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The aim of this paper is to show the concise chemico-physical adsorbent performance of water purification systems utilizing geo- (e.g., allophane, clinoptilolite, and smectite) and bio-polymer materials (e.g., chitosan or cellulose nanocomposite materials) and to propose an optimal ground-water remediation technique. The performance of geo-materials is evaluated based on the individual sorption and immobilization capacities for various priority substances and pollutants (e.g., lead, zinc, cadmium, copper, arsenic, and others), their availability, and cost-efficient use. A systematic assessment of the sorption potential of geo-materials in comparison to other available sorbents used for the removal of harmful aqueous metal ions is made through a literature review. This paper introduces novel sustainable technologies based on natural and tailored silicate-polymerized substances (geo-materials and geopolymers), and highlights their applicability in the treatment of water and solid matter contaminated by heavy metal ions. The advantages of geo-materials and geopolymers over other commercially available sorbents used for heavy metal ion removal from solution are presented through a literature review. Benefits and current challenges of geo-materials and geopolymers applications in water processing technologies and in environmental remediation are discussed, with recognition of their performance, individual sorption and immobilization capacities, availability, and cost-efficient use. The applications described here comprise: (i) the removal of heavy metal ions from contaminated water using in-situ remediation strategies; (ii) heavy metal ion immobilization through co-precipitation with silicate binders in underground stabilization and waste solidification scenarios; and (iii) a proposal for a new geo-material/geopolymer-based solidification and stabilization technology for efficient, sustainable, and simultaneous treatment of soil/sediment and groundwater at environmental hotspots. Clay-substituted geopolymers, smectite, and zeolites are distinguished by their superb sorption and immobilization capacities for heavy metal ions, while biosorbents can play an important role in the removal of metals, metalloids (e.g., arsenic), and other contaminants. More research on individual removal mechanisms of heavy metals will provide new clues on the development of remediation strategies in advanced scientific and field applications, and on atomic-to-micron scale processes occurring at the solid–liquid interface. © 2022

Silicate mineral weathering and the resulting formation of clay minerals are key processes at the Earth’s surface. Reverse weathering reactions regulate the evolution of ocean pH and chemistry, atmospheric carbon dioxide budget, soil formation and associated nutrient and element transfer within local and global biogeochemical cycles. A key element released during weathering processes is silicon (Si), that enters the biogeochemical cycle as dissolved silicic acid (Si(OH)4 or DSi). During the transport of DSi through the hydro-, bio-, pedo- and lithosphere towards the ocean, DSi is involved in the formation of new silicate minerals (i.e., clay minerals) in particular in the critical zone (CZ). Here, DSi is frequently precipitating as gel-like, amorphous phases such as short range ordered hydroxyaluminosilicate phases (HAS: e.g., allophane) or as hydrous ferric silicates (HFS: e.g., hisingerite). These highly reactive minerals are known precursors to the formation of important soil clay minerals e.g., within the smectite group.The individual reaction pathways and the environmental controls underlying HAS and HFS formation within the CZ are not yet well constrained. Si isotope fractionation throughout HAS and HFS formation is a key tool to decode and assess such enigmatic reaction mechanisms. Therefore, a series of allophane-hisingerite precipitation experiments has been performed to investigate Si isotope fractionation to potentially resolve mechanisms and conditions underlying the formation of HAS and HFS phases. Kinetic and equilibrium Si isotope fractionation between reactive fluid and solid phases are studied at high temporal resolution. Isotope exchange mechanisms are investigated using the three-isotope method, which is a novel proxy to trace the direction and the progress of low-temperature water-mineral/rock interactions.

The formation of CaCO3 under ambient and low temperature environmental conditions has been extensively studied during the last decades. However, available data on the formation kinetics and mechanisms of CaCO3 at temperatures far below 0 °C are sparse. Here, we present CaCO3 formation pathways at -15 °C using a hypersaline sodium chloride solution at distinct molar Mg:Ca ratios of 0, 0.5, and 1. The (trans)formation process is monitored by pH and in-situ Raman spectroscopy. The freeze-dried precipitates are characterized by X-ray diffraction and the morphology is studied by scanning electron microscopy. These preliminary results help to understand the formation mechanisms of CaCO3 at temperatures below zero degree centigrade from homogeneous media and to refine experimental setups for mimicking extreme environmental carbonate formation conditions, e.g., in Antarctica or extraterrestrial environments.

The dinosaur–bird transition involved several anatomical, biomechanical, and physiological modifications of the theropod bauplan. Non-avian maniraptoran theropods, such as Troodon , are key to better understand changes in thermophysiology and reproduction occurring during this transition. Here, we applied dual clumped isotope (Δ 47 and Δ 48 ) thermometry, a technique that resolves mineralization temperature and other nonthermal information recorded in carbonates, to eggshells from Troodon , modern reptiles, and modern birds. Troodon eggshells show variable temperatures, namely 42 and 29 ± 2 °C, supporting the hypothesis of an endothermic thermophysiology with a heterothermic strategy for this extinct taxon. Dual clumped isotope data also reveal physiological differences in the reproductive systems between Troodon , reptiles, and birds. Troodon and modern reptiles mineralize their eggshells indistinguishable from dual clumped isotope equilibrium, while birds precipitate eggshells characterized by a positive disequilibrium offset in Δ 48 . Analyses of inorganic calcites suggest that the observed disequilibrium pattern in birds is linked to an amorphous calcium carbonate (ACC) precursor, a carbonate phase known to accelerate eggshell formation in birds. Lack of disequilibrium patterns in reptile and Troodon eggshells implies these vertebrates had not acquired the fast, ACC-based eggshell calcification process characteristic of birds. Observation that Troodon retained a slow reptile-like calcification suggests that it possessed two functional ovaries and was limited in the number of eggs it could produce; thus its large clutches would have been laid by several females. Dual clumped isotope analysis of eggshells of extinct vertebrates sheds light on physiological information otherwise inaccessible in the fossil record.

Calcitic valves of non-marine ostracodes are important geochemical archives. Investigations of the relationship between the isotopic ranges of modern ostracode populations and their host water provide important information on local or regional conditions and influences. Here we present the first δ18Oostracode and δ13Costracode dataset of the freshwater ostracode species Cytheridella ilosvayi along with characterization of the precipitating water - chemical composition, δDwater, δ18Owater, δ13CDIC values - covering a large geographical range (Florida to Brazil). With this data we extended a newly developed approach based on the estimation of δ18O values of monthly equilibrium calcites as references for the interpretation of δ18Oostracode values.The expected apparent oxygen isotope fractionation between CaCO3 - and H2O is correlated with temperature with smaller values occurring at higher temperatures as valid at isotope equilibrium (δ18Ocalcite_eq). Additional to a species-specific offset, unusual high deviations of δ18Oostracode vs. δ18Owater values most likely reflect the time lag between valve calcification and sampling. Coincidence between δ18Oostracode and δ18Ocalcite_eq is restricted to few months indicating a seasonal calcification of Cytheridella. There is a characteristic pattern in its difference between mean δ18Oostracode and δ18Ocalcite_eq which implies that Cytheridella provides a synchronous life cycle in its geographical range with two calcification periods in spring (May, June) and autumn (October). This ubiquitous life cycle of Cytheridella in the entire study area is considered to be phylogenetically inherited. It might have originally been adapted to environmental conditions but has been conserved during the migration and radiation of the group over the Neotropical realm.

The physicochemical characterization of the groundwater from the southern part of the Pannonian Basin of the Neogene age was investigated. High concentrations of manganese and nitrate as well as selected polycyclic aromatic hydrocarbons (PAHs) above legislation were monitored as the main challenges. The novel cost-effective nano-geopolymer remediation technique for groundwater purification was proposed due to the existing conventional one. Organic and inorganic parameters were conducted on adapted pollution indices: the Nemerow and the single-factor pollution index, the ecological risk factor as well as the chosen rations of particular PAHs (pyrolytic or petrogenic origin) for water. The statistical factor analysis of the principal component analysis grouping of Ca and Mg ions in the groundwater suggests the dissolution of sedimentary rocks, mostly limestone. The high correlation between SO42−, KMnO4 cons. and TOC indicates point source pollution, originating from the leakage of municipal wastewater pipes. Chloride, Al, Zn and the total phosphorus in the solution have both a crustal and anthropogenic origin. The concentrations of SO42−, Mg, Na, K and Cl are extremely low. Cost-effective technologies, such as high-performance clay minerals, zeolites and calcium–aluminum–silicate–hydrates, were selected for manganese removal, e.g., clinoptilolite (natural zeolite), one of the highest in this class with an adsorption capacity equal to 4.22 mg/g. An important aspect related to this research is the inclusion of, e.g., manganese as the complexing agent and of chlorides in the second Watch List which lies under the Water Framework Directive. Graphic abstract: [Figure not available: see fulltext.].

Green inhibitors (GI) are eco-friendly organic molecules capable of inhibiting the nucleation and precipitation of solids, like CaCO3 minerals. Although increasingly used in technical settings, the...

ZusammenfassungUm notwendige Reinigungsarbeiten zur Aufrechterhaltung der Drainagewirkung von Drainagerohren in Tunneln zu minimieren, wurden im gegenständlichen Projekt Kunststoffe mit verschiedenen aktiven Wirkstoffen modifiziert, welche die Versinterungsneigung an den Rohroberflächen reduzieren sollen. Ausgehend von dieser praktischen Fragestellung wurden sieben verschiedene Rezepturen hinsichtlich ihres Potentials zur Verringerung der karbonatischen Versinterungen und zur industriellen Verarbeitbarkeit bewertet. Die hergestellten Compounds aus Matrix-Kunststoff, einem kommerziell verfügbaren Polyethylen-Rohr Typ und dem jeweiligen Wirkstoff sind zu Prüfkörpern verarbeitet und sowohl in Labor- als auch in Feldversuchen in realen Tunnelbauwerken ausgelagert worden. Anschließend fand die Beurteilung der Probekörper hinsichtlich der aufgewachsenen Versinterungen mittels chemischem Säureaufschluss, sowie optischen Analyseverfahren statt. Hinsichtlich der Verringerung der Versinterung zeigten das Polyethylen-Glykol Copolymer sowie das Compound mit Zeolith die besten Effekte.

The oxygen and clumped isotope signatures of Mg calcites are routinely used as environmental proxies in a broad range of surroundings, where Mg calcite forms either by classical nucleation or via an amorphous calcium magnesium carbonate (ACMC) precursor. Although the (trans)formation of ACMC to Mg calcite has been identified for an increasing number of settings, the behavior of both isotope proxies throughout this stage is still unexplored. In the present study ACMC (trans)formation experiments were carried out at constant pH (8.30 ± 0.03) and temperature (25.00 ± 0.03 °C) to yield high Mg calcite (up to 20 mol% Mg). The experimental data indicate that the oxygen isotope values of the amorphous and/or crystalline precipitate (δ$^{18}$O$_{prec}$, analyzed as Mg calcite) are affected by the (trans)formation pathway, whereas clumped isotopes (Δ$_{47prec}$ = Δ$_{47Mg-calcite}$) are not. The oxygen isotope evolution of the solid phase can be explained by the instantaneous trapping of the isotopic composition of the aqueous (bi)carbonate complexes. This entrapment results in remarkably high 10$^{3}$ln(α$_{prec-H2O}$) values of ∼33‰ at the initial ACMC formation stage. During the ACMC transformation process the oxygen isotope equilibrium is approached rapidly between Mg calcite and water (Δ$^{18}$O$_{Mg calcite-water}$ = 30.3 ± 0.4‰) and no isotopic memory of the initial to the final Mg calcite at the end of the experiment occurs. The implications for oxygen and clumped isotope signatures of Mg calcite formed via ACMC are discussed in the aspects of various scenarios of (trans)formation conditions and their use as environmental proxies.

Barium isotope fractionation during calcite and aragonite inorganic precipitation was studied in mixed flow reactors as a function of precipitation rate at 25 °C and pH = 6.3 ± 0.1. The measured Ba isotope fractionation that occurs between calcite and the forming fluid in the investigated range of calcite growth rates (10-8.0 ≤ Rp(calcite) ≤ 10−7.3 mol/m2/s) is insignificant. Barium isotope fractionation between aragonite and the fluid decreases with increasing precipitation rate from Δ137/134Baaragonite-fluid = +0.25 ± 0.06‰ for Rp(aragonite) ≤ 10−8.7 mol/m2/s to −0.10 ± 0.08‰ for Rp(aragonite) = 10−7.6 mol/m2/s, thus reflecting preferential incorporation of either heavy or light Ba isotopes in aragonite at slow and fast growth rates, respectively. The dependence of Ba isotope fractionation on aragonite growth rate is well described by the surface reaction kinetic model developed by DePaolo (2011) when the values +0.27‰ and −2.0 ± 0.2‰ are used for the equilibrium and kinetic Ba isotope fractionation factor, respectively. The enrichment of aragonite in the heavier Ba isotopes is consistent with the equilibrium fractionation factor of +0.34‰, calculated here between Ba-substituted aragonite and Ba2+ (aq), from first-principles calculations. This positive fractionation is related to a shorter average Ba[sbnd]O bond length in the aragonite structure while the coordination number does not change much (i.e. 9). The lack of isotope fractionation between the Ba aquo ions and the 6-coordinated Ba in calcite likely suggests that the coordination reduction required for the incorporation in the lattice of Ba adsorbed at calcite growing sites proceeds without isotope fractionation with the fluid. Otherwise the precipitated calcite should have been enriched in heavy isotopes by ∼0.17‰, as predicted by first-principles calculations. These results are the first experimental measurements of Ba isotope fractionation during inorganic calcite and aragonite mineral formation and set the basis for understanding the mechanisms controlling Ba isotope composition in CaCO3 minerals that is an essential perquisite for application of this isotopic system in natural samples.

This study aims to differentiate the potential recharge areas and flow mechanisms in the North-eastern Basin, Palestine. The results differentiate the recharge into three main groups. The first is ...

The high-precision analysis of the abundance of the dominant m/z 47 CO2 isotopologue derived from acid digestion of carbonate minerals (13C18O16O; denoted by Δ47) forms the basis for carbonate clumped isotope thermometry. Since the first measurements were published 16 years ago, considerable effort has gone into characterizing the relationship between Δ47 and carbonate precipitation temperature, and in identifying carbonates that do not achieve isotopic equilibrium. Mass spectrometry is now capable of the paired measurement of the primary m/z 47 and m/z 48-isotopologues (Δ47 and Δ48; 12C18O2 is denoted by Δ48), which has the potential to place additional constraints on kinetic isotope effects in carbonate minerals and trace distinct reaction pathways. Here, we explored factors that contribute to calcite mineral equilibrium and disequilibrium in Δ47 and Δ48 using a combination of experiments and theoretical calculations with three types of models. We precipitated calcite at pH 8.3 with carbonic anhydrase (CA) to approach quasi-isotopic equilibrium in the dissolved inorganic carbon pool and report values for Δ47, Δ48, and oxygen isotopes (δ18O) for calcite grown over a temperature range from 5 to 25 oC and compare our findings to predictions from an ion-by-ion model that support equilibrium precipitation. We also compare results to the Devils Hole slow-growing cave calcite, and other published temperature calibration data. We report the following combined equilibrium calibration relationships: Δ48 CDES 90 = (0.429 ± 0.010) Δ47 CDES 90 - (0.006 ± 0.006); r2 = 0.98; Δ47 I-CDES = (0.037 ± 0.001) × 106T-2 + (0.178 ± 0.009); r2 = 0.99; Δ48 CDES 90 = (0.015 ± 0.0005) × 106T-2 + (0.078 ± 0.006); r2 = 0.98. We used paired measurements of Δ47 and Δ48 to constrain kinetic isotope effects in calcite precipitated at pH ranging from 8.3-11 and temperatures from 5 to 25 oC, with and without CA present, and observe kinetic enrichments in Δ47, negative (hyperstochastic) values for Δ48, and depleted values of δ18O, compared to equilibrium values. Experimentally constrained kinetic trajectories, when compared with an ion-by-ion model and IsoDIC theoretical predictions, are consistent with CO2 hydration/hydroxylation. Mixing drives elevated Δ47 and Δ48 values and was assessed using mixing experiments with endmembers of varying isotopic compositions and compared to a Δ47 and Δ48 mixing model that constrains nonlinear mixing trajectories for calcite. While mixing may induce artifacts in two-component mixtures when endmember bulk compositions differ by more than 7 ‰, or if endmember Δ47 and Δ48 differ by more than 0.03 ‰, this should be detectable and potentially correctible using paired clumped isotope measurements and is unlikely to be important for some materials.

Retrograde clay mineral reactions (i.e., reverse weathering), including glauconite formation, are first-order controls on element (re)cycling vs sequestration in modern and ancient marine sediments. Here, we report substantial K–Mg–Fe sequestration by glauconite formation in shallow marine settings from the Triassic to the Holocene, averaging 4 ± 3 mmol K·cm−²·kyr− 1, 4 ± 2 mmol Mg·cm−²·kyr− 1 and 10 ± 6 mmol Fe·cm−²·kyr− 1, which is ~ 2 orders of magnitude higher compared to deep-sea settings. Upscaling of glauconite abundances in shallow-water (− 1, ~ 0.04–0.06 Tmol Mg·yr− 1 and ~ 0.11–0.14 Tmol Fe·yr− 1. We conclude that authigenic clay elemental uptake had a large impact on the global marine K, Mg and Fe cycles throughout Earth`s history, in particular during ‘greenhouse’ periods with sea level highstand. Quantifying authigenic clay formation is key for better understanding past and present geochemical cycling in marine sediments.

Retrograde clay mineral reactions (reverse weathering), including glauconite formation, are first-order controls on element sequestration in marine sediments. Here, we report substantial element sequestration by glauconite formation in shallow marine settings from the Triassic to the Holocene, averaging 3 ± 2 mmol·cm−²·kyr−1 for K, Mg and Al, 16 ± 9 mmol·cm−²·kyr−1 for Si and 6 ± 3 mmol·cm−²·kyr−1 for Fe, which is ~2 orders of magnitude higher than estimates for deep-sea settings. Upscaling of glauconite abundances in shallow-water (0–200 m) environments predicts a present-day global uptake of ~≤ 0.1 Tmol·yr−1 of K, Mg and Al, and ~0.1–0.4 Tmol·yr−1 of Fe and Si, which is ~half of the estimated Mesozoic elemental flux. Clay mineral authigenesis had a large impact on the global marine element cycles throughout Earth’s history, in particular during ‘greenhouse’ periods with sea level highstand, and is key for better understanding past and present geochemical cycling in marine sediments.

ZusammenfassungAusgehend von der Problematik aufwändiger Instandhaltungsarbeiten für die Funktionstüchtigkeit von Drainagerohren in Tunnelbauwerken wurde das interdisziplinäre Forschungsprojekt „PolyDrain“ initiiert. Im Rahmen des Forschungsprojekts werden diesbezüglich kritische Bauwerke in Österreich erhoben und vielversprechende Methoden zur Verringerung von zumeist karbonatischen Versinterungen in Drainagerohren untersucht. Durch gezielte Materialmodifikationen der Drainagerohre soll der Instandhaltungsaufwand zukünftiger oder zu sanierender Tunnelbauwerke reduziert werden, indem Reinigungsintervalle gestreckt und/oder Reinigungen rascher durchgeführt werden können. Der gewählte Ansatz umfasst die maßgeschneiderte Modifizierung von Kunststoff-Drainagerohrmaterialien. Dadurch ist es möglich, mechanisch widerstandsfähigere Rohre zu erzeugen und/oder das Versinterungsverhalten im Drainagerohr, inklusive der Drainageschlitze, zu reduzieren. Bevor eine Umsetzung im großtechnischen Maßstab möglich ist, ist es allerdings wichtig, nicht nur die kurzzeitige Wirksamkeit – im Projekt auch im Labor – zu untersuchen.

The incorporation of magnesium and sulfate in calcite is frequently used to characterize and trace the environmental conditions occurring during carbonate mineral formation. Although both ions are simultaneously incorporated in the growing calcite, the effect of sulfate on magnesium incorporation in calcite is still under-explored. In this study, we examine the Mg incorporation in low-Mg calcite as a function of growth rate at 25 °C and 1 bar pCO2 in the presence and absence of aqueous sulfate. The obtained results suggest that high calcite growth rates induce a significant increase in the partitioning coefficient of Mg between the precipitated low-Mg calcite and aqueous solution (i.e. D Mg = n Mg / n Ca calcite [ Mg 2 + ] / [ Ca 2 + ] solution ). Obtained DMg values exhibit similar dependence to mineral growth rate for experiments performed in the presence and absence of sulfate, however a systematic shift to lower DMg values is observed for calcites formed in the presence of sulfate. The lower DMg values of calcites formed in sulfate-bearing solutions are attributed to the incorporated SO4 ions which provoke expansion in the unit cell along the c-axis of the newly formed calcite. A larger unit cell is unfavorable for the substitution of Ca by smaller Mg ions in calcite. The coupled effect of (i) sulfate uptake during calcite growth and (ii) precipitation rate on DMg can be expressed by the equation D Mg = 0.03726 - 0.02345 × - l o g r p - 7 - X S O 4 × 0.004607 + 0.002109 × - l o g r p - 7 ; (−8 ≤ log(rp) ≤ −7; 0 ≤ Xso4 ≤ 2.6; T = 25 °C) and is valid for 0.01 ≤ DMg ≤ 0.04. In analogy to Mg also SO4 ions are inhibiting calcite growth, thus promoting the formation of aragonite due to adsorption phenomena and blocking of calcite surface sites. These results improve our understanding on physicochemical parameters controlling CaCO3 composition and mineral polymorphism and are discussed in their relevance for the use of magnesium and sulfate environmental proxies in natural surroundings.

The chemical resistance of eco-concrete with high levels (35–65 wt-%) of limestone substitution against Ca-leaching behaviour and sulphate attack was investigated by immersing powdered material in a 10 g L−1 Na2SO4 solution. Time-resolved hydrochemical characterisation of the reactive solutions was coupled with chemical, structural and mineralogical characterisation of the experimental solid materials to describe and to quantify alteration phenomena like the dissolution of portlandite and AFm-phases, transformation of C-S-H gel and the precipitation of ettringite, calcite and hydrogarnet. Nucleation and crystal growth dynamics of ettringite are controlled by the availability of Ca, reactive Al, solution pH and potentially the amount of clay minerals and/or superplasticiser used in the eco-concrete material. The experimental approach allows revealing competing reaction pathways and kinetics causing concrete damage in sulphate-loaded environments and to tailor eco-concrete towards an elevated degree of chemical resistance.

Carbon dioxide is known as an important agent in aqueous media to induce chemical attack on building materials. The leaching behavior of pea gravels, which are used as backfill material in continuous tunneling, is not entirely resolved until now. Evaluating the durability and economical advantage of individual backfill materials requires a proper experimental design to survey the dissolution reactions and to develop a useful modelling approach to calculate dissolution for carbonate bearing pea gravels. In this study a combined flow through reactor unit was developed, where conditions for chemical attack on gravel material can be simulated by changing flow rate and/or CO2 partial pressure. The addition of CO2(gas) was adjusted by pHstat conditions. Solution chemistry was monitored in-situ and by analyzing samples throughout experimental runs. For 5 natural gravels with different calcite(dolomite)/quartz ratios, the dissolution rates of Ca2+ for carbonates (RCa_cc; normalized on exposed carbonate surfaces) were found to reflect mineralogy, carbonate content, flow rates and thus saturation state conditions. RCa_dol values for dolomite are significantly lower (10−12

Boundary walls are neglected but important parts of historic urban environments, and they are often prone to serious deterioration. Understanding moisture and salt dynamics within boundary walls ca...

Biogenic carbonate minerals are widely used as archives in paleoenvironmental research, providing substantial information for past depositional and diagenetic regimes. However, nearly all biogenic carbonates undergo post-mortem diagenetic alteration to variable degrees. Diagenetic features are essentially caused by complex fluid-solid interaction including recrystallization and neomorphosis of shell architecture and related geochemical resetting. A common conception is that a given primary shell texture is replaced by a secondary fabric via micro-scale dissolution-reprecipitation reactions that may reach geochemical and/or isotopic equilibrium with the diagenetic fluid. Here we document that the process of petrographic and geochemical alteration of a biogenic carbonate archive progresses stepwise, and the re-equilibration processes can be separated in space and time. More specifically, attached and bound aqueous fluids within the shell organic matter and fluid inclusions likely play a crucial role in the early stages of alteration within a relatively rock-buffered system. Degradation of organics was observed via decreased sulfur concentration and decreased fluorescence. In this early stage of alteration, the conversion of micro-scale aragonite biominerals to metastable diagenetic calcite (meso)crystals is documented by RAMAN spectroscopy, electron backscatter diffraction (EBSD), and a decrease in strontium concentrations. Further stabilization to larger, neomorphosed calcite crystals resulted from re-equilibration with external fluids and was evidenced by EBSD, oxygen isotope data, and further reduction of strontium. Spatial chemical and isotope data were used to decipher the impact of fluid availability and transfer behavior, i.e. carbonate-buffered versus diagenetic-fluid buffered, and isotope and element exchange behavior, and analyzed in context to textural alteration features. These data suggest that during diagenesis, the evolution to more sustainable (diagenetically induced) fabrics is accompanied by individual reaction steps traced by elemental and isotopic signatures. Kinetics, and thus degree of diagenetic alteration of biominerals at a given exposure to physicochemical alteration conditions is initially strongly controlled by the micro- to nano-scale internal architecture governing the availability and transfer of aqueous fluids. Results shown here have significance for those concerned with biogenic carbonate archives and have wider implications for a mechanistic understanding of carbonate diagenesis.

Lithium (Li) isotopes in marine carbonates have considerable potential as a proxy to constrain past changes in silicate weathering fluxes and improve our understanding of Earth's climate. To date the majority of Li isotope studies on marine carbonates have focussed on calcium carbonates. The determination of the Li isotope fractionation between dolomite and a dolomitizing fluid would allow us to extend investigations to deep times (i.e. Precambrian) when dolostones were the most abundant marine carbonate archives. Dolostones often contain a significant proportion of detrital silicate material, which dominates the Li budget; thus, pretreatment needs to be designed so that only the isotope composition of the carbonate-associated Li is measured. This study aims to serve two main goals: (1) to determine the Li isotope fractionation between Ca–Mg carbonates and solution, and (2) to develop a method for leaching the carbonate-associated Li out of dolostone while not affecting the Li contained within the detrital portion of the rock. We synthesized Ca–Mg carbonates at high temperatures (150 to 220 ∘C) and measured the Li isotope composition (δ7Li) of the precipitated solids and their respective reactive solutions. The relationship of the Li isotope fractionation factor with temperature was obtained: 103ln⁡αprec-sol=-(2.56±0.27)106(1)/T2+(5.8±1.3) Competitive nucleation and growth between dolomite and magnesite were observed during the experiments; however, there was no notable effect of their relative proportion on the apparent Li isotope fractionation. We found that Li isotope fractionation between the precipitated solid and solution is higher for Ca–Mg carbonates than for Ca carbonates. If the temperature of a precipitating solution is known or can be estimated independently, the above equation could be used in conjunction with the Li isotope composition of dolostones to derive the composition of the solution and hence make inferences about the past Li cycle. In addition, we also conducted leaching experiments on a Neoproterozoic dolostone and a Holocene coral. Results show that leaching with 0.05 M hydrochloric acid (HCl) or 0.5 % acetic acid (HAc) at room temperature for 60 min releases Li from the carbonate fraction without a significant contribution of Li from the siliciclastic detrital component. These experimental and analytical developments provide a basis for the use of Li isotopes in dolostones as a palaeo-environmental proxy, which will contribute to further advance our understanding of the evolution of Earth's surface environments.

Hydrated aluminosilicates were synthesized with and without aqueous heavy metals (Me), such as cobalt (Co), chromium (Cr), and zinc (Zn), by a sol–gel process at different initial molar ratios of Ca/(Si + Al) (0.6–1.6) and Me/Si (0.0–2.0), and constant Al/Si ratio (0.05) using equilibrium-approaching experiments. The chemical composition of the reactive solutions during aluminosilicate precipitation and maturation was monitored by ICP-OES. The mineralogy, nanostructure, and chemical composition of the precipitates were studied by XRD and high-resolution TEM. At Me/Si ratios ≤ 0.2, calcium–aluminium–silicate–hydrates (C–A–S–H) with a defect 14 A tobermorite-like structure formed, whereas at a Me/Si ratio of 2.0, either trioctahedral Co- and Zn-smectite or amorphous Cr gels precipitated, independent of the initial Ca/(Si + Al) ratio used for gel synthesis. The immobilization capacities for $$ {\text{Co}}^{2 + } $$ , $$ {\text{Cr}}^{3 + } $$ , and $$ {\text{Zn}}^{2 + } $$ by C–A–S–H, Cr gel, and trioctahedral smectite are 3–40 mg/g, 30–152 mg/g, and 122–141 mg/g, respectively. The immobilization mechanism of heavy metals is based on a combination of isomorphous substitution, interlayer cation exchange, surface (ad)sorption, and surface precipitation. In engineered systems, such as underground concrete structures and nuclear waste disposal sites, hydrated aluminosilicates should exhibit a high detoxication potential for aqueous heavy metals.

Shotcrete is often used for the construction and stabilization of tunnels and other underground structures, where it is susceptible to different forms of physical and chemical attacks affecting its durability. An advanced understanding of the factors that limit the durability of shotcrete is crucial to develop tailored strategies for enhancing its service life. The main focus of this contribution is to shed light on the durability of shotcrete by revising the literature, highlighting what is missing and needs to be addressed, assessing how the knowledge about concrete durability can be transferred to shotcrete, and providing recommendations for durable shotcrete structures.

Major types of chemical concrete degradation such as carbonation, leaching and acid attacks are strongly associated with decreasing internal, surface and/or external pH. Thus, a precise pH determination is crucial for the assessment regarding the degree of corrosion and corresponding development of prevention strategies. Conventional pH measurement methods for concrete, such as pH visualization via color change of phenolphthalein indicator, pH analyses of extracted pore solutions and surface pH characterizations using flat surface electrodes have proven to hold significant limitations and inadequacies. This contribution presents the application of sensor foils based on luminescent, pH sensitive dyes for quantification and imaging of the spatial distribution of surface pH of concrete within a pH range between 9.35 and 12.35. For this purpose, an imaging technique called time-domain dual lifetime referencing (t-DLR) was used. High-resolution pH images of concrete samples exposed to carbonation and biogenic acid corrosion were successfully recorded and consequently compared to the state-of-the-art methods for pH assessment on concrete-based construction materials.

Zur systematischen Erfassung von Isotopendaten osterreichischer Lagerstatten wurden erstmals stabile Mg-Isostope (δ26MgDSM-3) ausgewahlter ostalpiner Spatmagnesitlagerstatten/-vorkommen (Hohentauern/Sunk, Hochfilzen, Breitenau, Radenthein/Millstatter Alpe, Kaswassergraben) und des kryptokristallinen Kraubath Magnesits bestimmt. Zusatzlich wurde aus Vergleichsgrunden und zur Charakterisierung wichtiger Typen von Magnesitlagerstatten auch auslandisches Material (Bela Stena/Serbien, Bushveld/Sudadfrika, Poldasht/NW Iran) untersucht. Dabei wurden fur die global wichtigen Typen von Magnesitlagerstatten signifikat unterschiedliche δ26MgDSM-3-Werte ermittelt: Kraubath-Typ −2.88 ‰ bis −1.80 ‰, Veitsch-Typ −1.54 bis −0.49 ‰, Bela Stena-Typ −1.07 bis −0.42 ‰, Poldasht-Typ −1.04 bis +1.01 ‰. Diese lassen sich weitestgehend auf die unterschiedlichen Bildungsprozesse (z. B. Evaporation, Metasomatose) zuruckfuhren.