We report a novel method for reliably removing the Mg-hydroxide interlayer from Mg-hydroxy-interlayered smectite (Mg-HIS). In this method, named FORM, Mg-HIS-rich clay samples are treated with formic acid (HCOOH) vapour, which reacts with Mg-hydroxy from Mg-HIS interlayers to form crystalline α-Mg formate (Mg(HCOO)₂). This method represents a simple addition to the widely used ethylene glycol treatment workflow used for clay-rich samples in X-ray diffraction analysis, and provides a straightforward approach for identifying or characterizing Mg-HIS during standard X-ray diffraction studies without additional analyses or equipment.

The reuse of dredged marine sediments is increasingly promoted as a sustainable alternative to disposal; however, the presence of contamination often severely limits their direct application in engineering works. In particular, contamination by heavy metals represents a critical issue due to their persistence, toxicity and strong interaction with fine-grained soil constituents, which may significantly affect both environmental safety and mechanical behavior. Among inorganic pollutants, Lead (Pb) is one of the most problematic elements, as it poses severe environmental risks and can influence interparticle interactions, pore fluid chemistry and cementation mechanisms. In this study, fine-grained marine sediments were artificially contaminated with lead through controlled spiking procedures in order to reproduce a representative and reproducible contamination scenario. The paper investigates the performances of Pb-contaminated sediments stabilized using innovative low-cement binders, combining traditional hydraulic binders with natural and waste-derived additives. A comprehensive geo–chemo–mechanical characterisation was carried out, including microstructural, geochemical and geotechnical investigations. Selected results are presented for representative mixtures, focusing on the comparison between conventional cement-based stabilisation and alternative solutions incorporating non-calcined mussel shell powder and biochar. The results highlight the role of binder composition on microstructural evolution, Lead immobilization mechanisms and mechanical response in terms of compressibility and strength. The proposed innovative binder solutions provide chemo-mechanical performances comparable to traditional cement treatments while reducing cement content and improving environmental compatibility, supporting their potential application in sustainable sediment management strategies.

Abstract Claystones and related sedimentary lithologies are considered as potential host rocks for the storage of high-level radioactive waste. The properties of claystones, which govern their barrier performance, can vary significantly between sites and formations. This study summarizes relevant barrier properties, with a particular emphasis on those dependent on burial history and maximum rock temperatures. Given the large number of properties influencing barrier quality, ranking them by relative importance is necessary. The predictable, non-linear behaviour of certain characteristics with geological burial depth allows for a substantial reduction in the number of properties requiring determination. Based on a set of representative repository-relevant rock lithologies, a case study comparison of potential claystone host rocks is presented. Hydraulic conductivity was assumed to be the most critical barrier property, with optimal values in rocks that reached peak diagenesis at burial depths exceeding 2000 m. To further distinguish claystone types and related lithologies in terms of barrier suitability, either cation-exchange capacity, reflecting the content of smectitic layers, or maximum temperature of palaeoburial heating ( T maxgeo ) can be used as an example. Pore-size distribution, correlating with the average particle distance, was particularly suited to estimating maximum burial depth, as it is less affected by thermal anomalies, pore fluid composition or cementation effects. Overall, combining key barrier properties with burial depth-dependent behaviour enables efficient assessment and comparison of claystone formations for deep high-level radioactive waste disposal. A quantitative comparison of various claystones, however, requires establishing a reactive solute transport model that simulates radionuclide release fluxes at specific timescales.

The aim of this study has been to evaluate the effectiveness of biogenic calcium carbonate derived from uncalcined mussel shells as a partial cement substitute for the mechanical improvement of fine marine sediments. If mechanical properties of the resulting shell-cement-sediment mixtures were not significantly inferior compared to those with pure cement, this could open a promising path towards simultaneous valorisation of two high-impact marine wastes: dredged sediments and discarded mollusc shells. Within this context two related research questions have been addressed. The first, a more fundamental one, focused on quantifying and understanding potential differences between biogenic and commonly used geogenic sources of calcium carbonate as partial cement replacement. Within this context a systematic comparison was conducted between mussel shell powder and limestone. The effects of two particle sizes (fine and coarse) and two replacement ratios (25% and 50%) were assessed. The results indicate that replacing 25% of cement with fine mussel shell powder yields the best mechanical performance, with an average increase of 7% in consistency index (CI) and 15% in extended shear strength from texturometer apparatus (STEXT) compared to mixtures with limestone. The enhanced performance is primarily attributed to the biogenic nature of the carbonate (aragonite), its elongated morphology, and its higher specific surface area (3.43 m2/g), which together promote pozzolanic reactions and the nucleation of hydration products. The second, more practical research question explored the actual effectiveness of shell powder as a cement substitute. A multidisciplinary and multiscale characterization was conducted on selected mixtures composed of a highly plastic clayey silt sediment from the Port of Taranto, treated with three different types of cement (Portland, blast furnace slag, and calcium sulphoaluminate), and with cement partially replaced by fine mussel shell powder at two replacement ratios (25% and 50%). The analyses performed (CI, STEXT, pHw, XRD, MIP, SEM) confirm that Portland and blast furnace slag cement-based mixtures incorporating mussel shell powder at a 25% replacement level achieve mechanical and structural performance comparable to or even slightly higher than that of the corresponding cement-only mixtures. Specifically, average increases in CI (about 9%) and STEXT (about 3%) are recorded in shell-containing mixtures respect to the traditional ones. Furthermore, shell-containing mixtures exhibit increased microporosity and reduced macroporosity, associated with a denser microstructure. In contrast, the sediment treated with calcium sulphoaluminate cement did not exhibit clear signs of cementation. This result may be attributed to the nature of the hydration products of this type of cement and the presence of high amounts of soluble sulphates. Overall, the findings demonstrate that mussel shell powder is a technically effective and environmentally sustainable solution for the stabilization of marine sediments, yielding performance that matches or even moderately exceeds that of conventional cement-based treatments, potentially contributing to reduced binder consumption, a lower carbon footprint, and the advancement of circular economy practices in the sustainable management of port materials.

An experimental investigation on the mineralogical evolution and mechanical behaviour of Alkali Activated Binders (AABs) based on the activation of mussel shell powder (MSP) is developed. Two alkaline solutions of different chemical composition are considered for the activation (i.e., 12M NaOH solution and a mixture of 12M NaOH and Na2SiO3 solutions). Physical and mechanical behaviour of the binders are analysed by means of Ultrasonic Velocities (UV) measurements and Unconfined Compressive Strength (UCS) tests. The reactivity of the activated MSP is monitored over time using Thermogravimetric analysis (TGA). The mineralogical investigations are fundamental to support the interpretation of the mechanical performance of the binders. The alkaline environment induced by the activators affects the reactivity of MSP, promoting the precipitation of new crystalline carbonate hydrated phases. Moreover, the availability of silica species in the system favours the formation of silicate hydrated gels. From a macroscopic point of view, the binder activated with a mixture of NaOH and Na2SiO3 solution shows a relevant improvement of UCS consistent with the precipitation of stable cementitious compounds.. An insight into the mechanical effects induced by AAB based on MSP on a dredged marine sediment is provided, highlighting the role of silicon availability on the effectiveness of the treatment.

Earth materials are subsoils used in construction due to their natural cementing properties. These properties originates from its clay fraction, which becomes cohesive during drying. Unlike common cement, earth materials are recyclable and have no CO2 emission apart from manufacturing. Unfortunately, earth materials containing the abundant clay mineral smectite exhibit large swelling and shrinkage strains. Such earth materials are considered unsuitable for construction unless a stabiliser is added, which is commonly Portland cement or quicklime. This study explored the use of MgO-based cementitious Binder (MB) as alternative with a focus on the mineralogical effect of MB on smectite during hydration. A series of MB/smectite blends and MB components/smectite was cured up to six months to investigate the mineralogical changes and the formation of magnesium (alumino) silicate hydrate. The results showed that MB transformed smectite into Mg-hydroxy-interlayered smectite (Mg-HIS) within hours. The reason is the dissolution of MgO, a main constituent of MB. The dissolved Mg precipitates as Mg-hydroxy in the interlayer and transforms the smectite to Mg-HIS in this process. This is causing a pH increase and may prevent a complete HIS formation as the MgO dissolution mechanism will change once the pH is above the point-of-zero charge of MgO. An advantage of the smectite to Mg-HIS transformation is the strongly reduced the swelling/shrinkage properties of the clay. This suggests that adding MB to smectite could be a superior binding approach compared to quicklime, which primarily causes clay particle flocculation.

Burnt oil shale (BOS), obtained from the combustion of oil shale, is a promising supplementary cementitious material (SCM) based on its chemistry and mineralogy. This paper summarizes the use of BOS and its hydration in blended cements. It presents new data on the effect of combinations of alkali activators and Ca(NO3)2 in blended cements containing 50 % Portland cement (OPC) where BOS is combined with limestone, fly ash and ground granulated blast furnace slag. These chemical admixtures increase the slope of the correlation between compressive strength and heat of hydration of BOS containing mixes, providing an increase in compressive strength from 1 to 7 days for similar heat release to the control system. In contrast, the slope is not affected in absence of BOS. The change is due to a higher volume of hydrates from BOS increased hydration for a given C3S degree of hydration, likely from a less exothermic dissolution of BOS amorphous component. These admixtures increase the reactivity of both BOS and OPC at different curing times and depending on the type of alkali activator. They promote ettringite and portlandite precipitation, inducing a refinement of the microstructure, particularly around BOS particles. The information presented should pave the way to a broader and more effective use of BOS in blended cements with particularly low clinker contents.

An experimental investigation on the use of mussel shell powder (MSP) as a precursor for Alkali Activated Binders (AAB) is presented in this study. The results of this study opens up new perspectives on the production of biowaste-based binders (mussel shells) for the mechanical improvement of soils. Two alkaline solutions of different chemical composition were considered for this study, namely 12 molar sodium hydroxide solution (12M NaOH) and a mixture of NaOH and sodium silicate (Na2SiO3) solution. Mineralogical and microstructural changes of AAB were monitored over time by means of X-ray Diffraction (XRD), Thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM) and Mercury Intrusion Porosimetry (MIP). The alkaline environment induced by 12M NaOH promotes the dissolution of calcium carbonate and the precipitation of metastable gels, then transformed into crystalline carbonate hydrates (i.e., pirssonite and gaylussite). The availability of silica in the system, induced by the use of NaOH+Na2SiO3, favors also the development of a second class of reactions (i.e. pozzolanic reactions) responsible for the precipitation of silicate hydrated gels. As a consequence, the binder activated by 12M NaOH solution showed a reduction of Unconfined Compressive Strength (UCS) over time due to the transformation of metastable carbonate gel into crystals, whereas the binder activated with NaOH+Na2SiO3 showed a higher improvement of UCS for the precipitation of stable cementitious compounds. The carbon footprint of alkali-activated mussel shell binder was evaluated and compared with ordinary Portland cement. An insight into the mechanical effects induced by the Alkali Activated Mussel Shells Binders (AAMSB) on a dredged marine sediment was provided, highlighting the role of silicon availability in the alkaline activator on the effectiveness of the treatment.

This article reports some of the results of an experimental research dealing with the reuse of two highly impacting wastes of marine origin, i.e., dredged sediments and mussel shells. Traditionally, commercial cement has been for long used for the mechanical improvement in ex-situ management options of dredged sediments. However, the environmental impact of cement production pushes toward more sustainable binder materials. This study contributes to such a general objective by investigating the effectiveness of shell powder as a partial replacement of cement for the stabilization of dredged sediments. Specifically, the experimental programme involved both traditional cement-based sediment stabilization solutions and original ones where different sediment-shell powder-cement mixtures where prepared and tested. The results of multiscale investigations, including physicochemical and geomechanical tests, indicate a promising potential for mussel shells to reduce compressibility and increase strength properties of sediments, thus contributing to more sustainable waste management practices.

The article reports results from an experimental study on the chemo-mechanical treatment of dredged marine sediments making use of sustainable and original solutions. Specifically, the research entails the use of seashells and biochar as additives for the chemo-mechanical improvement of dredged fine-grained sediments that were artificially polluted by kerosene. The study includes unconfined compression tests, chemical analyses, and SEM photographs of various sediment-based mixtures. Evidence is provided that seashells represent a viable alternative to cement, as they were found to be as effective as cement when partially replacing it. When the sediment is polluted, the overall strength of the mixture reduces but shell powder is still a viable solution, both for its mechanical and chemical efficacy. The addition of biochar is more effective when just cement is used for treatments.

The present study contributes to developing a novel eco-friendly solution for the mechanical stabilisation of dredged marine sediments by using mussel shells – another high-impact waste of marine origin – in the partial replacement of cements. What are the underlying chemo-mechanical interactions affecting the evolution of such mixtures? Can mussel shells replace cement without compromising useful geomechanical and geochemical properties of the stabilised sediments? Can such mixtures still be modelled as soils when it comes to their geotechnical design and analysis? The paper answers these questions by assessing the mechanical performance of mixtures formed by sediments stabilised with three types of cement and a mussel shell powder and comparing them with those of the same sediments treated with cement only. Multiple beneficial effects of the use of mussel shell powder, as a peculiar source of calcium carbonate from its biogenic origin, have been demonstrated: it acts as a void filler; enhances the electrolytic exchanges between sediment and cement, and increases the contact area between the mineral particles promoting the chemical hydration reactions. As a result, for fixed replacement ratios, the original mixtures still exhibit soil-like behaviour consistent with traditional geomechanics and even better performance than the control mixtures.

The research shows the results of a micro to macro testing programme carried out on contaminated marine sediments from a natural deposit to assess the effects of bio-chemo-mechanical coupled processes which may act in complex natural environments and affect the geotechnical properties of the clays. The research has been triggered by the emblematic case of the contaminated Mar Piccolo (MP) basin in Taranto (Southern Italy), where the high degree of pollution recorded in the clayey sediments at the sea bottom, has been found to worsen water quality and promote bioaccumulation of pollutants in several species. Several samples of sediments collected in the basin from the top layer exhibited peculiar geotechnical properties, in terms of plasticity and activity indexes, compressibility and hydraulic permeability. The results of the geotechnical testing were interpreted taking into account the XRD mineralogical results and the chemical composition of the soil matrix. Furthermore, thermogravimetry tests results were examined to explore the nature of the sediment skeleton and of its organic matter content, based on the main thermal reactions occurring within different temperature ranges. Lastly, scanning electron microscopy and mercury intrusion porosimetry were performed to assess the sediment pore size distribution as well as their content in microfossils and diatoms. The original multiscale analysis carried out on some selected sediment samples showed that the biogeochemical degradation of organic matter and the presence of microfossils and diatoms significantly affect the micro to macro behaviour of marine sediments.

Glauconite forms in shallow marine basins under oxic to suboxic conditions. It is an Fe -rich sheet silicate often found in calcareous sandstones. How soils evolve on glauconitic sandstones (calcarenite) is poorly addressed: therefore, we investigated the evolutional trajectories. These soils should be enriched in Fe, depleted in K and contain kaolinite and smectite resulting from weathering. We investigated 11 soil profiles on glauconitic calcarenite in a Mediterranean area. The elemental contents, fractions of Fe and Al, soil mineralogy, magnetic susceptibility and stable isotopic composition (C, O) of the bulk soil and carbonates were analysed to explore pedogenesis. The carbonates reflect a former marine basin having onshore organic matter resulting from freshwater input. With soil formation, the primary carbonates were replaced by pedogenic carbonates having a lower 813C and 818O signal. Several sites were influenced by human activity since ancient times, reflected by the magnetic susceptibility. The shallow soils had a low weathering degree (CIA of 55 to 70). The better developed Vertisols exhibited a CIA value of up to 85. All soils contained smectite and quartz and, depending on the weathering degree, calcite. Kaolinite formation was connected to high Ca, K, Mg and Na losses. The high oxalate- and dithionite-extractable Fe contents are explained by glauconite weathering. Kaolinite is inherited from the parent material but also actively forms in the soils probably through precipitation from soil water. Due to the presence of smectite and oxyhydroxides the soils sequester a high amount of soil organic carbon (up to 30 kg/m2). Topography exerts a distinct influence on weathering and soil formation. Deepest soils and an advanced weathering stage were measured on footslope sites and shallow soils having a low weathering degree on crest/ shoulder sites. Soils on glauconitic calcarenite represent a unique weathering environment that should be investigated even more at the micro -scale.

The presence of bound water in clay has a significant impact on the physical and chemical properties of clay, particularly its strength, permeability, and creep behavior. In this paper, the bound water in clay has been studied from the perspective of water potential. Initially, the adsorption isotherms of powders and consolidated samples for Na- and Ca-bentonite and illite were measured, and the bound water content was determined by subtracting the capillary water in the isotherms, with the capillary water being calculated by mercury intrusion porosimetry tests. The results indicated that bound water is independent of the void ratio and pore structure of clay, which is consistent with previous studies. Then, metadynamics was conducted to determine the adsorption free energy landscapes of the three clays, and the lowest suctions of the three clay minerals were determined to be -1.7, -5.4, and -2.1 GPa, respectively. Finally, through a comparison of the simulations and experiments in this study and in the literature, three important conclusions were drawn. Firstly, the lowest water potential for montmorillonite exhibits a linear relationship with the hydration free energy of exchangeable cations. Secondly, the critical water potential for tightly bound water is determined as the first inflection point in the relationship between water potential and water content, and the critical value of montmorillonite is found to be correlated to the valence of exchangeable cations. Lastly, the boundary between loosely bound water and capillary water is determined as the starting point of capillary water formation. Overall, this research highlights the importance of considering water potential as a key factor in understanding the behavior of bound water in clay.

Water is a ubiquitous adsorbate relevant for many natural systems and engineering applications. Water adsorption behavior on clays, sediments, soils, and related geomaterials was studied for over a century and fueled a continuous discussion on the meaning of water sorption as a measure of mineral surface area (MSA). Despite this, MSA quantification using nitrogen established itself as the most widely accepted approach despite the relevance of water for a wide spectrum of in-situ environmental conditions. Many attempts at water-based MSA measurements are reported in dispersed literature. To date, interlaboratory comparison of MSA has been hampered by disparate methodologies for conducting measurements using both water and nitrogen adsorbates. Water and nitrogen-based MSA both using the BET equation for a variety of minerals and mineral matrices relevant for earth, environmental, and clay science was compiled in this contribution. The historical development of water-based MSA determination is also reviewed. The overlay of multitude of factors including mineralogy, interlayer spaces, organic matter, structural water, electrostatic interactions, microstructure, sample preparation and measurement conditions, influencing both nitrogen and water-based MSA quantities are discussed and general guidance is provided on the interpretation of complex MSA datasets.

The article reports the results of an experimental activity conducted on dredged fine-grained marine sediments and aimed to find out novel eco-friendly solutions for their mechanical stabilisation. The main idea of this research is to use seashells, i.e., another waste material, to partially replace cement binders in the mechanical stabilisation of sediments for the production of a new stable material that can potentially be used in construction. To this aim, an original procedure has been developed to obtain a powder of mussel shells without their calcination. Physical properties, one-dimensional compression behaviour and permeability of the novel mixtures including sediments, mussel shell powder and cements are presented for different curing times. The efficacy of the solutions is assessed also by comparison with the performance of control mixtures prepared by mixing the same sediments with cement only. The effects of the different treatments on the soil properties were analysed, demonstrating multiple beneficial effects of using the mussel shell powder. Evidence is provided that seashells represent a viable alternative to cement, as they were found to be as effective as traditional hydraulic binders, when replacing them up to 1/4, in enhance geomechanical and geochemical performance of the stabilized material.

The constraints associated with the availability of huge amounts of natural resources for infrastructure and agricultural development call for the reuse and recycling of anthropogenically created geomaterials, which is in line with the UN Sustainable Development Goals. In this context, valorisation of dredged sediments (DSs), obtained from water bodies such as rivers, lakes and oceans, as a resource material is worth considering. Unfortunately, DSs might be contaminated and exhibit a higher moisture-holding capacity due to higher contents of organic matter and clay minerals/colloids. These attributes pose a serious question towards dumping of DSs in the deep sea (in the case of marine sediments), a practice that prevails presently despite endangering marine life. Hence, the way forward would be to characterise them holistically, followed by adequate treatment to make them ecologically synergetic before developing a strategy for their valorisation. In this regard, many studies have been focused on the characterisation and treatment of DSs to make them an environmentally safe man-made resource. With this in mind, a critical synthesis of the published literature pertaining to the (a) characterisation; (b) treatment, remediation and immobilisation of contaminants; and (c) utilisation of DS was conducted, and the salient findings are presented in this paper. Based on this study, it was observed that DS acts as a sink for emerging contaminants for which no remediation strategies are available. Moreover, the study emphasised the lacuna in upscaling the existing treatment and stabilisation techniques to field conditions while highlighting the concept of circular economy.

Smectites, like other clay minerals, have been shown to promote ice nucleation in the immersion freezing mode and likely contribute to the population of ice-nucleating particles (INPs) in the atmosphere. Smectites are layered aluminosilicates, which form platelets that depending on composition might swell or even delaminate in water by intercalation of water molecules between their layers. They comprise among others montmorillonites, hectorites, beidellites, and nontronites. In this study, we investigate the ice nucleation (IN) activity of a variety of natural and synthetic smectite samples with different exchangeable cations. The montmorillonites STx-1b and SAz-1, the nontronite SWa-1, and the hectorite SHCa-1 are all rich in Ca2+ as the exchangeable cation; the bentonite MX-80 is rich in Na+ with a minor contribution of Ca2+, and the synthetic Laponite is a pure Na+ smectite. The bentonite SAu-1 is rich in Mg2+ with a minor contribution of Na+, and the synthetic interstratified mica-montmorillonite Barasym carries NH4+ as the exchangeable cation. In emulsion freezing experiments, all samples except Laponite exhibited one or two heterogeneous freezing peaks with onsets between 239 and 248 K and a quite large variation in IN activity yet without clear correlation with the exchangeable cation, with the type of smectite, or with mineralogical impurities in the samples. To further investigate the role of the exchangeable cation, we performed ion exchange experiments. Replacing NH(4 )(+)with Ca2+ in Barasym reduced its IN activity to that of other Ca-rich montmorillonites. In contrast, stepwise exchange of the native cations in STx-1b once with Y3+ and once with Cu2+ showed no influence on IN activity. However, aging of smectite suspensions in pure water up to several months revealed a decrease in IN activity with time, which we attribute to the delamination of smectites in aqueous suspensions, which may proceed over long timescales. The dependence of IN activity on platelet stacking and thickness can be explained if the hydroxylated chains forming at the edges are the location of ice nucleation in smectites, since the edges need to be thick enough to host a critical ice embryo. We hypothesize that at least three smectite layers need to be stacked together to host a critical ice embryo on clay mineral edges and that the larger the surface edge area is, the higher the freezing temperature. Comparison with reported platelet thicknesses of the investigated smectite samples suggests that the observed freezing temperatures are indeed limited by the surface area provided by the mostly very thin platelets. Specifically, Laponite, which did not show any IN activity, is known to delaminate into single layers of about 1 nm thickness, which would be too thin to host a critical ice embryo.

Global warming in mid-latitude alpine regions results in permafrost thawing, together with greater availability of carbon and nutrients in soils and frequent freeze-thaw cycles. Yet it is unclear how these multifactorial changes will shape the 1 m-deep permafrost microbiome in the future, and how this will in turn modulate microbiallymediated feedbacks between mountain soils and climate (e.g. soil CO2 emissions). To unravel the responses of the alpine permafrost microbiome to in situ warming, we established a three-year experiment in a permafrost monitoring summit in the Alps. Specifically, we simulated conditions of warming by transplanting permafrost soils from a depth of 160 cm either to the active-layer topsoils in the north-facing slope or in the warmer south-facing slope, near the summit. qPCR-based and amplicon sequencing analyses indicated an augmented microbial abundance in the transplanted permafrost, driven by the increase in copiotrophic prokaryotic taxa (e.g. Noviherbaspirillum and Massilia) and metabolically versatile psychrotrophs (e.g. Tundrisphaera and Granulicella); which acclimatized to the changing environment and potentially benefited from substrates released upon thawing. Metabolically restricted Patescibacteria lineages vastly decreased with warming, as reflected in the loss of alpha-diversity in the transplanted soils. Ascomycetous sapro-pathotrophs (e.g. Tetracladium) and a few lichenized fungi (e.g. Aspicilia) expanded in the transplanted permafrost, particularly in soils transplanted to the warmer south-facing slope, replacing basidiomycetous yeasts (e.g. Glaciozyma). The transplantation-induced loosening of microbial association networks in the permafrost could potentially indicate lesser cooperative interactions between neighboring microorganisms. Broader substrate-use microbial activities measured in the transplanted permafrost could relate to altered soil C dynamics. The three-year simulated warming did not, however, enhance heterotrophic respiration, which was limited by the carbon-depleted permafrost conditions. Collectively, our quantitative findings suggest the vulnerability of the alpine permafrost microbiome to warming, which might improve predictions on microbially-modulated transformations of moun-tain soil ecosystems under the future climate. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).