This study explores nitrogen transformations in groundwater from an agricultural area utilizing organic fertilizer (wastewater from yeast production) by integrating isotope analysis, microbial gene abundance, and the isotope FRactionation And Mixing Evaluation (FRAME) model to trace and quantify nitrogen cycling pathways. Groundwater samples with elevated nitrate concentrations were subjected to controlled laboratory incubations with application of a novel low-level ¹⁵N tracing strategy to investigate microbial processes. Isotope analyses of nitrate, nitrite, and nitrous oxide (N₂O), coupled with microbial gene quantification via quantitative polymerase chain reaction (qPCR), revealed a shift from archaeal-driven nitrification to bacterial denitrification in post-incubation suboxic conditions, stimulated by glucose addition. FRAME modelling further identified bacterial denitrification as the dominant pathway of N₂O production, which was supported by increased nosZI, nirK, and nirS gene abundance and observed isotope effects. Simultaneously with the intensive nitrate reduction, it was observed that the majority of nitrite is likely produced through nitrification processes linked to dissolved organic nitrogen (DON) oxidation. Nitrate reduction had a minor contribution to the total nitrite pool. The results demonstrate the efficacy of integrating multi-compound isotope studies and microbial analyses to unravel nitrogen cycling mechanisms. This approach provides a robust framework for addressing nitrogen pollution in groundwater systems and improving water quality management strategies.

Ophicarbonates provide an important natural record of mineral carbonation during serpentinization of ultramafic rocks and therefore offer insight into the mechanisms and limits of CO₂ fixation in low-temperature geological environments. This paper presents a synthesis and process-oriented reinterpretation of stable-isotope published and previously unpublished data, petrographic, and mineralogical evidence for carbonate formation under fluid-limited serpentinization conditions. Using mineralogical constraints together with a compiled δ¹³C–δ¹⁸O dataset that includes legacy measurements from the 1980s–1990s, we evaluate how multi-stage carbonate precipitation reflects evolving water–rock ratio, redox state, transport limitation, and deformation-controlled permeability. Particular attention is given to systematic differences between vein-hosted carbonates and dispersed intergranular or scattered-grain ophicarbonates, as these textural–isotopic relationships help identify fluid flux, carbon source, and reaction progress in ultramafic systems. The analysis shows that carbonation does not proceed uniformly but is restricted to overlapping reactive windows controlled by fluid availability, nucleation kinetics, and permeability evolution. These constraints help explain why carbonation may either intensify or stall during progressive serpentinization. The Author further discuss why kinetic barriers and Mg–Ca partitioning may redirect carbonate mineralogy toward calcite or metastable Mg-rich phases even where dolomite or magnesite may be thermodynamically favored. The results highlight the importance of coupling isotopic signatures with petrographic context in reconstructing carbonation pathways and provide a broader framework for understanding natural mineral sequestration of carbon in heterogeneous serpentinite systems.

Permafrost is rapidly degrading in the sporadic zone, including palsa mires in Scandinavia. Peatlands in the area have likely accumulated heavy metals from atmospheric deposition of industrial contaminants in the wider region. As the palsa mire chemical composition is not well known, and in other permafrost regions the permafrost thaw may contribute elevated heavy metal concentrations in surface waters, we hypothesized that palsa mires may act as a source of inorganic input to the local aquatic environment. We verified this hypothesis in a short‐term study of water and sediment composition in the area of Skalluvaara palsa mire in northern Finland. During a time of likely palsas thaw, we compared the physical and chemical parameters in the collected water and aquatic sediment samples from the Skalluvaara palsa mire and its drainage to other streams, rivers, and lakes (in the area facing Varanger Fjord that is, the Jääräjoki‐Nuorgam area). The determined levels of water temperature, conductivity, pH, oxidation–reduction potential (ORP), and isotope ratios (δ ¹⁷ O, δ ¹⁸ O, and δ ² H), and the elemental and ionic concentrations, total organic carbon (TOC), and chlorophyll a concentration showed clear differences for objects related to the Skalluvaara palsa mire and outside of it, as revealed in the principal component analysis (PCA). In particular, elevated rock weathering indices and anomalous concentrations of Ni, Zn, and Hg were found in these aquatic environments. However, the highest concentrations of several metals and metalloids, including heavy metals, were found in the water not impacted by palsa mires, and their concentrations correlated with TOC concentrations. We conclude that other sources are more important inorganic inputs in the area, and it may be possibly connected to the erosion of peat or soil, which requires further investigation.

The common products of acidogenesis, the key stage in the process of anaerobic digestion, are lactate, butyrate, propionate, and acetate. They were decomposed in the Up-flow Anaerobic Sludge Blanket bioreactors working in continuous-flow open systems. A comprehensive analysis of variations in both isotopic ratios and concentrations of organic acids in the effluents was conducted to enhance comprehension of methanogenic processes. The analysis of carbon isotope fractionation in the CO₂-CH₄ system, as evidenced by the α¹³C_CO2-CH4 factor, has indicated that acetate decarboxylation has occurred. Furthermore, a decline in CO₂ levels was observed, accompanied by the predominance of butyrate and propionate, despite the presence of acetic acid in the effluents from all the bioreactors. Butyric acid demonstrated the greatest resistance to decomposition, resulting in ¹³C-enrichment of DIC. Lactic acid was utilised almost entirely. The observations presented above were subsequently validated through statistical analysis. A comparative analysis of the δ¹³C(CH₄) and δ¹³C(CO₂) values of our study with those of other natural substrates (detritic lignite, xylite, maize silage, and cattle manure) was undertaken, and it was found that isotope fractionation differs significantly in closed (potential thermodynamic processes) and open systems (expected Rayleigh processes). In the context of open systems, the isotope fractionation factor α¹³C_CO2-CH4 during methaneogenesis has been observed to attain values that are consistent with those observed in CH₄ oxidation. The study revealed that the presence of acetate in the substrate (i.e., the M4 bioreactor) led to the generation of CO₂ with a higher proportion of light carbon isotopes. This, in turn, resulted in a shift in the isotope fractionation factor (i.e., α¹³C_CO2-CH4) to values below 1.03. Our results suggest that methanogenic pathway signatures in open, continuous-flow systems may only be partially apparent. This is because substrate depletion drives Rayleigh-type isotope enrichment, while the dominance of a single substrate and its constant inflow stabilise pathway expression and shift control towards substrate dynamics rather than intrinsic microbial changes. Our finding suggests that isotope-based diagnostics could enhance process control in biogas plants by identifying substrate-driven limitations and facilitating more efficient and stable CH₄ production.

Norway spruce (Picea abies L.) growing in mountain forests is a sensitive indicator of environmental change, but its growth response may be strongly modified by local site conditions, which is important for sustainable forest management under climate change. This study examined two spruce populations in the upper montane zone of the Śnieżnik Massif, Eastern Sudetes, southwestern Poland: one growing on a raised bog (Sadzonki—TS) and the other on mineral soil (Owczarnia—OW). Tree-ring width (TRW) chronologies were developed from 59 sampled trees represented by increment cores and stem discs, covering 1781–2023 for TS and 1800–2023 for OW. Annual δ¹³C analysis was performed for a selected TS tree, and decadal wood geochemistry was analyzed for a selected disc. Spruces growing on the raised bog showed tree-ring widths that were less than half those of trees growing on mineral soil. TRW was mainly controlled by summer or spring–summer temperature, while precipitation had a stronger positive effect at the mineral-soil site. δ¹³C showed weak relationships with TRW but negative correlations with mean annual and summer temperature. Elevated concentrations of Na, K, Ca, Mg, Fe, Mn, Cu, Zn, and Pb occurred mainly in 1941–1950 and 1971–1980, indicating the influence of historical air pollution. The contrasting growth trends and health status of the two populations demonstrate that local habitat conditions strongly shape spruce responses to environmental change and should be considered in sustainable mountain forest conservation and adaptation strategies.

Mining exploitation of cement/concrete components experience sometimes problems caused by tectonic process and water hazards during mining of polyhalite-bearing sulphate rocks. Polyhalite is a hydrated K-Mg-Ca sulphate mineral of high economic significance, including construction materials industry. On the other hand, traditional tectonic analyses for seismic/water events prediction, often emphasize external forces and mining-induced stress relaxation. They rarely arise questions on primary origin such forces. Potential cumulation of stress, resulted from internal geochemical-mineralogical origin of such forces, of large-scale compression/tension and mass-movement are often neglected. A universal, approach here concerns the role of geochemical control of volume-temperature variations combined with post-sedimentary transformation of anhydrite to polyhalite what apparently implicates substantial problems during any mining carried out in anhydrite bodies. Such 100% transformation: a) increase volume of elemental cells by c.a. +137,76 %, b) is exothermic, c) elevates pressure d) results stress, e) implicates deformations: compressive inside and tensile outside, f) forms elevations, g) results chaotic K/Ar ages with millions of years discrepancies, h) may result sesimtectonic-water-H2S combined hazards and apparent subsidence. Such transformations have critical implications for general view in tectonic forces and formation of deposits, geological documentation and mining of them, particularly in addressing water, stability hazards during resource extraction and environmental issues [subsidence/deformations, earthquakes, water regime/pollution/salinisation, H2S etc]. The geochemical reactions, accelerated by deep-mine drainage activity, may result in fast [even days/years] geochemically negligible anhydrite-to-polyhalite volume-grow transitions, which however results in seismotectonic- water- and H2S-hazars, especially in anhydrite-dolomite-halite mining systems. They are pivotal in shaping mechanical properties of rocks and their deformations and movement. The study underscores the need for integrated geochemical and structural analyses to better understand these phenomena and mitigate associated risks from exploration to resource extraction [economy, safety, water-brine-subsidence environmental hazards] and geoengineering.