Isotopic Composition Of Water Research Articles

Reflection of Daily, Seasonal and Interannual Variations in Run-Off of a Small River in the Water Isotopic Composition (δ2H, δ18O): A Case of the Ala-Archa Mountain River Basin with Glaciation (Kyrgyzstan, Central Asia)

Small intermountain river basins are most suitable for developing new methods to estimate water balance due to their well-defined catchment boundaries, relatively rapid runoff processes, and accessible landscapes for study. In general terms, dissecting the hydrograph of a small mountain river requires calibration of the flow model against multi-year data sets, including (a) glacier mass balance and snow water content, (b) radiation balance calculation, (c) estimation of the groundwater contribution, and (d) water discharge measurements. The minimum primary data set is limited to the precipitation and temperature distributions at the catchment. This approach postulates that the conditions for the formation of all components of river flow are known in advance. It is reduced to calculating the dynamic balance between precipitation (input part) and runoff, ablation, and evaporation (output part). In practice, accurately accounting for the inflow and outflow components of the balance, as well as the impact of regulating reservoirs, can be a challenging task that requires significant effort and expense, even for the extensively researched catchments. Our studies indicate the potential benefits of an approach based on one-time, but detailed, observations of stable isotope composition, temperature, and water chemistry, in addition to standard datasets. This paper presents the results of the 2022–2023 work conducted in the basin of the small mountain river Ala-Archa, located on the northern slope of the Kyrgyz Range in Tien-Shan, which was chosen as an example due to its well-studied nature. Our approach could identify previously unknown factors of flow formation and assess the time and effectiveness of work in similar conditions.

Fluid Chemical and Isotopic Signatures Insighting the Hydrothermal Control of the Wahongshan-Wenquan Fracture Zone (WWFZ), NE Tibetan Plateau

Compared to the southern Tibetan Plateau, the northern part has been regarded as relatively lacking geothermal resources. However, there is no lack of natural hot springs exposed in beads along large-scale fracture systems, and research on them is currently limited to individual hot springs or geothermal systems. This paper focuses on the Wahongshan-Wenquan Fracture Zone (WWFZ), analyzes the formation of five hydrothermal activity zones along the fracture zone in terms of differences in hot water hydrochemical and isotopic composition, and then explores the hot springs’ hydrothermal control in the fracture zone. The results show that the main fractures of the WWFZ are the regional heat control structures, and its near-north–south- and near-east–west-oriented fractures form a fracture system that provides favorable channels for deep hydrothermal convection. Ice and snow meltwater from the Elashan Mountains, with an average elevation of more than 4,500 m above sea level, infiltrates along the fractures, and is heated by deep circulation to form deep geothermal reservoirs. There is no detectable mantle contribution source heat to the hot spring gases, and the heat source is mainly natural heat conduction warming, but the “low-velocity body (LVB)” in the middle and lower crust may be the primary heat source of the high geothermal background in the area. The hot springs’ hydrochemical components show a certain regularity, and the main ionic components, TDS, and water temperature tend to increase away from the main rupture, reflecting the WWFZ controlling effect on hydrothermal transport. In the future, the geothermal research in this area should focus on the hydrothermal control properties of different levels, the nature of fractures, and the thermal contribution of the LVB in the middle and lower crust.

Oven Design for In‐Situ Thermal Extraction of Volatiles From Lunar Regolith

AbstractExtracting volatiles from lunar regolith for analysis or utilization is one of the most important aspects of future lunar exploration. However, the low thermal conductivity of lunar regolith poses a challenge. Here, we conduct simulations to analyze the heat and mass transfer processes within the sample inside the oven. We identify three main factors affecting oven heat‐up rate: water ice content (WIC) in the regolith, oven diameter, and power supply. Taking these factors into account, we devise an oven design and apply it to three case studies: (a) assessing water ice and isotopic composition in Permanently Shadowed Regions, akin to Chang'e‐7 mini‐fly probe missions; (b) measuring noble gases, as Chang'e‐7 and Luna‐27 landers; and (c) large‐scale in‐situ resources utilization (ISRU). The simulation results indicate that water ice can be extracted using sufficiently high heating power without issues. However, the complete extraction of noble gases is challenging and may require alternative heating methods. For ISRU purposes, large ovens can be subdivided into smaller ones by adding internal structures, for example, honeycomb, to improve the heat‐up rate by at least 1.5 times. Additionally, we find that the oven can serve as a scientific payload for WIC measurement using the heating curve. A flowchart of this new WIC measurement method is provided, offering an alternative method to mass spectrometry or spectroscopy measurements.

Nitrogen Assimilation and Nitrification in Surface Waters of the Amazon and Pará Estuaries

AbstractUnder increasing anthropogenic impacts, the hydrology, weathering, turbidity, and biogeochemistry of the Amazon and Pará river catchments are changing, potentially affecting the concentration and speciation of nitrogen (N) entering the estuary, as well as the subsequent primary productivity. Primary production and several N‐cycling rates have been studied in the northern river plume, and new studies focusing on specific processes in the river mouth emerged. Yet, a general overview is still lacking. For the first time, we provide an overview of primary production along with nitrification, ammonium (NH4+), nitrate (NO3−), and amino acid uptake rates in the Amazon and Pará river mouths which exhibit different degrees of catchment land use. Our results indicate that the Amazon supplies tenfold more NH4+ and NO3−, and its nitrification rates are four times higher than in the Pará River. The stable isotope composition of ambient water and NO3− confirmed that nitrification is a dominant pathway, with fluxes reaching 8.5 × 108 mol N d−1 in the Amazon. Nutrients are transported to regions with reduced turbidity and little nitrification, facilitating NH4+ (0.2–2.4 × 108 mol N d−1) and carbon uptake (4.6 and 14.0 × 108 mol C d−1 in the Pará and the Amazon, respectively) by phytoplankton. The lower N‐cycling rates measured in the Pará relative to the Amazon River mouth likely originate from differences in river discharge and watershed characteristics.

Isotope Hydrograph Separation Reveals Rainfall on the Glaciers Will Enhance Ice Meltwater Discharge to the Himalayan Rivers

AbstractThe Indian Summer Monsoon (ISM) and meltwater from the Himalayan are the two most important sources of water in the Indian subcontinent. However, the impact of ISM on Himalayan glaciers and subsequent stream hydrology remains largely unknown. To provide new insight into the impact of rainfall on glacial hydrology, here we present hydro‐meteorological and time‐series observations of meltwater stable water isotope compositions from the snout of the Chorabari glacier in the Upper Ganga Basin, Central Himalayas across the ablation season corresponding to 2019. We observe that rainfall events (>2 mm d−1) on the glacier enhance discharge driven by ice meltwater in River Mandakini. Energy balance calculations reveal that one of the drivers behind enhanced ice meltwater contribution could be rain‐induced melting of the glacier where rainfall on the ice surface melts the glacier producing up to 13% of the total discharge at the glacier snout. Further, rainfall on glacier surface have other control on glacial processes—for example, snow metamorphism, ice flow dynamics such as short‐term acceleration in ice speed flow, and reorganization of the englacial and subglacial drainage network—that are poorly studied and needs further investigation. We conclude rainfall events on the glacier have a complex control on mountain hydrology. This study, therefore, provides an interpretative framework that calls for additional assessments of the direct and indirect impact of rainfall in glacial hydrology.

Authigenic quartz reveals the triple oxygen isotope composition and diagenetic temperature of saline brines

Triple oxygen isotope compositions of authigenic minerals are an emerging tool for the reconstruction of fluid temperatures and the fluid isotopic composition. In this study, we analyzed euhedral authigenic quartz crystals from a halite deposit of the Upper Permian Zechstein evaporitic basin for their triple oxygen isotope composition using laser fluorination isotope ratio mass spectrometry. In the triple oxygen isotope space, additional information, such as the triple oxygen isotope composition of the ambient water, provides insights into equilibrium conditions during quartz formation that cannot be identified from δ18O alone. The triple oxygen isotope composition of authigenic quartz shows, that single oxygen isotope (δ18O) thermometry is not applicable for samples from evaporitic environments, where the fluids' δ18O deviates from dynamic oxygen isotope equilibrium. By combining the Craig and Gordon evaporation model with H2O – SiO2 triple oxygen isotope equilibrium fractionation, we reconstruct the formation temperature of authigenic quartz and the triple oxygen isotope composition of the marine-derived saline brine pore fluid in equilibrium with the quartz. We obtain temperatures of 90 to 130 °C that is interpreted as crystallization temperatures of microcrystalline quartz in pore fluid of halite during burial diagenesis. The triple oxygen isotope composition of authigenic quartz from evaporitic environments is suited as a geochemical tracer for fluid oxygen isotope compositions and ancient fluid or diagenetic temperatures.

CHIRAL SWITCHING CONTROL OF PHARMACEUTICAL SUBSTANCES

Objective: The aim of this study was to demonstrate that chiral switching should be recognized as a widespread phenomenon that extends beyond the production of pure enantiomeric drugs. Methods: To investigate the optical activity of substances from various chemical classes, enantiomers of chiral compounds (Sigma-Aldrich, USA) were chosen: valine and its racemic form (D-valine, L-valine, and racemic valine with optical purity ≥ 99%), L-ascorbic acid (content ≥ 99%), carbohydrates (D-glucose, D-galactose, L-galactose, contents ≥ 99.5%). Solutions were prepared using deuterium-depleted water (DDW–"light" water, D/H=4 ppm), natural deionized high-ohmic water (BD, D/H=140 ppm), and heavy water (99.9% D2O; Sigma-Aldrich). Optical activity was measured using the Atago POL-1/2 polarimeter. Results: One of the components in the racemic medication mixture can act as an inert agent, exhibit toxicity, or undergo undesirable biotransformation mechanisms, resulting in the formation of products with unknown properties. It has been established that a change in the deuterium/protium (D/H) ratio in water leads to a change in the equilibrium and kinetic characteristics of optically active compounds across various chemical classes, such as amino acids, carboxylic acids, and carbohydrates. An inequality was observed in the absolute values of the optical rotation of the L-and D-isomers of valine and galactose, depending on the D/H isotope ratio. The impact of chiral water clusters on optical rotation accounts for the sudden shift in the specific rotation of dilute solutions (less than 0.5%) of L-ascorbic acid in water, based on the D/H ratio. The influence of the isotopic composition of water was confirmed by studying the temperature-dependent mutarotation kinetics of D-glucose and L-and D-galactose in Arrhenius coordinates. The mutarotation process in natural high-resistivity water is characterized by an activation energy (Ea) of 40.8±1.4 kJ mol-1, while in deuterium-depleted water, Ea = 63.6±3.5 kJ mol-1. This results in a kinetic isotope effect for deuterium (KIED) of 1.6. Conclusion: Methodological approaches have been developed to control chiral switching based on the isotopic composition of water in vivo and in vitro. The study of changes in the optical activity of hierarchical structures in the human body, the influence of solvent properties on the mechanisms of optical rotation, as well as the use of KIED values, can be utilized to monitor various chiral transitions in vitro and living organisms.

Spatial and temporal stable water isotope data from the upper snowpack at the EastGRIP camp site, NE Greenland, sampled in summer 2018

Abstract. Stable water isotopes stored in snow, firn and ice are used to reconstruct climatic parameters. The imprint of these parameters at the snow surface and their preservation in the upper snowpack are determined by a number of processes influencing the recording of the environmental signal. Here, we present a dataset of approximately 3800 snow samples analysed for their stable water isotope composition, which were obtained during the summer season next to the deep drilling site of the East Greenland Ice Core Project in northeast Greenland (75.635411° N, 36.000250° W). Sampling was carried out every third day between 14 May and 3 August 2018 along a 39 m long transect. Three depth intervals in the top 10 cm were sampled at 30 positions with a higher resolution closer to the surface (0–1 and 1–4 cm depth vs. 4–10 cm). The sample analysis was carried out at two renowned stable water isotope laboratories that produced isotope data with the overall highest uncertainty of 0.09 ‰ for δ18O and 0.8 ‰ for δD. This unique dataset shows the strongest δ18O variability closest to the surface, damped and delayed variations in the lowest layer, and a trend towards increasing homogeneity towards the end of the season, especially in the deepest layer. Additional information on the snow height and its temporal changes suggests a non-uniform spatial imprint of the seasonal climatic information in this area, potentially following the stratigraphic noise of the surface. The data can be used to study the relation between snow height (changes) and the imprint and preservation of the isotopic composition at a site with 10–14 cm w.e. yr−1 accumulation. The high-temporal-resolution sampling allows additional analyses on (post-)depositional processes, such as vapour–snow exchange. The data can be accessed at https://doi.org/10.1594/PANGAEA.956626 (Zuhr et al., 2023a).

Different responses of oxygen and hydrogen isotopes in leaf and tree-ring organic matter to lethal soil drought.

The oxygen and hydrogen isotopic composition (δ18O, δ2H) of plant tissues are key tools for the reconstruction of hydrological and plant physiological processes and may therefore be used to disentangle the reasons for tree mortality. However, how both elements respond to soil drought conditions before death has rarely been investigated. To test this, we performed a greenhouse study and determined predisposing fertilization and lethal soil drought effects on δ18O and δ2H values of organic matter in leaves and tree rings of living and dead saplings of five European tree species. For mechanistic insights, we additionally measured isotopic (i.e. δ18O and δ2H values of leaf and twig water), physiological (i.e. leaf water potential and gas-exchange) and metabolic traits (i.e. leaf and stem non-structural carbohydrate concentration, carbon-to-nitrogen ratios). Across all species, lethal soil drought generally caused a homogenous 2H-enrichment in leaf and tree-ring organic matter, but a low and heterogenous δ18O response in the same tissues. Unlike δ18O values, δ2H values of tree-ring organic matter were correlated with those of leaf and twig water and with plant physiological traits across treatments and species. The 2H-enrichment in plant organic matter also went along with a decrease in stem starch concentrations under soil drought compared with well-watered conditions. In contrast, the predisposing fertilization had generally no significant effect on any tested isotopic, physiological and metabolic traits. We propose that the 2H-enrichment in the dead trees is related to (i) the plant water isotopic composition, (ii) metabolic processes shaping leaf non-structural carbohydrates, (iii) the use of carbon reserves for growth and (iv) species-specific physiological adjustments. The homogenous stress imprint on δ2H but not on δ18O suggests that the former could be used as a proxy to reconstruct soil droughts and underlying processes of tree mortality.

Value of long-term isotope monitoring of an index lake for tracking changes in lake water balances across a northern freshwater landscape

Study regionThe Peace-Athabasca Delta, northeastern Alberta, a Ramsar Wetland of International Importance. Study focusTo explore the cause of change in water isotope composition at an ‘index lake’ (δSSL; ‘PAD 18’), a terminal basin where inflow equals evaporation, and the consequences for characterizing lake water balance across a region subject to the same atmospheric conditions. For two decades, water isotope composition at PAD 18 provided a relatively constant, reliable estimate of δSSL, but experienced a pronounced shift in 2020–2021 when average flux-weighted ice-free season relative humidity increased by 4.6% from 66.2% (2015–2019) to 70.8% (2020–2021). Using flux-weighted air temperature and relative humidity data from 2020–2021, an independent calculation of δSSL was determined to be equivalent to the average isotope composition of PAD 18 during 2020–2021. New hydrological insightsResults reveal re-equilibration of the lake water with the atmosphere following the rise of relative humidity readily provides an explanation for the change in isotope composition of PAD 18. We demonstrate the importance of accurate characterization of δSSL, via the index lake method, for isotope-mass balance calculations using evaporation-to-inflow ratios from measurement of water isotope compositions of 61 lakes across the PAD in July 2021. Findings highlight the value of an index lake and appropriate parameterization of isotope-mass balance models for assessment and ongoing monitoring of water balances of nearby lakes, especially amidst future climatic variability.

Extracting paleo-weathering signals from authigenic phases in lake sediments: A case-study of Lake Baikal

Authigenic phases in lake sediments hold the potential to record changes in the isotope compositions of past lake water, potentially yielding valuable information on secular changes in continental weathering patterns and rates, including over past glacial cycles.Here, different leaching approaches are investigated with the aim of extracting Sr, Nd, Pb, and Be hosted in authigenic Fe-Mn (oxy)hydroxide sediment phases for precise isotope measurements. Elemental Al/Mn, Ca/Mn, and P/Mn ratios obtained via a mild reductive leach agree well with the composition of marine authigenic Fe-Mn phases. For core top sediments, leached Sr isotope compositions obtained with this leach agree well with the composition of lake water. The Be and Nd isotope compositions of core top leachates are consistent with the spatial variability observed in the water column. Due to high concentrations in Fe-Mn phases, leachate compositions are dominated by authigenic Be, Sr, Nd, and Pb, even in cases when as much as 40% of leached phases (by mass) are non-authigenic. These lines of evidence suggest that the mild reductive leach successfully extracts the modern lake isotope composition from modern sediments in terms of the isotope systems investigated. We further show that the leaching method is also reliable for older sediments (<340 ka): leached paleo-Sr isotope compositions are consistent between the current and previous interglacial periods, as well as for glacial periods. This suggests that reconstructed water isotope compositions are not affected by early diagenetic processes, instead reflecting environmental factors around the lake that determine the composition of weathering fluxes. Although more difficult to assess for Be, Nd, and Pb due to the heterogeneity of modern lake water, the data we present indicate the overall robustness of the leaching approach.These promising results open up lakes as archives for paleo-weathering reconstructions. Given that marine reconstructions face some important limitations (e.g., integration of basin-wide changes in weathering processes, long residence times for Sr, etc.Fe), lake records provide an avenue to improve our understanding of changes in regional weathering processes over glacial-interglacial timescales. The mild reductive leach used here may also be useful for meteoric Be studies in marine shelf settings, to prevent leaching of terrestrial sedimentary Fe-Mn oxy(hydroxide) phases.

Triple oxygen isotope systematics of CO2 hydroxylation

Kinetic isotope effects occurring during carbonate precipitation impact the accuracy of paleoclimate records. One rate-limiting process is CO2 absorption, which, at high pH, primarily proceeds through hydroxylation, where aqueous CO2 and OH− react to form HCO3−. In this study, we investigated the triple oxygen isotope fractionation (18O/16O and 17O/16O) associated with the hydroxylation reaction. We experimentally determined the extent of the kinetic isotope effects superimposed on the reacting CO2 and OH− during hydroxylation, using high-pH precipitation reactions. These results were compared to the equilibrium triple oxygen isotope fractionation between H2O and OH− modeled using quantum chemical computations.Our quantum chemical modeling confirms the previously suggested equilibrium θeq.H2O/OH- of 0.5296 at 25 °C. Our empirical data show a kinetic isotope effect superimposed on the OH− involved in the hydroxylation reaction of approximately −16.4‰ for the fractionation of 18O/16O and a corresponding slope of 0.514 in triple oxygen isotope space. The θeffectiveH2O/OH- for the fractionation between water and the reacting OH− is 0.523.In order to identify and potentially correct kinetic isotope effects in carbonates, it is important to understand the fractionations occurring during precipitation. Our results enable a more accurate modeling of kinetic isotope effects in triple oxygen isotope space, particularly the slope of hydroxylation. The θhydroxylation is dependent on the isotope composition of the ambient water, CO2, and the temperature. We estimate that θhydroxylation is approximately 0.532 for carbonates growing in 25 °C seawater.

Stable Isotopes Constrain Water Seepage From Gnammas Into Bare Granitic Bedrock

AbstractSubtle bedrock depressions called gnammas allow the water in ephemeral pools to maintain contact with bare rock, thus serving as natural rock‐weathering experiments. Following filling by precipitation, evaporation is often assumed to be the sole process of water loss from gnammas. We evaluated this assumption by monitoring evolving stable isotope compositions of gnamma waters hosted in granite of Colorado's Front Range. Surprisingly, we found that a significant fraction of the water was lost by seepage through the underlying bedrock. Seepage dominated, with only 10%–20% loss by evaporation. We propose a conceptual model of gnamma formation in which enhanced weathering of the bedrock beneath the gnamma increases the water holding capacity and permeability of the underlying rock that in turn promotes efficient water loss through seepage and further weathering of the surrounding rock. This model has implications for bare‐rock weathering and hence the evolution of landscapes over geologic timescales.

Neodymium isotope composition and rare earth element distribution of East Antarctic continental shelf and deep waters

Circumpolar Deep Water (CDW) and Antarctic Bottom Water (AABW) play key roles in the Earth's climate system. Both water masses form critical components of the Antarctic Circumpolar Current and Meridional Overturning Circulation and therefore directly influence the large-scale redistribution of heat, nutrients and carbon. Reconstruction of past CDW transport and AABW production and export has been a key target in palaeoceanography. One promising proxy to achieve this has been the neodymium (Nd) isotope composition of seawater. The biogeochemical processes controlling Nd in the ocean, however, remain underconstrained, and modern observations of Nd isotopes in the Southern Ocean are still geographically limited.To overcome this limitation, 61 seawater samples were collected for Nd isotope and rare earth element (REE) analysis at nine stations along the Wilkes Land continental margin and in the Australian-Antarctic Basin (65°S 125°E) near East Antarctica. The results show that the different water masses have the following Nd isotope characteristics: Antarctic Surface Water (AASW), εNd = −9.0 ± 1.0 (2SD; n = 22); Modified CDW (MCDW), εNd = −8.8 ± 0.8 (2SD; n = 22); AABW, εNd = −8.3 ± 0.5 (2SD; n = 17).There is no evidence of continental REE inputs to surface waters on the Wilkes Land margin. Observed zonal variability of Nd isotope composition in AASW can be attributed to seasonal competition between the poleward flow of warm AASW from the AAG and the westward export of cold surface shelf waters by the Antarctic Slope Current.In terms of deep and bottom waters, mixing of upwelled CDW with AASW and AABW exclusively controls the Nd isotope composition of MCDW, with no indication of boundary processes modifying the Nd isotope composition of MCDW as it encroaches the shelf or slope. The regional Nd isotope signature for AABW is intermediate between published data for the Atlantic sector AABW (εNd = −9.1 ± 0.7) and Pacific sector AABW (εNd = −7.4 ± 0.9). In the absence of active convection, this Nd isotope signature can be explained by a mixture of advected AABW from the Adélie Land coast with a more dominant component of local MCDW and CDW.The data presented in this study constitute the first Nd isotope data set in this part of the Southern Ocean and suggest conservative behaviour of Nd in proximity to the old East Antarctic continent.

Modelling water isotopologues (1H2H16O, 1H217O) in the coupled numerical climate model iLOVECLIM (version 1.1.5)

Abstract. Stable water isotopes are used to infer changes in the hydrological cycle for different climate periods and various climatic archives. Following previous developments of δ18O in the coupled climate model of intermediate complexity, iLOVECLIM, we present here the implementation of the 1H2H16O and 1H217O water isotopes in the different components of this model and calculate the associated secondary markers deuterium excess (d-excess) and oxygen-17 excess (17O-excess) in the atmosphere and ocean. So far, the latter has only been modelled by the atmospheric model LMDZ4. Results of a 5000-year equilibrium simulation under preindustrial conditions are analysed and compared to observations and several isotope-enabled models for the atmosphere and ocean components. In the atmospheric component, the model correctly reproduces the first-order global distribution of the δ2H and d-excess as observed in the data (R=0.56 for δ2H and 0.36 for d-excess), even if local differences are observed. The model–data correlation is within the range of other water-isotope-enabled general circulation models. The main isotopic effects and the latitudinal gradient are properly modelled, similarly to previous water-isotope-enabled general circulation model simulations, despite a simplified atmospheric component in iLOVECLIM. One exception is observed in Antarctica where the model does not correctly estimate the water isotope composition, a consequence of the non-conservative behaviour of the advection scheme at a very low moisture content. The modelled 17O-excess presents a too-important dispersion of the values in comparison to the observations and is not correctly reproduced in the model, mainly because of the complex processes involved in the 17O-excess isotopic value. For the ocean, the model simulates an adequate isotopic ratio in comparison to the observations, except for local areas such as the surface of the Arabian Sea, a part of the Arctic and the western equatorial Indian Ocean. Data–model evaluation also presents a good match for the δ2H over the entire water column in the Atlantic Ocean, reflecting the influence of the different water masses.

Distribution of stable Н, О and С isotopes in natural waters in the area of the Taz oil and gas condensate field (Yamalo-Nenets autonomous region)

Relevance. The study of isotopic composition of water and dissolved substances makes it possible to determine not only their genesis, but also the fractionation processes occurring in the “water–rock–gas–organic matter” system over time, i. e. as different stages of the evolution of water composition pass through. Interest in the groundwater of the Arctic regions of Western Siberia is additionally associated with the widespread occurrence of oil deposits at the depths of formation waters and the possible influence of cryogenic metamorphization processes on composition of near-surface waters. Aim. To study and compare the isotopic composition of oxygen, hydrogen and carbon in natural waters of the Yamalo-Nenets autonomous region to identify conditional isotopic markers, as well as to be able to trace the evolution of the isotopic composition of waters along a vertical section in the area of the Taz oil and gas condensate field. Objects. Surface (river, soil and lake), underground waters of the active water exchange zone of the Yamalo-Nenets autonomous region and formation waters of oil and gas deposits of the Taz field. Methods. The study of the isotopic composition of oxygen, hydrogen, and carbon of water-dissolved carbon dioxide was carried out in the Research Equipment Sharing Center at the Institute of Geology and Mineralogy SB RAS using Isotope Ratio Mass Spectrometer FinniganTM MAT 253 equipped with H/Device and GasBench II for sample preparation. Results and conclusions. The paper introduces the data on isotopic composition of O, H and C for natural waters of the Yamalo-Nenets autonomous region. The authors have determined the characteristic trends in changes in the isotopic composition of water and dissolved carbon dioxide for various water bodies. Surface and underground waters with active water exchange in terms of isotopic composition (δD and δ18О) are infiltration. As water moves down the section, with an increase in the time of interaction of the “water–rock” system and increase in temperatures, the isotopic composition becomes significantly heavier with a slope from the GMWL to the right. The authors compiled the diagram of the evolution of water-dissolved carbon isotopic composition in the region according to the obtained and some literature data. Despite the wide range of δ13C values from –30.4 to 23.6 ‰, there are, obviously, only two sources of carbon dioxide in the region: biogenic and atmospheric, with biogenic being predominant for groundwater.

Rapid decrease of the Labrador Sea’s influence on black spruce ecosystems with distance inland

In eastern Canada, Black spruce (Picea mariana Mill. B.S.P.) grows in a wide variety of climates, from maritime-oceanic conditions near the Labrador Sea, to more continental climates, inland. Along this gradient, timing and provenance of heat and moisture that support growth are uncertain, weakening our capacity to predict the response of boreal ecosystems to climate variability. Here, we measured the stable oxygen isotopic composition of black spruce tree-ring cellulose at three sites in eastern Canada and provide evidence of a rapid decrease of Labrador Sea’s influence on adjacent ecosystems. Our results report a landwards decrease in the oxygen isotope composition of both tree-ring cellulose (δ18OTRC) and precipitation water (δ18Op). We also reveal a rapid landwards decoupling between δ18OTRC variability (1950-2013), maximum temperature and Sea Surface Temperature variations over the Northwest Atlantic. Thus, despite their apparent ecological homogeneity, eastern Canada’s black spruce ecosystems rely on heterogeneous sources of heat and moisture.

Water Uptake Characteristics of Stipa bungeana Trin: Affected by Subsidence in the Coal Mining Areas of Northwest China

Revealing the water use pattern of plants influenced by coal-mining-caused land subsidence is crucial to understand plant–water interactions and guide ecological restoration. However, available information on herbaceous plants, the dominant species in most arid and semi-arid regions with abundant coal resources, remains inadequate. We investigated the water use patterns of Stipa bungeana Trin. by measuring soil water content, root distribution, and stable isotopes of hydrogen (δ2H) and oxygen (δ18O) of soil water and plant stem water both before and after a rainfall event. The results revealed that prior to rainfall, both areas exhibited a low soil water content with no discernible difference in soil drought. However, the soil waters δ2H and δ18O were found to be more enriched at varying depths within the subsidence area, indicating a heightened level of soil evaporation. Both soil water content and soil water isotopic composition responded sensitively to rainfall, with rainfall primarily replenishing the shallow layer (0–20 cm), thereby reflecting an infiltration mode dominated by piston flow. More water seeped into deeper soil layers in the subsidence area compared to the non-subsidence area, with more preferential flow. Before rainfall, the sources of plant water uptake were consistent both at shallow and deep soil layers, implying that the proportion of water uptake gradually decreased with increasing depth. After rainfall, the sources of plant water uptake differed slightly between the two soil layers. The plants in non-subsidence and subsidence areas dominantly extracted soil water at depths greater than 10 cm and 20 cm, respectively. The root system in the subsidence area was more developed than that in the non-subsidence area. Plant water uptake was primarily influenced by the spatial distribution of roots, as well as the post-rainfall water distribution, regardless of whether they were in the subsidence area or not. Although land subsidence affected soil water transport, the water uptake pattern of Stipa bungeana Trin. was similar before and after rainfall, indicating the adaptive growth of plants through their roots in the subsidence area. The high adaptability of herbs such as Stipa bungeana Trin. makes them a viable option for vegetation restoration in subsidence areas. This study has significant implications for evaluating plant–water relationships in subsidence areas due to coal mining, thereby providing a fundamental basis and valuable reference for ecological restoration and management strategies within such affected regions.

Comparative Analysis of Water Isotopic Compositions: Evaluating Isotope Analyzer for Soil and Extraction Method for Stem Water

Stable isotopes of water (δ2H and δ18O) are reliable tracers for the investigation of plant–soil–water interactions in forest ecosystems. However, variations in isotopic compositions may arise due to differences in analytical instruments and water extraction methods. In this study, we conducted three different experiments to identify isotopic differences caused by analytical and methodological variations. First, we analyzed soil water by using the two most commonly applied methods: isotope ratio mass spectrometry (IRMS) and cavity ring-down spectroscopy (CRDS). Second, we compared the isotopes in xylem water extracted from the stems of nine tree species using cryogenic vacuum distillation (CVD) with different heating times. Third, we compared the compositions in xylem water extracted with three different methods: mechanical squeezing using a pressure chamber (PC), an induction module (IM), and CVD. The differences in isotopic composition between IRMS and CRDS were significant but minimal. Soil properties were not significant factors contributing to differences between the two instruments. For the xylem water extraction with CVD, each of the nine tree species required heating for more than three hours. Significant differences were observed in δ2H among the three extraction methods for xylem water. Xylem water extracted by CVD showed more depleted values compared to those obtained by PC and IM. Our results highlight the importance of considering analytical and methodological variations in stable isotope analysis.

Shallow and deep groundwater moderate methane dynamics in a high Arctic glacial catchment

Glacial groundwater can mobilize deep-seated methane from beneath glaciers and permafrost in the Arctic, leading to atmospheric emissions of this greenhouse gas. We present a temporal, hydro-chemical dataset of methane-rich groundwater collected during two melt seasons from a high Arctic glacial forefield to explore the seasonal dynamics of methane emissions. We use methane and ion concentrations and the isotopic composition of water and methane to investigate the sources of groundwater and the origin of the methane that the groundwater transports to the surface. Our results suggest two sources of groundwater, one shallow and one deep, which mix, and moderate methane dynamics. During summer, deep methane-rich groundwater is diluted by shallow oxygenated groundwater, leading to some microbial methane oxidation prior to its emergence at the surface. Characterization of the microbial compositions in the groundwater shows that microbial activity is an important seasonal methane sink along this flow-path. In the groundwater pool studied, we found that potential methane emissions were reduced by an average of 29% (±14%) throughout the summer due to microbial oxidation. During winter, deep groundwater remains active while many shallow systems shut down due to freezing, reducing subsurface methane oxidation, and potentially permitting larger methane emissions. Our results suggest that ratios of the different groundwater sources will change in the future as aquifer capacities and recharge volumes increase in a warming climate.