Stable Oxygen Isotope Research Articles

Stable isotopes of carbon (δ13C) and oxygen (δ18O) from vaquita (Phocoena sinus) bones as indicators of habitat use in the Upper Gulf of California

The vaquita (Phocoena sinus) is an endemic species of the Upper Gulf of California (UGC), which is in a critical state of extinction. Bycatch has been considered the main factor leading to its potential extinction; however, the impact of the damming of the Colorado River on the species’ ecology has not been studied. Stable isotopes of carbon (δ13C) and oxygen (δ18O) from vaquita bones were analyzed as indicators of the carbon source of primary producers and habitat use in the UGC from 1982 to 1993. Based on the Colorado River’s flow into the UGC, two periods were markedly different: from 1982 to 1988, when freshwater arrived, and from 1989 to 1993, when the flow was null. Sea surface salinity (SSS) data showed the inverse of the river’s flow pattern, being significantly lower at the end of the 1980s than at the beginning of the 1990s. In agreement with the above, sea surface temperature (SST)/SSS diagrams showed the presence of two water masses inside a gradient from 33.8 to 35.2 psu. The δ13C was significantly different between both periods, with a mean value of -9.1‰ at the end of the 1980s and a mean value of -10.8‰ at the beginning of the 1990s. This means that, when the river flow was dammed, the carbon source of primary producers changed significantly in the UGC. However, the δ18O was not significantly different between both periods, with values of 30.4‰ and 30.5‰, respectively. Comparing the vaquita’s average values of δ18O from this study with those of other marine mammals obtained from previous studies revealed that the vaquita is the most enriched marine mammal species, which could be the result of the high evaporation and salinity that currently occur in the UGC, the vaquita’s habitat. A longer temporal series might show changes in δ18O, which have been detected in other species living in the UGC. From a conservation point of view, the results showed that the impact of environmental variability on the trophic ecology of the vaquita has potential effects on the species’ health.

Investigating Induced Infiltration by Municipal Production Wells Using Stable Isotopes of Water (δ18O and δ2H), Four Mile Creek, Ohio

Many municipalities around the world place their production wells in shallow alluvial aquifers that are adjacent to streams. Pumping these wells then induces the infiltration of surface water into the aquifer, allowing the greater extraction of water without significantly depleting the aquifer. However, induced infiltration poses a risk of introducing contamination from surface water into groundwater systems. The goal of this study was to quantify the amount of induced infiltration due to municipal pumping at the Four Mile Creek well field in Oxford, Ohio, using stable isotopes of water oxygen (δ18O) and deuterium (δ2H). In areas of municipal pumping, we sampled water from the production wells, Four Mile Creek, and from monitoring wells that we hypothesized to be both influenced and not influenced by induced infiltration. Samples were collected over 10 months in 2012 and over 12 months in 2021. In 2012, surface water δ18O values ranged from −3.89 to −8.04‰, and δ2H ranged from −26.55 to −55.65‰ at sampling sites. PW1 δ18O values ranged from −4.71 to −7.39‰ with a mean of −6.61 and −32.01 to −47.86‰ with a mean of −42.74‰ for δ2H. PW2 δ18O values ranged from −5.74 to −7.34‰, with a mean of −6.45‰, and δ2H ranged from −36.29 to −47.82‰ with a mean of −42.43‰. PW3 had lower values of both δ18O and δ2H, ranging from −6.36 to −8.02‰ and −47.7 to −40.35‰, and with means of −7.08 and −45.11, respectively. In 2021/2022, surface water δ18O values ranged from −5.32 to −7.93‰, and the δ2H ranged from −36.14 to −50.56‰. PW1 δ18O values ranged from −6.15 to −7.54‰ with a mean of −7.13‰, and δ2H ranged from −43.52 to −49.01‰ with a mean of −45.99‰. PW2 δ18O values ranged from −5.72 to −7.34‰, with a mean of −6.70‰, and δ2H ranged from −36.69 to −46.14‰, with a mean of −43.61‰. Using the time averaged values of δ18O of groundwater, production wells and surface water, the percentages of surface water resulting from induced infiltration in 2012 were 57%, 59% and 15% at the three wells, respectively, while in 2021, PW1 had 35% and PW2 91%. The amount of induced infiltration was apparently related to the pumping rates of the production wells, the length of time of pumping and the distance between Four Mile Creek and production wells. Our results indicate that stable isotopes of water provide a reliable method of quantifying groundwater/surface water interaction in alluvial aquifers.

Causes for overestimation of the moisture recycling in an alpine meadow ecosystem of the Shule River Basin, Tibetan Plateau, China

Terrestrial moisture recycling is an essential hydrological component and a significant source of the atmosphere’s humidity budget in arid and semi-arid inland regions. Investigations on moisture recycling using the stable hydrogen and oxygen isotopes is currently a focal point in hydrologic research. However, the direct quantification of recycling ratio based on isotopic composition of evapotranspiration vapor is lacking. So, this causes challenges to compare studies, based in the same region and time period but with different methodologies. In this study, we measured the isotopic compositions of evapotranspiration vapor (δ18OET/δDET) from June to September 2018 in an alpine meadow ecosystem at the Shule River Basin by combining the Keeling plot model and in-situ chamber measurement. Using this data, the moisture recycled rate (mrr) was assessed based on the two-component (Model A) and three-component isotopic mixing models (Model B), respectively. Based on Model A and δ18OET, the analysis revealed that the mean recycled rate for the entire observation period was 35 %, while it was 26 % during the westerly period (the months dominated by the north branch of prevailing westerlies) and 44 % during the monsoon period (when subtropical moisture from the Indian monsoon penetrated the region). The recycled rate based on Model A and δDET was slightly larger with a mean value of 41 % during the entire observation period. The recycled rate based on Model B was also significantly higher in comparison with Model A, while the causes for this difference could be the assumption of substituting xylem water for transpiration vapor and the plant water source δD offset. The contribution of recycled moisture was notable lower for heavy rainfall comparing with light rainfall. Our findings provided a new perspective for the investigations of alpine meadow ecosystem hydrological processes.

Using stable oxygen isotope dual-inlet isotope-ratio mass spectrometry to elucidate uranium transport and mixed 230Th/U calcite formation ages at the seminal Devils Hole, Nevada, natural laboratory.

Vein calcite in Devils Hole has been precipitating continuously in oxygen-isotope equilibrium at a constant temperature for over 500 000years, providing an unmatched δ18O paleoclimate time series. A substantial issue is that coeval calcite (based on matching δ18O values) has uranium-series ages differing by 12 000years. An unparalleled high-accuracy δ18O chronology series from continuously submerged calcite was used to correct the published uranium-series ages of non-continuously formed calcite in two cores, cyclically exposed by water-table decline during glacial-interglacial transitions. This method relies on the premise that the δ18O values of coevally precipitated calcite are identical, allowing matching calcite δ18O values to establish formation ages. Exposed calcite can have apparent ages that are 12 000years too young due to unrecognized uranium mobility and resulting mixed ages identified in over 50 mixed uranium-series ages from previous studies. Secondary uranium in fluids, sourced from the formation or dissolution of porous carbonate deposits (folia) with high uranium-238 (238U) concentrations, has migrated up to 10mm into vein calcite. The continuously submerged Devils Hole δ18O chronology is not explained by orbital forcing. Rather, this chronology represents a regional climate record in the southern Great Basin of sea-surface-temperature (SST) variations off California, variations that preceded the last and penultimate deglaciations by 5000 to approximately 10 000years. Temporal discrepancies between the continuously submerged Devils Hole chronology and other regional δ18O records (e.g., the Leviathan chronology) can be explained by unrecognized cryptic, pernicious uranium mobility, leading to model estimations that may be thousands of years younger than actual ages. Consequently, paleo-moisture availability, water-table, and groundwater recharge models based on these mixed uranium-series ages are too young by as much as 12 000years. The potential for post-formation uranium addition in subaerial cores and speleothems underscores the need for caution in uranium-series dating, highlighting δ18O time-series comparisons as a method for identifying mixed ages.

Regional differences in the effects of atmospheric moisture residence time on precipitation isotopes over Eurasia

Regional variations in atmospheric moisture residence time (RT) highlight the need to obtain independent observation indexes to constrain different model-based estimates. Stable isotopes of oxygen and hydrogen naturally exist in water molecules that can provide such observational constraints. We analyzed the relationship between RT and precipitation isotopes (δ2H and δ18O) across different climatic zones in Eurasia from 1980 to 2020. Our analysis reveals that: (1) Both precipitation isotopes and RT showed significant increasing trends during 1980–2020. The increase in RT corresponds to weakened net isotopic distillation over Eurasia, suggesting reduced atmospheric circulation intensity under warming conditions. (2) The spatial patterns of RT and precipitation isotopes vary significantly among different moisture source regions, reflecting distinct moisture transport and precipitation formation processes. (3) On long-term scales, RT generally shows positive correlations with precipitation isotopes, except in plateau regions. The RT-δ18O relationship exhibits latitude-dependent variations, with similar slopes in regions sharing common moisture sources. These findings enhance our understanding of the long-term controls on precipitation isotopic composition and atmospheric moisture cycling patterns across Eurasia.

Distinguishing West Florida gag (Mycteroperca microlepis) nurseries with otolith stable isotopes

Numerous reef fishes utilize estuarine nurseries following spawning in marine habitats. Nursery origin affects their life cycle space use, and otolith chemistry can be an effective tool for tracking movement over this lifetime scale. Gag Mycteroperca microlepis occupy West Florida (WF), USA, estuaries as juveniles and have a spatially complex life cycle with ontogenetic habitat shifts and offshore spawning. We tested whether age-0 gag otolith stable isotope values distinguished WF nurseries and assessed isotopic variability at multiple temporal and spatial scales. Northern and southern juveniles had distinct otolith carbon (δ13C) and oxygen (δ18O) stable isotope values despite evidence of interannual variability, and both year-specific and combined year models had high (>80%) classification accuracies. We investigated long-term stability of otolith δ13C and δ18O by comparing age-0 gag collected during 2009-2012 and 2020-2021. The δ18O values of southern age-0 otoliths decreased over time, thus decreasing inter-regional differences and the classification accuracy of the combined year model (79%). Concomitantly, age-0 otoliths became depleted in 13C across regions, which may result from increased limestone dissolution (i.e. dekarstification) in the Floridan aquifer. We identified greater decadal variability in region-specific stable isotope values than has been documented in previous studies, indicating that a cohort-specific approach will likely be required to estimate gag lifetime movement.

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.

Isotopic heterogeneity in U.S. Urban water supply systems reflects climatic, environmental, and sociodemographic factors: Implications for forensic identification.

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.

Water Transformation Relationship in Inner Mongolia Section of the Yellow River Basin Based on Stable Hydrogen and Oxygen Isotopes

By collecting the atmospheric precipitation, surface water, and groundwater in the Inner Mongolia section of the Yellow River Basin in July 2021 （wet season）, October （normal season）, and April 2022 （dry season）, stable isotope technology was used to analyze the temporal and spatial changes in hydrogen and oxygen stable isotopes in the "three rivers" of the basin, and the MixSIAR mixing model was used to reveal the water body transformation relationship. The results showed that the mean difference in the groundwater isotope was small in the abundance period, flat period, and dry period in the Mongolia section of the Yellow River Basin. The groundwater regeneration was slow, the retention time was long, the seasonal variation was not obvious, and the δD value of surface water was higher in the abundance period than in the normal period and dry period. According to the δ18O and δD diagrams, the slope and intercept of surface water lines in the three periods were smaller than those of local precipitation lines, and surface water was affected by evaporative fractionation after receiving precipitation recharge. The δD values of surface water on the north bank of the Yellow River showed a trend of first increasing and then decreasing from upstream to downstream, while the δD values of surface water on the south bank of the Yellow River showed a trend of gradually decreasing from upstream to downstream. The recharge contribution of groundwater in surface water in the high-water period accounted for 2.9%, precipitation accounted for 97.1%, surface water accounted for 5.0%, atmospheric precipitation accounted for 95.0%, surface water accounted for 56.6%, and precipitation accounted for 43.4%, and the recharge contributions of precipitation and surface water to groundwater in the high water period were 47.6% and 52.4%, respectively. Those in the normal period were 30.7% and 69.3%, and those in the dry period were 37.8% and 62.2%, respectively. Atmospheric precipitation was the main replenishment source of surface water, showing that the replenishment ratio in the wet season was larger than that in the normal season and dry season, which was closely related to the total precipitation and its distribution in each period. Surface water was the main replenishment source of groundwater, showing that dry season &gt; normal season &gt; wet season.

Radiocarbon dating and isotopic paleoecology of Notiomastodon platensis (Mammalia: Proboscidea) from the late Pleistocene of Minas Gerais, Brazil

Proboscidea is a group of large mammals abundant in the fossil record and in Brazil it is represented by Notiomastodon platensis (Ameghino, 1888). To improve the understanding on its taxonomy, chronology, annual diet, and habitats paleoenvironmental aspects, we conducted a morphological description, absolute dating, and analysis of stable isotopes of carbon and oxygen (δ13C and δ18O) in Notiomastodon' remains from the northern (Norte de Minas) and western (Triângulo Mineiro) mesoregions of Minas Gerais State, Brazil. The material includes isolated teeth, mandibular portions, and postcranial bones at different levels of fragmentation, associated with at least eight adults and one juvenile. The only individual from Triângulo, found in Campina Verde municipality, was dated at 27,715–27,903 Cal yr BP. It presented a mixed diet based on C4 plants (piC4 = 90 %; δ13C = 0.5 ‰), which implies the occupation of an open environment, mostly pasture. The region was relatively humid (δ18O = 24.7 ‰), which is supported by the existence of humidity corridors in the Amazon region. A similar phytophysiognomy was inferred for the Norte de Minas region between at least 21,966–22,279 Cal yr BP and 18,944–19,157 Cal yr BP. However, one specimen showed a different δ13C value (piC3 = 0.87 %; δ13C = −10.2 ‰). This indicates it lived in a transitional environment between low-density forest and arboreal savannah. This likely occurred during a period that favored the expansion of trees and shrubs. The region underwent climate change, from relatively humid conditions (δ18O = 25.6 ± 0.2 ‰) to expressively dry (δ18O = 34.6 ‰) between the dated periods, a change corroborated by some palynological data. The multiannual paleoecological analysis, based on sequential sampling of three dentin layers of an incisor, indicated the relative stability of vegetation and climate despite fluctuations in hydrology. The perceived disassociation between vegetation dynamics and local hydrology corroborates the idea that factors other than precipitation may play a significant role in the environmental dynamics of the Cerrado biome.

A dual bivalve approach for interpreting past sea surface temperatures and seasonality from shell midden sites using oxygen isotope sclerochronology

Stable oxygen isotope (δ18O) analysis of archaeological shellfish remains combined with sclerochronology can be used to precisely reconstruct past sea surface temperature (pSST), season(s) of shellfish collection, and thus the season(s) of archaeological site occupation. Our study tests if δ18Oshell and sclerochronological analyses of marine bivalve species Leukoma staminea – with previously unassessed seasonality and pSST potential – can provide additional insights not captured by the better studied species, Saxidmous gigantea in British Columbia (BC, Canada). We analyzed live-collected L. staminea and S. gigantea shells from Sechelt, BC, and compared results to archaeological shell data from Powell River, BC, in the territory of the Tla'amin First Nation (1065 to 797 cal. B.P.). The seasonality of shellfish harvest differed between species, with S. gigantea preferentially collected in the spring, whereas L. staminea collected year-round. This highlights that sole-species seasonality studies may miss important variability harvesting strategies. Additionally, comparisons between instrumental (5.7 to 20.4 °C) and reconstructed SST from modern L. staminea δ18Oshell (5.6 to 18.4 °C) showed good agreement in annual range. Our results indicate that archaeological S. gigantea record a wider range of pSST (−1.6 to 22.9 °C) than archaeological L. staminea (5.8 to 25.9 °C), suggesting that S. gigantea may be a more sensitive palaeotemperature recorder. Further, we found that using the same reconstructed δ18Owater value for both species in pSST reconstruction caused an overestimation of temperature. Accordingly, we argue that it is critical to calibrate the equation with corresponding species-specific δ18Oshell values, regardless of both having aragonite mineral structures. Our study highlights the potential of L. staminea to broaden seasonality interpretations while clarifying that its use for pSST reconstruction may not capture the lower range of temperature.

Stable isotope and hydrogeological measurements: Implications for transit time and mixing ratio in a riparian system of the Danube River

Riverbank filtration has a very important role in the supply of drinking water globally. However, this water source is vulnerable, because rivers are easily contaminated. To assess its vulnerability, it is essential to understand the properties of the aquifer including the sources of the water and the transit time. Therefore, a comprehensive investigation of the Hungarian Danube River-riverbank system was conducted on two of its islands (Szentendre and Csepel). Water level, temperature and electrical conductivity were monitored in the wells located in the riverbank, and water samples were collected regularly from the wells and the river for stable hydrogen and oxygen isotope analyses over a year. It was found that the wells located at different distances from the Danube River have various responses to the hydrological changes occurring in the river. Transit time distributions (TTD) belonging to different production wells were determined by the lumped parameter method, based on the convolution integral. Differences in the TTDs of the wells are explained by their distance from the Danube River, spatial variations in the aquifer hydraulic properties and the varying pumping rates. Additionally, the estimated mixing ratio of different water sources (i.e., Danube River and background shallow groundwater infiltrated from precipitation) to the exploited water suggests that the contribution of precipitation is less than 20 %.Furthermore, the stable water isotope data of the Danube River in the Budapest area was measured from 1998 to 2021 was gathered and evaluated. It appears that the δ18O values of the Danube River at Budapest show systematically higher values than those from Vienna, indicating lowland water contribution and some evaporation effect.

Oxygen isotope dendrochronology allows dating of historical timbers across a wide geographical region.

We explore the applicability and geographic reach of two northwest European stable oxygen isotope (δ18O) chronologies for the precision dating of annually resolved δ18O series developed from late 15th-century oak (Quercus sp.) roof timbers from St. James’ Church in Bruges, Belgium. In doing so this study assesses ring-width dendrochronology and provenance analysis alongside oxygen isotope dendrochronology in Belgium and its surrounding regions.The δ18O-series of the historical timbers display a high internal coherence, allowing the construction of a mean isotope series (1325 to 1468 CE). Cross-dating against master chronologies for Central England, U.K. and Fontainebleau, France, provide reliable matches that surpass statistical thresholds and quality control measures, corroborating the dating results obtained from conventional ring-width dating.Oxygen stable isotope dendrochronology emerges as a valuable tool for precise dating of historical timber structures. This pilot study demonstrates the applicability of existing reference chronologies beyond their core regions and underscores its significance in cultural heritage studies. Despite the demanding nature of the technique in terms of time and expertise, the potential benefits warrant continued investment in expanding the temporal and geographic coverage of well-replicated oxygen isotope reference chronologies.

Stable isotope of Mesolithic remains of Pila wernei of the Nile area, Sudan: A tool for palaeoenvironment reconstruction

The article deals with stable isotopes of oxygen and carbon on current and archaeological semi-aquatic gastropod shell of the Pila wernei from Sudan and reports some new 14C analyses on archaeological Pila specimens. This, with the aim of obtaining new information on climatic and environmental changes in the al-Khiday area during the first phase of Holocene. The Pila shells come from a well-preserved shell midden present at al-Khiday and dated 8700-7000 cal yr BP. The area of al-Khiday was inhabited since at least 10 ka. Pila wernei species has never been studied in detail; this study demonstrates that the O and C isotope composition of aragonite shell is able to record the environmental and diet changes during the gastropod life. The comparison between the isotope data obtained on present-day and archaeological shells show a prevalence of C4 plants and higher rainfall during the Mesolithic. Two climatic fluctuations have been recognised: the first one indicating wetter conditions from 8650-8400 to 8500-8050 cal yr BP (decrease of the δ18O values), the second one pointing less wetter conditions from 8500-8050 to 7850-7600 cal yr BP (increase of δ18O values). Despite the difficulties in studying semi-aquatic gastropods due to their lifestyle habit, the identification of climatic fluctuations in the Early Holocene confirms the reliability of this proxy for climatic reconstructions. Despite the high number of isotopic analyses (1556) used in this work, they were not sufficient to mirror the fast climate changes characterising the studied period and finally obtain a detailed reconstruction for nearly the two millennia considered. Nonetheless, future projects may benefit greatly from unveiling the shell-environment relationship of the species.

Timing and origin of the Lomagundi-Jatuli Event: Insights from U[sbnd]Pb geochronology, C-O-Fe isotopes and REE compositions from the Jingshan Group, North China Craton

The Lomagundi-Jatuli Event (LJE) represents perhaps the largest and longest positive carbon isotope excursion of Earth history. However, the synchroneity, scale, and linkage of the LJE to Earth's early history of atmospheric oxygenation remain controversial. Strata of the Paleoproterozoic Jingshan Group of the North China Craton that preserve the isotopic record of the LJE excursion in marble layers and abundant graphite deposits provide an opportunity to elucidate the significance of the LJE. Carbon isotopic values (δ13CV-PDB) of the LJE based on analysis of 20 samples of the Lugezhuang Formation, lower Jingshan Group, range from −0.8 to +9.6 ‰ and display positive co-variance with stable oxygen isotope values (δ18OV-PDB). The positive carbon isotope excursion is constrained to 2140.6 ± 8.5 Ma (MSWD = 0.82, n = 25) based on magmatic zircon UPb geochronology of biotite granulite. Variation of facies-dependent carbon isotope values, the presence of graphite deposits of the Douya Formation, upper Jingshan Group, and the absence of a Ce anomaly in PAAS normalized REE patterns of marble samples suggest that the positive carbon isotope excursion is not linked to a marked increase of organic carbon burial and associated significant atmosphere oxygenation. Elevated concentrations of iron and PAAS-normalized middle REE enrichment of analyzed Jingshan Group marble samples point to anoxic and ferruginous oceanic conditions during accumulation of Jingshan Group carbonate. A positive Eu anomaly (average = 1.58), low La (average = 0.23), (Nd/Yb)N (average = 1.27), and Y/Ho (average = 36.6) anomalies, and negative iron isotope values (average δ56Fe = −0.12 ‰) are consistent with accumulation of Paleoproterozoic Jingshan Group carbonate in a restricted marine setting that was affected by high temperature hydrothermal fluids. Enrichment of the studied samples in heavy carbon isotope suggests elevated bio-productivity in the restricted, redox stratified marine setting in which Jingshan Group carbonate accumulated. Thus, it is likely that the positive stable carbon isotope excursion associated with Jingshan Group strata as well as other contemporaneous isotope excursions are local signals that are linked to a global perturbation of the carbon cycle.

Multistage selective diagenesis increasing poro-perm properties of Anisian sponge-microbial-coral patch reefs and adjacent facies in the Muschelkalk of Upper Silesia, Southern Poland

Carbonate rocks, particularly reefs and circum-reef facies, are significant reservoir rocks whose reservoir properties depend on their primary composition and diagenetic history. This paper reconstructs the influence of multistage selective diagenesis on the pore system evolution and porosity-permeability properties of the Anisian tropical reef system (Karchowice and Diplopora Beds) in the Muschelkalk of Upper Silesia, southern Poland, using field and slab observations, standard and cathodoluminescence petrography, bulk and SIMS carbon and oxygen stable isotope analyses, porosity-permeability plug study, and computer image analysis of macroporosity (>5 mm across). The reef system comprises two distinct levels of sponge-microbial(-coral) reef mounds surrounded by diverse bioclastic, peloidal, coated-grain, and micritic facies rich in Balanoglossites burrows. The strata experienced complex diagenetic alterations related to various fluids (marine, evaporitic, meteoric) and diagenetic environments (shallow substratal, burial, telogenetic), including (in chronological order): 1) early-marine precipitation of isopachous fibrous rims; 2) early dissolution during emersion; 3) brine-reflux dolomitization; 4) patchy silicification; 5) recrystallization; 6) burial calcite cementation by heated marine fluid; 7) deposition of vadose silt; 8) meteoric calcite cementation; 9) chemical compaction; 10) fracturing; and 11) final karstification, dedolomitization, FeO precipitation, and Liesegang ring formation by meteoric water during Cenozoic telogenesis. Many processes were selective and affected the same (more permeable) parts of the rocks. The strata exhibit porosities reaching 50% (combined plug porosity of 6–35% and macroporosity of up to 20%) and plug permeabilities of 0.07–70 mD, with the highest values occurring in the reefs and burrowed facies. The dominant late-stage telogenic dissolution pores originated from selective removal of dolomitized micrite within burrows and between sponge-microbial automicrite as well as dolomite crystals. The study illustrates the transition of the reef system from tight to porous due to multistage selective diagenesis and fluid flow, which enhanced subtle permeability differences between various types of micrite. This is the first case where four different fluids (dolomitizing, early dissolving, calcite-forming, and late dissolving) selectively migrated through the same rock parts at different times and modified them one after another.

Effects of different surface water flow frequencies on water use characteristics of Tamarix ramosissima in the hinterland of the Taklamakan Desert

Tamarix ramosissima is a dominant species in desert ecosystems and an ecological barrier species in arid areas, playing a crucial role in stabilizing dunes and preventing desertification. In this study, river water, groundwater, soil water, and T. ramosissima individual samples were collected from three sites in July and October 2023 at the Daliyaboyi Oasis located at the tail of the Kriya River in the hinterland of the Taklamakan Desert. The three sites are referred to as the center (SE), west (SW), and north (SN) sites within the Daliyaboyi Oasis, and each experienced different flood frequencies. The SE site experienced flooding in July and October, the SW site experienced flooding only in July, and the SN site experienced no flooding in July or October. The spatial and temporal variation in hydrogen and oxygen stable isotopes and line-conditional excess (lc-excess) in water and plant samples were analyzed, and the potential changes in water use of T. ramosissima were analyzed by the hydrogen and oxygen stable isotope and MixSIAR model. The findings indicated that the slope of SWL at the SE, SW, and SN sites was higher in July (6.77, 6.42, and 3.05, respectively) than in October (7.37, 3.30, and 2.14, respectively). The lc-excess value of the SE site did not exhibit seasonal changes; only the lc-excess values of soil water in SW and SN sites showed seasonal changes. MixSIAR results indicated frequent flood events at the SE site, with relatively constant proportions of water source utilization by T. ramosissima in July and October. In addition, shallow soil water (0–60 cm) and deeper soil water (60–80 cm) were the main water sources of T. ramosissima at SE. The SN site was slightly influenced by surface water, resulting in statistically non-significant changes in the water source utilization by T. ramosissima. Indeed, deep soil water (60–200 cm) and groundwater were the sources of water for T. ramosissima at this site. In contrast with October, the SW site experienced flood events in July, resulting in the utilization of water by T. ramosissima from the shallow soil (0–60 cm) and deep soil (60–280 cm) in July and October, respectively. Different surface water flow patterns led to different water use characteristics of T. ramosissima, which further demonstrated that T. ramosissima has high resilience and ecological plasticity. This work provides a useful reference for the implementation of effective ecological water transport measures in the Daliyaboyi Oasis and similar arid habitats.

Robinia pseudoacacia Quickly Adjusts Its Water Uptake after Rainfall in Seasonally Dry Regions

Precipitation is a key factor affecting plant growth and development in seasonally arid regions. However, most of the traditional hydrological methods mainly select typically sunny days for sampling, and the immediate water absorption strategy of plants during and after rainfall is still unclear. This study used stable hydrogen and oxygen isotope technology to study the soil moisture absorption rates of Robinia pseudoacacia and the soil moisture content at different soil layers at different sampling times (0, 6, 12, 18 and 24 h) after rainfall. The results showed that the moisture content of the shallow soil layer decreased, while that of the deep soil layer increased over time after rainfall. R. pseudoacacia mainly utilized water from the 0–20 and 20–40 cm soil layers at 6 h after rainfall, which accounted for 36.52% and 22.25% of the rainfall, respectively. At 24 h, the 40–60, 60–80 and 80–100 cm soil layers contributed 25.25%, 18.44% and 24.45% of the water content, respectively. The shallow soil layer retained more rainfall within 6 h after rain fell, and the water retention ratio of the medium–shallow soil layer (0–60 cm) increased to 48.4%, retaining more water at 14–20 h. At 12 h, the medium–shallow soil layer (0–60 cm), runoff and groundwater constituted 37.1%, 14.4% and 15.7% of the precipitation, respectively, and rainfall retained in the deep soil layer (60–100 cm) accounted for 32.8%. In summary, R. pseudoacacia tends to use a large amount of shallow soil water in seasonally arid regions when precipitation supplements the surface soil moisture content and it utilizes deep soil water when the rainfall infiltrates and recharges the deep soil layer. Since R. pseudoacacia is sensitive to precipitation, it can quickly adjust its water absorption depth range during the short-term rainfall period to absorb as much precipitation as possible.

Hydrochemical Characterisation of the Basement Aquifer with a Focus on the Origin of Nitrate in the Highly Urbanised Niamey Region, SW of Niger

This study investigated the basement aquifer beneath the urbanised city of Niamey and the agricultural fields of Kollo, SW of Niger. During the observation period spanning from 2021 to 2023, groundwater and surface water samples were collected for analysis of major ions and the stable isotopes oxygen-18 and deuterium (δ18O and δ2H) of water. To trace the origin of high nitrate concentrations (NO3−) found in several observation and drinking water wells in both areas, δ15N and δ18O isotope values of NO3− were analysed in groundwater and eluted soil samples. The observed hydrochemical patterns mainly reflect the heterogeneity of the weathered fringe of the basement aquifer. Decreasing concentrations of NO3− and δ18O and δ2H values were observed in relation to the distance of the Niger River and increasing thickness of the clay layer on the surface. The wells close to the river in Niamey show a dilution effect during the flood season, and the NO3− concentrations displayed a continuous increasing trend. The δ15N-NO3 and δ18O-NO3 values confirmed that septic tank water is spreading in the region of Niamey and that manure originating from livestock in Kollo is the main source of NO3−. The patterns of δ15N in the soil samples coincide with those of cattle’s manure spread in both areas. The shallow wells show significantly higher values of electric conductivity and NO3− concentrations compared to the deeper wells, which clearly indicates the influence of shallow septic tanks on water quality.

Mechanisms of secondary carbonate precipitation on felsic, intermediate and mafic igneous rocks: a case study for NW Scotland

Silicate weathering is a natural regulator of atmospheric carbon dioxide (CO 2 ), where the majority of carbonate is stored in the oceans. In some instances, carbonates may form via bedrock weathering in terrestrial landscapes, but this is commonly noted in ultramafic rock owing to its desirable mineralogy. In NW Scotland, carbonate minerals surround felsic, intermediate and mafic igneous bedrock. Their abundance suggests that these rocks could potentially be targeted for carbonation, given the absence of other known cation sources nearby. We present geochemical and mineralogical data for bedrock samples and mineralogy and stable carbon and oxygen isotope data for the carbonate samples. Whole-rock geochemistry demonstrates that major abundances of CaO and MgO are present in the bedrock samples and would be sourced from plagioclase and pyroxene, which are target minerals for CO 2 mineralization. The stable carbon and oxygen isotope data demonstrate that there are probably mixed carbon sources (atmospheric and organic), and other environmental factors including temperature, CO 2 degassing or evaporation and nearby waters influence the isotopic composition. Results suggest that rocks traditionally overlooked in CO 2 mineralization studies have the potential to serve as a feedstock for carbonation, given the abundance of secondary carbonates found in NW Scotland.