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Rationale: Heavy-labelled internal standards increasingly represent the gold standard for absolute quantitation in mass spectrometry (MS)-based bottom-up proteomics. The biggest drawbacks of using these standards are that they have high costs and lengthy lead times., Methods: We describe an efficient, low-cost optimised method to enable 'in-house' heavy labelling of synthetic tryptic peptides for absolute quantification using tandem LC-MS/MS mass spectrometry. Our methodology uses 18O water in a trypsin-catalysed oxygen exchange reaction at the carboxyl terminus with the overall aim of reducing the costs and lead time associated with sourcing heavy standards from commercial vendors., Results: Step-by-step instructions are provided on how to execute this protocol with high-throughput adaptations utilising a 96-well plate and a liquid-handling robot. Detailed notes on experimental setup, tips for troubleshooting and suggested improvements to maximise labelling efficiencies are highlighted to achieve the best results. Under optimum conditions, labelling efficiencies of peptides can reach from 95% to 100%., Conclusions: The application of the 'in-house' labelled standards in generating calibration curves to quantify endogenous peptide concentrations is just as effective as using the synthetically sourced standards while also having great cost reduction implications as well as saving time spent waiting for peptides to arrive. The protocol is highly adaptable and can be customized to fit the specific setup of any laboratory, maximizing achievable labelling efficiencies., (© 2024 The Author(s). Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd.)

Rationale: The oxygen stable isotope ratio (δ 18 O) of the sugar-rich fraction of fruit juice is important as a tracer of the geographical origin of raw material. This study sought to minimize the inter-day variation of δ 18 O attributable to the influence of water to accurately monitor geographical origin labeling., Methods: Two drying devices (freeze dryer and vacuum oven) were compared. Then, two humidity levels (normal and low humidity) at which the samples were placed after drying were compared. The low-humidity environment was constructed using a glove bag and pure argon gas. δ 18 O was measured using thermal conversion elemental analyzer/isotope ratio mass spectrometry. Improvements were made to the measurement method based on aforementioned analyses results, and the performance of the initial and improved methods was compared., Results: δ 18 O of juice dried in a vacuum oven was 3.30‰ lower than that of juice dried in a freeze dryer. Moreover, δ 18 O of juice samples exposed to normal humidity was 3.74‰ lower than that of samples exposed to low humidity. The combined inter-day and intra-day standard deviation was reduced from 1.20‰ in the initial method to 0.42‰ in the improved method., Conclusions: This study describes a pretreatment method for δ 18 O measurement in the sugar-rich fraction of fruit juice with less inter-day variation, and it will be useful for monitoring geographical origin labeling., (© 2024 John Wiley & Sons Ltd.)

Urban stormwater management systems, particularly storm sewers, are critical for managing runoff in urban areas. These systems are designed to function during wet weather events; however, field-based observations of these systems suggest that they may also be active flow pathways in dry weather conditions, ultimately contributing to streamflow. Unlike dry weather flow in wastewater systems, storm sewer dry weather flow has not been thoroughly explored. This research used stable isotopes of oxygen and hydrogen in water to examine the sources of dry weather flow from storm sewers in a highly urban catchment. A stable isotope mixing model was applied at the outfalls of two stormwater catchments and the receiving Black Creek, located in Toronto, Canada. Findings suggest that during dry periods, storm sewers receive non-stormwater inputs from tap water, wastewater, and groundwater, along with some precipitation, and that these sources may constitute up to 19 % of Black Creek's flow at the watershed scale. Seasonal patterns in flow and water sources were observed for the Black Creek and outfalls. At one outfall, dry weather flow was predominantly from the water distribution system (i.e., tap water and/or wastewater) throughout spring, summer, and fall. In contrast, at the second outfall, groundwater dominated in spring and summer, and groundwater and water distribution were equally proportioned in fall. Black Creek baseflow comprises a dynamic mix of water sources that at times are similar to the sources observed at the stormwater outfalls. Considering these findings, future work should incorporate strategic sampling of additional outfalls, and multiple years of data collection to explore inter-annual variability in these processes and focus on replicating a similar study in other urban watersheds with different climates and/or water infrastructure design. The study findings highlight that our understanding of dry weather flow from storm sewers is relatively limited, emphasizing the need for further exploration of this phenomenon to inform urban hydrological modelling, water quality studies, and urban water management., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2024. Published by Elsevier Ltd. All rights reserved.)

A recent article by DePalma et al. reported that the season of the End-Cretaceous mass extinction was confined to spring/summer on the basis of stable isotope analyses and supplementary observations. An independent study that was concurrently under review reached a similar conclusion using osteohistology and stable isotope analyses. We identified anomalies surrounding the stable isotope analyses reported by DePalma et al. Primary data are not provided, the laboratory where the analyses were performed is not identified, and the methods are insufficiently specified to enable accurate replication. Furthermore, isotopic graphs for carbon and oxygen contain irregularities such as missing data points, duplicate data points, and identical-length error bars for both elements despite different scales, that appear inconsistent with laboratory instrument outputs. A close examination of such methodological omissions and data irregularities can help to raise the standards for future studies of seasonality and prevent inaccurate claims or confirmation bias., Competing Interests: The authors declare that they have no competing interests., (© 2024 During et al.)

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 0.78 Bq L-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., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The forensic application of stable oxygen isotope data from human tissues depends on naturally occurring isotopic variation in drinking water across geographic areas. One factor which complicates interpretation of forensic data is local variability: if a wide range of drinking water values is in a small geographic region it may be difficult to identify or rule out that region as a location of origin. We examine data from community collection programs documenting tap water isotope variation within 30 cities\developed areas throughout the United States. Isotopic variation within individual developed areas ranged widely, from essentially nil to greater than 9‰ (δ18O interdecile range). Many (14/30) of the study areas exhibited multi-modal isotope distributions, even in cases where the isotopic range was very small (e.g., <2.0‰), suggesting that the use of multiple, isotopically different sources was common. Most variation was attributed to differences in the source-region altitude or degree of evaporation for different water sources, and we observe limited variation in areas where contrasts in these variables are small. Variation tended to be largest in cities across the western USA. We explored correlations between the magnitude of local isotopic variation and climatic, environmental, and socioeconomic variables. We found that higher levels of variation occurred at sites where local water resources were likely to be more isotopically heterogeneous and in lower supply, consistent with the development of supply systems in these areas that access diverse and isotopically heterogeneous water resources. We also found that variation was positively correlated with larger developed areas, suggesting that pressures related to city growth may affect the degree to which infrastructure tapping diverse water resources is developed. Collectively, our results suggest that the influence of local tap water isotope heterogeneity on the precision of forensic geolocation is systematic and somewhat predictable, information to be factored into future applications., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Stantis et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The site of San Valentino in San Vito al Tagliamento is one of the main urnfield cemeteries in northeastern Italy. Archaeological excavations carried out in the seventies brought to light a cremation cemetery consisting of mainly urn graves with pottery and metal artefacts as grave goods. These materials suggest that the individuals buried in San Valentino were not an isolated local community but had intense contacts with other north-Adriatic communities, in particular with the neighbouring Veneto area, as suggested by the close similarity of the biconical vessels with those recovered in the graves of Este. This paper provides the first osteological study of a preserved sample of individuals buried at San Valentino and uses an innovative multi-proxy approach to refine the chronology of the site through radiocarbon dating of bone apatite, investigate human mobility using strontium isotopes on calcined human remains, and reconstruct the funerary practices by combining FTIR-ATR data with carbon and oxygen isotope ratios on cremated bones. The results date the cemetery to the end of the Late Bronze Age and the Early Iron Age, with a sporadic occupation in the fourth century BC. Strontium isotopes and concentrations show the analysed individuals buried at San Valentino were a local community that exploited nearby food resources. Interestingly, variations in cremation conditions were detected between San Valentino and the contemporary sites of Velzeke, Blicquy, Grand Bois, and Herstal, located in Belgium, by using FTIR-ATR and carbon and oxygen isotope data. This multi-proxy approach applied to the study of cremated human remains can open new research possibilities, being potentially extendable to the study of many pre- and proto-historic and historic communities that practised cremation., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Capuzzo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Unravelling the complexities of transpiration can be assisted by understanding the oxygen isotope composition of transpired water vapour (δE). It is often assumed that δE is at steady state, thereby mirroring the oxygen isotope composition of source water (δsource), but this assumption has never been tested at the whole-tree scale. This study utilized the unique infrastructure of 12 whole-tree chambers enclosing Eucalyptus parramattensis E.C.Hall trees to measure δE along with concurrent temperature and gas exchange data. Six chambers tracked ambient air temperature and six were exposed to an ambient +3 °C warming treatment. Day time means for δE were within 1.2‰ of δsource (-3.3‰) but varied considerably throughout the day. Our observations show that E. parramattensis trees are seldom transpiring at isotopic steady state over a diel period, but transpiration approaches source water isotopic composition over longer time periods., (© The Author(s) 2024. Published by Oxford University Press.)

The evolution and formation mechanisms of chemical components in surface water can reflect changes in the geological background of a basin and the extent of human interference. The Yangtze River basin is the largest water source area in China, yet its main ion sources and formation mechanisms are not fully understood. This study uses a combination of hydrochemistry, stable isotopes (δ 18 O, δD), the Craig-Gordon model, and the APCS-MLR model to quantitatively assess the water source replenishment and evaporation intensity of surface water in the Yangtze River. The study reveals the primary ion sources and controlling factors of surface water in the Yangtze River. The results show that the hydrochemical type in the upstream is mainly HCO 3 - -Ca 2+ and Na + -K + , while in the midstream and downstream it is primarily HCO 3 - -Ca 2+ and SO 4 2- -Ca 2+ . The evolution of hydrochemical types is mainly controlled by rock weathering and human inputs. The surface water sources in the Yangtze River are directly replenished by precipitation, with the evaporation ratio in the upstream (0.66) being higher than in the midstream (0.63) and downstream (0.47). The lc-excess in the upstream (-0.32 ‰) is lower than in the midstream (1.21 ‰) and downstream (-0.27 ‰), indicating more intense evaporation in the upstream. The hydrochemical composition of the Yangtze River surface water mainly comes from geological factors (80.5 %), industrial factors (11.1 %), agricultural factors (6.4 %), and unknown factors (2.0 %). This study enhances the understanding of the chemical composition, water source replenishment, ion sources, and evolution mechanisms of the Yangtze River surface water, providing a basis for maintaining water quality and sustainable development in the Yangtze River basin., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Stable isotope analysis of fish muscle tissue has been used to quantify fish migratory behavior in many systems, and these chemical tracers are especially useful for euryhaline fishes that traverse significant salinities and gradients in baseline signatures. However, the removal of muscle tissues often requires lethal sampling. Fish scales may be removed non-lethally and offer potential alternatives to stable isotope ratios from muscle to indicate recent feeding histories. For this study, red drum Sciaenops ocellatus were collected in subtropical estuaries in the northwestern Gulf of Mexico and analyzed for stable isotope (𝛿 13 C and 𝛿 15 N) compositions of scale exteriors. Decalcification of scale samples was deemed unnecessary given the preservation of linearity and minimal offsets between paired decalcified and untreated scale samples. Stable isotope signatures of muscle tissue and scales were closely matched and indicated high degrees of residence within bays at fine spatial scales. This study also surveyed the existing body of literature comparing scale and muscle isotope values from the same individuals and found that the majority reports linear relationships with slopes close to unity, although species-specific offsets and intercepts vary. This work expands the body of literature indicating that scales are a viable non-lethal alternative for stable isotope assessments of dietary and habitat use histories for mobile fishes., (© 2023 Fisheries Society of the British Isles.)

In recent years, it has become evident that human activities have significantly disrupted the nitrogen cycle surpassing acceptable environmental thresholds. In this study, chemical and isotopic tracers were combined with a mathematical mass balance model (EMMA), PHREEQC inverse mixing model, and statistical analyses to evaluate groundwater quality, across an area experiencing substantial human activities, with a specific focus on tracing the origin of nitrate (NO 3 - ) with potential water mixing processes. This multi-technique approach was applied to an unconfined aquifer underlying an agricultural area setting in an inter-mountain depression (i.e., the "Pampa de Pocho Plain" in Argentina). Here, the primary identified geochemical processes occurring in the investigated groundwater system include the dissolution of carbonate salts, cation exchange, and hydrolysis of alumino-silicates along with incorporating ions from precipitation. It was observed that the chemistry of groundwater, predominantly of sodium bicarbonate with sulfate water types, is controlled by the area's geology, recharge from precipitation, and stream water infiltration originating from the surrounding hills. Chemical results reveal that 60% of groundwater samples have NO 3 - concentrations exceeding the regional natural background level, confirming the impact of human activities on groundwater quality. The dual plot of δ 15 N NO3 versus δ 18 O NO3 values indicates that groundwater is affected by NO 3 - sources overlapping manure/sewage with organic-rich soil. The mathematical EMMA model and PHREEQC inverse modeling, suggest organic-rich soil as an important source of nitrogen in the aquifer. Here, 64 % of samples exhibit a main mixture of organic-rich soil with manure, whereas 36 % of samples are affected mainly by a mixture of manure and fertilizer. This study demonstrates the utility of combining isotope tracers with mathematical modeling and statistical analyses for a better understanding of groundwater quality deterioration in situations where isotopic signatures of contamination sources overlap., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The 1997/1998 El Niño event caused mass coral bleaching and mortality in many tropical and subtropical regions, including corals on Green Island, Taiwan, in the northwestern Pacific Ocean. This study analyzed coral carbon isotope ratios (δ 13 C), oxygen isotope ratios (δ 18 O), and Sr/Ca ratios for 29 years, including the 1997/1998 El Niño period, to examine how high water temperature events are recorded in coral geochemical indicators. Sr/Ca ratios in coral skeletons from Green Island show the lowest peak, means the highest temperature during the 1997/1998 El Niño period. However, we couldn't observe high-temperature events on δ 18 O. Furthermore, a negative δ 13 C shift was observed after El Niño events. The regime shift of δ 13 C might have been caused by temporal bleaching and/or a decrease in symbiotic algae due to high water temperature stress under the continuous decrease in δ 13 C in DIC due to the Suess effect., (© 2024. The Author(s).)

Preserved biological communities can provide baseline data about the historical ecosystems and environmental conditions that preceded recent anthropogenic alteration. Freshwater mussel shells show particularly good preservation, and the shell assemblages commonly found during archaeological excavations can offer insights into past ecosystems. We studied assemblages of Unio pictorum mussel shells from palaeochannel silts associated with the Late Bronze Age site of Must Farm in eastern England (c. 850 BC), on an ancient tributary of the modern-day River Nene. We compared archaeological shells from two sediment horizons (broadly 1300-700 BC) to live individuals collected from two analogous sites on the present-day Nene. Size and growth rate, interannual growth variability and stable isotope (δ 18 O and δ 13 C) composition were compared between the populations. Size and the von Bertalanffy growth parameter L ∞ differed among all four populations. Mean lengths and L ∞ were higher in the two modern populations (mean lengths 77.3 ± SE 0.8 and 73.8 ± SE 1.1 mm, L ∞ 91.8 ± 5.4 and 79.0 ± 8.1 mm) than the ancient populations (mean lengths 58.1 ± SE 1.6 mm and 68.4 ± SE 0.9 mm; L ∞ 71.5 ± 16.9 and 76.8 ± 6.2 mm). Modern individuals also showed greater variation in age-corrected year-to-year growth. δ 13 C was lower in modern shells (-11.8‰ for modern shells, -9.03‰ and -9.02‰ for ancient shell populations), potentially reflecting altered hydrological and nutrient regimes. δ 18 O and δ 13 C were positively correlated for all but one sampled ancient shell, but not modern shells. These results reflect changes in local environmental conditions, particularly the transition from a shallow, slow-flowing tributary to a deeper, canalised river with faster flow, as well as effects of anthropogenic nutrient enrichment. The findings demonstrate the importance of long-term data in studying anthropogenic ecosystem alteration and avoiding shifting baseline syndrome in conservation planning., (Global Change Biology© 2024 The Author(s). Global Change Biology published by John Wiley & Sons Ltd.)

Isotopic evidence of groundwater and stream water is frequently used to investigate water exchanges with groundwater. Monthly sampling of rain, stream water, and groundwater was conducted at Tims Branch watershed in South Carolina for the oxygen and hydrogen stable isotope ( δ 2 H and δ 18 O) measurement, as well as pH and oxidation-reduction potential (ORP). Together with a mass balance perspective, it was determined that it takes a few weeks to one month for groundwater in the hyporheic zone to fully exchange with stream water. From hydrodynamic modelling, we show that substantial (up to 70 %) groundwater exchange occurs at gaining and losing sites. Groundwater exfiltration, i.e. inflow into stream water, contributes up to 4 % to stream water, with the remainder from upstream exfiltration. A 2-4 % per day renewal rate of adjacent groundwater would indirectly indicate a groundwater residence time in the order of half a month to a full month (assuming either a well-mixed case or large dispersion rate in pulse flow case), in agreement with a greatly reduced variability of δ 2 H and δ 18 O of groundwater compared to stream water and rain. This reduced variability of stable isotope signal from groundwater confirms our hypothesis that riparian groundwater mixing at Tims Branch is more of a mixed type rather than a pulse flow type. A monthly time scale is sufficient for groundwater to become anoxic at exit points into stream water resulting in the episodic production of natural organic matter- and iron-rich flocs upon oxidation.

This study aimed to synthesise and interpret stable isotopic data ( δ 2 H and δ 18 O) from various sources to understand the isotope hydrology around coal mine operations in Elk Valley, B.C., Canada. The data, including precipitation, groundwaters, seeps, and mine rock drains, were used to construct a local meteoric water line (LMWL) for the Elk Valley, evaluate the spatiotemporal isotopic composition of its groundwater, and assess mine seepage and mine rock drain discharge. The study revealed a robust LMWL relation ( δ 2 H = 7.4 ± 0.2 · δ 18 O - 4.3 ± 4.1). The groundwater and seep data indicated a winter season bias and a north-south latitudinal gradient, suggesting rapid near-surface groundwater flow without significant post-precipitation evaporation. Porewater isotope samples from unsaturated mine rock piles (MRPs) showed site-specific evaporation patterns, potentially due to convective air flows or exothermic sulphide oxidation. This research revealed the influence of groundwater and meltwater on rock drain discharge. Based on evaporative mass balance calculations, MRPs seasonally contributed ca. 5 %(December base flow) and 22 % (snowmelt) to drain discharge. The findings underscore the value of stable isotope data collections in the Elk Valley to help better define and quantify the hydrology-hydrogeology, including a better understanding of evaporative conditions in MRPs.

Ocean warming will continue to affect the growth, body condition and geographic distributions of marine fishes and understanding these effects is an urgent challenge for fisheries research and management. Determining how temperature is recorded in fish otolith carbonate, provides an additional chronological tool to investigate thermal histories, preferences and patterns of movement throughout an individual's life history. The influence of three water temperature treatments (22°C, 25°C, and 28°C) on hatchery-reared juvenile stout whiting, Sillago robusta, was tested using a controlled outdoor mesocosm system. Fish were measured for change in length and weight, and body condition was determined using bioelectrical impedance analysis. Sagittal otoliths were analysed for stable oxygen (δ 18 O otolith ) and carbon (δ 13 C otolith ) isotopes via isotope ratio mass spectrometry. Whiting kept at 22°C were significantly smaller and had diminished body condition compared to fish in 25°C and 28°C, which did not significantly differ from each other. The δ 18 O otolith values of stout whiting demonstrated a negative temperature-dependent fractionation relationship which was similar in slope but had a different intercept to the relationships reported for inorganic aragonite and other marine fish species. The δ 13 C otolith values also showed a negative relationship with water temperature, and the calculated proportion of metabolic carbon M in otoliths differed between fish reared in the coolest (22°C) and warmest (28°C) temperature treatments. Overall, the results suggest that stout whiting may have reached an upper growth threshold between 25°C and 28°C, and that growth and body condition may be optimised during warmer seasons and toward the northerly regions of their distribution. Otolith oxygen thermometry shows promise as a natural tracer of thermal life history, and species-specific fractionation equations should be utilised when possible to prevent errors in temperature reconstructions of wild-caught fish., Competing Interests: Declaration of competing interest The authors declare no competing financial interests or personal relationships that may have influenced the research reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Tamarix ramosissima has an important role in stabilizing sand dunes in desert ecosystems. Understanding the water use strategies of T. ramosissima is essential to understand its adaptations on coppice dunes. We utilized the stable isotopes δ 2 H and δ 18 O in soil water, groundwater, and xylem water to identify monthly differences in water sources. Additionally. we explored rooting depth using 2 H 2 O as an artificial tracer. In May, T. ramosissima derived 75% of its water from shallow and middle soil layers. In July, it absorbed 90% water from middle and deep soil layers. In August and September, it acquired approximately 80% of its water from deep soil layers. The labelling using 2 H as an artificial tracer indicated that the root system of T. ramosissima could reach depths >500 cm in the coppice dunes. 2 H absorption was observed at depths of 100, 200, 300 and 400 cm. Soil water is the dominant water source for T. ramosissima in the coppice dunes because groundwater is at depths >30 m. The flexible water-use strategies of T. ramosissima enable it to effectively utilize different available water sources to adapt to the arid environment. These findings improve our understanding of water uptake patterns and drought adaptation strategies of T. ramosissima in the coppice dunes of desert ecosystems., (© 2024 Wiley‐VCH GmbH. Published by John Wiley & Sons Ltd.)

Objective: Water is an essential nutrient for all organisms and is important for maintaining life and health. We aimed to develop a biomarker-calibrated equation for predicting water turnover (WT) and pre-formed water (PW) using the doubly labelled water (DLW) method., Design: Cross-sectional study., Setting: General older population from the Kyoto-Kameoka Study, Japan., Participants: The 141 participants aged ≥ 65 years were divided into a model developing ( n 71) and a validation cohort group ( n 70) using a random number generation. WT and PW was measured using the DLW method in May-June of 2012. In developing the cohort, equations for predicting WT and PW were developed by multivariate stepwise regression using all data from the questionnaires in the Kyoto-Kameoka study (including factors such as dietary intake and personal characteristics). WT and PW measured using the DLW method were compared with the estimates from the regression equations developed using the Wilcoxon signed-rank test and correlation analysis in validation cohort., Results: The median WT and PW for 141 participants were 2·81 and 2·28 l/d, respectively. In the multivariate model, WT ( R 2 = 0·652) and PW ( R 2 = 0·623) were moderately predicted using variables, such as height, weight and fluid intake from beverages based on questionnaire data. WT ( r = 0·527) and PW ( r = 0·477) predicted that using this model was positively correlated with the values measured by the DLW method., Conclusions: Our results showed factors associated with water requirement and indicated a methodological approach of calibrating the self-reported dietary intake data using biomarkers of water consumption.

Accurate characterization of the movement of water through catchments, particularly during precipitation event response, is critical for hydrological efforts such as contaminant transport modeling or prediction of extreme flows. Abiotic hydrogeochemical tracers are commonly used to track sources and ages of surface waters but provide limited details about transit pathways or the spatial dynamics of water storage and release. Alternatively, biotic material in streams is derived from thousands of taxa originating from a variety of environments within watersheds, including groundwater, sediment, and upslope terrestrial environments, and this material can be characterized with genetic sequencing and bioinformatics. We analyzed the stable water isotopes (δ18O and δ2H) and microbiome composition (16S rRNA gene amplicon sequencing) of the Marys River of western Oregon, USA during an early season storm to describe the processes, storage, and flowpaths that shape surface water hydrology. Stable water isotopes (δ18O and δ2H) typified an event response in which stream water is composed largely of 'old' water introduced to the catchment before the storm, a common though not well understood phenomenon. In contrast, microbial biodiversity spiked during the storm, consisting of early- and late-event communities clearly distinguishable from pre-event communities. We applied concentration-discharge (cQ) analysis to individual microbial taxa and found that most Alphaproteobacteria sequences were positively correlated (i.e., were mobilized) with discharge, whereas most sequences from phyla Gammaproteobacteria and Bacteroidota were negatively correlated with discharge (i.e., were diluted). Source predictions using the prokaryote habitat preference database ProkAtlas found that freshwater-associated microbes composed a smaller fraction of the microbial community during the stream rise and a larger fraction during the recession, while soil and biofilm-associated microbes increased during the storm and remained high during recession. This suggests that the "old" water discharged during the storm was likely stored and released from, or passed through, soil- and biofilm-rich environments, demonstrating that this approach adds new, biologically derived tracer information about the hydrologic pathways active during and after this event. Overall, this study demonstrates an approach for integrating information-rich DNA into water resource investigations, incorporating tools from both hydrology and microbiology to demonstrate that microbial DNA is useful not only as an indicator of biodiversity but also functions as an innovative hydrologic tracer., Competing Interests: The authors have declared that no competing interests exist., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

The abrupt decline in sardine catches in the Sea of Japan and the East China Sea (SJ-ECS) in 2014 and 2019 and the recovery in the following years call into question the current assumption that sardines in the SJ-ECS form a self-recruiting subpopulation. To test this hypothesis, we analysed otolith stable oxygen and carbon isotope profiles (δ 18 O, δ 13 C) of age-0 and age-1 sardines from 2010 and 2013-2015 year-classes captured in the SJ-ECS, as geographic markers for nursery areas. Age-0 sardines generally showed a significant ontogenetic decrease in otolith δ 18 O from larval to juvenile stages. However, the majority of age-1 captured in spring 2011, 2015 and 2016 showed non-decreasing otolith δ 18 O profiles, suggesting that the age-0 off the Japanese coast were not the main source of recruitment. Different migration groups were thus indicated: the "locals" growing up off the Japanese coast and the migrating "nonlocals". The isotope profiles of the "nonlocals" overlapped with those of age-0 captured in the subarctic North Pacific, suggesting that they may be migrants from the Pacific, or perhaps an unobserved northward migration group in the SJ-ECS. Our results highlight the considerable uncertainty in the population structure assumed in current stock assessment models for Japanese sardine., (© 2024. The Author(s).)

The complex relationships within desert ecosystems and their environmental conditions are reflected in patterns of plant water use. Thus, understanding the sources of water used by plants in these areas is crucial for effective resource management. In this study, we investigated the water use pattern of Haloxylon ammodendron in Semnan province, in the central plateau of Iran, using the stable isotope analysis. We employed a simple, homemade cryogenic vacuum distillation (CVD) system to directly extract water from soil samples and different plant components for subsequent analysis by mass spectrometer. The contribution of each possible water source to the plant xylem water was estimated using the IsoSource mixing model. The pattern of δ 18 O values in the xylem water of H. ammodendron indicated its reliance on groundwater as a primary water resource during the wet season. Additionally, the correlation of sand particles with both δ 2 H and δ 18 O was found to be 0.32. Moreover, the δ 18 O values of H. ammodendron xylem water were mainly similar to those of groundwater, suggesting the species' dominant use of groundwater. The findings of this study provide valuable insights for strategically planting H. ammodendron to mitigate impacts on groundwater resources and ensure long-term sustainability in arid and semi-arid regions., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Chemical and isotopic indicators were used to recognize the origin of hydrothermal groundwater, to assess the mineralization processes and groundwater quality, to identify the source of solutes and the likely mixing with cold, and elucidate the fluid geothermometry in the Jérid field of Southern Tunisia. The results show that the geothermal groundwater is neutral to slightly alkaline. They are characterized by SO 4 -Cl-Na-Ca water type. The dissolution of evaporates and pyrite-bearing rocks is the dominant mineralization process. The groundwater quality index indicates that the majority of samples are very hard and belong to poor to unsuitable for drinking classes. Applications and calculations of hydrogeochemical parameters, including SAR, %Na, PI, Kr, and MAR, showed that the majority of samples are unsuitable for agricultural practices. The human health risk was assessed based on hazard quotient and total hazard index through ingestion and dermal contact with iron-rich groundwater. The consumption of CI groundwaters does not present non-carcinogenic risk to adults and children. The δ 18 O and δ 2 H signatures indicate that the geothermal groundwater was recharged by ocean precipitation during cold and wet paleoclimatic periods. The slight enrichment of oxygen-18 and deuterium contents suggests a limited mixing effect between geothermal water and cold groundwater within the same aquifer. This mixing effect is confirmed by the Na-K-Mg and the chloride-enthalpy diagrams. The K-Mg and SiO 2 geothermometers provided fairly reliable reservoir temperature values, ranging between 69.6 and 99 °C. Calculated geothermal potential values, varying between 469 and 16987 kWth, which allow several applications such as domestic and agricultural heating., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Increases in temperatures and atmospheric CO2 concentration influence the growth performance of trees worldwide. The direction and intensity of tree growth and physiological responses to changing climate do, however, vary according to environmental conditions. Here we present complex, long-term, tree-physiological responses to unprecedented temperature increase in East Asia. For this purpose, we studied radial growth and isotopic (δ13C and δ18O) variations using tree-ring data for the past 100 yr of dominant Quercus mongolica trees from the cool-temperate forests from Hallasan, South Korea. Overall, we found that tree stem basal area increment, intercellular CO2 concentration and intrinsic water-use efficiency significantly increased over the last century. We observed, however, short-term variability in the trends of these variables among four periods identified by change point analysis. In comparison, δ18O did not show significant changes over time, suggesting no major hydrological changes in this precipitation-rich area. The strength and direction of growth-climate relationships also varied during the past 100 yr. Basal area increment (BAI) did not show significant relationships with the climate over the 1924-1949 and 1975-1999 periods. However, over 1950-1974, BAI was negatively affected by both temperature and precipitation, while after 2000, a temperature stimulus was observed. Finally, over the past two decades, the increase in Q. mongolica tree growth accelerated and was associated with high spring-summer temperatures and atmospheric CO2 concentrations and decreasing intrinsic water-use efficiency, δ18O and vapour pressure deficit, suggesting that the photosynthetic rate continued increasing under no water limitations. Our results indicate that the performance of dominant trees of one of the most widely distributed species in East Asia has benefited from recent global changes, mainly over the past two decades. Such findings are essential for projections of forest dynamics and carbon sequestration under climate change., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.)

Mountainous zones are often characterized by complex orography and contacts between different aquifers that usually complicate the use of isotope hydrology techniques. The Apennine chain (Italy) and 10 mountain and mid-mountain areas belonging to it are the objective of this study. An original isotopic data treatment, able to identify the most probable recharge area for several springs/springs' groups/wells, has been developed. The method consists of a two-step approach: (1) the determination of the spring/wells computed isotope recharge elevation; (2) an advanced δ 18 O precipitation distribution model over the study area supported by statistical and GIS-based procedures implemented by two processes: first, the clipping of precipitation δ 18 O values (depicted from the δ 18 O-elevation relationships obtained for each study area) over a most probable recharge area for each analyzed spring or well and, second, the calculation of the overlapping distribution between the spring/well mean δ 18 O values ± σ and the precipitation δ 18 O content for each outcropping aquifer. A new regional δ 18 O gradient covering 150 km latitudinal length of central Italy has been defined. Seven LMWL and δ 18 O-elevation relationships able to represent the local precipitation isotopic composition have been obtained. The mean elevation of the springs and wells recharge areas have been assessed by a comparison between the obtained gradient with nine δ 18 O gradients available in the literature and those obtained at a local scale. The new isotopic modeling approach can stress whether the mere isotope modeling based on the stable isotope of oxygen agrees with the hydrogeological setting of the study areas., (© 2024 National Ground Water Association.)

Noble gases, oxygen-hydrogen isotope ratios, and ion compositions were measured at three sampling points (KUM, OTN, and ASO) from December 2013 to July 2021. The 3 He/ 4 He values at the three sampling points remained stable in the range of 3-4 Ra throughout the observation period, suggesting that the supply of deep-seated gases to the aquifer was stable. The 4 He/ 20 Ne values of KUM and OTN indicate that the supply of surface-source fluids to the aquifer decreased relative to that of deep-seated fluids at KUM and OTN. In contrast, in the ASO site, both the surface- and deep-seated fluids supplied to the aquifer were stable. The δD-δ 18 O relationship indicated the supply of deep-seated water to the KUM and OTN aquifers but not to the ASO aquifer. Nevertheless, the δD-δ 18 O relationship remained stable throughout the observation period, suggesting that the supply of deep-seated water to the three stations was stable. The Li/Cl and 1/Cl relationships for the three sampling points were plotted within a narrow range throughout the observation period, suggesting that the groundwater recharge was stable. Neither spikes nor step changes owing to the 2016 Kumamoto earthquake were observed in any of the data. These results indicate that the KUM and OTN aquifers are constantly supplied with deep fluids from the fluid-rich zone beneath the Kumamoto region, and that only deep-seated gas was supplied to the ASO aquifer. We also confirmed that these supply conditions were unaffected by the 2016 Kumamoto earthquake or the subsequent aftershock activity., (© 2024 The Authors. Groundwater published by Wiley Periodicals LLC on behalf of National Ground Water Association.)

Objectives: We aimed to validate dietary assessment methods against the gold standard, doubly labeled water (DLW), for estimating total energy intake (TEI)., Methods: PubMed, Scopus, Web of Science, and Google Scholar databases were searched until May 2023. Inclusion criteria encompassed studies involving participants aged 1-18 years, employing dietary assessment methods like food records, dietary histories, food frequency questionnaire (FFQ), or 24-h recalls estimating TEI alongside DLW to measure total energy expenditure (TEE). Data were pooled using random-effects meta-analysis models., Results: Thirty-three studies were identified, with sample sizes ranging from 9 to 118 participants. Meta-analysis of 22 studies identified underestimation of TEI (mean difference [MD] = -262.9 kcal/day [95% CI: -380.0, -145.8]; I 2  = 93.55%) for food records compared with TEE estimated by DLW. Other dietary assessment methods, including food recalls (n = 9) (MD = 54.2 kcal/day [95% CI: -19.8, 128.1]; I 2  = 49.62%), FFQ (n = 7) (MD = 44.5 kcal/day [95% CI: -317.8, 406.8]; I 2  = 94.94%), and diet history (n = 3) (MD = -130.8 kcal/day [95% CI: -455.8, 194.1]; I 2  = 77.48%), showed no significant differences in TEI compared with DLW-estimated TEE. All studies were of high quality., Conclusion: Food records may underestimate TEI, yet additional research is needed to identify the most accurate methods for assessing children's dietary intake., (© 2024 World Obesity Federation.)

To investigate the variation and fractionation of stable isotopes from irrigation water to soil, grapes, and wine, δ 2 H, δ 18 O, and δ 17 O in different samples from 10 regions in China were determined using a water isotope analyser. The values were significantly different among regions according to the chemometric analysis. All isotopes were significantly and positively correlated with irrigation water-soil and grape-wine. A significant water isotopic fractionation effect was observed from the irrigation water to the soil, grapes, and wine. Stable isotope distribution characteristics correlated with longitude, latitude, altitude, temperature, precipitation, station pressure and wind speed. The linear discriminant analysis (LDA), random forest (RF), support vector machine (SVM), and feed-forward neural network (FNN) models 58.33-100 %, 80-100 %, 53.33-100 %, and 73.33-100 % accurate for distinguishing the geographical origins of all samples from training and test data, respectively. These findings provide a theoretical basis for authenticating the geographic origin of Chinese wines using stable isotope analysis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The environmental threat posed by stibnite is an important geoenvironmental issue of current concern. To better understand stibnite oxidation pathways, aerobic abiotic batch experiments were conducted in aqueous solution with varying δ 18 O H2O value at initial neutral pH for different lengths of time (15-300 days). The sulfate oxygen and sulfur isotope compositions as well as concentrations of sulfur and antimony species were determined. The sulfur isotope fractionation factor (Δ 34 S SO4-stibnite ) values decreased from 0.8‰ to -2.1‰ during the first 90 days, and increased to 2.6‰ at the 180 days, indicating the dominated intermediate sulfur species such as S 2 O 3 2- , S 0 , and H 2 S (g) involved in Sb 2 S 3 oxidation processes. The incorporation of O into sulfate derived from O 2 (∼100%) indicated that the dissociated O 2 was only directly adsorbed on the stibnite-S sites in the initial stage (0-90 days). The proportion of O incorporation into sulfate from water (27%-52%) increased in the late stage (90-300 days), which suggested the oxidation mechanism changed to hydroxyl attack on stibnite-S sites promoted by nearby adsorbed O 2 on stibnite-Sb sites. The exchange of oxygen between sulfite and water may also contributed to the increase of water derived O into SO 4 2- . The new insight of stibnite oxidation pathway contributes to the understanding of sulfide oxidation mechanism and helps to interpret field data., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

The importance of stable carbon and oxygen isotopes in tree-ring-based climate reconstructions is increasingly recognized, especially in regions where traditional dendrochronological parameters, such as tree-ring width, usually fail. However, the effects of elevation and other site conditions on climate signals in tree-ring stable isotope (TRSI) chronologies remain unclear. Here, we assess the sensitivities to precipitation and drought of tree-ring width (TRW) and δ 13 C and δ 18 O TRSI chronologies of 136 living oaks (Quercus spp.) from five different elevational zones between 130 and 630 m asl in eastern Slovakia. Our results show that while the mean δ 13 C values were stable across the elevational gradient, TRW gradually decreased with increasing elevation, and the mean δ 18 O values significantly differed between the lower and higher sites. Despite these variations, we observed strong coherency among all the elevation-specific TRW and TRSI chronologies. We also found that mainly mid-May to July precipitation and mid-May to August drought controlled TRW and the δ 13 C values, whereas the δ 18 O reflected an overall lower climate signal. Our results show a relatively stable drought signal across the elevational range, with shorter seasonal response windows at higher elevations. Furthermore, our study indicates that carbon TRSI and TRW oak chronologies capture distinct summer drought signals independently of elevation and therefore have a strong paleoclimatic potential across eastern Europe., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Objectives: Contemporary migrations show form and intensity of interaction between homeland and host communities to shape social dynamics and identities. We apply here a contemporary theoretical framework and biogeochemical analyses to elucidate the scale, processes, and impacts of migration in the Tiwanaku polity (6th-11th c. CE) by inferring the mobility of individuals interred at the Tiwanaku-affiliated site of Omo M10 (Moquegua Valley, Peru)., Materials and Methods: For each of 124 individuals, we captured paleomobility across the life-course by analyzing up to four enamel and bone samples that formed during discrete developmental periods for radiogenic strontium ( 87 Sr/ 86 Sr) and stable oxygen (δ 18 O carbonate(VPDB) ) isotopes., Results: At Omo M10, archaeological human enamel and bone values range from 87 Sr/ 86 Sr = 0.70632-0.72183 and δ 18 O carbonate(VPDB)  = -13.4‰ to +1.7‰, with a mean of 87 Sr/ 86 Sr = 0.70763 ± 0.00164 (1σ, n = 334) and δ 18 O = -7.8‰ ± 1.9‰ (1σ, n = 334)., Discussion: Together with archaeological evidence, we interpret these data as evidence for multigenerational interaction between communities in the high-altitude Tiwanaku heartland and at the site of Omo M10. Our results suggest that one-fourth of individuals spent some part of their life outside of Moquegua and one in eight individuals from Omo M10 were first-generation migrants. Greater mobility of females and juveniles at Omo M10 indicates that gender and family were important social constructs in maintaining relationships and cultural continuity in provincial Tiwanaku life, and communities maintained autochthonous migration streams with Tiwanaku-affiliated populations throughout the south-central Andes. Intra-individual biogeochemical analyses of migration at Omo M10 contribute a nuanced perspective on the diverse experiences of multigenerational Tiwanaku colonies., (© 2024 Wiley Periodicals LLC.)

Hazelnuts' features and price are influenced by their geographical origin, making them susceptible to fraud, especially counterfeit claims regarding their provenance. Stable isotope analysis is a recognised approach to establish the geographical origin of foods, yet its potential in hazelnut authentication remains unexplored. In this prospective study, we assessed multiple isotopic markers in hazelnuts from different origins and evaluated the most promising variables for geographical authentication by chemometric tools. Our findings indicate that bulk δ 18 O, along with δ 2 H and δ 13 C in the main fatty acid methyl esters, exhibit significant potential in discriminating geographical origins, and 87 Sr/ 86 Sr analysis could serve as a proficient confirmatory tool. Though no single marker alone can differentiate between all the studied origins, employing a multi-isotopic approach based on PLS-DA models achieved up to 92.5 % accuracy in leave-10 %-out cross-validation. These findings will probably lay the groundwork for developing robust models for hazelnut geographical authentication based on larger datasets., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

North China type coalfield are gradually mining deep, and the mixing of groundwater is intensified. Hydrogen and oxygen isotopes are important elements for tracing groundwater movement. The fractionation response mechanism under mining conditions is not clear. In this paper, combined with numerical simulation, MixSIAR isotope mixing model and other methods, according to the δD, δ 18 O and hydrochemical information of various water bodies, the impact of coal mining on hydrogen and oxygen isotope fractionation is analyzed from multiple perspectives. The results show that summer soil water is the main source of recharge for limestone water, accounting for 30.7%-41.5%, and the Zhan River is the main source of recharge for limestone water. Before groundwater recharge, evaporation leads to the increase of δ 18 O in surface water by 0.31‰-5.58‰, water loss by 1.81%-28.00%, the increase of δ 18 O in soil water by 0.47‰-6.33‰, and water loss by 2.74%-35.80%. Compared with the coal mining layer, the degree of hydrogen and oxygen isotope drift and water-rock interaction in the coal mine stopping layer are significantly improved. The results of numerical simulation show that the pumping activity reduces the 18 O concentration in the mining layer. The ion ratio is used as a new variable to eliminate the influence of water-rock interaction when calculating the mixing ratio. The results show that the limestone water is in a state of receiving external recharge, and mixing effect increases the δ 18 O in limestone water by 0.86‰ on average, and the δD increases by 0.72‰ on average. The research results explain the controlled process of hydrogen and oxygen isotope fractionation under mining conditions, which is of great significance to coal mine safety production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Stable isotope techniques are precise methods for studying various aspects of hydrology, such as precipitation characteristics. However, understanding the variations in the stable isotope content in precipitation is challenging in Iran due to numerous climatic and geographic factors. To address this, forty-two precipitation sampling stations were selected across Iran to assess the fractional importance of these climatic and geographic parameters influencing stable isotopes. Additionally, deep learning models were employed to simulate the stable isotope content, with missing data initially addressed using the predictive mean matching (PMM) method. Subsequently, the recursive feature elimination (RFE) technique was applied to identify influential parameters impacting Iran's precipitation stable isotope content. Following this, long short-term memory (LSTM) and deep neural network (DNN) models were utilized to predict stable isotope values in precipitation. Interpolated maps of these values across Iran were developed using inverse distance weighting (IDW), while an interpolated reconstruction error (RE) map was generated to quantify deviations between observed and predicted values at study stations, offering insights into model precision. Validation using evaluation metrics demonstrated that the model based on DNN exhibited higher accuracy. Furthermore, RE maps confirmed acceptable accuracy in simulating the stable isotope content, albeit with minor weaknesses observed in simulation maps. The methodology outlined in this study holds promise for application in regions worldwide characterized by diverse climatic conditions.

Outcrops play an important role in groundwater recharge. Understanding groundwater origins, dynamics and its correlation with different water sources is essential for effective water resources management and planning in terms of quantity and quality. In the case of the Guarani Aquifer System (GAS) outcrop areas are particularly vulnerable to groundwater pollution due to direct recharge processes. This study focuses on the Alto Jacaré-Pepira sub-basin, a watershed near Brotas, a city in the central region of the state of São Paulo, Brazil, where groundwater is vital for supporting tourism, agriculture, urban water supply, creeks, river and wetlands. The area has a humid tropical climate with periods of both intense rainfall and drought, and the rivers remain perennial throughout the year. Therefore, the aim of this study is to investigate the interconnections between a spring and its potential sources of contribution, namely rain and groundwater, in order to elucidate the relationships between the different water sources. To achieve this, on-site monitoring of groundwater depth, rainfall amount, and stable isotope ratios (deuterium ( 2 H) and oxygen-18 ( 18 O)) from rain, spring discharge, and a monitoring well was carried out from 2013 to 2021. The results indicate that the mean and standard deviations for δ 18 O in rainwater exhibit higher variability, resulting in -4.49 ± 3.18 ‰ VSMOW, while δ 18 O values from the well show minor variations, similar to those of the spring, recording -7.25 ± 0.32 ‰ and -6.94 ± 0.28 ‰ VSMOW, respectively. The mixing model's outcomes reveal seasonal variations in water sources contribution and indicate that groundwater accounts for approximately 80 % of spring discharge throughout the year. Incorporating stable isotopes into hydrological monitoring provides valuable data for complementing watershed analysis. The values obtained support the significance of the aquifer as a primary source, thereby offering critical insights into stream dynamics of the region.

Understanding the critical thresholds of dissolved oxygen (O 2 ) that trigger adaptive physiological responses in aquatic organisms is long hampered by a lack of robust, non-lethal or non-invasive methodologies. The isotope fractionation of triple O 2 isotopes ( 18 O/ 17 O/ 16 O) during respiration is linked to the amount of oxygen utilised, offering a potential avenue for new insights. Our experimental research involved measuring the oxygen isotope fractionation of dissolved O 2 in closed-system aquatic respirometry experiments with wild sticklebacks ( Gasterosteus aculeatus ). These fish were either naturally adapted or experimentally acclimated to hypoxic and normoxic conditions. The aim was to observe their oxygen usage and isotope fractionation in response to increasingly severe hypoxia. Initial observations revealed a progressive 18 O enrichment from the preferential uptake of 16 O to a dissolved oxygen threshold of 3-5 mg O 2 L -1 , followed by an apparent reversal in oxygen isotope fractionation, which is mixing of 16 O and 17 O with the remaining O 2 pool across all populations and indicative of a systematic change in oxygen metabolism among the fish. Unexpectedly, sticklebacks adapted to hypoxia but acclimated to normoxia exhibited stronger oxygen isotope fractionation compared to those adapted to normoxia and acclimated to hypoxia, contradicting the hypothesis that hypoxia adaptation would lead to reduced isotope discrimination due to more efficient oxygen uptake. These preliminary experimental results highlight the novel potential of using dissolved O 2 isotopes as a non-invasive, non-lethal method to quantitatively assess metabolic thresholds in aquatic organisms. This approach could significantly improve our understanding of the critical oxygen responses and adaptation mechanisms in fish and other aquatic organisms across different oxygen environments, marking a significant step forward in aquatic ecological and physiological research.

To determine contamination sources and pathways, the use of multiple isotopes, including metal isotopes, can increase the reliability of environmental forensic techniques. This study differentiated contamination sources in groundwater of a mine area and elucidated geochemical processes using Cu, Zn, S-O, and O-H isotopes. Sulfate reduction and sulfide precipitation were elucidated using concentrations of dissolved sulfides, δ 34 S SO4 , δ 18 O SO4 , and δ 66 Zn. The overlying contaminated soil was possibly responsible for the contamination of groundwater at <5 mbgl, which was suggested by low δ 65 Cu values (0.419-1.120‰) reflecting those of soil (0.279-1.115‰). The existence of dissolved Cu as Cu(I) may prevent the increase in δ 65 Cu during leaching of contaminated soil in the sulfate-reducing environment. In contrast, the groundwater at >5 mbgl seemed to be highly affected by the contamination plume from the adit water, which was suggested by high SO 4 2- concentrations (407-447 mg L -1 ) and δ 65 Cu (0.252-2.275‰) and δ 66 Zn (-0.105‰-0.362‰) values at a multilevel sampler approaching those of the adit seepages. Additionally, the O-H isotopic ratios were distinguished between <5 mbgl and >5 mbgl. Using δ 65 Cu and δ 66 Zn to support the determination of groundwater contamination sources may be encouraged, particularly where the isotopic signatures are distinct for each source., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

A "once-in-a-millennium" super rainstorm battered Zhengzhou, central China, from 07/17/2021 to 07/22/2021 (named "7.20" Zhengzhou rainstorm). It killed 398 people and caused billions of dollars in damage. A pressing question is whether rainstorms of this intensity can be effectively documented by geological archives to understand better their historical variabilities beyond the range of meteorological data. Here, four land snail shells were collected from Zhengzhou, and weekly to daily resolved snail shell δ 18 O records from June to September of 2021 were obtained by gas-source mass spectrometry and secondary ion mass spectrometry. The daily resolved records show a dramatic negative shift between 06/18/2021 and 09/18/2021, which has been attributed to the "7.20" Zhengzhou rainstorm. Moreover, the measured amplitude of this shift is consistent with the theoretical value estimated from the flux balance model and instrumental data for the "7.20" Zhengzhou rainstorm. Our results suggest that the ultra-high resolution δ 18 O of land snail shells have the potential to reconstruct local synoptic scale rainstorms quantitatively, and thus fossil snail shells in sedimentary strata can be valuable material for investigating the historical variability of local rainstorms under different climate backgrounds., (Copyright © 2024 Science China Press. Published by Elsevier B.V. All rights reserved.)

Identifying and quantifying water nitrate pollution is crucial for managing aquatic environment of a bay. Dongshan Bay, a significant semi-enclosed bay in the southeastern coastal area of Fujian Province, features mangrove and coral reef ecosystems at its estuary and bay mouth, respectively. Dongshan Bay is impacted by human activities such as mariculture. We quantified and analyzed nitrate pollution status in the surface waters of Dongshan Bay by measuring physicochemical parameters, stable isotopes (δ 15 N-NO 3 - , δ 18 O-NO 3 - and δ 15 N-NH 4 + ) of the surface waters, and using statistical methods including the MixSIAR isotope mixing model. The results showed that the concentrations of chlorophyll a and dissolved inorganic nitrogen in the surface waters exhibited a noticeable gradient change, decreasing from the estuary of the Zhangjiang River to the mouth of Dongshan Bay. The maximum concentrations of chlorophyll a, NH 4 + , NO 3 - and NO 2 - were 45.2 μg·L -1 , 52.67 μmol·L -1 , 379.2 μmol·L -1 and 3.93 μmol·L -1 , respectively. The nitrogen and oxygen isotope values of NH 4 + and NO 3 - in the surface waters showed significant spatial variations. According to the MixSIAR model results, nitrogen sources in the surface waters of Dongshan Bay were mainly freshwater inputs of the Zhangjiang River estuary, aquaculture wastewater, and groundwater. The freshwater input from the Zhangjiang River estuary contributed the most (25.2%), while aquaculture wastewater, groundwater and urban sewage accounted for 24.6%, 19.0%, and 15.1%, respectively. It is evident that freshwater input from the Zhangjiang River estuary is the primary source of nitrate in the surface waters of Dongshan Bay.

Disentangling the factors influencing the climate sensitivity of trees is crucial to understanding the susceptibility of forests to climate change. Reducing tree-to-tree competition and mixing tree species are two strategies often promoted to reduce the drought sensitivity of trees, but it is unclear how effective these measures are in different ecosystems. Here, we studied the growth and physiological responses to climate and severe droughts of silver fir and Douglas-fir growing in pure and mixed conditions at three sites in Switzerland. We used tree-ring width data and carbon (δ13C), oxygen (δ18O) and hydrogen (δ2H) stable isotope ratios from tree-ring cellulose to gain novel information on water relations and the physiology of trees in response to drought and how tree species mixture and competition modulate these responses. We found significant differences in isotope ratios between trees growing in pure and mixed conditions for the two species, although these differences varied between sites, e.g. trees growing in mixed conditions had higher δ13C values and tree-ring width than trees growing in pure conditions for two of the sites. For both species, differences between trees in pure and mixed conditions regarding their sensitivity to temperature, precipitation, climatic water balance and vapor pressure deficit were minor. Furthermore, trees growing in pure and mixed conditions showed similar responses of tree-ring width and isotope ratios to the past severe droughts of 2003, 2015 and 2018. Competition had only a significantly negative effect on δ13C of silver fir, which may suggest a decrease in photosynthesis due to higher competition for light and nutrients. Our study highlights that tree species mixture may have only moderate effects on the radial growth and physiological responses of silver fir and Douglas-fir to climatic conditions and that site condition effects may dominate over mixture effects., (© The Author(s) 2024. Published by Oxford University Press.)

Understanding the major factors influencing groundwater chemistry and its evolution in irrigation areas is crucial for efficient irrigation management. Major ions and isotopes (δD-H 2 O together with δ 18 O-H 2 O) were used to identify the natural and anthropogenic factors contributing to groundwater salinization in the shallow aquifer of the Wadi Guenniche Plain (WGP) in the Mediterranean region of Tunisia. A comprehensive geochemical investigation of groundwater was conducted during both the low irrigation season (L-IR) and the high irrigation season (H-IR). The results show that the variation range and average concentrations of almost all the ions in both the L-IR and H-IR seasons are high. The groundwater in both seasons is characterized by high electrical conductivity and CaMgCl/SO 4 and NaCl types. The dissolution of halite and gypsum, the precipitation of calcite and dolomite, and Na-Ca exchange are the main chemical reactions in the geochemical evolution of groundwater in the Wadi Guenniche Shallow Aquifer (WGSA). Stable isotopes of hydrogen and oxygen (δ 18 O-H 2 O and δD-H 2 O) indicate that groundwater in WGSA originated from local precipitation. In the H-IR season, the δ 18 O-H 2 O and δD-H 2 O values indicate that the groundwater experienced noticeable evaporation. The enriched isotopic signatures reveal that the WGSA's groundwater was influenced by irrigation return flow and seawater intrusion. The proportions of mixing with seawater were found to vary between 0.12% and 5.95%, and between 0.13% and 8.42% during the L-IR and H-IR seasons, respectively. Irrigation return flow and the associated evaporation increase the dissolved solids content in groundwater during the irrigation season. The long-term human activities (fertilization, irrigation, and septic waste infiltration) are the main drives of the high nitrate-N concentrations in groundwater. In coastal irrigation areas suffering from water scarcity, these results can help planners and policy makers understand the complexities of groundwater salinization to enable more sustainable management and development., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Uncontrolled coal mining using non-scientific methods has presented a major threat to the quality of environment, particularly the water resources in eastern himalayan sub-region of India. Water bodies in the vicinity of mining areas are contaminated by acid mine drainage (AMD) that is released into streams and rivers. This study attempted to assess the impact of AMD, deciphering hydrogeochemical processes, seasonal fluctuations, and stable isotope features of water bodies flowing through and around coal mining areas. Self-organizing maps (SOMs) used to separate and categorize AMD, AMD-impacted and non-AMD impacted water from the different study locations for two sampling seasons revealed four clusters (C), with C1 and C2 impacted by AMD, C3 and C4 showing negligible to no impact of AMD. AMD impacted water was SO 4 2- - Mg 2+ - Ca 2+ hydrochemical type with sulphide oxidation and evaporation dominating water chemistry, followed by silicate weathering during both the sampling seasons. Water with negligible-to-no AMD-impact was Mg 2+ - Ca 2+ - SO 4 2- to Ca 2+ - HCO 3 - to mixed hydrochemical type with rock weathering and dissolution, followed by ion exchange as major factors controlling water chemistry during both the sampling seasons. Most of physicochemical parameters of C1 and C2 exceeded the prescribed limits, whereas in C3 and C4 water samples, parameters were found within the prescribed limits. Stable isotopes of hydrogen (δ 2 H) and oxygen (δ 18 O) during post-monsoon (PoM) varied between -41.04 ‰ and -29.98 ‰, and -6.60 ‰ to -3.94 ‰; and during pre-monsoon (PrM) varied between -58.18 ‰ and - 33.76 ‰ and -8.60 ‰ to -5.46 ‰. Deuterium excess (d-excess) ranged between 1.57 ‰ and 12.47 ‰ during PoM and 5.70 ‰ to 15.17 ‰ during PrM season. The stable isotopes analysis revealed that evaporation, mineral dissolution and mixing with rainwater are the key factors in study area., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Premise: The Aptian-Albian (121.4-100.5 Ma) was a greenhouse period with global temperatures estimated as 10-15°C warmer than pre-industrial conditions, so it is surprising that the most reliable CO 2 estimates from this time are <1400 ppm. This low CO 2 during a warm period implies a very high Earth-system sensitivity in the range of 6 to 9°C per CO 2 doubling between the Aptian-Albian and today., Methods: We applied a well-vetted paleo-CO 2 proxy based on leaf gas-exchange principles (Franks model) to two Pseudotorellia species from three stratigraphically similar samples at the Tevshiin Govi lignite mine in central Mongolia (~119.7-100.5 Ma)., Results: Our median estimated CO 2 concentration from the three respective samples was 2132, 2405, and 2770 ppm. The primary reason for the high estimated CO 2 but with relatively large uncertainties is the very low stomatal density in both species, where small variations propagate to large changes in estimated CO 2 . Indeed, we found that at least 15 leaves are required before the aggregate estimated CO 2 approaches that of the full data set., Conclusions: Our three CO 2 estimates all exceeded 2000 ppm, translating to an Earth-system sensitivity (~3-5°C/CO 2 doubling) that is more in keeping with the current understanding of the long-term climate system. Because of our large sample size, the directly measured inputs did not contribute much to the overall uncertainty in estimated CO 2 ; instead, the inferred inputs were responsible for most of the overall uncertainty and thus should be scrutinized for their value choices., (© 2024 Botanical Society of America.)

Nitrate (NO 3 - ) pollution in irrigation canals is of great concern because it threatens canal water use; however, little is known about it at present. Herein, a combination of positive matrix factorization (PMF), isotope tracers, and Mixing Stable Isotope Analysis in R (MixSIAR) was developed to identify anthropogenic impacts and quantitative sources of NO 3 - in a rural-urban canal in China. The NO 3 - concentration (0.99-1.93 mg/L) of canal water increased along the flow direction and was higher than the internationally recognized eutrophication risk value in autumn and spring. The inputs of the Fuhe River, NH 4 + fertilizer, soil nitrogen, manure & sewage, and rainfall were the main driving factors of canal water NO 3 - based on principal component analysis and PMF, which was supported by evidence from δ 15 N/δ 18 O-NO 3 - . According to the chemical and isotopic analyses, nitrogen transformation was weak, highlighting the potential of δ 15 N/δ 18 O-NO 3 - to trace NO 3 - sources in canal water. The MixSIAR and PMF results with a <15% divergence emphasized the predominance of the Fuhe River (contributing >50%) and anthropogenic impacts (NH 4 + fertilizer plus manure & sewage, >37%) on NO 3 - in the entire canal, reflecting the effectiveness of the model analysis. According to the MixSIAR model, (1) higher NO 3 - concentration in canal water was caused by the general enhancement of human activities in spring and (2) NO 3 - source contributions were associated with land-use patterns. The high contributions of NH 4 + fertilizer and manure & sewage showed inverse spatial variations, suggesting the necessity of reducing excessive fertilizer use in the agricultural area and controlling blind wastewater release in the urban area. These findings provide valuable insights into NO 3 - dynamics and fate for sustainable management of canal water resources. Nevertheless, long-term chemical and isotopic monitoring with alternative modeling should be strengthened for the accurate evaluation of canal NO 3 - pollution in future studies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Ecological water replenishment (EWR) changes the recharge conditions, flow fields, and physicochemical properties of regional groundwater. However, the resulting impacts on mechanisms regulating the sources and transformation of groundwater nitrate remain unclear. This study investigated how EWR influences the sources and transformation processes of groundwater nitrate using an integrated approach of Water chemistry analysis and stable isotopes (δ 15 N-NO 3 - and δ 18 O-NO 3 - ) along with microbial techniques. The results showed that groundwater NO 3 -N decreased from 12.98 ± 7.39 mg/L to 7.04 ± 8.52 mg/L after EWR. Water chemistry and isotopic characterization suggested that groundwater nitrate mainly originated from sewage and manure. The Bayesian isotope mixing model (MixSIAR) indicated that EWR increased the average contribution of sewage and manure sources to groundwater nitrate from 46 % to 61 %, whereas that of sources of chemical fertilizer decreased from 43 % to 21 %. Microbial community analysis revealed that EWR resulted in a substantial decrease in the relative abundance of Pseudomonas spp denitrificans, from 13.7 % to 0.6 %. Both water chemistry and microbial analysis indicated that EWR weakened denitrification and enhanced nitrification in groundwater. EWR increases the contribution of nitrate to groundwater by promoting the release of sewage and feces in the unsaturated zone. However, the dilution effect caused by EWR was stronger than the contribution of sewage and fecal sources to groundwater nitrate. As a result, EWR helped to reduce groundwater nitrate concentrations. This study showed the effectiveness of integrated isotope and microbial techniques for delineating the sources and transformations of groundwater nitrate influenced by EWR., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

The Middle Ages in the Iberian Peninsula is a period of special interest for studying the relationship of climate change with historical and socioeconomic processes. Between the 8th and 15th centuries AD, the Peninsula was characterized not only by complex political, cultural, and social transitions but also by major variations in the climate. The objective of this study was to examine differences in diet and mobility between distinct populations of the Peninsula and explore the possible relationship of diet, mobility, and culture with environmental variables and geographical settings. For this purpose, we obtained stable isotopic ratios of carbon and oxygen (δ13C and δ18O) from the enamel apatite of first upper incisors from 145 individuals at eight archeological sites that represent both Christian and Islamic communities and both rural and urban social settings. Results revealed a dietary difference between Christian and Islamic populations, observing a greater contribution of C4 plants, possibly sorghum, in the diet of the latter, especially in a rural setting. The disparity in oxygen isotopic ratios between populations from the North and South of the Peninsula is consistent with modern climatic differences between these regions. In this line, intraregional variability in oxygen isotopic ratios may hint at diachronic occupation phases under varying climatic conditions. The few isotopic outliers in our sample suggest overall low mobility levels., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Martín-Alonso et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The application of stable isotope analysis (SIA) to the fields of ecology and animal biology has rapidly expanded over the past three decades, particularly with regards to water analysis. SIA now provides the opportunity to monitor migration patterns, examine food webs, and assess habitat changes in current and past study systems. While carbon and nitrogen SIA of biological samples have become common, analyses of oxygen or hydrogen are used more sparingly despite their promising utility for tracing water sources and animal metabolism. Common ecological applications of oxygen or hydrogen SIA require injecting enriched isotope tracers. As such, methods for processing and analyzing biological samples are tailored for enriched tracer techniques, which require lower precision than other techniques given the large signal-to-noise ratio of the data. However, instrumentation advancements are creating new opportunities to expand the applications of high-throughput oxygen and hydrogen SIA. To support these applications, we update methods to distill and measure water derived from biological samples with consistent precision equal to, or better than, ± 0.1 ‰ for δ 17 O, ± 0.3 ‰ for δ 18 O, ± 1 ‰ for δ 2 H, ± 2 ‰ for d -excess, and ± 15 per meg for Δ 17 O.

The Himalayas experienced long-term climate changes and recent extreme weather events that affected plant growth and the physiology of tree species at high-elevation sites. This study presents the first statistically robust δ 18 O TR chronologies for two native pine species, Pinus roxburghii, and Pinus wallichiana, in the lower Nepalese Himalaya. The isotope chronologies exhibited 0.88‰ differences in overall mean isotope values attributed to varying elevations (460-2000 m asl). Comparative analysis of climate response using data sets from different sources and resolutions revealed the superiority of the APHRODITE (Asian Precipitation - Highly-Resolved Observational Data Integration Towards Evaluation) data set calibrated for the South Asian Summer Monsoon (SASM)-dominated region. Both species exhibited negative correlations with monsoon precipitation and positive correlations with temperature. However, during the peak monsoon season (July-August), daily resolved climate data disentangled statistically insignificant relationships, and revealed that δ 18 O TR is influenced by atmospheric moisture. Both congeneric species showed a decoupling between the chronologies after 1995. However, no significant change in air moisture origin and monsoon regime between the study sites was observed, indicating a consistent dominant moisture source during different monsoon seasons. Besides, we also observed the decreased inter-series correlation of both δ 18 O TR chronologies after 1995, with P. wallichiana experiencing a steeper decrease than P. roxburghii. The weakening correlations between and within the chronologies coincided with a regional drought during 1993-1995 in both sites, highlighting the strong regulation of local climate on the impact of regional extreme climate events. Our findings emphasise the importance of employing climate data with optimal spatial and temporal resolution for improved δ 18 O TR -climate relationships at the intra-annual scale while considering the influence of site-specific local environmental conditions. Assessing climate data sets with station data is vital for accurately interpreting climate change's impact on forest response and long-term climate reconstructions., (© 2024. The Author(s).)

Understanding an animal's metabolic rate and thermal history is pivotal for ecological research. Recent studies have proposed the use of stable carbon and oxygen isotopes (δ 13 C and δ 18 O) in biogenic carbonates as proxies of metabolic rate and experienced temperature, respectively, to overcome the challenges of directly measuring these data in the field. Our study represents the first experimental investigation to develop δ 13 C and δ 18 O proxies in octopus. Octopus berrima hatchlings were raised in captivity, at varying water temperatures, for up to 110 days. O. berrima statoliths were then subsequently analysed for δ 13 C and δ 18 O values. The proportion of metabolically derived carbon, or respired carbon (C resp ), increased as the octopus grew (slope = 0.076, R 2  = 0.72), suggesting an influence of somatic growth rate and body mass on δ 13 C values. Additionally, we identified an inverse correlation between δ 18 O values and environmental temperature (slope = -0.163, R 2  = 0.91), which was subsequently used to develop a thermal reconstruction model. Our experiment aids in interpreting stable isotopic values in statoliths and their application as temperature and metabolic proxies in wild-caught octopus. Such proxies will increase our monitoring capabilities of these ecologically and commercially significant cephalopods and contribute to their conservation and effective management., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

We studied δ 13 C, δ 15 N and δ 18 O values, and total mercury (THg) concentrations in muscle samples from deep-sea predators - five beaked whale species and sperm whales - stranded along the coast of Hokkaido, in the north of Japan in 2010 and 2019. The δ 13 C, δ 15 N and δ 18 O values, THg concentrations, and body length (BL) of Stejneger's beaked whales were similar to those of Hubbs' beaked whales, which belong to the same genus. In contrast, δ 13 C values, THg concentrations, and BL of Sato's beaked whales were markedly different from those of Baird's beaked whales, which belong to the same genus. Stejneger's and Hubbs' beaked whales living around Hokkaido may compete in their ecological niches, whereas Sato's and Baird's beaked whales may segregate their ecological niches. Although Cuvier's beaked whales and sperm whales belong to different genera and their BLs were significantly different, their δ 13 C and δ 15 N values were similar, probably because they can dive and stay in deeper waters than other beaked whale species. The δ 13 C values in combined samples from all whales increased with increasing BL, probably owing to the larger whale species' dietary preference for squid. The δ 13 C values in combined samples from all whales were positively correlated with THg concentrations, whereas the δ 15 N values in the combined samples were negatively correlated. The δ 18 O values in combined samples from most whales tended to be positively correlated with THg concentrations. These correlations may be explained by a higher THg load from deep-sea feeding than from pelagic feeding and by a feeding shift towards lower trophic levels.

The Lower Quang Tri River Group, situated in central Vietnam, faces a myriad of challenges, notably the decline in groundwater levels and the salinisation of both groundwater and surface water, significantly impacting water availability for domestic, agricultural, and industrial purposes. To address these pressing concerns, this study adopts a comprehensive methodology integrating hydrogeological measurements, isotopic techniques, and chemical analyses of various water sources, including local precipitation, surface water bodies, reservoirs, and groundwater samples. Utilising the deuterium and oxygen-18 signatures ( δ 2 H and δ 18 O) in water molecules as environmental tracers for the assessment of base flow and water sources enables a nuanced understanding of the intricate interaction between surface water and groundwater. Research findings elucidate that during the dry season, groundwater recharge primarily stems from water in the reservoirs over approximately seven months. Base flow contributes between 80 and 85 % of streamflow during the rainy season, escalating to 100 % during the dry season. The mean travelling time of the base flow is estimated at 120 ± 10 days using the sine curve model developed by Rodgers et al. The insights gleaned from this study are poised to play a pivotal role in guiding the local water resources managers in licensing for the exploitation of a right quantities of groundwater as sustainable management strategies in the region.