Stable Isotope Characteristics Research Articles

In Situ Ecological Floating Bed Remediation Alters Internal Trophic Structure: A Case Study of Meiliang Bay, Lake Taihu

Ecological floating beds are effective in mitigating lake eutrophication. To examine the effects of their in situ remediation processes on the food sources and trophic structures of consumers, particularly fish, this study used stable isotope techniques to compare cage enclosures, net enclosures, and natural lake area in Meiliang Bay, Lake Taihu. The results revealed that among basic carbon sources, only the δ13C values of phytoplankton and POM differed significantly, while most consumers showed no significant differences in carbon and nitrogen stable isotope characteristics across the three remediation areas. In cage enclosures, the food chain transitioned from being grazing-based, dominated by phytoplankton, to detritus-based, primarily relying on SOM. In contrast, net enclosures enhanced the utilization of phytoplankton. The trophic levels of most consumers in cage enclosures were significantly lower than those in net enclosures and the natural lake area. Trophic niche indices indicated that cage enclosures exhibited the highest trophic diversity and the lowest trophic redundancy. The in situ remediation using ecological floating beds altered the food resource conditions within the remediation areas due to differences in the degree of enclosure provided by the floating beds and interception facilities. These changes have consequently reshaped the internal trophic structure through trophic cascade effects.

Characteristics of water stable isotopes and runoff sources of a small permafrost basin in northeastern China

Permafrost degradation may have significant impacts on regional water cycles, while little is known about the recharge sources of runoff in permafrost regions, hindering our capability to predict river discharges. Here, a small permafrost basin in Northeast China was selected as the study area. We analyzed isotopic tracers of 186 precipitation, river water, and supra-permafrost water samples collected from May to October 2021. We further calculated the contribution of supra-permafrost water and precipitation to river discharges. The δ18O and δD of precipitation exhibited a significant correlation with air temperature (p<0.05). Similar values and trends were observed in the stable isotope changes of river water and supra-permafrost water, indicating a close hydraulic relationship between the two water sources. Hydrograph separation revealed that supra-permafrost water and precipitation are the first and second end-member of river water in the basin, with a contribution of 85% and 15%, respectively. Overall, our results suggest that supra-permafrost water is the main recharge source of runoff, highlighting the importance of permafrost in the regulation of runoff in small catchments.

Exploring, sampling, and interpreting lunar volatiles in polar cold traps

Numerous missions to the Moon have identified and documented volatile deposits associated with permanently shadowed regions. A series of science goals for the Artemis Program is to explore these volatile deposits and return samples to Earth. Volatiles in these reservoirs may consist of a variety of species whose stable isotope characteristics could elucidate both their sources and the processes instrumental in their formation. For example, the δD of potential contributors to the deposits can be used to identify a uniquely light solar wind component. Because of the exceptionally low temperatures of these volatile deposits, examining and interpreting their stable isotope systems to fulfill Artemis science goals through sampling, preserving, curating, and analyzing these samples are far more difficult than for other sample return missions. Collecting and preserving the samples at cryogenic temperatures dramatically increases science yield but is technologically demanding and poses increased risk during transport.

Characteristics of Stable Carbon and Nitrogen Isotopes in Different Ecological Plant Groups and Sediments Collected from 14 Softwater Lakes in Poland

Softwater lakes with specific, rare, and protected aquatic plant vegetation are very sensitive to increased trophic and water chemical changes, especially alkalization. These changes might be reflected in the stable carbon and nitrogen isotopes of the organic matter (OM) of those plants (δ13CORG and δ15NORG) and sediments (δ13CORG and δ15NTN) which they cocreated. To recognize the relationship between OM in the aquatic plants of softwater lakes and the cocreated sediments, we analyzed the plants δ13CORG and δ15NORG in light of four ecological groups (as well as the sediments δ13CORG and δ15NTN in which these plants thrived). Studies were performed in July 2020 on 14 softwater lakes in northern Poland with varying pH gradients from 4.86 to 9.20. For each lake, a single stand was examined for each species detected. The goal was to investigate each species at 10 sites, but this target was not reached for several species. Among the investigated ecological groups, isoetids and mosses showed the least variation in obtained values. In contrast, elodeids exhibited the highest variation in δ13C results due to their diverse carbon uptake strategies, involving both CO2 and HCO3− forms. Moreover, the δ13C values of charophytes and elodeids were highly related to the increasing pH of water. The slight differences between the δ13C results of plants and sediments in isoetid stands further support this finding. Furthermore, we noticed an increase in sediment δ13CORG values along the alkalization gradient, suggesting that macrophytes were the primary source of OM for the sediments. The positive correlation between the δ13C values of plants and sediments (r = 0.69, p < 0.05) might also confirm that the macrophytes were a significant source of OM in sediments. Regarding δ15N values, we did not find significant differentiation between plants and sediments across ecological groups. However, sediment consistently exhibited 15N-enrichment compared to plant material. This enrichment is likely attributed to the accumulation of 15N during the decomposition of the deposited material. This study confirms the possibility of tracking changes in the aquatic vegetation of softwater lakes based primarily on the sediment δ13CORG values along the alkalization gradient.

Characteristics of tritium, stable isotopes and chemical components in monthly precipitation at Hiroshima, Japan.

This article mainly discusses tritium concentrations in monthly precipitation at Hiroshima City during 2021. The tritium concentrations, which were measured with a low background liquid scintillation counter, fluctuated from 0.16 to 0.78BqL-1. Additionally, hydrogen and oxygen stable isotopes and ionic species were measured in order to characterize precipitation, and their trends including tritium concentrations were compared with data collected in other regions of Japan in previous studies. Although the results showed the characteristics of precipitation were similar to those observed in the other regions, the tritium concentrations were found to be contrary to behavior expected from the latitude effect and some of the observed ionic components were suggested to be continental in origin. Since these results are not common at other sites in Japan, the tritium concentration in the westernmost region of Honshu, including Hiroshima City, may be influenced by Asian continental influences.

A novel method for tracing gasoline using GC-IRMS and Relief-Stacking fusion model

Due to China’s vast geographical expanse and the complexity of its natural environment, traditional methods are not suitable for tracing the origins of gasoline samples from different regions of China. The aim of this study is to trace the origins of gasoline samples through the analysis of carbon stable isotopic characteristics from 60 gasoline samples collected across four major regions in China. In this study, a novel method that combines gas chromatography-isotope ratio mass spectrometry (GC-IRMS) with Relief-Stacking was proposed for the first time, significantly enhancing the precision of the provenance results. Firstly, eight characteristic components were identified by Relief feature selection model for the first time and applied to the assessment of carbon stable isotope ratios across different regions. The discovery of these components effectively reduces data redundancy, thereby enhancing the accuracy of provenance analysis. Subsequently, five effective source tracing models (XGBoost, Random Forest, CatBoost, LightGBM, and KNN) were selected based on the CEI values. To further enhance the learning efficiency of the sourcing models, this study integrated the five selected source tracing models using three different methods(voting, stacking, and blending) and validated the performance of the optimal sourcing model. The results indicated that the Stacking fusion model achieves a CEI value of 0.923, significantly outperforming other fusion models. This advantage is attributed to the Stacking fusion model combining the s trengths of Boosting and Bagging ensemble methods and leveraging the advantages of individual classifiers within the model. The method proposed in this study can effectively address the limitations of previous tracing methods and offer valuable insights for the development of platforms related to stable isotope source tracing. In future research, through appropriate parameter adjustments and feature adaptations, the Relief-Stacking model can likewise be applied to source tracing studies in other countries characterized by extensive geographic ranges and variable environmental conditions.

Stable isotopic characterization and sources of ammonium in wet deposition at the Danjiangkou Reservoir

Ammonium nitrogen (NHx) in atmospheric wet deposition is a primary external nitrogen source for reservoir-type water sources, and identifying its sources is crucial for controlling nitrogen pollution in water. This study aimed to examine the NHx characteristics and sources in wet deposition in the Xichuan reservoir area of the Danjiangkou Reservoir, the South-to-North Water Diversion Project (SNWDP) water source, from September 2019 to August 2020. Major inorganic nitrogen concentrations in precipitation and ammonia-nitrogen isotope (δ15N–NH4+) values were measured, and the sources were analyzed using the Bayesian mixing model. The results showed that NH4+ was the main inorganic nitrogen form in wet deposition, with a concentration ranged of 0.16–5.26 mg L−1. The δ15N–NH4+ values ranged from −14.7‰ to +6.3‰, with significant isotopic effects from agricultural sources and climatic conditions, showing higher values in summer and lower values in winter. The release of ammonia (NH3) from agricultural sources was the primary NHx source (58.0%–76.6%), with fertilizer application being the most significant contributor (32.1%–46.6%). Seasonally, the relative contribution of agricultural sources to NH4+ in wet deposition was higher in autumn and winter. Spatially, agricultural activities significantly impacted atmospheric nitrogen accumulation across the reservoir area. This study quantified NHx sources in wet deposition, providing isotopic evidence and scientific references for nitrogen control measures and atmospheric nitrogen cycling studies.

Organic petrography, biomarkers, and stable isotope (δ13C, δD, δ15N, δ18O) compositions of liptinite-rich coals

Liptinite-rich coals were evaluated using organic petrography, biomarkers, and stable isotopes to investigate their origin and paleoenvironmental significance, particularly, to explore fractionation characteristics of stable isotopes (δ13C, δD, δ15N, and δ18O) between bulk coal, extractable organic matter (EOM), and extracted coal residue (ER). The samples were collected from Cenozoic coal seams from the Yunnan and Liaoning Provinces in China. The samples are characterized by the enrichment of different types of liptinite. The late Pliocene sample YNP (liptinite = 73.5%) is dominated by sporinite and bituminite, whereas the late Pliocene sample YND (liptinite = 65.5%) is characterized by isolated resinite particles and amorphous resinite. The liptinite in the Eocene sample SB (46.0%) is represented by blocky resinite with homogeneous morphology. The differences in distribution and morphology of liptinite are due to the different coal-forming plants and depositional environments, as indicated by the biomarker compositions. Biomarker results indicated that the sample YNP was formed mainly by Pinaceae and angiosperms under oxidizing conditions with bacterial/fungal degradation, whereas the sample YND was derived from the woody parts of gymnosperms with lower contributions of angiosperms under reducing conditions with low microbial activity. The sample SB predominantly originated from Cupressaceae/Pinaceae under reducing conditions with a lack of bacterial/fungal degradation.The fractionations of δ13C, δD, δ15N, and δ18O between bulk coal, EOM, and ER in the liptinite-rich coals are different. The δ13C values of bulk coal, EOM, and ER are mostly controlled by precursor paleovegetation and isotopic composition of CO2. The lower δ13C values of samples YNP and YND from the late Pliocene compared to that of the Eocene sample SB resulted from the change of palaeoconditions (e.g., δ13C of atmospheric CO2, cooling, and decrease of CO2 concentration). The δ13C values of EOM in the samples YNP and YND are about 3‰ lower than δ13C values of bulk coal/ER, whereas δ13C fractionation between EOM and bulk coal/ER is small (< 0.8‰) in the sample SB, probably due to the very limited microbial/fungal degradation. The δD values of EOM are 50 to 90‰ lower than that of bulk coal/ER within the same sample, reflecting different isotopic compositions of monomeric compounds compared to the macromolecular matrix of kerogen most probably due to differences in H-isotope fractionation during biosynthesis. The δ15N of bulk coal and ER show limited fractionation (< 0.5‰) and are mainly controlled by precursor paleovegetation and microbial induced degradation processes. The studied liptinite-rich coals yield higher δ18O values than those detected in humic coals. The differences of δ18O values (bulk coal, EOM, ER) between the samples YNP/YND and the corresponding δ18O values of the sample SB indicate that this isotope parameter is mostly controlled by the δ18O value of source water. The weaker fractionation of oxygen isotope between EOM and bulk coal/ER compared to δ13C and δD may be attributed to the fact that oxygen-containing compounds within EOM did not experience a cleavage or any change of the O-containing bonds. The calculated δ18O and δD values of source rain waters fall in the range of modern rain waters at different sites.

The Characteristics and Application of Deuterium and Oxygen Isotopes to Karst Groundwater, Southwest China

Stable isotopes in natural water bodies serve as hydrologic tracers, with a history of extensive application in karst groundwater research. The present paper is a systematic review of previous research results, with the objective of sorting out and summarizing the stable isotopic characteristics of karst groundwater in southwest China, which is the most typical karst region worldwide. Comprehensive analysis reveals that the deuterium and oxygen isotope values of most karst groundwater are characterized temporally as ‘enriched in the rainy season and depleted in the dry season’, which is the opposite of the pattern of precipitation. While the spatial distribution feature is basically consistent with the spatial variation pattern of precipitation, which is characterized as ‘depleted from the coast to the interior’. Additionally, the main applications of stable isotopes to karst groundwater are discussed, including karst groundwater recharge source and recharge elevation identification, research on karst groundwater in the hydrological cycle, the hydrological process of karst groundwater, and karst groundwater contamination tracking. Finally, we looked forward to future research on karst groundwater based on deuterium and oxygen isotopes. It is our hope that this review may provide insight into the study of karst groundwater.

Stable isotope characteristics of precipitation in Malaysia: establishment of local meteoric water line

Stable isotope characteristics of precipitation in Malaysia: establishment of local meteoric water line

Hydrochemical and Stable Isotopic Characteristics and Transformation Relationship of Water Bodies in the Guohe River Basin, Anhui Province

The Guohe River Basin in Anhui Province was selected as the research area for this study. By collecting surface water, shallow groundwater, and middle-deep groundwater samples, various hydrochemical parameters and stable isotopes of water in different water bodies were analyzed using methods such as the Gibbs diagram, ion ratios, and MixSIAR model to reveal and quantify the transformation relationships between these water bodies. The results indicated that both surface water and groundwater in the study area were predominantly neutral to weakly alkaline. The hydrochemical types of surface water were mainly characterized by Cl·SO4·HCO3-Na and Cl·SO4-Na types, whereas the shallow groundwater exhibited HCO3-Ca·Mg and HCO3-Mg·Na types, and the middle-deep groundwater was of the Cl·HCO3-Na type. The hydrochemical characteristics of various water bodies were influenced by multiple factors such as rock weathering, evaporation concentration, and positive cation exchange. The distribution characteristics of δ18O and δ2H values in surface water and groundwater indicated that atmospheric precipitation was the main water source. The δ18O and δ2H in groundwater were significantly correlated with K+, Na+, Cl-, SO42-, and NO3-. According to the analysis using the MixSIAR model, the contribution of atmospheric precipitation to surface water was 46.5 %, whereas the contribution from shallow groundwater was 53.5 %. The sources of shallow groundwater were identified as atmospheric precipitation (57.4 %) and surface water (42.6 %), and the main source of supply for middle-deep groundwater was lateral flow from upstream groundwater.

Water quality and stable isotope characteristics of Akaike, a temporary pond at the northern foot of Mt. Fuji, August 2021

Water quality and stable isotope characteristics of Akaike, a temporary pond at the northern foot of Mt. Fuji, August 2021

Assessment of Bitumen-Influenced Aquifers in Southwestern Iran Based on Groundwater Geochemistry and Stable Isotopes Characteristics

Assessment of Bitumen-Influenced Aquifers in Southwestern Iran Based on Groundwater Geochemistry and Stable Isotopes Characteristics

Origin and Geochemical Characterization of Groundwater from Coal Seam: A Case Study of Balasu Coalfield, Ordos Basin.

The hydrochemical characteristics of groundwater are of great significance for studying the source, development, and utilization of groundwater. This study investigated the characteristics of anions and cations, total dissolved solids (TDS), hydrochemical types, and hydrogen and oxygen isotopes of surface water and groundwater in the Balasu coalfield. By conducting experiments using inductively coupled plasma emission electron spectrometry, ion chromatography, acid-base titration, and gravimetric analysis, the characteristics of ion concentration and TDS in different aquifers were analyzed to determine the possible source of groundwater in C2 (number 2 coal seam in Yan'an Formation). The Piper trilinear diagram was used to determine the hydrochemical types of aquifers, and the source of groundwater was determined based on the stable isotope characteristics of hydrogen and oxygen. The changes in ion, TDS, hydrogen, and oxygen isotopes of surface water and groundwater were analyzed, and the groundwater differences between the two sets of coal seams were compared. The research results indicate that the groundwater in C2 (number 2 coal seam in Yan'an Formation) is caused by the original sedimentary water and the infiltration of Zhiluo Formation and A1 (strata at the top of the Yan'an Formation to number 2 coal seam). However, C4 (number 3 coal seam in Yan'an Formation) is hindered by the well-developed mudstone in A3 (bottom of number 2 coal seam to the top of number 3 coal seam), which hinders the infiltration of groundwater. The study emphasizes that the overlying strata can have a significant impact on the coal seam when the moisture content is high and there is a lack of overlap, thereby promoting changes in the moisture content of the coal seam. This study provides some insights into the safety of coal mines, especially in mining areas with a high coal seam moisture content.

Evapotranspiration variation of soil‐plant‐atmosphere continuum in subalpine scrubland of Qilian Mountains in China

AbstractThe water cycle in the soil‐plant‐atmosphere continuum is an important element of hydrological and ecological studies, and differences in the composition characteristics of hydrogen and oxygen stable isotopes in different water bodies can indicate water cycling processes. In this study, hydrogen and oxygen isotopes of precipitation, soil water and plant water samples had been collected in the subalpine scrubland of the Qilian Mountains from May to October 2019. The Craig‐Gordon model, the isotopic steady‐state (ISS) assumption, the Keeling Plot model and the two‐source mixing model were used to analyse the stable isotope compositions of different water bodies, the stable isotope characteristics of water vapour of soil evaporation and plant transpiration and the variation of evapotranspiration in the SPAC of the subalpine scrubland. The results showed that plant transpiration (FT) contributed 87.28% and 86.95% to evapotranspiration and soil evaporation (FE) contributed 12.72% and 13.05% to evapotranspiration in the growing season on semi‐sunny and semi‐shaded aspects, respectively, indicating that evapotranspiration in the subalpine scrubland mainly came from the transpiration of scrubland plants. In the early of the growing season (May–June), due to the rapid expansion of plant leaves, the contribution of transpiration to evapotranspiration was at a high level, which intensified transpiration and led to a gradual increase of the transpiration contribution. In the middle of the growing season (July–August), owing to better conditions of rain and heat that made plants grow vigorously, plant transpiration made the highest contribution to evapotranspiration more than 90%, which caused to an overwhelming contribution of plant transpiration to evapotranspiration. In the later of growing season (September to October), the contribution of plant transpiration to evapotranspiration decreased significantly while that of soil evaporation increased, which was because plant photosynthesis and respiration gradually declined for losing their leaves of scrub plants and the relative atmospheric humidity was lower.

Dataset of stable isotopes of precipitation in the Eurasian continent

Abstract. Stable isotopes in precipitation can effectively reveal the process of atmospheric water circulation, serving as an effective tool for hydrological and water resource research, climate change, and ecosystem studies. The scarcity of stable isotope data in precipitation has hindered comprehension of the regional hydrology, climate, and ecology due to discontinuities on a temporal scale and unevenness on a spatial scale. To this end, we collated stable hydrogen and oxygen isotope data in precipitation from 842 stations in Eurasia from 1961 to 2022, totalling 51 752 data records. Stable isotopes in precipitation across various regions of Eurasia, as a whole, decrease with increasing latitude and distance from the coast. In the summer, stable isotopes in precipitation are relatively enriched, while in the winter, they are relatively depleted. In recent decades, the stable isotope values of Eurasian precipitation show an overall trend of increasing variation with the advancement of years, which is associated with global warming. Geographical location, underlying surface conditions, seasons, and atmospheric circulation are all factors that determine the characteristics of stable isotopes in precipitation. The dataset of stable isotopes in Eurasian precipitation provides a powerful tool for understanding changes in regional atmospheric water circulation and assists in conducting hydrological, meteorological, and ecological studies in related regions. The datasets are available at https://doi.org/10.17632/rbn35yrbd2.2 (Zhu, 2024).

Mineralogy, geochemistry, and stable isotope characteristics of Paleozoic carbonate-hosted vein-type barite deposits from Silifke–Mersin, Southern Türkiye

Mineralogy, geochemistry, and stable isotope characteristics of Paleozoic carbonate-hosted vein-type barite deposits from Silifke–Mersin, Southern Türkiye

Variations of stable isotopic characteristics of shallow lake-river water system and its indicative significance in Lake Poyang wetland, China

Variations of stable isotopic characteristics of shallow lake-river water system and its indicative significance in Lake Poyang wetland, China

Temporal and spatial variation in the food web structure in artificial reef areas and adjacent habitats in Haizhou Bay

Artificial reef is regarded as an effective tool for restoring habitats and supporting the marine ecosystem. While the energy flow and material exchange in the food web of artificial reef ecosystem still remain vacant and should be further understood. In this study, stable isotopic characteristics (δ13C and δ15N) were used to identify the trophic niches and potential carbon sources of consumers (fish and invertebrates) in artificial reef areas and adjacent habitats in Haizhou Bay (the estuary area (EA), the aquaculture area (AA), the artificial reef area (AR), the natural area (NA) and the comprehensive effect area (CEA)) in spring and autumn. The results showed that the average δ13C for all consumers decreased from − 16.99 ± 2.07‰ to − 21.81 ± 1.66‰, and the average δ15N ranged from 11.37 ± 0.35‰ to 14.69 ± 0.64‰ in all seasons. A SIBER model revealed highly similar trophic niche among habitats in autumn, and lower overlap in spring. The SIMMR model showed that phytoplankton and sedimentary organic matter (SOM) were the major contributors to consumers, and particulate organic matter (POM) accounted for less contribution. In AA and NA phytoplankton and SOM generally contributed fairly equally to most fish, while single SOM sources were major contributors to nearly all the species in AR and CEA. Our findings reveal that ARs can serve as seascape mosaics to increase fish community diversity because of their high variation in the δ13C value and the trophic niches from EA to the NA. Preliminary multidisciplinary studies are needed for the mitigation of effects before any implementations deployed to the offshore waters that influence habitat connectivity, especially some habitat–specific migratory species.

Spatio-temporal variation characteristics of stable isotopes of tap water and its potential as a proxy for surface water in Sichuan, China

The stability and safety of tap water are essential for human health and economic and social development. The stable isotopes can be used to reveal characteristics of tap water and link it with its source. In this paper, 1556 tap water samples were collected from Sichuan, China and the stable isotope ratios for these samples were determined. The δ2H ranges from −126.4 ‰ to −26.4 ‰, and the range of δ18O is −17.04 ‰ to −2.08 ‰, reflecting the tap water sources are affected by complex spatial features and changing meteorological elements. Stable isotopes in tap water usually reach the maximum values in summer, indicating that heavy isotope enrichment is easily achievable by the large amount of evaporation from water sources during the summer season. By using spatial interpolation and isoscapes, we can find that there is a strong correlation between both simulated tap water δ2H and river water δ2H, with the maximum difference not exceeding 10.0 ‰, while the overall mean relative error is 6 %. Consequently, it is feasible to use tap water isotopes as a proxy for surface water isotopes in representative watersheds where surface water is the main source of water. The study shows the variation characteristics and influencing factors of tap water isotopes and enriches the isotope database of tap water in China. Meanwhile, the utilize of stable isotopes in tap water as a proxy for surface water expands the application field of tap water stable isotopes and opens new perspectives for indirectly obtaining isotope data of surface water.