Search Results (13)

This study investigates the potential of strontium isotopes as a geographical tracer for Vignola cherries. Despite several studies having employed this indicator to trace the origin of food products, the mechanisms underlying the fractionation and translocation of strontium from soil to edible parts remain poorly understood. In this study, the ⁹¹Zr/⁹⁰Zr ratio was used as a normalization pair to correct measurements of ⁸⁷Sr/⁸⁶Sr and ⁸⁸Sr/⁸⁶Sr (δ⁸⁸Sr). Soil, cherry branches, and fruit samples were collected from various producers and locations. Isotopic analyses were carried out using a double-focusing multi-collector–inductively coupled plasma/mass spectrometer (MC-ICP/MS). External correction was applied using the ⁹¹Zr/⁹⁰Zr ratio, assuming both equal and different fractionation factors for Sr and Zr isotopes. Results from both correction models showed improved accuracy by accounting for fluctuations in instrumental mass bias. Regarding the translocation of strontium, the data indicate an increase in ⁸⁸Sr of approximately 0.2‰ from soil to plant tissue. This trend was consistent across all sampled locations. Full article

Reliance on groundwater is outpacing natural replenishment, a growing imbalance that requires detailed and multi-faceted water resource understanding. This study integrated water-stable isotopes and hydrogeochemical species to examine hydrogeochemical processes during groundwater recharge and evolution in the Lake Malawi basin aquifer systems. The findings provide insights into groundwater source provenance, with non-evaporated modern precipitation dominating recharge inputs. Grouped hydrochemical facies exhibit five groundwater water types, prominently featuring Ca-Mg-HCO₃. Modelled hydrogeochemical data underscore dominant silicate dissolution reactions with the likely precipitation of calcite and/or high-Mg dolomitic carbonate constrained by ion exchange. Isotope hydrology reinforces water resource system conceptualisation. Coupled isotopic-hydrogeochemical lines of evidence reveal a discernible spatial-seasonal inhomogeneity in groundwater chemical character, revealing a complex interplay of meteoric water input, evaporative effects, recharge processes, and mixing dynamics. Findings show that measurable nitrate across Malawi highlights a widespread human impact on groundwater quality and an urgent need for detailed modelling to predict future trends of nitrate in groundwater with respect to extensive fertiliser use and an ever-increasing number of pit latrines and septic systems arising from rapid population growth. This study not only refined the Lake Malawi basin aquifer systems conceptualisation but also provided isotopic evidence of groundwater and lake water mixing. This study sets a base for groundwater management and policy decisions in support of the Integrated Water Resources Management principles and Sustainable Development Goal 6 objectives for groundwater sustainability in the transboundary Lake Malawi basin. Full article

Accurate discharge measurement is mandatory for any hydrological study. While the “velocity” measurement method is adapted to laminar flows, the “dilution” method is more appropriate for turbulent streams. As most low-gradient streams worldwide are neither laminar nor turbulent, a methodological gap appears. In this study, we demonstrate that the application of the “dilution” method to a low-gradient small stream gives very satisfactory results in addition to revealing surface/subsurface processes. A variety of chemical and isotopic tracers were injected into the stream (anions, fluorescent dyes, and chloride and hydrogen isotopes). We report the first use of ³⁷Cl for stream discharge measurement and show that ³⁷Cl and ²H can be reliably used as quantitative tracers. Discharge uncertainty calculations show that deuterium is the most accurate tracer method used. We also compare the differences in the tailing part of the restitution curves of tracers and investigate the role of transient surface and hyporheic zones in solute transport in light of a simple transport modelling approach. We conclude that isotopic tracers can be used as “environmentally friendly” tracers for discrete stream discharge measurements and that the application of multi-tracers tests in rivers opens the path to a better understanding of surface–subsurface interaction processes. Full article

Many non-traditional isotopes, such as chlorine, magnesium, calcium, etc., are widely used as groundwater tracers. A new sample processing protocol of purification and concentration for isotopic analysis is presented to overcome many of the major drawbacks of existing methods. Contemporary sample preparation often requires several laborious off-line procedures in a ultra clean laboratory prior to instrumental determination; additionally, interference ions in real samples are difficult to completely remove, especially when the concentration of those ions is equal to that of the target ions. The new protocol includes the following steps: (i) one-step purification using a newly developed isotopic preparative chromatograph (IPC) with a background suppressed mode to obtain extremely pure components that only have target ions and H₂O; (ii) enrichment of the collected pure solution from the previous step using a newly developed ultra clean concentrator filled with high purity nitrogen; (iii) transforming the enriched target ion into suitable speciation inside the ultra clean concentrator; (iv) finally, sending the enriched solutions to a multi-collector inductively coupled-plasma mass-spectrometer (MC-ICP-MS) or thermal ionization mass spectrometer (TIMS). The present method was validated using certified reference materials and real samples for both chlorine and magnesium; the precision of chlorine ratio value was generally below 0.22‰ and that of Mg was below 0.12‰. This processing protocol provides a potential method for isotope sample preparation and analysis in a small number of geological samples with low concentrations of many other elements or compounds such as nitrate, sulfate, lithium, calcium, strontium, etc. Full article

The Taxco mining district is a well-known international producer of silver, jewelry, and precious metal handicrafts. Inappropriate disposal wastes from anthropogenic activities have been deteriorating the hydric resources and threatening the inhabitants’ health, since they use the springwater for human consumption and domestic activities. A multi-tracer approach combining measurements of hydrochemical data, trace elements, and isotopes δ²H, δ¹⁸O, ³H, and ⁸⁷Sr/⁸⁶Sr ratios was undertaken for 18 springwater samples. δ¹⁸O and δ²H indicate that the springwater comes from the rain and had experienced some degree of isotopic fractionation by atmospheric evaporation in some samples at lower altitudes. ³H values on the springwater showed the existence of old and new water. Three groups of springwater were identified according to age: local flow in rhyolites, intermediate flow through red beds to the outcrop point in sandstone and shales, and deep flow in greenschist. The results of this study show the utility of ⁸⁷Sr/⁸⁶Sr ratios in identifying the water–rock interactions and springwater flow paths, suggesting that more widespread use of the strontium isotopic fingerprint is warranted. Full article

The geological and hydrogeological approach of the structure of the basin OuladBouSbaâ led to the definition of the geometry of the main aquifers. In general, the profiles show the complexity of the geological configuration. The filling of the depression of OuladBouSbaâ is from the Eo-Cretacian. At this level, the aquifer is recharged by direct water infiltration. The quaternary, Eocene, and Cenomanian-Turonian formations constitute the main aquifers. Horizontal as well as vertical heterogeneity lead to a higher diversification of aquifer characteristics. To define the origins and understand the groundwater flows in this complex zone, we used a multi-tracer approach with the analysis of major elements and the isotopes of δ²H and δ¹⁸O. The chemical composition is mainly governed by the interaction with the rock with low electrical conductivity except in areas around domestic landfills. Geochemical results analyzing groundwater in the Piper diagram show two distinct chemical facies: the sulfated calcium and magnesium, and the hyper-chloride calcium. The levels of δ¹⁸O range from −7.60 to −4.25 while those of δ²H vary between −53.07 and −27.03. Analyses of signature isotopes differentiate two groups. The first contains high levels of heavy isotopes (highest levels of δ²H and δ¹⁸O) having therefore been submitted to evaporation. The second with lower levels of δ²H and δ¹⁸O did not undergo evaporation. The first one belongs to the unconfined free aquifer while the second corresponds to the captive aquifer. Full article

Understanding hydrogeological processes at the origin of thermal and mineral groundwater are necessary to ensure their sustainable management. However, many processes are involved in their genesis and often only one or two processes are investigated at the same time. Here, we propose to use an innovative combination of geochemical, isotopic (³⁴S, ¹⁴C, ¹⁸O, ²H) and geothermometry tools to identify, for the first time in a multi-composite geological context, all processes at the origin of diversified thermo-mineral waters. 19 springs covering a wide range of temperature and chemical composition emerging on a restricted area of Corsica Island (France) were selected. Geochemical results highlight five geochemical provinces, suggesting a common origin for some of them. Geothermometry tools show the unexpected involvement of a common deep groundwater reservoir within this non-active zone. Water stable isotopes highlight a contrasted altitude in recharge areas supplying lowland springs. This suggests that different flow patterns have to be involved to explain the wide geochemical diversity observed and to allow the design of a very first conceptual groundwater-flow model. This paper demonstrates the efficiency of the combination of the selected tools as tracers of water–rock interaction, independently of flow depth, intrinsic water properties, geological conditions and interaction time disparities. Full article

A multi-component geochemical dataset was collected from groundwater and surface-water bodies associated with the urban Fountain Creek alluvial aquifer, Colorado, USA, to facilitate analysis of recharge sources, geochemical interactions, and groundwater-residence times. Results indicate that groundwater can be separated into three distinct geochemical zones based on location within the flow system and proximity to surface water, and these zones can be used to infer sources of recharge and groundwater movement through the aquifer. Rare-earth-element concentrations and detections of wastewater-indicator compounds indicate the presence of effluent from wastewater-treatment plants in both groundwater and surface water. Effluent presence in groundwater indicates that streams in the area lose to groundwater in some seasons and are a source of focused groundwater recharge. Distributions of pharmaceuticals and wastewater-indicator compounds also inform an understanding of groundwater–surface-water interactions. Noble-gas isotopes corroborate rare-earth-element data in indicating geochemical evolution within the aquifer from recharge area to discharge area and qualitatively indicate variable groundwater-residence times and mixing with pre-modern groundwater. Quantitative groundwater-residence times calculated from ³H/³He, SF₆, and lumped-parameter modeling generally are less than 20 years, but the presence of mixing with older groundwater of an unknown age is also indicated at selected locations. Future investigations would benefit by including groundwater-age tracers suited to quantification of mixing for both young (years to decades) and old (centuries and millennia) groundwater. This multi-faceted analysis facilitated development of a conceptual model for the investigated groundwater-flow system and illustrates the application of an encompassing suite of analytes in exploring hydrologic and geochemical interactions in complex systems. Full article

The karst aquifer of the Ljubljanica River catchment, which has numerous springs and sinks, presents an interesting environment for studying hydrogeological processes. This study aims to explore the behavior of U isotopes and to evaluate their use as tracers of hydrogeochemical processes as an alternative to classical geochemical tracers (i.e., physicochemical parameters, elemental ratios, and alkalinity) involved in water–rock interactions and water flow in this karst water system. Basic hydrochemical parameters, as well as the spatiotemporal variations of total U concentrations, ²³⁴U/²³⁸U activity ratios, and δ²³⁸U values, were monitored in water samples from springs and sinks under different hydrological conditions. The bedrock as the source of dissolved and detrital U was also analyzed. Multi-collector inductively couple plasma-mass spectrometry results reveal variations of the ²³⁴U/²³⁸U activity ratios, which are consistently negatively correlated with the discharge at most analyzed sites. Large ²³⁸U/²³⁵U isotope fractionation occurred during bedrock weathering, and the large variability of the measured δ²³⁸U values is seemingly unrelated to the lithological characteristics of the bedrock or discharge. Our results confirm that ²³⁴U/²³⁸U activity ratios in water can be used as a tracer for studying changes in groundwater flows and the mixing of waters of different origins under different hydrological conditions. Full article

The Dahab watershed comprises three aquifers; the alluvial Quaternary, the Early Cambrian sandstone, and the fractured Pre-Cambrian basement aquifers. The Dahab watershed is located in the southeastern part of the arid Sinai Peninsula, where low precipitation and groundwater over-exploitation deteriorate the groundwater quality in the alluvial coastal plain aquifer located downstream. Multi-isotopes including δ¹⁸O and δ²H, ⁸⁷Sr/⁸⁶Sr, δ⁸¹Br and δ¹¹B coupled with groundwater geochemistry were utilized to assess the recharge source(s), water-rock interaction, and seawater mixing to aid sustainable groundwater management strategies. Br and Cl concentrations, used to measure groundwater salinity, were low in the upstream groundwater, while higher concentrations were observed in the deep drilled wells located downstream, in the main well field. The δ¹⁸O and δ²H isotopes were depleted in the upstream aquifers, but enriched in the shallow coastal aquifer, indicating slight evaporation and seawater intrusion. Higher mean values of ⁸⁷Sr/⁸⁶Sr and δ⁸¹Br were observed in the fresh groundwater from high in the watershed (⁸⁷Sr/⁸⁶Sr = 0.707716 and δ⁸¹Br = +2.05‰), while lower mean values were observed in the saline groundwater located downstream in the main well field (⁸⁷Sr/⁸⁶Sr = 0.706631 and δ⁸¹Br = +0.11‰). The cumulative mass balance mixing curves and the geochemical NETPATH model confirm the change of groundwater quality from the upper to lower watershed caused by the leaching and evaporation processes, as well as mixing with seawater. The corrected ¹⁴C age dating and stable isotopes show that the Quaternary and Pre-Cambrian basement aquifers contain modern groundwater, while the Early Cambrian aquifer holds paleo-groundwater, which has received considerable recharge from recent precipitation. The mixing ratiosin the Quaternary coastal aquifer range between 5% and 13% seawater to 95% and 87% fresh groundwater, respectively. These results indicate that future groundwater withdrawal must be well managed in order to limit further salinization. Groundwater withdrawal from the Quaternary coastal aquifer must be below the natural average recharge in order to be sustainable. Full article

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

Knowledge about water flow paths is essential for understanding biogeochemical fluxes in developed agricultural landscapes, i.e., the input of nutrients into surface waters, soil erosion, or pesticide fate. Several methods are available to study rainfall-runoff processes and flux partitioning: hydrometric based approaches, chemical tracers, modeling, and stable isotope applications. In this study a multi-method approach was conducted to gain insights into the hydrological fluxes and process understanding within the complex anthropogenic-influenced catchment of the Vollnkirchener Bach, Germany. Our results indicate that the catchment responds differently to precipitation input signals and dominant runoff-generation processes change throughout the year. Rainfall-induced runoff events during dry periods are characterized by a temporarily active combined sewer overflow. During stormflow, a large contribution of fast event water is observed. At low flow conditions losing and gaining conditions occur in parallel. However, when catchment’s moisture conditions are high, an ephemeral source from clay shale-graywacke dominated forested sites becomes active. The study reveals that the collection of detailed distributed hydrometric data combined with isotopic tracers, provides fundamental information on the complex catchment behavior, which can finally be utilized for conceptualizing water fluxes at a small catchment scale. Full article

Submarine groundwater discharge (SGD) into the ocean is of general interest because it acts as vehicle for the transport of dissolved contaminants and/or nutrients into the coastal sea and because it may be accompanied by the loss of significant volumes of freshwater. Due to the large-scale and long-term nature of the related hydrological processes, environmental tracers are required for SGD investigation. The water parameters of electrical conductivity and temperature, the naturally occurring radionuclides of radon and radium as well as the stable water isotopes ¹⁸O and ²H have proven in previous studies their general suitability for the detection and quantification of SGD. However, individual hydrogeological settings require a site-specific application of this “tool box”. This study evaluates and compares the applicability of the abovementioned tracers for investigating SGD from a distinct submarine source in a karst environment at Cabbé, southern France. The specific advantages and disadvantages of each individual parameter under the given hydrogeological conditions are discussed. Radon appeared to be the most suitable environmental tracer in the site specific context. The water temperature was less reliable due to the little temperature difference between seawater and groundwater and since the diurnal variation of the air temperature masks potential SGD signals. Radium isotopes are less applicable in the studied region due to the lack of a well-developed subterranean estuary. The stable water isotopes showed results consistent with the salinity and radon data; however, the significantly higher effort required for stable isotope analyses is disadvantageous. A multi-temporal thermal remote sensing approach proved to be a powerful tool for initial SGD surveying. Full article