Search Results (116)

Aquatic plants, as sedentary lifestyle organisms that accumulate chemical substances from their surroundings, can serve as valuable indicators of long-term anthropogenic pressure. In Poland, water monitoring is limited both spatially and temporally, which hampers a comprehensive assessment of water quality. Since the implementation of the Water Framework Directive (WFD), biotic elements, including macrophytes, have played an increasingly important role in water monitoring. Moreover, running waters, due to their dynamic nature, are susceptible to episodic pollution inputs that may be difficult to detect during isolated, point-in-time sampling campaigns. The analysis of stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope signatures in macrophytes enables the identification of elemental sources, including potential pollutants. Research conducted between 2008 and 2011 encompassed 38 sites along 15 rivers and 108 sites across 21 lakes in northern Poland. This study focused on the isotope signatures of three pondweed species: Stuckenia pectinata, Potamogeton perfoliatus, and Potamogeton crispus. The results revealed statistically significant differences in the δ¹³C and δ¹⁵N values of plant organic matter between river and lake environments. Higher δ¹⁵N values were observed in rivers, whereas higher δ¹³C values were recorded in lakes. Spearman correlation analysis showed a negative relationship between δ¹³C and δ¹⁵N, as well as correlations between δ¹⁵N and the concentrations of Ca²⁺ and HCO₃⁻. A positive correlation was also found between δ¹³C and dissolved oxygen levels. These findings confirm the utility of δ¹³C and, in particular, δ¹⁵N as indicators of anthropogenic eutrophication, including potentially domestic sewage input and its impact on aquatic ecosystems. Full article

The hydrochemical characteristics and evolution mechanisms of groundwater are critical for accurately understanding the input–output budget of hydrochemical constituents in pristine groundwater. However, few studies have analyzed the changes in mineral precipitation and dissolution equilibrium along the groundwater flow path, especially in arid regions. This study integrated hydrochemical analysis, stable isotopes, and inverse hydrochemical modeling to identify groundwater recharge sources, hydrochemical evolution, and controlling mechanisms in an arid endorheic watershed, northwestern China. A stable isotope signature indicated that groundwater is primarily recharged by high-altitude meteoric precipitation and glacial snowmelt. The regional hydrochemical type evolved from HCO₃·Cl-Ca·Mg·Na types in phreatic aquifers to more complex HCO₃·Cl-Ca·Mg Na and HCO₃·Cl-Na Mg types in confined aquifers and a Cl-Mg·Na type in high-salinity groundwater. The dissolution of halite, gypsum, calcite, K-feldspar, and albite was identified as the primary source of dissolved substances and a key factor controlling the hydrochemical characteristics. Meanwhile, hydrochemical evolution is influenced by cation exchange, mineral dissolution–precipitation, and carbonate equilibrium mechanisms. Inverse hydrochemical modeling demonstrated that high-salinity groundwater has experienced intensive evaporation and quantified the transfer amounts of associated minerals. This study offers deeper insight into hydrochemical evolution in the Golmud River watershed and elucidates mineral transport and enrichment mechanisms, providing a theoretical basis for investigating hydrochemical metallogenic processes. Full article

Carbon isotopes in magmatic systems serve as powerful tracers for understanding magma evolution, mantle processes, the deep carbon cycle, and the origin of Earth’s carbon. This review provides a comprehensive overview of carbon isotope measurements and behavior in magmatic systems, highlighting recent technological advancements and scientific insights. We begin by examining methods for measuring δ¹³C in volcanic gases, vesicles, glasses, melt, and fluid inclusions. We then explore the behavior of carbon isotopes in magmatic systems, especially during magmatic degassing. Finally, we evaluate what recent advances mean for our understanding of the carbon isotope signature of the Earth’s upper mantle. Full article

Stable isotope analysis is a powerful tool for inferring and quantifying transformation processes, but its effectiveness relies on understanding the magnitude and variability of isotopic fractionation associated with specific reactions. Potassium permanganate (KMnO₄) is widely used as an efficient oxidant for the degradation of trichloroethylene (TCE); however, the influence of environmental factors on the isotope fractionation during this process remains unclear. In this study, compound-specific isotope analysis (CSIA) was conducted to investigate the variability in carbon isotope effects during the KMnO₄-mediated degradation of TCE under varying conditions, including initial concentrations of KMnO₄ and TCE, the presence of humic acid (HA), pH levels, and inorganic ions. The results showed that the overall carbon isotope enrichment factors (ε) of TCE ranged from −26.5 ± 0.5‰ to −22.8 ± 0.9‰, indicating relatively small variations across conditions. At low KMnO₄/TCE molar ratio (n(KMnO₄)/n(TCE)), incomplete oxidation and/or MnO₂-mediated oxidation of TCE likely resulted in smaller ε. For dense, non-aqueous phase liquid (DNAPL) TCE, which represents extremely high concentrations, the ε value was −13.0 ± 1.7‰ during KMnO₄ oxidation. This may be attributed to the slow dissolution of isotopically light TCE from the DNAPL phase, altering the δ¹³C signature of the reacted TCE and resulting in a significantly larger ε value than observed for dissolved-phase TCE oxidation. The ε values increased with rising pH, probably due to the decrease in oxidation potential (E₀) of KMnO₄ from pH ~2 to ~12, as well as the emergence of different degradation pathways and intermediates under varying pH conditions. Both SO₄²⁻ and NO₃⁻ slightly influenced the ε values, potentially due to the formation of H₂SO₄ and HNO₃ at lower pH, which may act as auxiliary oxidants and contribute to TCE degradation. A high concentration (50 mM) of HA led to a decrease in ε values, likely due to competitive interactions between HA and TCE for KMnO₄, which reduced the effective oxidation of TCE. Overall, the carbon isotope enrichment factors for KMnO₄-mediated TCE degradation are relatively stable, although certain environmental conditions can exert minor influences. These findings highlight the need for caution when applying quantitative assessment based on CSIA for KMnO₄ oxidation of TCE. Full article

This study critically examines the early Cretaceous carbonate-hosted Zn-Pb (±Ba±Cu) deposits of the Malayer-Esfahan (MEMB) and Yazd-Anarak (YAMB) metallogenic belts in Iran, which have been inaccurately classified as Mississippi Valley type (MVT) deposits by Nejadhadad et al. (2025). Our findings reveal significant differences in mineralogy, fluid inclusion characteristics, and geochemical signatures compared to typical MVT deposits. These deposits are more akin to Irish-type Zn-Pb mineralization and formed in extensional and passive margin environments around the Nain–Baft back-arc basin. The normal faults in this back-arc rift can transform significantly during inversion and compressional tectonics, reactivating to behave as reverse faults and leading to new geological structures and landscapes. Our study highlights barite replacement as a crucial factor in forming sediment-hosted Zn-Pb (±Ba±Cu) and barite-sulfide deposits. Based on textural evidence, fluid inclusion data, and sulfur isotope analyses, we propose that barite plays a fundamental role in controlling subsequent Zn-Pb (±Ba±Cu) mineralization by serving as both a favorable host and a significant sulfur source. Furthermore, diagenetic barite may act as a precursor to diverse types of sediment-hosted Zn-Pb (±Ba±Cu) mineralization, refining genetic models for these deposits. Sulfur isotope analyses of Irish-type deposits show a broad δ³⁴S range (−28‰ to +5‰), indicative of bacterial sulfate reduction (BSR). Nevertheless, more positive δ³⁴S values (+1‰ to +36‰) and textural evidence in shale-hosted massive sulfide (SHMS) deposits suggest a greater role for thermochemical sulfate reduction (TSR) in sulfide mineralization. Full article

Determining carbon sources and sinks is crucial for understanding the global carbon cycle; however, the enigma of the ‘missing’ sinks remains unresolved. Recent studies have proposed carbonate weathering as a potential carbon sink, underscoring the need to clarify its mechanisms. Previous investigations of carbonate weathering largely relied on soil profiles, which were limited by the rarity of incipient weathering layers. Therefore, we have little knowledge about carbonate incipient weathering processes. To address this gap, spheroidal weathered dolostones were collected from Neoproterozoic Liangjiehe Formation (Nanhua System) in Guizhou, China. The pristine dolostone exhibits δ¹³C values ranging from −5.26 to −3.35‰ and δ¹⁸O values from −13.79 to −12.83‰. These isotopic signatures suggest that the dolostone formed under the high-latitude, cold climatic conditions that were prevalent during the Nanhua Period. Comprehensive petrographic and geochemical analyses of the spheroidal weathered dolostones revealed two distinct stages of incipient weathering. In Stage I, nickel (Ni) and cobalt (Co) contents decrease. The δ¹³C values fluctuate between −7.61 and −2.52‰, while the δ¹⁸O values range from −12.22 to −8.06‰. These observations indicate a weakly acidic microenvironment. In Stage II, there is an enrichment in manganese (Mn), with the δ¹³C values extending from −16.56 to −12.43‰ and the δ¹⁸O values from −8.46 to −7.03‰. These clues suggest a transition to a neutral microenvironment, with the isotopic compositions of carbon and oxygen in the dolomite influenced by atmospheric carbon dioxide (CO₂) and atmospheric precipitation. This study presents a pioneering investigation into the mineralogical and geochemical variations associated with carbonate incipient weathering processes. The variation in C-O isotopes during carbonate incipient weathering may indicate the re-precipitation of HCO₃⁻, suggesting that the carbon sink contribution of carbonate weathering to the global carbon cycle could be overestimated. Full article

The Aït Abdellah copper deposit in the Bou Azzer-El Graara inlier of the Moroccan Anti-Atlas provides key insights into structurally and lithologically controlled mineralization in Precambrian terranes. The deposit is hosted in feldspathic sandstones of the Tiddiline Group, which unconformably overlie the Bou Azzer ophiolite, and is spatially associated with a NE–SW-trending shear zone. This zone is characterized by mylonitic fabrics, calcite veining, and an extensive network of fractures, reflecting a two-stage deformation history involving early ductile shearing followed by brittle faulting and brecciation. These structural features enhanced rock permeability, enabling fluid flow and metal precipitation. Copper mineralization includes primary sulfides such as chalcopyrite, bornite, pyrite, chalcocite, digenite, and covellite, as well as supergene minerals like malachite, azurite, and chrysocolla. Sulfur isotope values (δ³⁴S = +5.9% to +22.8%) indicate a mixed sulfur source, likely derived from both ophiolitic rocks and volcano-sedimentary sequences. Carbon and oxygen isotope data suggest fluid interaction with marine carbonates and meteoric waters, potentially linked to post-Snowball Earth deglaciation processes. Fluid inclusion studies reveal homogenization temperatures ranging from 195 °C to 310 °C and salinities between 5.7 and 23.2 wt.% NaCl equivalent, supporting a model of fluid mixing between magmatic-hydrothermal and volcano-sedimentary sources. The paragenetic evolution of the deposit comprises three stages: (1) early hydrothermal precipitation of quartz, dolomite, sericite, pyrite, and early chalcopyrite and bornite; (2) a main mineralizing stage characterized by fracturing and deposition of bornite, chalcopyrite, and Ag-bearing sulfosalts; and (3) a late supergene phase with oxidation and secondary enrichment. The Aït Abdellah deposit is best classified as a shear zone-hosted copper system with a complex, multistage mineralization history. The integrated analysis of structural features, mineral assemblages, isotopic signatures, and fluid inclusion data reveals a dynamic interplay between deformation processes, hydrothermal alteration, and evolving fluid sources. Full article

Superdeep diamonds and their syngenetic inclusions are crucial for understanding Earth’s deep carbon cycle and slab–mantle redox dynamics. The origins of these diamonds, especially their links to iron (Fe) carbides and ferropericlase with varying Mg# [=Mg/(Mg+Fe)_at], however, remain elusive. In this study, we performed high pressure–temperature (P-T) experiments (10–16 GPa and 1200–1700 K) across cold-to-warm subduction zones using a multi-anvil press. The results reveal a stepwise Fe-mediated carbonate reduction process for the formation of superdeep diamonds: MgCO₃ → Fe-carbides (Fe₃C/Fe₇C₃) → graphite/diamond. This mechanism explains two phenomena regarding superdeep diamonds: (1) anomalous ¹³C depletion results from kinetic isotope fractionation during ¹²C enrichment into the intermediate Fe-carbides; (2) nitrogen scarcity is due to Fe-carbides acting as nitrogen sinks. Ferropericlase [(Mg,Fe)O] formed during the reactions in our experiments shows Mg# variations (0.2–0.9), similar to those found in natural samples. High Mg# (>0.7) variants from lower temperature experiments indicate diamond crystallization from carbonatitic melts in the shallow lower mantle, while the broad Mg# range (0.2–0.9) from experiments at higher temperatures suggests multi-depth formation processes as found in Brazilian diamonds. These findings suggest that slab–mantle interactions produce superdeep diamonds with distinctive Fe-carbides and ferropericlase assemblages as inclusions, coupled with their ¹³C- and nitrogen-depleted signatures, which underscore thermochemical carbon cycling as a key factor in deep carbon storage and mantle mineralogy. Full article

Understanding the trophic interactions and community structure of zooplankton is essential for assessing energy transfer in marine ecosystems. This study investigates the spatial and seasonal variations in stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes of dominant mesozooplankton groups across three sub-basins of the Eastern Mediterranean (North Aegean, Cretan, and South Ionian Seas) during two seasonal surveys (October 2014 and May 2015). Zooplankton samples were collected using a WP-2 net and analyzed for taxonomic composition, abundance, biomass, and stable isotopic signatures to assess trophic positioning. The results indicate that copepods dominated the zooplankton community at all stations, with Clausocalanus and Oithona juveniles being the most abundant taxa. Salps contributed significantly at certain stations, reflecting regional variations in the planktonic food web structure. Zooplankton δ¹⁵N values exhibited pronounced spatial and seasonal differences, with higher enrichment observed in 2014 compared to 2015. The calculated trophic positions highlight the variability in feeding strategies among copepod species, with Calanus helgolandicus occupying the highest trophic position (TP = 3.34) and Lucicutia spp. the lowest (TP = 1.22). Isotopic niche analysis identified two distinct feeding guilds: a group relying on phytoplankton and microzooplankton and another exhibiting broader trophic plasticity, including omnivorous and carnivorous taxa. These findings underscore the complexity of zooplankton trophic interactions in the Eastern Mediterranean and the role of regional hydrographic conditions in shaping the food web structure. This study provides essential baseline data for future research on the impacts of climate change and nutrient variability on Mediterranean marine ecosystems. Full article

The present study was undertaken for the first time in India to generate a database of isotopic signatures of authentic Indian honey to verify the regulatory criteria laid down by the Food Safety and Standards Authority of India (FSSAI). In this study, ninety-eight (98) authentic honey samples from nineteen (19) different botanical sources were collected from five (05) geographical regions of India and analyzed to generate a database of stable carbon isotope ratios (¹³C/¹²C) by Elemental Analyzer/Liquid Chromatography–Isotopic Ratio Mass Spectrometry (EA/LC-IRMS). The samples were analyzed for the parameters δ¹³C_Honey(δ¹³C_H), δ¹³C_Protein(δ¹³C_P), δ¹³C individual sugars, ∆δ¹³C_{Protein-Honey}(δ¹³C_P-H), C4 sugar, ∆δ¹³C_{Fructose-Glucose}(δ¹³C_Fru-Glu), ∆δ¹³C_max, and foreign oligosaccharides (FOs), as per the official methods of analysis of the Association of Official Analytical Chemists (AOAC 998.12) and the FSSAI. The results were evaluated against the published literature and Indian regulatory criteria for authentic honey. The δ¹³C value for honey (δ¹³C_H) ranged from −22.07 to −29.02‰. It was found that 94% of Indian honey samples met the criteria for Δδ¹³C_P-H (≥−1.0‰), Δδ¹³C_Fru-Glu (±1.0‰), and C4 sugar content (7% maximum), with negative C4 sugar values treated as 0% as prescribed by the AOAC method. Further, 86% of samples met the FO criteria (maximum 0.7% peak area). Thus, the data of this study provide scientific backing for these four (04) parameters as per the FSSAI regulation. However, the non-compliance of a high number (47%) of authentic honey samples for Δδ¹³C_max (±2.1‰) compels further systematic investigation with a special focus on bee feeding practices. Further, in the present study, it was found that honey samples with a Δδ¹³C_P-H greater than +1‰ and a C4 sugar content more negative than −7% also did not comply with the Δδ¹³C_max criteria. Hence, Δδ¹³C_P-H values (>+1‰ equivalent to C4 sugar < −7%) could be an indicator of C3 adulteration to some extent. Full article

Rough surfaces known as stylolites are common geological features that are developed by pressure solution, especially in carbonate rocks, where they are used as strain markers and as stress gauges. As applications are developing in various geological settings, questions arise regarding the uncertainties associated with quantitative estimates of paleostress using stylolite roughness. This contribution reports for the first time a measurement of the temperature at which pressure solution was active by applying clumped isotopes thermometry to calcite cement found in jogs linking the tips of the stylolites. This authigenic calcite formed as a redistribution of the surrounding dissolved material by the same dissolution processes that formed the extensive stylolite network. We compare the depth derived from these temperatures to the depth calculated from the vertical stress inversion of a bedding parallel stylolite population documented on a slab of the Calcare Massiccio formation (early Jurassic) formerly collected in the Umbria-Marches Arcuate Ridge (Northern Apennines, Italy). We further validate the coevality between the jog development and the pressure solution by simulating the stress field around the stylolite tip. Calcite clumped isotopes constrain crystallization to temperatures between 35 and 40 °C from a common fluid with a δ¹⁸O signature around −1.3‰ SMOW. Additional δ¹⁸O isotopes on numerous jogs allows the range of precipitation temperature to be extended to from 25 to 53 °C, corresponding to a depth range of 650 to 1900 m. This may be directly compared to the results of stylolite roughness inversion for stress, which predict a range of vertical stress from 14 to 46 MPa, corresponding to depths from 400 to 2000 m. The overall correlation between these two independent depth estimates suggests that sedimentary stylolites can reliably be used as a depth gauge, independently of the thermal gradient. Beyond the method validation, our study also reveals some mechanisms of pressure solution and the associated p,T conditions favouring their development in carbonates. Full article

Geochemical proxies are a reliable tool in deciphering the paleoenvironment and diagenetic alteration in carbonate rock units. The Lower Cretaceous Yamama Formation (LCYF) is an important carbonate unit of the Saudi Arabia region which has been studied in detail to evaluate the paleoenvironment and diagenetic alteration through geochemical studies. This study presents new data on petrography, stable isotopes, and trace and rare-earth elements to enhance our understanding on paleoenvironments, redox conditions, and paleosalinity during the deposition of these carbonate units. Field studies show that the formation is composed of thick-to-thin-bedded limestone. Petrographic studies show that the formation is mostly composed of mudstone, wackestone, packstone, and grainstone facies. The stable isotopic values of carbon (δ¹³C V-PDB = +0.58‰ to +2.23‰) and oxygen (δ¹⁸O V-PDB = −6.38‰ to −4.48‰) are directly within the range of marine signatures. CaCO₃’s dominance over SiO₂ and Al₂O₃ indicates minimal detrital contribution during the LCYF precipitation. The REE pattern suggests coeval marine signatures which include (i) a slight LREE depletion compared to HREEs (av. Nd/Yb_N = 0.70), (ii) negative Ce anomalies (av. Ce/Ce* = 0.5), and (iii) a positive La anomaly (av. La/La* = 1.70). Micritic limestone has low Hf (bdl to 0.4 µg/g), Sc (bdl to 2.5 µg/g), and Th (bdl to 0.8 µg/g) content, which suggests negligible detrital influence. The Ce content of different facies (Ce = 1u.80 to 12.85 µg/g) suggests that their deposition took place under oxic to dysoxic conditions. However, there is moderate variation during the deposition of MF-I, with higher Ce values as compared to MF-II, MF-III, and MF-IV, which suggests that the deposition of MF-I mostly took place in anoxic to dysoxic conditions. Full article

Recently, there has been increasing interest in organic carbon (OC) certification of soil as an incentive for farmers to adopt sustainable agricultural practices. In this context, this pilot project combines geochemical and geophysical methods to map the distribution of OC contents in agricultural fields, allowing us to detect variations in time and space. Here we demonstrated a relationship between soil OC contents estimated in the laboratory and the apparent electrical conductivity (ECa) measured in the field. Specifically, geochemical elemental analyses were used to evaluate the OC content and relative isotopic signature in collected soil samples from a hazelnut orchard in the Emilia–Romagna region of Northeastern Italy, while the geophysical Electromagnetic Induction (EMI) method enabled the in situ mapping of the ECa distribution in the same soil field. According to the results, geochemical and geophysical data were found to be reciprocally related, as both the organic matter and soil moisture were mainly incorporated into the fine sediments (i.e., clay) of the soil. Therefore, such a relation was used to create a map of the OC content distribution in the investigated field, which could be used to monitor the soil C sequestration on small-scale farmland and eventually develop precision agricultural services. In the future, this method could be used by farmers and regional and/or national policymakers to periodically certify the farm’s soil conditions and verify the effectiveness of carbon sequestration. These measures would enable farmers to pursue Common Agricultural Policy (CAP) incentives for the reduction of CO₂ emissions. Full article

To propose breeding strategies for drought conditions, we investigated gene expression associated with morphophysiological traits in four S7 popcorn (Zea mays var. everta) inbred lines using a partial diallel cross design with two testers. We evaluated morphological traits (plant height; the dry mass of stems, leaves, and reproductive organs; and root weight density (RWD) across five soil sections), water status indicators (leaf water content, cumulative evapotranspiration, agronomic water use efficiency, and carbon isotope signatures), anatomical traits (stomatal number and index), and leaf pigments. Significant variations were observed between lines and hybrids for plant height, shoot biomass traits, water status indicators, and RWD across all soil sections, particularly under water deficit conditions. Overall, the inbred lines were more adversely affected by drought than the hybrids. Dominance gene effects played a significant role in increasing anthocyanin content, cumulative evapotranspiration, stable carbon isotope signatures, and RWD in most soil sections. The superior water utilization observed in hybrids compared to inbred lines suggests that exploiting heterosis is likely the most effective strategy for developing drought-resilient popcorn plants. Full article

The evolution of Jurassic carbonates is globally significant for understanding the depositional framework, diagenetic phases and sedimentary characteristics of shallow marine shelf deposits. For this purpose, two outcrop sections of the Jurassic carbonates with a road distance of 121 km in the Trans Indus Ranges, NW Himalayas, were included in this study. Geological fieldwork was conducted for sedimentological data, and representative samples were collected for microfacies analysis and diagenetic evolution complemented by carbon and oxygen isotope analysis. Results show that eight microfacies were identified in both sections where mudstone microfacies was only present in the Chichali section, whereas wackestone and packstone facies widely existed in both sections. The diagenetic evolution interpreted that dolomitization and stylolization were pronounced in the Paniala section, while micritization and calcite cementation were prevalent in the Chichali section. The interpreted depositional setting implies the wide range from supratidal to outer ramp shallow marine for the Chichali section, suggesting a wide range and relatively deeper environment, alongside merely intertidal to middle ramp settings for Paniala section. Diagenetic evolution suggests marine to meteoric influence in the Chichali section, while burial and uplift phases were dominant in the Paniala section. The diagenetic events were also validated by the isotopic analysis, where most of the samples with values up to −4‰ VPDB δ¹⁸O, corresponding to a carbon isotope range of up to +4‰, were interpreted as the burial phase of diagenesis; meanwhile, a few samples with −2 δ¹³C and −7‰ VPDB δ¹⁸O isotope signatures were marked as meteoric influx in the Paniala section. This study indicates the diversity of the depositional environment and diagenetic heterogeneity by integration of thin sections using isotope data, which are quite applicable to shallow marine carbonates. Full article