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Nitrogen, because of its abundance and variety of carrier phases, is a unique tracer of physico-chemical processes occurring throughout star and planet formations. The refractory organic matter is commonly considered as the main carrier of nitrogen in the most primitive objects of our Solar System. However, nitrogen in the form of ammonium (NH 4 +) was observed in the Ivuna-type carbonaceous (CI) chondrites Alais in 1834, and Orgueil just after its fall in 1864, as well as more recently on Ceres, comet 67P/Churyumov-Gerasimenko, and possibly on some asteroids. In the present study, we have measured the nitrogen content and isotopic composition in various nitrogen-bearing phases of several samples of the Orgueil meteorite, with different degrees of terrestrial weathering. Water-soluble NH 4 + is present in Orgueil at a mean concentration of 0.07 ± 0.01 wt%, with a mean isotopic composition of δ 15N = +72 ± 9 ‰ (14N/15N = 254 ± 2), confirming its extra-terrestrial origin. In the most terrestrially altered sample of Orgueil that we analysed, the isotopic composition is δ 15N = +50 ± 12 ‰ (14N/15N = 259 ± 3). NH 4 + is in species that are thermally stable up to 383 K, possibly ammonium inorganic/organic salts and ammoniated phyllosilicates. We also show that the nitrogen in Orgueil is distributed among the insoluble organic matter (IOM) (35 ± 5 %), ammonium (27 ± 5 %), and other minor water-soluble species (e.g., nitrate, amines etc.: < 6 %). The remaining nitrogen (34 ± 14 %) is mainly in an unidentified organic matter (UOM), which may be IOM lost during its extraction and/or acid hydrolysable functional groups bounded to the IOM and/or organic nitrogen trapped within minerals. The three main carriers of nitrogen in Orgueil have δ 15N (and 14N/15N) values of +32 ± 1 ‰ (264 ± 0.3) for IOM, +39 ± 16 ‰ (262 ± 4) for UOM, and +72 ± 9 ‰ (254 ± 2) for NH 4 +. Although IOM and NH 4 + have significantly different δ 15N, we cannot exclude that these phases could be compositionally related because IOM is heterogeneous in 15N. Ammonium could have been produced via heating and/or aqueous alteration processes of organic matter in the CI parent body. Alternatively, or additionnally, ammonium could be a tracer of the accretion and/or later deposit of NH 3 ice, NH 3 hydrates, and/or NH 4 + salts on the CI parent body. As shown by previous studies, Ryugu grains sampled by the Hayabusa2 mission (JAXA) have heterogeneous compositions at the millimeter scale, with nitrogen concentrations and δ 15N similar or lower than Orgueil, possibly because of different parent body processing. The present study suggests that the lack or loss of 15N-rich NH 4 + in some Ryugu grains may explain some of these differences with Orgueil. [ABSTRACT FROM AUTHOR]

Zwei Diterpensynthasen aus dem Bakterium Chitinophaga pinensis wurden charakterisiert. Das erste Enzym produzierte hauptsächlich das umgelagerte Diterpen Palmatol, eine aus Oktokorallen bekannte Verbindung, während das zweite Enzym das neue korallenartige Eunicellan Chitinol herstellte. Die Mechanismen beider Enzyme wurden durch Isotopenmarkierungsexperimente, DFT‐Berechnungen und mit einem Substratanalogon, das eine gesättigte Doppelbindung enthält, eingehend untersucht. Letzteres führte zur Bildung von Abbruchprodukten führte, die zusätzliche Einblicke in die Natur der Intermediate der Cyclisierungskaskade lieferten. Die Bildung korallenartiger Diterpene wirft interessante Fragen zu den Funktionen dieser Verbindungen in so unterschiedlichen Organismen wie Bakterien und Korallen auf. [ABSTRACT FROM AUTHOR]

Isotopic labeling is an attractive modality that has been widely used in many aspects of chemistry, the life sciences, and medical research; especially deuterated drugs and radioactive molecules have been used in the diagnosis and treatment of cancer and neurodegenerative diseases. The widespread application and rapid development of isotopically labeled molecules has led to an increased demand for new isotopic labeling chemical methods to synthesize highly specific molecules bearing defined nuclides. Multicomponent reactions (MCRs) are modular build-up approaches for the rapid generation of complex molecules often containing biologically relevant scaffold structures. There is great potential to use MCRs to construct isotopically labeled molecules because assembly speed and reaction diversity are key advantages of MCR. In this review, we provide an overview of the recent literature on this topic that can provide insight into the application of MCRs in the field of isotopic labeling. [ABSTRACT FROM AUTHOR]

Objectives: While some metals have been reported as carcinogens or potential carcinogens, only few modern-standard datasets including a large number of elements are available. The present analysis established a first trace elements spectrum by relating the concentration of metals and trace elements in the serum of sarcoma patients with survival data. Methods: Patients with sarcoma and controls were retrospectively selected from the International Sarcoma Kindred Study database (ISKS). As part of the ISKS study, blood samples were prospectively collected at the Leon Bérard Cancer Center from February 2012 to July 2019. Stable specimens and copper isotopes (65Cu/63Cu) were analyzed using Triple Quadrupole Inductively Coupled Plasma Mass Spectrometer (ICP-MS) and the Multicollector MC-ICP-MS Nu Plasma HR 500. Wilcoxon rank sum test, log-rank test, and multivariate Cox regression models were used for statistics. Results: In total, 151 patients and 59 healthy controls were included. At the time of blood sample collection, 62% of patients had locally advanced or metastatic disease. Copper (Cu), copper/zinc (Cu/Zn) and potassium/rubidium (K/Rb) ratio were significantly higher in patients compared to controls and were also significantly higher in patients with advanced compared to early-stage sarcoma. Whereas S and Se were significantly correlated in patients, no correlation was observed in controls. Importantly, levels of K, Rb, Se, Fe, P, Si, S, δ65Cu, Cu, S/Se and Cu/Zn ratio were independently associated with overall survival. Conclusions: These results depict the metallomic spectrum in sarcoma and highlight substantial variation associated with survival, enhancing our understanding of sarcoma's biology. [ABSTRACT FROM AUTHOR]

This study provided insight into the origin, age, and formation conditions of the Late Oligocene sulfate lithofacies that were deposited in the SW Erzincan Basin throughout a broad region. Primary, secondary gypsum, and anhydrite make up the majority of sulfates, which are interbedded with clastic, volcanic, volcaniclastic and carbonated rocks. During the early-late diagenetic processes, primary gypsum changes into secondary gypsum along with primary anhydrite that is growing within the host-sediment. In the lithofacies, sedimentary structures created by tectonism and diagenesis are commonly found. The distribution of element concentrations shows that continental detrital input has a significant impact. Fe- and Mg-rich clays imply alkaline and hot-humid environmental conditions in the basin. The negative trend relationship of CaO with MgO refers to carbonation in the environment, while Sr, Ba, U, Mo, Ni, Cu and Zn values and Co, Ni/Co (0.98), Co/Zn (11.3), Cu/Zn (1.39) ratios and the high positive correlation of Cu with Al2O3 (r = +0.72) indicate the dominance of biologic factor, high salinity and reducing conditions in sulfates. The presence and values of Fe–Mn-rich alteration zones detected by field, mineralogical and geochemical studies within the gypsum revealed the hydrothermal solution activity in the region. 87Sr/86Sr, 18O/16O, 34S/32S and δ13C isotope data are consistent with Late Oligocene marine sulfates and suggest occasional mixing of freshwater. In addition, the origin and age data revealed by this study; It contributed to the paleogeographic evolution of the northern branch of Neotethys (Inner Tauride Ocean), which extends along the Central and northern-central Anatolia and Eastern Anatolia basins line, which includes Paleogene evaporitic deposits in Turkey, where the study area is located. Accordingly, it is obvious that the Neotethys, which extends along the basins from west to east, is quite shallow (lagoonal and coastal sabkha, etc.) and started to close further east during the Middle-Late Miocene (Erzurum-Pasinler- Horasan, Erzurum-Hınıs-Tekman, Iğdır-Tuzluca lacustrine basins, etc.). [ABSTRACT FROM AUTHOR]

[Display omitted] • First multi-proxy chronostratigraphy of lower Cambrian Byrd Group. • Biostratigraphy demonstrates Cambrian Stages 3–4 age, supported by new ID-TIMS date. • MICE and Sinsk δ13C chemostratigraphic events in upper Shackleton Limestone. Antarctica and Australia were sutured together at the equator during the major pulse of animal biodiversification associated with the Cambrian radiation. However, the lack of detailed systematic chemostratigraphic and biostratigraphic sampling of lower Cambrian sedimentary successions from Antarctica has significantly impeded precise age determination and correlation with Cambrian strata on other palaeocontinents. This study is the first to present integrated, simultaneously sampled biostratigraphic and chemostratigraphic (δ13C isotopes) data from the same measured stratigraphic sections through the lower Cambrian Byrd Group in the Transantarctic Mountains. Shelly fossil assemblages (brachiopods, tommotiids, molluscs, bradoriids, trilobites) from the Holyoake Range and Churchill Mountains facilitate direct correlation with the Dailyatia odyssei Zone of South Australia (Cambrian Stages 3–4), and trilobites provide strong correlation between the Starshot Formation and the Cymbric Vale Formation in western New South Wales. A new ID-TIMS radiometric date of 514.96 ± 0.16 Ma from a tuff in the lower Cymbric Vale Formation is similar to dates from tuff beds in the Third Plain Creek Member of the Mernmerna Formation in the Flinders Ranges, providing an important absolute-age tie point between these lower Cambrian successions. Chemostratigraphic data from the upper Shackleton Limestone in the Holyoake Range capture a negative δ13C excursion that can be correlated to negative values within the multi-peaked MICE (cycles V–VIII in Siberia). Integrated faunal and chemostratigraphic data indicate a Cambrian Stages 3–4 age, giving robust chronostratigraphic context for the upper Shackleton Limestone–Holyoake Formation–Starshot Formation succession for the first time, permitting reconstruction of the depositional history of the lower Cambrian of Antarctica and global correlation of Byrd Group strata. [ABSTRACT FROM AUTHOR]

ABSTRACT Studying initial geothermal fluids and tectonic active zones is crucial for exploiting intermediate high‐temperature geothermal resources. This study aims to investigate the genesis, circulation and environmental implications of geothermal water in the Riduo–Cuona Rift (RCR) of the eastern Tibetan Plateau. By integrating hydrochemical analysis, stable isotope geochemistry (δ2H, δ18O and 87Sr/86Sr), and noble gas isotope characteristics, the research seeks to develop comprehensive geothermal circulation models in the RCR. (M1) The spatial distribution of geothermal waters near the molten magmatic domes indicated 87Sr/86Sr ranges consistent with those of the rock, respectively. The high Ca, Mg ‘hardness’ spring waters were attributed to strata surrounding the dome resulting from the last leaching, as confirmed by the estimated higher hydraulic head, mainly located in ‘immature water.’ (M2) The spatial distribution of geothermal waters corresponding to an orogenic belt revealed HCO3·SO4–Na as the dominant hydrochemical facies in the northern RCR. Research suggests that springs exhibit greater circulation depths and that spring solute SO4 is related to the Gangdise magmatic arc leaching. (M3) However, the active tectonic zone's springs 87Sr/86Sr (0.705763–0.709754) indicated evaporite characteristics. The thermal reservoir temperature in this structural junction zone is the highest (256.75°C–287.03°C). The high trace alkali element concentrations, particularly of B, F and As, exceeded the WHO guideline; the drainage system analysis indicates regional nonnegligible environmental risks in the Gudui. Establishing these models can clarify the relationships between geothermal fluids, tectonic structures and regional faults, providing insights into geothermal resource potential, environmental risks and possible strategies for sustainable resource exploitation in the region. [ABSTRACT FROM AUTHOR]

In order to explore the hydrochemical characteristics and evolution process of groundwater at different depths (5-600 m) in the Yinchuan Plain, a systematic analysis was conducted on the hydrochemical and isotopic characteristics of groundwater at 9 different depths in the study area by using groundwater level dynamics, Person correlation analysis, saturation index, and hydrochemical methods (Piper plot, Gibbs plot and ion ratio coefficient). Besides, the tritium and 14C dating methods were used to estimate the ages of shallow (5-30 m) and deep groundwater (150-600 m). The results indicate that the chemical types of shallow groundwater in the study area are CI SO4-Na Mg or SO4. CI HCO3. Na Mg, which are mainly affected by evaporation and fractional crystallization. Deep groundwater in 150-300 m and 400-600 m is HCO3, CO3-Na Mg or HCO3-Na Mg, which are controlled by rock weathering. Isotopes indicate that shallow groundwater is significantly recharged by irrigation water, with groundwater ages ranging from 9 a to>68 a. Deep groundwater in 150-600 m originated from the western mountainous areas, with ages ranging from 7 325 a to 25 554 a. The ion ratio coefficient method and saturation index indicate that ions in groundwater mainly comes from weathering and dissolution of carbonate, evaporite, and silicate rocks. Cation exchange also affects the changes in chemical components in groundwater. [ABSTRACT FROM AUTHOR]

Few studies have examined the N kinetics of individual feeds with stable isotope tracing. We hypothesized that N partitioning to milk and excreta pools as well as the rates of the processes that drive this partitioning would differ for alfalfa silage, corn silage, corn grain, and soybean meal. Feed ingredients were endogenously labeled with 15N and included in 4 diets to create treatments with the same dietary composition and different labeled feed. Diets were fed to 12 late-lactation dairy cows for 4 d (96 h) and feces, urine, and milk collection proceeded during the 4 d of 15N enrichment and for 3 d (80 h) after cessation of label feeding. Nonlinear models of 15N enrichment and decay were fit to milk (MN), urine (UN), and fecal N (FN) in R with the nlme package, and feed-specific parameter estimates were compared. The estimated proportions of feed N that were excreted in feces supported our understanding that N from soybean meal and corn grain is more digestible than N from alfalfa and corn silage. Estimates for the N partitioning between milk and urine from the 2 concentrate feeds (soybean meal and corn grain) indicated that UN/MN ratios were less than or equal to 1:1, indicating either more or equal nitrogen partitioning to milk compared with urine. It is important to maintain factual accuracy in representing the results rather than implying a desired outcome unsupported by the data. In contrast, UN/MN ratios for forage feeds (corn and alfalfa silage) were >1:1, indicating more N partitioning to urine than milk. The modeled proportion of total FN that originated from feed N was 82.2%, which is in line with previous research using a similar 15N measurement timeframe. However, the proportion of urinary and MN originating from feed N was much lower (60.5% for urine, 57.9% for milk), suggesting that approximately 40% of urinary and MN directly originate from body N sources related to protein turnover. The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. [Display omitted] [ABSTRACT FROM AUTHOR]

Introduction: Tropical cloud forest ecosystems are expected to face reduced water inputs due to climatic changes. Methods: Here, we study the ecophysiological responses of trees and epiphytes within in an Asian cloud forest to investigate the contributions of rainfall, fog, and soil to leaf water in 60 tree and 30 vascular epiphyte species. We measured multiple functional traits, and δ² H, and δ18O isotope ratios for leaf water, soil water, rainfall, and fog in the wettest (July) and driest (February) months. Using a Bayesian stable isotope mixing model, we quantified the relative contributions of soil water, fog, and rainfall to leaf water. Results and discussion: Rainfall contributes almost all the leaf water of the epiphytes in July, whereas fog is the major source in February. Epiphytes cannot tap xylem water from host trees, and hence depended on fog water when rainfall was low. Most of leaf water was absorbed from soil water in July, while fog was an important source for leaf water in February despite the soil moisture content value was high. In February, lower temperatures, along with reduced photosynthesis and transpiration rates, likely contributed to decreased soil water uptake, while maintaining higher soil moisture levels despite the limited rainfall. These contrasting contributions of different water sources to leaf water under low and high rainfall and for different plant groups outline the communityl-evel ecophysiological responses to changes in rainfall. While direct measurements of water flux, particularly in roots and stems, are needed, our results provide valuable insights on tropical cloud forest hydrology under scenarios of decreased fog immersion due to climatic changes. [ABSTRACT FROM AUTHOR]

Salt marshes are one of the three blue carbon ecosystems recognized by the Intergovernmental Panel on Climate Change (IPCC). However, coastal salt marshes in China are facing the risk of degradation. To reveal the status of the salt marsh wetland ecosystem in Liaohe Estuary, an Ecopath model composed of 14 functional groups was constructed based on the 2019 ecological survey data. A comprehensive analysis of the system’s food web structure, energy flow processes, and overall ecosystem characteristics was conducted. The results show that the energy flow in the Liaohe Estuary salt marsh wetland ecosystem is mainly distributed in three integrated trophic levels. The utilization rates of trophic levels II and III are low, easily causing blockages in the lower trophic levels of the ecosystem’s energy flow. The total system throughput of the Liaohe Estuary salt marsh wetland ecosystem is 49,099.039 t·km²·a−1 ;. The system connectivity index and the system omnivory index are 0.207 and 0.109, respectively. Compared with other wetland systems, the ecosystem has a larger scale, but the overall ecosystem characteristic index reveals lower stability and complexity of the Liaohe Estuary salt marsh wetland system. [ABSTRACT FROM AUTHOR]

Die Chlororaphene A und B sind strukturell einzigartige nichtkanonische C17‐Sesquiterpenoide aus Pseudomonas chlororaphis, die von zwei SAM‐abhängigen Methyltransferasen und einer Typ‐I‐Terpensynthase hergestellt werden. Diese Studie befasst sich in Isotopenmarkierungsexperimenten und DFT‐Berechnungen mit dem Mechanismus ihrer Entstehung. Die Ergebnisse zeigen eine erstaunliche Komplexität der Verteilung der Markierungen innerhalb eines Cyclopentan‐Kerns, der mit zwei acyclischen Fragmenten in Chlororaphen A und B in umgekehrter Weise verbunden ist. Darüber hinaus wurde die Aufnahme von bis zu 14 Deuteriumatomen aus D2O beobachtet. Diese Ergebnisse lassen sich durch eine wiederholte mehrstufige Umlagerungssequenz im Spätstadium erklären. Die absoluten Konfigurationen der Chlororaphene und ihrer biosynthetischen Zwischenprodukte wurden in stereoselektiven Markierungsexperimenten aufgeklärt. [ABSTRACT FROM AUTHOR]

We study structurable algebras and their associated Freudenthal triple systems over commutative rings. The automorphism groups of these triple systems are exceptional groups of type E 7 , and we realize groups of type E 6 as centralizers. When 6 is invertible, we further give a geometric description of homogeneous spaces of type E 7 / E 6 , and show that they parametrize principal isotopes of Brown algebras. As opposed to the situation over fields, we show that such isotopes may be non-isomorphic. [ABSTRACT FROM AUTHOR]

Stone circles of the Wielbark culture, such as those found in Grzybnica, have long fascinated researchers, who debate their function and significance. The aim of the presented study is to determine the origins and subsistence strategies of the population buried near the stone circles in Grzybnica, which may help highlight the role of these sites within Wielbark communities. For analysis, human remains from the cemetery in Grzybnica, West Pomeranian Voivodeship, Poland, were utilized. Radiocarbon dating of five samples, stable isotope analysis of carbon and nitrogen in two samples, and strontium isotope analysis in 20 cremated human remains and 12 plant samples were conducted. Radiocarbon dating confirmed the earlier dating of the site to the period between approximately 80 and 260 CE. Dietary studies indicated that the individuals buried here regularly consumed millet (mean δ13C = –17.8) and animal protein (mean δ15N = 9.5). This diet corresponds with the variability described for the Wielbark culture site in Rogowo. The strontium isotope analysis revealed significant variation between the river valley (0.7157–0.7264) and the adjacent upland (0.7109–0.7138). The isotopic values in humans were homogeneous, ranging from 0.7113 to 0.7130, indicating no outliers that might suggest the presence of migrants. The variability observed in humans corresponds with the values observed on the upland. The results suggest that the group of individuals buried in Grzybnica was a small community that sourced their food from the upland. It is possible that this community was involved in the care of the stone circles, and the circles themselves may have been places of gatherings for local communities. However, it should be noted that only about 20 % of the graves found at the site were analyzed. The lack of migrants may be due to the low mobility of this group or methodological limitations related to the post-glacial nature of the geological substrate. Alternatively, it could also be due to the limitations associated with studying cremated remains, which allow for the reconstruction of events from only about 10 years prior. [ABSTRACT FROM AUTHOR]

The δ7Li of marine carbonates has been interpreted as an archive of the evolution of seawater δ7Li, and therefore continental weathering, through geological time. However, little is known about the incorporation of Li into calcium carbonate minerals and, consequently, the controls on Li partitioning (D Li) and isotopic fractionation (Δ7Li solid-fluid) associated with Li incorporation. Crucially, we lack a fundamental understanding of how Li partitioning and Δ7Li solid-fluid change in response to the chemical and physical conditions of crystal formation. Here, we present D Li and Δ7Li solid-fluid data from a series of inorganic calcite precipitation experiments where temperature, and solution pH and dissolved inorganic carbon (DIC) were independently varied. We find D Li values in the range 0.8–1.5 × 10−3, which show no relationship with temperature, a strong positive correlation with pH, and a weak positive correlation with DIC. At face value, these patterns are inconsistent with the results of previous precipitation studies. However, the correlations with pH and DIC are consistent with a strong precipitation rate control on D Li that aligns well with previous data, with a likely secondary influence from the incorporation of Li-HCO 3 0 ion pairs from solution. We find Δ7Li solid-fluid values in the range −6 to −2 ‰, which show no relationship with temperature or pH, and a weak positive correlation with DIC and crystal precipitation rate. These results do not agree with previously published data. Considered alongside previously published data, we observe no consistent relationship between Δ7Li solid-fluid and any reported physical or chemical experimental parameter, highlighting the need for substantial further work to determine whether systematic controls on Li isotopic fractionation exist in carbonate minerals, and whether they may be environmentally significant. [ABSTRACT FROM AUTHOR]

In two forensic cases, radiocarbon (14C) bomb-pulse datings of human bones have been performed and analyzed using detailed models to correct for collagen-carbon turnover rates and reservoir effects. The modeled corrections are discussed and the resulting 14C ages compared to later information on actual time of birth and death of the individuals. Simple time lag corrections of bone dates are found to be inadequate, whereas modeling based on age dependent turnover rates and bomb-pulse levels through life combined with substantial reservoir age corrections can explain the observed 14C results. [ABSTRACT FROM AUTHOR]

Conjugated ladder polymers (cLPs) represent an intriguing class of macromolecules, characterized by their multi‐stranded structure, with continuous fused π‐conjugated rings forming the backbone. Isotope substitution, such as deuteration and carbon‐13 labeling, offers unique approaches to address the significant challenges associated with elucidating the structure and solution phase dynamics of these polymers. For instance, selective deuteration can highlight parts of the polymer by controlling the scattering length density of specific molecular sections, thereby enhancing the contrast for neutron scattering experiments. In this context, deuteration of side‐chains in cLPs represents a promising approach to uncover the elusive polymer physics properties of their backbone. The synthesis of two distinct types of cLPs with perdeuterated side‐chains are reported here. During the synthesis, 13C isotope labeling was also employed to verify the low levels of defects in the synthesized polymers. Demonstrating these synthetic successes lays the foundation for rigorous characterization of the defects, conformation, and dynamics of cLPs. [ABSTRACT FROM AUTHOR]

The saturation of natural gas hydrates is a key parameter for characterizing hydrate reservoirs, estimating hydrate reserves, and developing hydrate as an energy resource. Several methods have been proposed to estimate hydrate saturation, although most of these studies rely on logging and seismic data. However, the methods for estimating hydrate saturation from recovered core sediments have not been thoroughly reviewed, which hinders a deeper understanding, proper application, and the use of these experimental data to integrate geophysical and numerical model results with the actual geological conditions. In this paper, the methods widely used for estimating natural gas hydrate saturation from core sediments, including those based on pore water chemistry (Cl− concentration, δD, and δ18O values), gas volumetric analysis, and temperature anomaly, have been summarized in terms of the principle, estimation strategy, and issues to be considered of each method. The applicability, advantages and disadvantages, and scope of application of each method are also compared and discussed. All methods for estimating gas hydrate saturation have certain limitations. A comprehensive application of results from multiple methods could lead to a better understanding of the amount of gas hydrate in sediments, although the chlorinity of pore water is the most commonly used method of estimation. [ABSTRACT FROM AUTHOR]

Makassar coastal area has experienced rapid development and has shown various negative impacts from groundwater overexploitation, such as seawater intrusion. This study aimed to assess seawater intrusion based on geochemical and isotopic data in the Makassar coastal area. The research was carried out by field measurement and taking the groundwater samples to the laboratory for geochemical and isotope tests. Geochemical analysis of seawater intrusion was based on TDS, EC, Cl-, Simpson ratio, Ca enrichment, BEX, Na/Cl ratio, and the piper trilinear diagram typer of water. Isotope analysis of seawater intrusion is based on comparing oxygen (d18O) and deuterium (dD) isotopic data from groundwater samples with seawater, river, and rainwater. The results showed that some areas near the sea indicated seawater intrusion in both the semi-unconfined and unconfined aquifers. The indicated seawater intrusion spread in the north Tallo, Mamajang, and Tamalate subdistricts. [ABSTRACT FROM AUTHOR]

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Makassar coastal area has experienced rapid development and has shown various negative impacts from groundwater overexploitation, such as seawater intrusion. This study aimed to assess seawater intrusion based on geochemical and isotopic data in the Makassar coastal area. The research was carried out by field measurement and taking the groundwater samples to the laboratory for geochemical and isotope tests. Geochemical analysis of seawater intrusion was based on TDS, EC, Cl-, Simpson ratio, Ca enrichment, BEX, Na/Cl ratio, and the piper trilinear diagram typer of water. Isotope analysis of seawater intrusion is based on comparing oxygen and deuterium isotopic data from groundwater samples with seawater, river, and rainwater. The results showed that some areas near the sea indicated seawater intrusion in both the semi-unconfined and unconfined aquifers. The indicated seawater intrusion spread in the north Tallo, Mamajang, and Tamalate subdistricts.

Understanding the hydrochemical evolution of surface water and groundwater is crucial for protecting regional ecological environments. Currently, there are few quantitative studies on the relative contributions of different processes to salinity enrichment of water bodies. In this study, sixty-seven water samples were collected for chemical, and isotopic analysis, along with simulation calculations. The results reveal distinct hydrochemical types of river water, phreatic water, lake water and hot spring water in the investigated area are Ca-Mg-HCO3, Na-Ca-HCO3, Na-SO4-HCO3 and Na-HCO3, respectively. Average temperature and depth of geothermal water storage are 196℃ and 1338 m, respectively. Average arsenic (As) content in hot spring water (298 μg/L) higher than that in lake water (39.2 μg/L), river water (9.59 μg/L) and phreatic water (4.02 μg/L). The ∑REEs content of river water in the study area is much higher than that of phreatic water and lake water. Result of δD and δ18O indicate that atmospheric precipitation is the source of recharge for all water bodies in the study area. Quantitative calculations indicate that evapo-concentration significantly enriches lake water salinity, contributing on average 90% of its salt content. In contrast, mineral dissolution contributes predominantly to the salinity of hot spring water (90.7%), phreatic water (65.8%), and river water (45.2%). Evapo-concentration emerges as the dominant mechanism for lake water salinity, while carbonate mineral dissolution primarily affects river water. Phreatic water and hot spring water are mainly controlled by the weathering and dissolution of silicate. The results can provide a theoretical basis for the study of the formation mechanism of water salinity in other regions with similar geological environment in the world. [ABSTRACT FROM AUTHOR]

The high levels of nitrate (NO3−) in the surface water have contributed to eutrophication and other eco-environmental damages worldwide. Although the excessive NO3− concentrations in rivers were often attributed to anthropogenic activities, some undisturbed or slightly disturbed rivers also had high NO3− levels. This study utilized multi-pronged approaches (i.e., river natural abundance isotopes, 15N-labeling techniques, and qPCR) to provide a comprehensive explanation of the reason for the high NO3− levels in a river draining forest-dominated terrene. The river natural abundance isotopes (δ15N/δ18O-NO3−) indicated that the soil source (i.e., soil organic nitrogen-SON and chemical fertilizer-CF) were the primary contributors to the NO3−, and the NO3− removal was probably prevalent in the basin scale. The 15N-labeling techniques quantitatively showed that denitrification and anammox were stronger than nitrification in the soils and sediments. Structural equation models suggested that nitrification in the soils was regulated by NH4+-N contents, which, in turn, were closely related to fertilization in spring. Denitrification and anammox were largely controlled by elevation and functional gene abundances (i.e., nirK and hzsB, respectively). The hydrological isotopes (i.e., δD/δ18O-H2O) indicated that the transport of NO3− from soil to the river was related to the intensity of runoff leaching to the soil, In contrast, the riverine NH4+ was largely from point sources; thus, increasing runoff led to a dilution effect. This study clearly showed that soil biogeochemistry and hydrological condition of a river basin jointly shaped the high NO3− levels in the almost undisturbed river. [ABSTRACT FROM AUTHOR]

Mass spectrometry (MS) is a versatile analytical tool used in various fields such as biochemistry, pharmacology, omics, and clinical analysis for determining and quantifying compounds based on their molecular mass and structure through the mass-to-charge ratio. While MS offers high specificity and selectivity, it encounters challenges including matrix effects, in-source fragmentation, and other interferences caused by natural isotopic abundance, as well as isomeric and isobaric compounds. These challenges can impede accurate qualitative and quantitative analysis. Visual aids such as graphical illustrations can help elucidate the chemical differences and similarities among isotopes, isomers, and isobaric compounds.

Die Diterpensynthase AfAS wurde aus Aspergillus fumigatiaffinis identifiziert. Ihre Aminosäuresequenz und – einem Strukturmodell zufolge – die Architektur des aktiven Zentrums sind denen der Fusicocca‐2,10(14)‐dien‐Synthase PaFS sehr ähnlich, AfAS produziert jedoch ein strukturell viel komplexeres Diterpen mit einem neuartigen 6–5–5–5 tetracyclischen Gerüst namens Asperfumen. Der Cyclisierungsmechanismus von AfAS wurde durch Isotopenmarkierungsexperimente und DFT‐Rechnungen aufgeklärt. Die Reaktionskaskade verläuft in ihren ersten Schritten über ähnliche Intermediate wie die PaFS‐Kaskade, divergiert dann aber durch einen ungewöhnlichen vicinalen Deprotonierungs‐Reprotonierungsprozess, der eine Skelettumlagerung am Startpunkt der Stufen auslöst, die zum einzigartigen Asperfumen‐Gerüst führen. Das Strukturmodell zeigte nur einen wesentlichen Unterschied zwischen den aktiven Zentren: Der PaFS‐Rest F65 ist in AfAS durch I65 ersetzt. Interessanterweise zeigten ortsspezifische Mutageneseexperimente mit beiden Diterpensynthasen, dass Position 65 als bidirektionaler funktioneller Schalter für die Biosynthese von tetracyclischem Asperfumen im Vergleich zu strukturell weniger komplexen Diterpenen dient. [ABSTRACT FROM AUTHOR]

Die Biosynthese von sechs kürzlich beschriebenen nicht‐kanonischen C16‐Sesquiterpenoiden, die nach antiken griechischen Philosophen benannt sind, darunter Archimeden, Aristotelen, Eratosthen, Pythagoren, α‐Democriten und Anaximandren, wurde durch Dichtefunktionaltheorie‐Rechnungen (DFT) und Isotopenmarkierungsexperimente untersucht. Die Ergebnisse zeigten für alle Verbindungen außer Archimeden einen einzigartigen Fragmentierungs‐Rekombinationsmechanismus, wie er bereits für die Sodorifen‐Biosynthese gezeigt wurde, zusätzlich zu einem bemerkenswerten „Tanz"‐Mechanismus für die Anaximandren‐Biosynthese. [ABSTRACT FROM AUTHOR]

Elites played a pivotal role in the formation of post-Roman Europe on both macro- and microlevels during the Early Medieval period. History and archaeology have long focused on their description and identification based on written sources or through their archaeological record. We provide a different perspective on this topic by integrating paleogenomic, archaeological, and isotopic data to gain insights into the role of one such elite group in a Langobard period community near Collegno, Italy dated to the 6-8th centuries CE. Our analysis of 28 newly sequenced genomes together with 24 previously published ones combined with isotope (Sr, C, N) measurements revealed that this community was established by and organized around a network of biologically and socially related individuals likely composed of multiple elite families that over time developed into a single extended pedigree. The community also included individuals with diverse genetic ancestries, maintaining its diversity by integrating newcomers and groups in later stages of its existence. This study highlights how shifts in political power and migration impacted the formation and development of a small rural community within a key region of the former Western Roman Empire after its dissolution and the emergence of a new kingdom. Furthermore, it suggests that Early Medieval elites had the capacity to incorporate individuals from varied backgrounds and that these elites were the result of (political) agency rather than belonging to biologically homogeneous groups. [ABSTRACT FROM AUTHOR]

The research progress of porous organic framework materials, represented by metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), used as novel adsorbents in the separation of gas-phase isotope and liquid-phase isotope in recent years is reviewed, the difficulties in the present study are clarified, and the future development trend is prospected, which provides reference for further research on the application of MOFs/COFs in isotope adsorption and separation. [ABSTRACT FROM AUTHOR]

The neutron activation of stable isotopes in environmental matrices, such as soil and groundwater, is a critical aspect of assessing the impact of radionuclide production facilities on the surrounding ecosystem. The envisioned Low-Energy Radioactive Ion Beams (LERIB) facility at the iThemba LABS, South Africa is anticipated to generate significant sources of ionising radiation. The study investigated the possible repercussions of neutron irradiation stemming from the facility, focusing on the activation of stable isotopic compositions in the environment. The investigation employed a combination of experimental and analytical techniques to characterize the neutron activation products in soil and groundwater samples collected from the vicinity. Samples were collected from designated areas for background radiological measurements and were irradiated with neutrons for a period of 1 h. The induced radioactivity measured by the High Purity Germanium detector included 24Na, 22Na, 54Mn, 52Mn, and 46Sc. The application of Darcy’s law for groundwater velocity suggests that radionuclides in groundwater will migrate at an average flow velocity of 0.8 m/day. The isotopes with longer half-lives have count rates at background concentrations; therefore, environmental impacts on the site and surrounding communities might be minimal. [ABSTRACT FROM AUTHOR]

Simple Summary: Preliminary investigations revealed that purple sea urchins are distributed in both the stone and algal areas of Daya Bay, with a greater density in the stone area than in the large algal area. This raises important scientific questions: What do the purple sea urchins in the stone area feed on? What is the dietary range of purple sea urchins? Therefore, we focused on purple sea urchins and employed stable isotope technology and 16S rDNA and 18S rDNA high-throughput sequencing techniques to conduct a systematic study on the feeding habits and gut microbiota community structure of purple sea urchins in the stone and algal areas of the central islet sea area of Daya Bay. We aimed to elucidate the feeding habits and dietary range of purple sea urchins. The results of this study provide a theoretical basis for the restoration of wild purple sea urchin resources and the selection of areas for restocking and release. Sea urchins play an important role in marine ecosystems. Owing to limitations in previous research methods, there has been insufficient understanding of the food sources and ecological functional value of purple sea urchins, leading to considerable controversy regarding their functional positioning. We focused on Daya Bay as the research area, utilizing stable isotope technology and high-throughput sequencing of 16S rDNA and 18S rDNA to analyze sea urchins and their potential food sources in stone and algae areas. The results showed that the δ13C range of purple sea urchins in the stone area is −11.42~−8.17‰, and the δ15N range is 9.15~10.31‰. However, in the algal area, the δ13C range is −13.97~−12.44‰, and the δ15N range is 8.75~10.14‰. There was a significant difference in δ13C between the two areas (p < 0.05), but there was no significant difference in δ15N (p > 0.05). The main food source for purple sea urchins in both areas is sediment. The sequencing results of 18S rDNA revealed that, in the algal area, the highest proportion in the sea urchin gut was Molluska (57.37%). In the stone area, the highest proportion was Arthropoda (76.71%). The sequencing results of 16S rDNA revealed that, in the algal area, Bacteroidetes was the dominant group in the sea urchin gut (28.87%), whereas, in the stone area, Proteobacteria was the dominant group (37.83%). Diversity detection revealed a significant difference in the number of gut microbes and eukaryotes between the stone and algal areas (p < 0.05). The results revealed that the main food source of purple sea urchins in both areas is sediment, but the organic nutritional value is greater in the algal area, and the richness of microbiota and eukaryotes in the gut of purple sea urchins in the stone area is greater. These results indicated that purple sea urchins are likely omnivores and that the area where they occur impacts their growth and development. The results of this study provide a theoretical basis for the restoration of wild purple sea urchin resources and the selection of areas for restocking and release. [ABSTRACT FROM AUTHOR]

Background: Anthropogenic ammonia emissions, primarily derived from agriculture, lead to air pollution, soil acidification, and surface water eutrophication, all of which adversely affect human health and ecosystems. Slurry treatment technologies in the form of additives represent an underutilized means of reducing gaseous emissions. Information regarding the potential of additives to reduce ammonia in soil surface‐applied slurries is scarce. Aim: This study aims to develop a 15N mass balance technique to quantitatively measure ammonia losses from different slurries containing multiple additives that are applied to outdoor soil‐filled containers. Methods: The experiments were performed under free‐air conditions. Isotopically labeled slurries from biogas, cattle, and pigs containing 18 additives were surface‐applied to soil‐filled containers and exposed for 72 or 48 h. The additives included inorganic and organic adsorbents, five amounts of sulfuric acids, molasses ± effective microorganisms, and water dilution. After termination of the ammonia loss period, a suite of soil preparation steps for the quantitative recovery of the labeled ammonium remaining in the soil was developed, and subsequently the loss of NH4‐N was determined. Results: In the control treatments, ammonia losses from biogas, cattle slurries, and pig slurries averaged 54.4%, 33.9%, and 11.0%, respectively. The adsorbents did not decrease or only slightly decreased ammonia emissions. Ammonia abatement by sulfuric acid was nearly complete at pH values of 5.9 and 5.8 for the biogas and pig slurry, respectively, and about 80% at pH 5.2 for the cattle slurry. In comparison, more moderately decreased pH values with sulfuric acid showed a similar reduction as molasses and a 1:1 dilution for the three slurries. Adding microorganisms to the molasses did not further decrease ammonia losses. Conclusion: The newly developed 15N mass balance technique, which allows a precise estimate of ammonia losses, can serve as a reference method to assess ammonia losses from field‐applied slurries containing various additives and as a standard comparison technique for other ammonia measurement techniques. [ABSTRACT FROM AUTHOR]

Copyright of Afyon Kocatepe University Journal of Science & Engineering / Afyon Kocatepe Üniversitesi Fen Ve Mühendislik Bilimleri Dergisi is the property of Afyon Kocatepe University, Faculty of Science & Literature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Oral intake of purified selenoneine and seafoods has been reported to result in selenoneine accumulation in erythrocytes in mice and human. In addition, Se-methylselenoneine was suggested to be produced as a metabolite of selenoneine in the urine and whole blood of humans. In order to confirm the molecular mechanism of production of Se-methylselenoneine, a stable isotope (Se-76) labeled selenoneine was biosynthesized using genetically modified fission yeast and administered to mice. The Se-76-labeled Se-methylselenoneine was detected in urine but Se-78 and Se-80-labeled Se-methylselenoneine arising from natural isotopes of Se was hardly detected. These results suggest that Se-methylselenoneine was a metabolite and the excreted form of selenoneine. The methylation of selenoneine in mice administered selenoneine continuously was evaluated by the analyses of organs using an online liquid chromatograph system with an inductively coupled plasma mass spectrometer (LC-ICP-MS). These experiments indicate that selenoneine is methylated in the liver and (or) kidneys. [ABSTRACT FROM AUTHOR]

Groundwater is the main clean water resource in northern China, and its quality is critical for both human health and social sustainable development. Due to complex anthropogenic and/or geogenic processes, the sources of groundwater contaminants are not easy to determine. The Tabu River Basin, located in northern China, is an agriculture and pasture interlaced area in which phreatic groundwater is the predominant water resource for domestic and agricultural purposes. Groundwater with abnormally high levels of NO3−, F−, and TDS was observed here based on 87 groundwater samples collected from the phreatic aquifer in 2022. In this study, hydrogeochemical and isotopic methods were used to trace groundwater contaminants in the phreatic aquifer, and a risk assessment was conducted to analyze their threat to human health. The results indicated that NO3− in the phreatic groundwater primarily originated from manure, the high concentration of TDS was highly associated with irrigation, and the enrichment of F− was mainly controlled by geogenic factors, including alkaline condition, competitive adsorption, the dissolution of fluorine-bearing minerals, and cation exchange. A principal component analysis (PCA) showed that both anthropogenic (PC1, 50.7%) and geogenic (PC2, 19.9%) factors determined the quality of the phreatic groundwater in the study area. The human health risk assessment demonstrated that 98.9%, 92.0%, and 80.5% of the groundwater samples exceeded the permissible limit of the total noncarcinogenic risk for children, adult females, and adult males, respectively. The monitoring results from 2022 to 2023 suggested that phreatic groundwater contamination could not be mitigated through natural attenuation under the existing external pressures. Measures need to be taken to decrease the contamination of phreatic groundwater and enhance the groundwater sustainability in the Tabu River Basin. The findings of this study can provide a reference for sustainable groundwater development in the Tabu River Basin and other arid and semi-arid regions worldwide. [ABSTRACT FROM AUTHOR]

The Hongjiang—Qianshan fault has abundant medium-low temperature geothermal resources. However, the excessive fluorine concentration in geothermal groundwater restricts the development and utilization of geothermal resources. 20 samples were collected in this region for identifying the genetic mechanism of medium-low temperature of fluoride-enriched geothermal resources. The hydrochemical results indicate that the hydrochemical characteristic of high fluoride geothermal groundwater is HCO3-Na. The groundwater environment is alkaline and weakly alkaline. The fluoride concentration in geothermal groundwater is 2−12 times greater than the upper limited value, while those in the surface water and shallow groundwater are within the permittable threshold range. The isotopic results reveal that the recharge elevations and circulation depth are 797−2186m and 893−1893m, respectively. Quartz provides the most reliable estimations of reservoir temperatures, ranging from 79.4℃ to 113.1℃. The fluoride in geothermal groundwater originates from the rock weathering and mineral dissolution. Cation exchange and alkaline condition are the main influence factors for fluorine enrichment. [ABSTRACT FROM AUTHOR]

Taking the observation spring (Xiangcheng Ranwu hot spring ) in Xiangcheng, Sichuan as the research object, we collect water samples from observation spring and other nearby hot springs and analyze the main chemical ions compositions, trace elements and hydrogen and oxygen isotope compositions to study water cycle characteristics and formation mechanism of the hot spring. The results show that, the hot spring hydrochemical type is Na-HCO3, and belongs to medium temperature, alkaline, low salinity hot spring and contains B, Li, Ba and other trace elements. Ions in hot springs are mainly dissolved from silicate minerals in surrounding rock during water-rock interaction. The stable hydrogen and oxygen isotopes (δ18 O and δD) composition indicates that the main source of the recharge for the hot spring is precipitation. According to the result of Si-enthalpy model, the geothermal reservoir temperature of the hot spring is 275*C and circulation depth of hot spring is 5. 3 km. The ratio of mixing cold water with hot water is about 84% -- 86 % which calculated by Si-enthalpy equation method. The genetic model of Xiangcheng Ranwu hot spring is that groundwater receives recharge from infiltration of precipitation m the mountain area, undergoes deep circulation and obtains heat from heat flow and flows up to the surface along the Xiangcheng fault, at the same rime mixed with shallow cold water. Finally, exposing in the river valley as a medium hot spring. We relocated earthquakes in the study area by the "multistage" method. The results suggest that the focal depth that located near the hot spring is deeper than geothermal water circulation depth, which indicate that the geothermal cycle can weaken the fault strength and control the seismic activity around the Xiangcheng hot spring. Based on above results, we can conclude that Xiangcheng Ranwu hot spring plays an important role in earthquakes formation in this area and is suitable for further geochemical observation of earthquake precursor. [ABSTRACT FROM AUTHOR]

Study region: The Nujiang Fault Zone near Baoshan in western Yunnan. Study focus: Major hydrochemical elements and stable isotopes of 15 hot spring water samples are analyzed to reveal hydrogeochemical evolution processes, recharge sources, geothermal conditions, and structural control genesis of the hot springs. New hydrological insight for the region: Baoshan is experiencing a wave of clean energy development, specifically geothermal energy. The Nujiang Fault Zone, which separates the Tengchong Block from the Baoshan Block, constitutes a low- to medium-temperature geothermal system characterized by numerous hot springs. The hot springs under investigation are located near Baoshan along the Nujiang Fault. Four hydrochemical types have been identified, with HCO3-Ca⋅Mg being the predominant type. The primary components of spring waters originate from the weathering or dissolution of carbonate and silicate minerals, as well as the reverse cation exchange. Stable isotopes indicate that these hot springs are predominantly formed by the atmospheric precipitation during the summer monsoon. The recharge areas are located in the mountainous regions around the Nujiang River, at elevations ranging from 1606 to 2504 m and temperatures between 3°C and 8°C. The estimated temperature of the geothermal reservoir ranges from 73°C to 192°C. During the ascent process, the mixing ratio of cold water is between 60 % and 79 %, and the circulation depth ranges from 1928 to 4221 m. The positive correlation between Li and Cl indicates that hot springs originate from the same parent geothermal fluid controlled by the Nujiang Fault or by two secondary faults intersecting at depths. The hot springs with shallower circulation depths are mainly composed of HCO3-Ca⋅Mg type, while the deeper circulating spring waters consist primarily of HCO3-Na type. The height difference between the discharge location of the hot springs and the surface of the Nujiang River correlates positively with the geothermal reservoir temperature. This paper emphasizes the hydrogeochemical characterization of hot springs within regional fault zones, which holds significant implications for the development and exploration of geothermal systems in similar structural control areas.

Study region: The Seohwa watershed, South Korea. Study focus: Agricultural practices and urbanization in watersheds increase nutrient loads (total nitrogen (TN), total phosphorus (TP), and nitrate-nitrogen (NO3--N)) in streams and deteriorate water quality. Between October 2017 and October 2018, water samples were collected from a small stream (MS), main tributary (TS), and sub-tributaries (ST) characterized by different land-use patterns. The objective of this study was to identify the sources that determine water quality in the respective streams and to estimate whether water quality was dependent on land-use patterns. New hydrological insights for the region: TN in MS progressively decreased downstream, whereas such spatial variation was not observed in TS and ST. For TP, TS and ST samples showed elevated concentrations during storm events, but not in MS. These observations resulted from TN and TP derived from natural and anthropogenic sources associated with land-use patterns. Interestingly, TN/TP ratios were strongly negatively correlated with the proportion of residential area (R2 = 0.92) rather than other land-use patterns such as agricultural area and forest. In addition, statistical analysis and dual isotopes of nitrate (NO3-) showed that the water quality in MS and the one in TS and ST were predominantly affected by natural sources and anthropogenic sources, respectively. Considering the effects of land-use patterns and rainfall on water quality, anthropogenic sources should be precisely identified to manage stream water in small watersheds more effectively.

Analyzing the isotopic composition of cosmic rays (CRs) provides valuable insights into the galactic environment and helps refine existing propagation models. A particular interest is devoted to secondary-to-primary ratios of light isotopic components of CRs, the measurement of which can provide complementary information with respect to secondary-to-primary ratios like B/C. Given the complexity of the concurrent measurement of velocity and momentum required to differentiate isotopes of the same Z, a task typically accomplished using magnetic spectrometers, existing measurements of these ratios only effectively characterize the low-energy region (below 1 GeV/nucl). This study introduces a novel technique for isotopic distinction in CRs at high energies up to 100 GeV/nucl based on multiple scattering, which, combined with the proposed measurement of velocity, represent an interesting alternative to magnetic spectrometers. The performance of this technique was assessed through a dedicated simulation using the GEANT4 package, with specific emphasis on Z = 1 isotopes.

Geothermal resources are increasingly gaining attention as a competitive, clean energy source to address the energy crisis and mitigate climate change. The Wugongshan area, situated in the southeast coast geothermal belt of China, is a typical geothermal anomaly and contains abundant medium‐ and low‐temperature geothermal resources. This study employed hydrogeochemical and isotopic techniques to explore the cyclic evolution of geothermal water in the western Wugongshan region, encompassing the recharge origin, water–rock interaction mechanisms, and residence time. The results show that the geothermal water in the western region of Wugongshan is weakly alkaline, with low enthalpy and mineralization levels. The hydrochemistry of geothermal waters is dominated by Na‐HCO3 and Na‐SO4, while the hydrochemistry types of cold springs are all Na‐HCO3. The hydrochemistry types of surface waters and rain waters are Na‐HCO3 or Ca‐HCO3. The δD and δ18O values reveal that the geothermal waters are recharged by atmospheric precipitation at an altitude between 550.0 and 1218.6 m. Molar ratios of major solutes and isotopic compositions of 87Sr/86Sr underscore the significant role of silicate weathering, dissolution, and cation exchange in controlling geothermal water chemistry. Additionally, geothermal waters experienced varying degrees of mixing with cold water during their ascent. The δ13C values suggest that the primary sources of carbon in the geothermal waters were biogenic and organic. The δ34S value suggests that the sulfates in geothermal water originate from sulfide minerals in the surrounding rock. Age dating using 3H and 14C isotopes suggests that geothermal waters have a residence time exceeding 1 kaBP and undergo a long‐distance cycling process. [ABSTRACT FROM AUTHOR]

Lop Nur is located at the eastmost end of the Tarim Basin in Xinjiang, Northwestern China. This study reviews the hydrochemical characteristics and evolution of underground brine in Lop Nur, based on analytical data from 429 water samples (mainly brine). It is found that in the NE–SW direction, from the periphery to the Luobei sub‐depression, while the hydrochemical type varies from the sodium sulfate subtype (S) to the magnesium sulfate subtype (M), the corresponding brine in the phase diagram transfers from the thenardite phase (Then) area, through the bloedite phase (Blo), epsomite phase (Eps), picromerite phase (Picro), finally reaching the sylvite phase (Syl) area. As for the degree of evolution, the sequence is the periphery < Luobei horizontally and the overlying glauberite brine < the underlying clastic brine vertically. It is concluded that the oxygen and hydrogen isotopic compositions of the brine have evidently been affected through the effects of evaporation and altitude, as well as the changes in local water circulation in recent years. Boron and chloride isotopic compositions show that the glauberite brine is formed under more arid conditions than the clastic one. The strontium isotopic composition indicates that the Lop Nur brine primarily originates from surface water; however, deep recharge may also be involved in the evolution of the brine, according to previous noble gas studies. It is confirmed that the brine in Lop Nur has become enriched with potassium prior to halite precipitation over the full course of the salt lake's evolution. Based on chemical compositions of brine from drillhole LDK01 and previous lithological studies, the evolution of the salt lake can be divided into three stages and it is inferred that the brine in Lop Nur may have undergone at least two significant concentration‐dilution periods. [ABSTRACT FROM AUTHOR]

Under increasing anthropogenic impacts, the hydrology, weathering, turbidity, and biogeochemistry of the Amazon and Pará river catchments are changing, potentially affecting the concentration and speciation of nitrogen (N) entering the estuary, as well as the subsequent primary productivity. Primary production and several N‐cycling rates have been studied in the northern river plume, and new studies focusing on specific processes in the river mouth emerged. Yet, a general overview is still lacking. For the first time, we provide an overview of primary production along with nitrification, ammonium (NH4+), nitrate (NO3−), and amino acid uptake rates in the Amazon and Pará river mouths which exhibit different degrees of catchment land use. Our results indicate that the Amazon supplies tenfold more NH4+ and NO3−, and its nitrification rates are four times higher than in the Pará River. The stable isotope composition of ambient water and NO3− confirmed that nitrification is a dominant pathway, with fluxes reaching 8.5 × 108 mol N d−1 in the Amazon. Nutrients are transported to regions with reduced turbidity and little nitrification, facilitating NH4+ (0.2–2.4 × 108 mol N d−1) and carbon uptake (4.6 and 14.0 × 108 mol C d−1 in the Pará and the Amazon, respectively) by phytoplankton. The lower N‐cycling rates measured in the Pará relative to the Amazon River mouth likely originate from differences in river discharge and watershed characteristics. Plain Language Summary: Riverine nitrogen can support intense production at the base of the food web in coastal oceans. Such productive ecosystems often show flourishing life and act as a strong atmospheric carbon sink. Since the extent of this nitrogen source is greatly influenced by the status of the river catchment area, it is crucial to have a good understanding of the amount and reactivity of riverine nitrogen at a given study site. Here, we used nitrogen isotope tracers to measure nitrogen assimilation and nitrification rates in the Amazon and Pará river mouths. We found that nitrification was happening at high rates in the Amazon River Mouth. In both estuaries, nitrate production is greater than consumption, allowing nitrate export beyond the turbid waters of the river mouths. Because the Amazon and Pará drainage basins are facing drastic changes, this nitrogen budget gives a baseline for nitrogen cycle pathways and export that will help to monitor the effect of these changes on estuarine nitrogen processes. Key Points: Nitrogen uptake and nitrification measurements reveal intense nitrification of autochthonous ammonium in the Amazon and Pará estuariesIn the turbid parts, nitrate produced via nitrification is not entirely consumed by primary production, leading to its exportRates of nitrogen cycle processes are 10 times higher in the Amazon River mouth, likely due to higher riverine nitrogen discharged [ABSTRACT FROM AUTHOR]

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Analyzing the isotopic composition of cosmic rays (CRs) provides valuable insights into the galactic environment and helps refine existing propagation models. A particular interest is devoted to secondary-to-primary ratios of light isotopic components of CRs, the measurement of which can provide complementary information with respect to secondary-to-primary ratios like B/C. Given the complexity of the concurrent measurement of velocity and momentum required to differentiate isotopes of the same Z, a task typically accomplished using magnetic spectrometers, existing measurements of these ratios only effectively characterize the low-energy region (below 1 GeV/nucl). This study introduces a novel technique for isotopic distinction in CRs at high energies up to 100 GeV/nucl based on multiple scattering, which, combined with the proposed measurement of velocity, represent an interesting alternative to magnetic spectrometers. The performance of this technique was assessed through a dedicated simulation using the GEANT4 package, with specific emphasis on Z = 1 isotopes. [ABSTRACT FROM AUTHOR]

The Woka-Cuona rift zone on the southeastern side of the Qinghai-Tibet Plateau is characterized by complex geological background conditions, comprising three independent or semi-grabens that traverse from south to north across the Himalayan and Gangdise terranes. Conducting research on the distribution patterns and genesis mechanisms of geothermal resources within the Woka-Cuona rift zone has certain guiding significance for understanding the genesis mechanisms of the geothermal system in the southern Tibetan rift and its exploitation. This paper utilized methods such as data collection, ground investigations, and geochemical analyses to analyze the distribution characteristics and evolutionary processes of geothermal waters in the Cuona rift area based on the geological background conditions of the study area. The research findings demonstrate a significant correlation between the occurrence of geothermal waters in the Cuona rift zone and geological structures, with most geothermal waters primarily distributed near intersections of graben boundary faults and east–west-trending faults. Different regions exhibit variations in the intensity of geothermal activity and geochemical characteristics, with the genesis of geothermal waters associated with deep magmatic activity, characterized by Na+ and K+ as the primary cations and Cl− as the primary anions. Geothermal waters mainly originate from atmospheric precipitation and snowmelt water from surrounding mountainous areas, with recharge elevations ranging from 4500 to 6200 m and an average elevation of 5400 m. [ABSTRACT FROM AUTHOR]

Studien an zwei Multiprodukt‐Sesterterpensynthasen aus Lentzea atacamensis führten zur Identifizierung der Synthasen für Lentzeadien (LaLDS) und Atacamatrien (LaATS). Das Hauptprodukt von LaLDS (Lentzeadien) ist eine neue Verbindung, während eines der Nebenprodukte (Lentzeatetraen) das Enantiomer von Brassitetraen B ist und ein anderes Nebenprodukt (Sestermobaraen F) von einer überraschend weit entfernt verwandten Sesterterpensynthase bekannt ist. LaATS stellt sechs neue Verbindungen her, darunter das Enantiomer des bekannten Sesterterpens Bm1. Bemerkenswert ist, dass die Produkte beider Enzyme nicht alle aus ein und derselben Ausgangskonformation von Geranylfarnesyldiphosphat erklärt werden können, was die Notwendigkeit einer Konformationsflexibilität des Substrats in den aktiven Zentren der Enzyme zeigt. Für Lentzeadien wurde eine faszinierende thermische [1,5]‐sigmatrope Umlagerung entdeckt, die an die Biosynthese von Vitamin D3 erinnert. Alle Enzymreaktionen und die [1,5]‐sigmatrope Umlagerung wurden durch Isotopenmarkierungsexperimente und DFT‐Berechnungen untersucht. Die Ergebnisse unterstreichen auch die Bedeutung von Konformationsänderungen während Terpencyclisierungen. [ABSTRACT FROM AUTHOR]

In this paper, we have successfully obtained the mean mass-density parameter ( ρ m ) using the nuclear masses AME2020 database and nuclear charge radius (CR) CR2013 database. The empirical formula is derived based on the relationship between ρ m and N ∕ Z (the ratio of the number of neutrons to protons). Subsequently, we obtained an empirical formula for the difference in ρ m between two neighboring isotopes. By utilizing this empirical formula along with the AME2020 and CR2013 databases, we then calculated 625 charge radii for nuclei with N ≥ 2 1. The root-mean-square deviation (RMSD) between the calculated values and the experimental values in the CR2013 database is 0.0075 fm. The predicted nuclear CR values are comparable to those of other researches, which some predictions closely matching the experimental values measured in recent years. Additionally, this work used the Back Propagation (BP) neural network to establish a model for describing and predicting the difference in the mean mass-density parameter between two neighboring isotopes. The RMSD between the calculated and experimental values obtained using this model is 0.0039 fm. Some of our predicted values have good accuracy and compared well with experimental values. Both of the above methods indicate that the nuclear CR relationship proposed in this paper based on the difference in mean mass-density parameter has simplicity and reliability. [ABSTRACT FROM AUTHOR]