, oxygen-18, and tritium) were used to determine the hydrogeochemical evolution and the main factors controlling the groundwater chemistry in Misaan, South of Iraq. Groundwater samples were collected and analyzed for major ions at 20 sites for two periods in 2016. Moreover, 6 rainfall samples were collected to determine local meteoric water line. The main water types are Ca-SO4, which is the dominate type for two periods, while a few wells were (Na-SO4) or (Mg-SO4) dominate. All available δ18O and δD data for the study area are plotted to the global meteoric water line (GMWL) and Local meteoric water line (AMWL). They indicated to the meteoric origin of all waters. They are exposed to evaporation before entering the aquifer. Using PHREEQC, Geochemical modeling was conducted to calculate mineral saturation indices for all water samples. These results show that dissolution of dolomite, gypsum, halite and siderite and precipitation of calcite, Sylvie and hematite are the main chemical reactions in the first period, whereas there are no specific reactions can be shown in the second period. Hydrogeochemical evolution of groundwater as modeled with NETPATH-WIN, the inverse geochemical modeling results showed that the main reaction controlling the groundwater quality is Dedolomitization process (dolomite dissolution driven by anhydrite dissolution and calcite precipitation).

Application of environmental isotopes in water resources management

Abstract: The application of environmental isotope as a tracer in water resources studies is presented. The main objectives of this paper are to investigate the distribution and origin of water resources involved in the study. Isotope technique is a useful tool in determining the groundwater recharge sources, ages of water bodies, interaction between surface water and groundwater, source of groundwater contamination, degree of mixing and for estimating subsurface residence time. The environmental isotopes, particularly stables isotopes of water (18O and 2H) are measured using Continuous Flow Isotope Ratio Mass Spectrometer (CF–IRMS). Oxygen and hydrogen isotope compositions are reported as delta (δ) and denoted as % or per mill, a variation which is relative to a known standard (Vienna Standard Mean Ocean Water, VSMOW). This study has successfully demonstrated the ability of isotope technique in delineating the water resources. The findings that are obtained from this study would greatly assist local water authorities or related agencies to manage their water resources for the socio–economic benefit of the region.