δD Variations Research Articles

A model framework for atmosphere–snow water vapor exchange and the associated isotope effects at Dome Argus, Antarctica – Part 1: The diurnal changes

Abstract. Ice-core water isotopes contain valuable information on past climate changes. However, such information can be altered by post-depositional processing after snow deposition. Atmosphere–snow water vapor exchange is one such process, but its influence remains poorly constrained. Here we constructed a box model to quantify the atmosphere–snow water vapor exchange fluxes and the associated isotope effects at sites with low snow accumulation rates, where the effects of atmosphere–snow water vapor exchange are suspected to be large. The model reproduced the observed diurnal variations in δ18O, δD, and deuterium excess (d-excess) in water vapor at Dome C, East Antarctica. According to the same model framework, we found that under average summer clear-sky conditions, atmosphere–snow water vapor exchange at Dome A can cause diurnal variations in atmospheric water vapor δ18O and δD of 4.8 ‰ ± 2.6 ‰ and 29 ‰ ± 19 ‰, with corresponding diurnal variations in surface snow δ18O and δD of 0.80 ‰ ± 0.35 ‰ and 1.6 ‰ ± 2.7 ‰. The modeled results under summer cloudy conditions display similar patterns to those under clear-sky conditions but with much smaller magnitudes of diurnal variations. However, under winter conditions at Dome A, the model predicts few to no diurnal changes in snow isotopes, consistent with the stable boundary condition in winter that inhibits effective vapor exchange between the atmosphere and snow. In addition, after 24 h and continuous simulations of 11 d, the model predicts significant enrichments in snow isotopes under summer conditions, while in winter, the depletions also accumulate after each 24 h simulation but with a much smaller magnitude of change compared to the results from summer simulations. If the modeled snow isotope enrichments in summer conditions and the depletions in winter conditions represent the general situation at Dome A, this likely suggests that atmosphere–snow water vapor exchange tends to increase snow isotope seasonality, and the annual net effect would be overall enrichments in snow isotopes since the effects in summer appear to be greater than those in winter. This trend will need to be further explored in the future with more comprehensive model studies and/or field observations and experiments.

Seasonal Variations and Controls on Triple Oxygen and Hydrogen Isotopes in Precipitation—A Case Study From Monitoring in Southwest China

AbstractPrecipitation δ18O has offered valuable insights into the evolution of the Asian monsoon. Recent researches focusing on precipitation Δ′17O has enhanced our understanding by offering new perspectives beyond those of δ18O, revealing insights into vapor sources and continental recycling. Nevertheless, there remains a lack of interannual triple oxygen isotope data, particularly in the Asian monsoon region. In this study, we analyzed the triple oxygen isotopes and hydrogen isotopes in monthly precipitation samples collected from Chongqing in Southwest China between 2019 and 2022 A.D. Seasonal variations in δD, δ18O, δ17O, and d‐excess values were observed, with lower values during the rainy season and higher values during the dry season, highlighting the impact of changes in moisture sources and local meteorological conditions on seasonal shifts in δD, δ18O, and δ17O. While, mean Δ′17O values were higher in rainy season and lower in dry season. Notably, during rainy season, there is a negative correlation between monthly Δ′17O values and the RH of the vapor source area, as well as a positive correlation with d‐excess. Recalculated Δ′17O values based on RH of oceanic moisture source, are higher than the measured values for this period, indicating the contribution of terrigenous moisture to precipitation in SW China. Precipitation Δ′17O values provide a more precise reflection of changes in moisture source, continental recycling, and evapotranspiration processes that drive water cycling compared Integrating modeling works in future will facilitate the use of precipitation Δ′17O values to quantify the impact of different moisture source on precipitation.

Magmatic degassing and fluid metasomatism promote compositional variation from I-type to peralkaline A-type granite in the late Cretaceous Fuzhou felsic complex, SE China

Abstract A-type granites generally have much lower water, higher temperature, and incompatible element concentrations than I-type granitoids. Yet it remains unclear why I-A-type granitic complexes occur in convergent plate margins. Here we conduct geochemical analyses on apatite and mafic minerals from the late Cretaceous I-A-type granitic complex in Fuzhou area, SE China, aiming to decipher differentiation, fluid metasomatism, and degassing that primarily control the compositional diversity of felsic magmas. Apatites in both rock types are F-rich and show large H2O and δD variations, i.e., 341–3892 ppm H2O and –325 to +336‰ δD in I-type granitoids; 67–1366 ppm H2O and –251 to +1439‰ δD in A-type granites. H2O in apatite is negatively correlated with La/Sm and Sr/Y in the I-type granitoids, whereas it is positively correlated with Ce and total rare earth element (REE) concentrations in the A-type granites. Once H2O increases up to hundreds of ppm, both rock types show a rapid decrease of H2O/Ce, an increase of F/Cl, and extensive H isotope fractionation. Arfvedsonite occurs as a late crystallizing mineral in the A-type granite and has much higher contents of Na2O, K2O, F, and high field strength elements (HFSE) than hornblende in the I-type granitoids, indicating the addition of F-HFSE-rich alkaline fluids during its magmatic evolution. The consumption of arfvedsonite and formation of aegirine further indicate the role of fluid metasomatism and H2 degassing via a reaction of 3Na3Fe5Si8O22(OH)2 + 2H2O = 9NaFeSi2O6 + 2Fe3O4 + 6SiO2+5H2. The combined geochemical data demonstrate that the systematic differences in mineral assemblage, whole-rock composition, magma temperature, H2O content, and δD of apatite between the I- and A-type granites are likely attributed to varying degrees of differentiation, fluid metasomatism and magmatic degassing. The I-type granitoids experienced hornblende, biotite, plagioclase, K-feldspar, and apatite fractionation and close-system degassing. The A-type granite was likely formed from the I-type monzogranitic magma that was metasomatized by the mantle-derived F-HFSE-rich alkaline fluids to produce the peralkaline magma, which further experienced K-feldspar + plagioclase + biotite + apatite fractionation and open-system degassing. Further numerical estimation indicates that the primary magma of Fuzhou granitic complex contained ~3.0 wt% H2O, and the lower water content of A-type granite was likely attributed to strong degassing during its emplacement. Our results indicate that some peralkaline A-type granites can be generated from relatively water-poor I-type granitic magmas by fluid metasomatism and degassing.

Volcanic Glass as a Proxy for Paleotopography Suggests New Features in Late-Miocene Oregon

Volcanic glass has been used extensively as a paleoaltimeter. Deuterium (2H) concentrations in glass have been found to be stable over geologic timescales, making δ2H (also known as δD) a reliable proxy for ancient water chemistry. However, continued work revolves around better understanding how different factors affect preserved water in volcanic ash. Here, we analyze δD in the Rattlesnake Tuff (RST), a widespread ca. 7 Ma ash-flow tuff, and create a paleoisoscape to assess variations in δD across Oregon during that time. To this end, 16 ash samples were collected across central and eastern Oregon from various flow units within the RST. Samples were analyzed for δD using a temperature conversion elemental analyzer (TC/EA) connected to a mass spectrometer and elemental composition using a scanning electron microscope (SEM). We compared the isotopic results to modern water and published ancient water proxy data to better constrain changes in climate and topography across Oregon throughout the Neogene. We also estimated wt. % H2O by calculating excess (non-stoichiometric) oxygen from SEM elemental data. We did not observe significant variations in δD among the flow units from single locations, nor was there a significant relationship between the prepared glass shard composition and wt. % H2O or δD, supporting the use of volcanic glass as a reliable paleoenvironmental indicator. Our results show significant spatial variation in δDwater values of RST, ranging from −107‰ to −154‰. δD values of ancient glass were similar to modern water near the Cascade Mountains but became relatively negative to the east near the inferred eruptive center of the RST, suggesting that a significant topographic feature existed in the vicinity of the RST eruptive center that has since subsided.

Triple isotopes (δD, δ18O, δ17O) characteristic of river water and groundwater in an arid watershed from Qaidam Basin, Northwestern China: implications for hydrological cycle

Combining traditional stable isotopes (δD and δ18O) and triple oxygen isotope (δ17O) is conducive to tracing hydrological cycle processes. The application of triple oxygen isotopes primarily focuses on precipitation, which is lacking in river water and groundwater. In this study, the spatial variations of δD, δ18O, δ17O, d-excess and 17O-excess of river water and groundwater in the Golmud River basin as well as the correlation between them were investigated to elucidate water origin and assess the evaporation influence on water bodies during flood season. Spatial changes in δD, δ18O and δ17O of river water exhibit a decrease-increase-stability pattern contrary to that observed for d-excess, 17O-excess has no distinct trend but is higher at both the source and downstream regions. The results show that river water and groundwater originate from precipitation in the mountainous area, and the meltwater in the source region also contribute to the river water with high d-excess and 17O-excess during flood season. The combination of d-excess and 17O-excess reveal that river water is also affected by evaporation and mixing of river water in tributaries. It was found that the river water is recharged in the mountains, undergoes evaporation in the upstream region and leaks into groundwater in the midstream region, which is recharged by the groundwater and evaporated again in the downstream region. This study could provide a more comprehensive understanding of the potential and value of triple oxygen isotopes in the hydrological cycle.

Influence of mining activities on hydrological processes in the mining district, Loess Plateau: insights from spatio-temporal variations of δD and δ18O

Under the influence of mining activities, investigating hydrological processes is an important cornerstone of water resources and eco-environment protection. In this study, the spatio-temporal variations of stable isotopic compositions (δD and δ18O) of river water and groundwater in five periods of a hydrological year were analyzed to identify the origin and hydraulic connection of water bodies in the mining district under mining disturbance. The δD and δ18O indicate that the water bodies in the study area are mainly recharged by local precipitation and undergo evaporation. There is a close hydraulic connection between river water, mine water, and groundwater, and the deep confined water is affected by the river water and phreatic water due to the developing water-conducting fractures. The δ18O of phreatic water in each period is depleted in the southwest and enriched in the northeast of the study area. The δ18O of confined water has an obvious spatial variation in the wet season due to the combined effects of opencast working and underground mining, whereas uniform spatial variation is observed in the dry season. Compared with the dry season, mining disturbances have a greater impact on river water and groundwater in the wet season. The difference in spatial variation of δ18O between phreatic and confined water may be attributed to the easier recovery of phreatic water than confined water after mining disturbance. This finding provides important information about the hydrological characteristics of the Pingshuo mining district.

Dual-path coupling V-shaped structure off-axis integrated cavity output spectroscopy (V-OA-ICOS) for water vapor stable isotope detection at 3.66 μm

Residual cavity mode noise and weak output signal are the main factors that restrict the detection performance of off-axis integrated cavity output spectroscopy (OA-ICOS). In order to overcome the above drawbacks, a novel V-shaped off-axis integrated cavity output spectroscopy (V-OA-ICOS) device was demonstrated, and the dual-path coupling method was further proposed. The dual-path coupling V-OA-ICOS device can not only suppress the residual cavity mode noise but also enhance the intensity of the output signal. The V-shaped resonator cavity ensures a more uniform and square-shaped spot pattern distribution on the surface of the highly reflective mirrors, significantly reducing spots overlap. The dual-path coupling method can re-couple the laser reflected by the front cavity mirror, thereby increasing the total energy and mode density of the cavity. The spectrum of water vapor stable isotopes HD16O and H216O at 3.66 μm was measured to illustrate the performance of the presented approach, the dual-path coupling V-OA-ICOS increases the signal-to-noise ratio (SNR) by a factor ∼ 2.1 compared to single path V-OA-ICOS and the signal intensity by a factor of ∼ 2. The δD variation was obtained by measuring the outdoor water vapor isotope using this device for three consecutive days. The variation range of δD is −220‰ ∼ −120‰. This work proposes a new cavity structure and optical re-coupling method, which offers a novel approach to enhance the performance of OA-ICOS devices.

Characteristics of Hydrogen–Oxygen Isotopes and Water Vapor Sources of Different Waters in the Ili Kashi River Basin

The Ili Kashi River Basin is an area with relatively abundant precipitation within the arid region of Northwest China. Using water samples from atmospheric precipitation, surface water, groundwater, and snow meltwater in the basin from July 2018 to June 2021, the isotope characteristics of the different water bodies in the study area were determined from the perspectives of altitude, season, and interannual changes. Combined with the meteorological data on precipitation and the HYSPLIT model, the water vapor sources of atmospheric precipitation in the Ili Kashi River Basin were tracked and analyzed. Studying the hydrogen and oxygen stable isotopes in the different water bodies in this area can provide substantial scientific support for the generation, development, and change processes of river water resources in Northwest China, and has practical significance for the utilization of water resources. The results derived are as follows. (1) Hydrogen–oxygen isotope changes in the Ili Kashi River Basin were broadly characterized by a continuous enrichment from low-to-high elevations in the summer to a maximum value, followed by gradual depletion, whereas the changes in δ18O and δD were reversed in autumn. (2) The river water values of δD and δ18O fluctuated between −107.15‰ and −68.13‰ and between −18.53‰ and −9.66‰, respectively, during the study period. (3) The variation in δ18O and δD in the precipitation was consistent, showing characteristics of summer enrichment and winter dilution, and the precipitation line equation is δD = 7.30δ18O + 9.29. (4) In autumn and winter, the groundwater δD and δ18O values fluctuated between −99.87‰ and −84.95‰ and between −15.50‰ and −10.38‰, respectively; during spring and summer, the δD and δ18O values varied from −99.27‰ to −87.07‰ and from −15.15‰ to −12.00‰, respectively. The hydrogen–oxygen stable isotope value of the ice–snow meltwater in autumn was higher than that in summer. (5) On the basis of the d-excess variation in each precipitation event over the 3 years and an analysis of the water vapor sources using the HPSPLIT backward trajectory tracking model, the source of water vapor in the study area is primarily the surrounding land water vapor, with the Atlantic Ocean being the main contributor of oceanic water vapor.

Relationship of seasonal variations in drip waterδ13CDIC,δ18O, and trace elements with surface and physical cave conditions of La Vallina cave, NW Spain

Abstract. Cave-monitoring studies clarify the climatic, surface vegetation, and karst processes affecting the cave system and lay the foundation for interpreting geochemical stalagmite records. Here we report the monitoring of cave air, bedrock chemistry, and drip water δ13CDIC, δ18O, and δD, as well as 16 trace elements, covering a full annual cycle spanning the 16 months between November 2019 and March 2021 in La Vallina cave in the northwestern Iberian Peninsula. While decreased rainfall and increased evapotranspiration in the summer months lead to a strong reduction in drip rates, there is little seasonal variation in δ18O and δD in a given drip, likely reflecting the discrete moderately mixed to well-mixed karst water reservoirs. Small differences in δ18O and δD between drip sites are attributed to variable evaporation intensity and/or transit times. The carbon isotope signature of the dissolved inorganic carbon of drip water (δ13CDIC) is likely driven by seasonal changes in the temperature controlling biological processes (vegetation and microbial soil activity), resulting in minimum δ13CDIC in summer and autumn months. Increased bedrock dissolution due to higher soil pCO2 in summer and autumn results in increased trace element concentrations of congruently dissolved elements. Cave air measurements (pCO2, δ13Cair, and temperature) indicate the seasonal ventilation (winter) and stagnation (summer) of cave air. The opposite effects of reduced cave air pCO2, seasonally variable biological activity, and increased drip rate limit the extent of the seasonal variation in degassing and prior calcite precipitation (PCP) supported by trace elements (Sr/Ca index). Estimated stalagmite growth rates using monitoring data suggest biannual phases of potential calcite precipitation in summer and winter and growth cessation during spring and autumn, depending on cave and drip water conditions and the location within the cave, which has important implications for the proxy interpretation of stalagmite records.

δ18O and δ2H isotopes, trace metals and major ions in groundwater around uranium and fluoride contaminated Indus valley Quaternary alluvial plain, SW Punjab, India: Implications on hydrogeochemical processes, irrigation use and source

Uranium and fluoride enrichment in groundwater along alluvial plains pose a severe threat to living beings like cancer, fluorosis and crop yield as witnessed around semi-arid southwest Punjab, India. In-situ groundwater was examined for major ions, stable isotopes and trace metals to understand the hydrogeochemical processes, contaminant origin and health risks around SW Punjab, India. Groundwater from a freshly drilled bore well is found to be hard, alkaline, and saline with total dissolved solids and salinity up to 1300 and 1500 mg L−1, respectively. Fluoride (up to 4 mg L−1) and uranium (up to 90.07 μg L−1) contents exceed permissible limits in most samples and originated from fertilizer inputs and aquifer leaching. Uranium contents decline with depth, while fluoride remains invariable. Decreased U contents are inferred to be caused by U(VI) reduction to U(IV) as evidenced by an increase in Fe2+ vs. Fe3+, S2− vs. S6+ and N3− vs. N5+ with depth. NaHCO3, NaCl + NaHCO3 and NaCl are the dominant water types for shallow (<38 m), intermediate (49–83 m) and deeper groundwater (105–128 m) with Na+ and HCO3− as the dominant cations and anions, respectively. Silicate weathering majorly controlled the groundwater geochemistry together with a partial contribution from cation exchange processes. Unsuitability for drinking and irrigation use is envisaged for all depths, while deeper groundwater is safe in regard to radiological risk. δ18O and δD variations are suggestive of evaporation dominance in shallow groundwater, while intermediate groundwater witness canal and groundwater mixing and deeper groundwater are recharged through higher altitude.

Abrupt Drying on the Southeast Coast of China During the Mid‐to‐Late Holocene Transition

AbstractIt is becoming increasingly clear that China experienced significant hydrological changes during the mid‐to‐late Holocene transition—a period characterized by societal changes. However, the nature of the hydroclimate anomaly as well as the direct consequences on societies in Southeast China remains unclear. Here, we present a leaf wax record from the Shuizhuyang peat deposit in Southeast China spanning the Holocene. The δD values of C29 n‐alkane (δDC29) showed a large positive shift up to 24‰ from 4.7 to 3.8 ka, which changed independent of vegetation proxies and could not be solely explained by precipitation δD variations. It is thus most likely to reflect abrupt drying, which is probably shaped by a more El Niño‐like mean state in the tropical Pacific Ocean. We hypothesize that such a significant change in hydroclimate might have promoted the development of mixed rice and millet farming on the southeast coast of China.

Spatial variability and post-depositional diffusion of stable isotopes in high accumulation regions of East Antarctica

Stable isotopes of Antarcticice cores are used extensively in reconstructing the past climate. Variations in snow accumulation patterns and post-depositional processes such as changes in isotope ratios due to diffusion may complicate these records. We analyzed the spatio-temporal variations of snow accumulation, stable isotopic composition, and factors controlling their distribution along two transects in the Dronning Maud Land (DML) and Princess Elizabeth Land (PEL) regions of East Antarctica. The δ18O and δD variations are dominantly influenced by snow accumulation in the DML region and temperature in the PEL region. To evaluate the extent of diffusion in isotope records, the isotope record of an ice core (IND-33) drilled after 5 years close to the DML transect was compared with the snow isotope records. A quantitative comparison of the snow core δ18O records with that of the ice core revealed signal attenuation ranging between 55 and 70%. Using a firn diffusion model, we estimated a diffusion length of 6 cm in IND-33 over 5 years. Our study revealed that while isotope diffusion exists even in high accumulation sites of coastal Antarctica, it does not significantly impact the dating and paleoclimatic interpretation of isotope records, unlike in low accumulation areas.

Characterizing the spatiotemporal dynamics of shallow soil water stable isotopic compositions on a karst hillslope in Southwestern China

• Soil water stable isotopic compositions (SWSIC) exhibited large spatiotemporal variations. • SWSIC showed less temporal stability than soil water content (SWC). • SWSIC variations were less explained by environmental controls compared to SWC variations. • Temporal stability analysis method can be used to select representative sites for SWSIC. Knowledge of the spatiotemporal dynamics of soil water content (SWC) and soil water stable isotopic compositions (SWSIC) is critical for understanding water exchanges across the atmosphere-land interface. However, compared with those of SWC, studies on the spatiotemporal characteristics of SWSIC are still scarce, which limits their use for more accurately characterizing terrestrial ecohydrological processes. To examine whether SWSIC and SWC share similar spatiotemporal features, their spatiotemporal patterns along with relevant controls were investigated at shallow soils (0–10 cm) on a karst hillslope in Southwest China, based on seven sampling campaigns conducted over a two-year period. The results revealed considerable spatiotemporal variations in SWSIC. Compared to SWC, δD values exhibited smaller spatial variations, while line-conditioned excess (lc-excess) values exhibited considerably larger ones, suggesting that soil evaporation heterogeneity might not be the primary reason for spatial variations in δD of soil water in this study. The spatial structures of SWSIC were less temporally stable than those of SWC due to the combined impact of land surface processes and temporal variations in isotopic compositions of input water on SWSIC. Moreover, the spatiotemporal patterns of SWSIC were less explained by environmental variables that were also differed from those of SWC, suggesting that the knowledge gained from SWC studies might not be directly transferable to understand SWSIC spatiotemporal characteristics. Nevertheless, it should be highlighted that the temporal stability analysis method initially proposed for studying SWC could be extended to select representative sites for monitoring areal average SWSIC, due to the temporal persistence of the SWSIC spatial structures. In addition, a negative correlation between the spatial mean and standard deviation of lc-excess was found, indicating that the associated spatial variability increased with areal mean kinetic fractionation signals caused by soil evaporation. These findings have important implications for designing SWSIC monitoring schemes, which in turn can improve the interpretation of SWSIC data for various application purposes.

Spatiotemporal Variation of Hydrogen and Oxygen Stable Isotopes in the Yarlung Tsangpo River Basin, Southern Tibetan Plateau

Characterization of spatiotemporal variation of the stable isotopes δ18O and δD in surface water is essential to trace the water cycle, indicate moisture sources, and reconstruct paleoaltimetry. In this study, river water, rainwater, and groundwater samples were collected in the Yarlung Tsangpo River (YTR) Basin before (BM) and after the monsoon precipitation (AM) to investigate the δ18O and δD spatiotemporal variation of natural water. Most of the river waters are distributed along GMWL and the line of d-excess = 10‰, indicating that they are mainly originated from precipitation. Temporally, the δ18O and δD of river water are higher in BM series (SWL: δD = 10.26δ18O+43.01, R2 = 0.98) than AM series (SWL: δD = 9.10δ18O + 26.73, R2 = 0.82). Spatially, the isotopic compositions of tributaries increase gradually from west to east (BM: δ18O = 0.65Lon (°)-73.89, R2 = 0.79; AM: δ18O = 0.45Lon (°)-57.81, R2 = 0.70) and from high altitude to low (BM: δ18O = −0.0025Alt(m)-73.89, R2 = 0.66; AM: δ18O = −0.0018Alt(m)-10.57, R2 = 0.58), which conforms to the “continent effect” and “altitude effect” of precipitation. In the lower reaches of the mainstream, rainwater is the main source, so the variations of δ18O and δD are normally elevated with the flow direction. Anomalously, in the middle reaches, the δ18Omainstream and δDmainstream values firstly increase and then decrease. From the Saga to Lhaze section, the higher positive values of δ18Omainstream are mainly caused by groundwater afflux, which has high δ18O and low d-excess values. The δ18Omainstream decrease from the Lhaze to Qushui section is attributed to the combined action of the import of depleted 18O and D groundwater and tributaries. Therefore, because of the recharge of groundwater with markedly different δ18O and δD values, the mainstream no longer simply inherits the isotopic composition from precipitation. These results suggest that in the YTR Basin, if the δ18O value of surface water is used to trace moisture sources or reconstruct the paleoaltimetry, it is necessary to rule out the influence from groundwater.

Continuous monitoring of surface water vapour isotopic compositions at Neumayer Station III, East Antarctica

Abstract. In this study, the first fully continuous monitoring of water vapour isotopic composition at Neumayer Station III, Antarctica, during the 2-year period from February 2017 to January 2019 is presented. Seasonal and synoptic-scale variations in both stable water isotopes H218O and HDO are reported, and their links to variations in key meteorological variables are analysed. In addition, the diurnal cycle of isotope variations during the summer months (December and January 2017/18 and 2018/19) has been examined. Changes in local temperature and specific humidity are the main drivers for the variability in δ18O and δD in vapour at Neumayer Station III, on both seasonal and shorter timescales. In contrast to the measured δ18O and δD variations, no seasonal cycle in the Deuterium excess signal (d) in vapour is detected. However, a rather high uncertainty in measured d values especially in austral winter limits the confidence of this finding. Overall, the d signal shows a stronger inverse correlation with specific humidity than with temperature, and this inverse correlation between d and specific humidity is stronger for the cloudy-sky conditions than for clear-sky conditions during summertime. Back-trajectory simulations performed with the FLEXPART model show that seasonal and synoptic variations in δ18O and δD in vapour coincide with changes in the main sources of water vapour transported to Neumayer Station III. In general, moisture transport pathways from the east lead to higher temperatures and more enriched δ18O values in vapour, while weather situations with southerly winds lead to lower temperatures and more depleted δ18O values. However, on several occasions, δ18O variations linked to wind direction changes were observed, which were not accompanied by a corresponding temperature change. Comparing isotopic compositions of water vapour at Neumayer Station III and snow samples taken in the vicinity of the station reveals almost identical slopes, both for the δ18O–δD relation and for the temperature–δ18O relation.

Global-scale altitude effect on leaf wax n-alkane δD values in terrestrial higher plants

Numerous field studies have shown that leaf wax n-alkane δD values (δDn-alkane) can be used as a proxy for paleoelevation reconstruction. However, the lack of systematic global analysis of δDn-alkane values with respect to altitude limits the reliability of δDn-alkane values for paleoaltimetry at the global scale. In this study, we analyzed the variation of δDn-alkane values with altitude in terrestrial higher plants based upon our compiled global δDn-alkane database. The general decrease in δDn-alkane values with altitude corresponds to the variation in precipitation δD (δDprec) with altitude, suggesting that the δDn-alkane values effectively reflect δDprec values. When eliminating the effect of latitude at the global scale, the global δDn-alkane-altitude lapse rate for all species was −1.01±0.10‰ (100 m)−1, while these lapse rates were −1.03±0.13‰ and −0.47±0.13‰ (100 m)−1 for dicots and monocots, respectively. Our study reveals that it is reliable to use δDn-alkane values to gain information about paleoelevation at the global scale, and the global δDn-alkane-altitude lapse rates provide an alternative to reconstruct paleoelevation at some δDn-alkane-uninvestigated areas.

Soil Water Dynamics Under Different Land Uses in Loess Hilly Region in China by Stable Isotopic Tracing

Exploring soil water dynamics under different land use types is important for water resource management and vegetation restoration in the Loess Plateau. In this study, we investigated the hydrogen and oxygen isotopic compositions of soil water from four different land use types to explore the mechanism of soil water movement and transformation and analyse the influence of land use. The results show that the range of stable isotopes (δD and δ18O) in soil water was smaller than that in precipitation. Values for δD and δ18O in soil water showed relatively similar temporal variation, heavy isotopes were enriched in the soil water in July and depleted in October. Stable isotope values in shallow (&lt;100 cm depth) soil water and deep (&gt;200 cm depth) soil water were low. The δD and δ18O values in woodlands decreased gradually with increasing depth. Across the four land use types, the maximum variation in δD and δ18O was in the shallow depth of the soil profile. Groundwater was recharged mainly from precipitation and then from soil water. The ratio of groundwater recharge by soil water under different land use types followed this rank order: woodland (35.70%) &gt; grassland (31.14%) &gt; shrubland (29.47%) &gt; cropland (29.18%). Matrix flow and preferential flow coexisted during infiltration, and the occurrence of preferential flow was related to the land use type. The main reason for the variation in isotopic composition in soil water is the difference in soil evaporation, which is influenced by different vegetation cover. Owing to the difference in soil evaporation and fractionation, precipitation on cropland, shrubland, and grassland can recharge more soil water than on woodland.

Triple Water Vapour–Isotopologues Record from Chhota Shigri, Western Himalaya, India: A Unified Interpretation based on δ17O, δ18O, δD and Comparison to Meteorological Parameters

The objective of this study is to investigate and understand the source and transportation of water vapour in the western Himalayan region—that is still missing—using water vapour stable isotopologues and air mass trajectory diagnostics. We report the first-time triple oxygen isotopic compositions of water vapour from high altitude western Himalaya (Chhota Shigri, India) and compare them with meteorological conditions at the site of investigation as well as tracked backwards through the Lagrangian air mass trajectory diagnostics. A total of 21 water vapour samples were collected using a quantitative cryogenic method. δ17O and δ18O values show a significant correlation coefficient of 0.999 (p &amp;lt;0.01). The temporal variations of δ17O, δ18O, δD, D-excess and 17O-excess are 1.2, 2.3, 17.3, 11.6 and 39‰ permeg, respectively. δ17O and δ18O exhibit significant (p &amp;lt; 0.05) diurnal variations along with meteorological parameters. Chhota Shigri vapour isotopic results show a clear difference in the 17O-excess value compared to near the south Indian Ocean and the Southern Ocean regions, reflecting the influence of local moisture recycling at the continental site. NCEP/NCAR reanalyses show lower Specific Humidity during the sampling period (September, ending month of the Indian summer monsoon) favouring evaporative conditions which are further corroborated through the Lagrangian moisture diagnostics suggesting frequent moisture uptake and moisture loss in specific regions.

Triple Oxygen Isotope Systematics in the Hydrologic Cycle

Research Article| January 01, 2021 Triple Oxygen Isotope Systematics in the Hydrologic Cycle Jakub Surma; Jakub Surma Institute of Geology and Mineralogy, University of Cologne, Zülpicher Straße 49b, Cologne, 50674, GermanyPresently at: Geoscience Center, Georg August University, Goldschmidtstraße 1 Göttingen, 37077, Germany * E-mail: jakub.surma@uni-goettingen.de Search for other works by this author on: GSW Google Scholar Sergey Assonov; Sergey Assonov Formerly at: Institute of Geology and Mineralogy, University of Cologne, Zülpicher Straße 49b Cologne, 50674, Germany Search for other works by this author on: GSW Google Scholar Michael Staubwasser Michael Staubwasser Institute of Geology and Mineralogy, University of Cologne, Zülpicher Straße 49b Cologne, 50674, Germany Search for other works by this author on: GSW Google Scholar Reviews in Mineralogy and Geochemistry (2021) 86 (1): 401–428. https://doi.org/10.2138/rmg.2021.86.12 Article history first online: 04 Jan 2021 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Jakub Surma, Sergey Assonov, Michael Staubwasser; Triple Oxygen Isotope Systematics in the Hydrologic Cycle. Reviews in Mineralogy and Geochemistry 2021;; 86 (1): 401–428. doi: https://doi.org/10.2138/rmg.2021.86.12 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyReviews in Mineralogy and Geochemistry Search Advanced Search The analysis of hydrogen (δD) and oxygen (δ18O) isotope ratios of H2O are widely used tools for studies of the hydrological cycle (Friedman 1953; Dansgaard 1954; Gonfiantini 1986; Gat 1996; Araguás-Araguás et al. 2000; Gat et al. 2000) and climate reconstruction (Dansgaard 1964; Johnsen et al. 1989; Petit et al. 1999). Natural variations of δD and δ18O in precipitation are well correlated and fall on a common global trend, the Global Meteoric Water Line (GMWL, Craig 1961): δD=8·... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Plateau river research: spatial-temporal variations of δ18O and δd in the water of the Yarlung Tsangpo River and their controlling factors

Stable isotope technology has been widely used to trace sources and evolution of water bodies, relationships between different water bodies and pollution sources. Based on δ18O and δD data from the Yarlung Tsangpo River in 2017, this paper analyzes the composition characteristics of δ18O and δD in the river water during the low-flow, high-flow and normal-flow seasons of the entire Yarlung Tsangpo River and further reveals the spatial evolution and influencing factors. The results show that the values of δ18O, δD and d-excess were different in time and space. The δ18O, δD and d-excess values of the Yarlung Tsangpo River in the low-flow season were significantly higher than in the high-flow season. This was mainly due to weak evaporation enrichment and precipitation supply effects on the river water during the wet season. From the perspective of season change, the d-excess in the low-season is significantly higher than in the high-flow season and the normal-flow season; from the perspective of spatial change, the d-excess shows the same spatial variation trend as the δ18O, which first decreases and then increases. Based on the investigation of δ18O and δD in the main and Branch rivers of the Yarlung Tsangpo River Basin, it was found that the upper reaches of the basin were mainly supplied by snowmelt, the lower reaches were mainly supplied by rainfall.