Modern microbialites grow in a variety of environments including the hypersaline, turbid, low alkalinity, high magnesium (Mg) and calcium (Ca) concentrations (and Mg/Ca similar to 4.5 mol/mol), shallow (less than 2 m deep) Storr's Lake on San Salvador Island, The Bahamas. Rather than growing via the trapping and binding of sediments, these largely micritic microbialites form via microbial processes creating crusts and mounds with laminated to clotted structures comprised of both high-Mg calcite and aragonite. The primary objective of this study was to determine whether the mineralogy of representative microbialite mounds dictates their pre-burial metal isotopic compositions. The Mg and Ca isotopic compositions (delta Mg-26, delta Ca-44/40) of two mounds collected from 0.6 to 1.1 m water depth range considerably, from -3.04 to -2.33 parts per thousand (relative to DSM3) and 0.38 to 0.94 parts per thousand (relative to SRM 915a), respectively. Along with Sr/Ca and Mg/Ca molar ratios, delta Mg-26 and delta Ca-44/40 are unambiguously related to mineralogy. This stands in contrast to the carbon and oxygen isotopic compositions of the microbial carbonates, which do not correlate solely with mineralogy. A simple bimineralic mixture of aragonite and high Mg calcite can explain the observations; such a mixture could be a consequence of both phases forming independently or as one phase recrystallizes from another prior to burial. To evaluate the latter hypothesis, we used a time-dependent advection-recrystallization model. We found that recrystallization of high-Mg calcite to aragonite would require an unreasonable Sr partition coefficient, while recrystallization of aragonite to high-Mg calcite could explain the observed geochemical variations in the two mounds. No microbial isotopic effect is apparent for Mg or Ca, however a difference is seen in the carbon isotopic composition of inorganic carbon where or when aragonite and high-Mg calcite form suggesting they form in two different (micro)environments. Consequently, investigations of ancient microbialites (and carbonates in general) need to consider whether mixtures of primary (original) carbonate minerals and/or recrystallization and transformation pre-burial could impact delta Mg-26, delta Ca-44/40, delta C-13 and their interpretation using a combination of isotopic, elemental, petrographic, and modeling methods. This is especially important for Mg, whose elemental and isotopic composition can be dominated by even small amounts of calcite or dolomite.

This study examines the potential of Midcontinent Rift rocks to facilitate long-term CO2 sequestration by providing the necessary Ca and Mg for carbonate mineralization. Surface samples were collected from the Oronto and Bayfield-Jacobsville Groups around Lake Superior and used for petrography and X-ray diffraction to determine their mineral composition. Also, X-ray fluorescence was also used to assess their bulk chemical composition. The samples were then exposed to CO2 and deionized water in Teflon-lined vessels at 90 degrees C, and the resulting leachate fluids were analyzed for the cation released during the testing. SEM microscopy was used to examine the samples for potential mineralization of carbonate minerals. The Oronto Group sediments consist primarily of feldspathic to feldspathic lithic arenites with a chlorite-dominated matrix, and the primary porosity is blocked by calcite and hematite cement. The Bayfield-Jacobsville sequences are porous quartz arenites to feldspathic quartz arenites that do not contain significant accumulation of Ca-, Mg-, and Fe-bearing minerals. The leachate fluids obtained from Oronto Group samples exhibit a maximum Ca release rate (5.2 x 10-4 mole/cm2.day), indicating rapid calcite cement dissolution and increased porosity and permeability. SEM/EDS microanalysis revealed areas where pore-filling calcite was preferentially dissolved. Longer-term rock-water reactions resulted in induced carbonate mineralization, as evidenced by calcite crystals observed in a sample reacted for 102 days. (c) 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

ABSTRACT: Wellbore integrity to ensure efficient, economical, and environmentally friendly operations is a significant and fundamental challenge for CO2 sequestration wells. The carbonation reaction between Portland cement and CO2 can change the microstructure of the cement skeleton, change the cement mechanical properties, damage the annular seal, and finally induce CO2 leakage. This study utilizes an integrated approach including a CO2-cement degradation test, mechanical tests for strength and elastic properties, X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) for composition analysis, and finite element analysis for failure evaluation. The mechanical test results show that the carbonation reaction can improve the sealing effect of the cement during the early stage of degradation (~2 weeks). Mechanical and geochemistry test results show that the carbonation reaction would fundamentally change the composition and microstructure of the cement matrix after long-term CO2 degradation, thereby inducing significant decreases in strength, and enhanced porosity, and permeability. The numerical results indicate that during long-term CO2 injection, the sealing effect of the cement would decrease gradually, and the cement sheath is more likely to fail under external loads arising from wellbore pressure and temperature variations. The mechanical and geochemical test results also show that the temporal variations of cement strength and Ca2+ composition have a strong similarity, which should be further analyzed for possible correlation. In summary, this study provides an integrated approach to qualitatively and quantitatively evaluate the cement degradation and predict failure of CO2 sequestration wells. The allowable wellbore pressure and temperature ranges can be provided for different degrees of cement sheath degradation to assist the field operations and cement slurry design of CO2 sequestration wells. 1. INTRODUCTION The unwanted leakage from the CO2-injection wells impedes the stable and economic industrialization of the CO2 geological sequestration. Therefore, maintaining wellbore integrity becomes a priority task to ensure a successful CO2 sequestration project (Zhang et al. 2019, Xu et al. 2022). For CO2-injection wells, the carbonation reaction between Portland cement and CO2 is a complicated process controlled by CO2 concentration, presence of water, age of the cement, pressure, temperature, and the level of intactness of the cement matrix (Zhang et al. 2021, 2022a). Oilwell cement and CO2 reaction have been extensively investigated by various laboratory studies, including the influence of pressure and temperature (Barlet-Gouedard et al. 2006; Omosebi et al. 2017), reaction period (Barlet-Gouedard et al. 2006), and presence of various additives (Barlet-Gouedard et al. 2006). The major chemical reactions between CO2 and different compositions in the cement are presented in Figure 1 and Equation 1 to 5 (Kashef-Haghighi et al. 2015).

Modern microbialites grow within the hypersaline, turbid, high magnesium (Mg) and calcium (Ca) content (and Mg/Ca ~4.5), shallow (<2m) Storr’s Lake on San Salvador Island, The Bahamas. The average alkalinity was 130±23 mg/L as CaCO 3 (±2SD; n=23) at the time of sample collection in January 2016. In Storr’s Lake, living planktonic, motile microorganisms and suspended algal and bacterial debris create high turbidity that rapidly attenuates sunlight penetration in the water column. Carbon (C) isotopes of microbialite carbonate samples suggest both photosynthesis and extracellular polymeric substance (EPS) degradation control organo-mineralization. High-Mg calcite (HMC) of ~14mol% Mg is dominant in the top irregular surfaces of the mounds, but aragonite is enriched in the interior. Aragonite occurs in all microbialites sampled from around the lake except one of the shallowest mounds, at 40cm water depth (depth at the time of sampling). Two mounds collected from the deep part of the lake (>110cm) were measured for Ca and Mg stable isotopes – notably one was buried in soft organic-rich calcareous ooze, but the other was not. Both δ 44/40 Ca and δ 26 Mg, ranging from 0.38 to 0.94‰ (rel. 915a) and -2.33 to -3

Interest in anthropogenic CO2 release and associated global climatic change has prompted numerous laboratory-scale and commercial efforts focused on capturing, sequestering or utilizing CO2 in the subsurface. Known carbonate mineral precipitating microorganisms, such as the anaerobic sulfate-reducing bacteria (SRB), could enhance the rate of conversion of CO2 into solid minerals and thereby improve long-term storage of captured gasses. The ability of SRB to induce carbonate mineral precipitation, when exposed to atmospheric and elevated pCO2, was investigated in laboratory scale tests with bacteria from organic-rich sediments collected from hypersaline Lake Estancia, New Mexico. The enriched SRB culture was inoculated in continuous gas flow and batch reactors under variable headspace pCO2 (0.0059 psi to 20 psi). Solution pH, redox conditions, sulfide, calcium and magnesium concentrations were monitored in the reactors. Those reactors containing SRB that were exposed to pCO2 of 14.7 psi or less showed Mg-calcite precipitation. Reactors exposed to 20 psi pCO2 did not exhibit any carbonate mineralization, likely due to the inhibition of bacterial metabolism caused by the high levels of CO2. Hydrogen, lactate and formate served as suitable electron donors for the SRB metabolism and related carbonate mineralization. Carbon isotopic studies confirmed that ∼53% of carbon in the precipitated carbonate minerals was derived from the CO2 headspace, with the remaining carbon being derived from the organic electron donors, and the bicarbonate ions available in the liquid medium. The ability of halotolerant SRB to induce the precipitation of carbonate minerals can potentially be applied to the long-term storage of anthropogenic CO2 in saline aquifers and other ideal subsurface rock units by converting the gas into solid immobile phases.

Microbialites found in the low-light-intensity, hypersaline waters of Storr's Lake (SL), San Salvador Island, the Bahamas, were investigated with respect to their morphology, mineralogy, and microbial diversity. Previously described microbialite morphologies, as well as a newly identified "multi-cuspate" morphology, were observed at various depths. Electron microscopy analysis revealed the presence of angular, blocky, and needle-shaped crystals with mineralized cyanobacterial filaments and remains of exopolymeric substances. X-ray diffraction studies confirmed the presence of both Mg-calcite and aragonite in the plateau-mushroom and pinnacle mound microbialites, whereas only Mg-calcite was identified in the other microbialite morphotypes. A comprehensive molecular analysis using barcoded pyrosequencing of five different microbial mat communities identified at least 12 dominant bacterial phyla. Cyanobacteria were generally low in abundance and ranged from ∼0.01% in the deeper pinnacle mounds to ∼3.2% in the shallow calcareous knobs. Other photosynthetic members included green nonsulfur bacteria of the phylum Chloroflexi and purple sulfur bacteria of the class Gammaproteobacteria. All mat types contained significant amounts of sulfate-reducing and dehalogenating bacteria. The low light intensity reaching the deeper microbialites, the lack of dominant cyanobacteria, and the abundance of sulfate reducers and Chloroflexi collectively suggest that sulfate reduction and anoxygenic photosynthetic processes influence the carbonate biomineralization process in these systems.

The isotopic composition of lead (Pb) in fugitive dust suspended by a vehicle from 13 unsurfaced roads in Missouri was measured to identify the source of Pb within an established long-term mining area. A three end-member model using Pb-207/Pb-206 and concentration as tracers resulted in fugitive dust samples plotting in the mixing field of well characterized heterogeneous end members. End members selected for this investigation include the (207)pb/(206)pb for) a Pb-mixture representing mine tailings, 2) aerosol Pb-impacted soils within close proximity to the Buick secondary recycling smelter, and 3) an average of soils, rock cores and drill cuttings representing the background conditions. Aqua regia total concentrations and 207pb/206pb of mining area dust suggest that 35.4-84.3% of the source Pb in dust is associated with the mine tailings mixture, 9.1-52.7% is associated with the smelter mixture, and 0-21.6% is associated with background materials. Isotope ratios varied minimally within the operational phases of sequential extraction suggesting that mixing of all three Pb mixtures occurs throughout. Labile forms of Pb were attributed to all three end members. The extractable carbonate phase had as much as 96.6% of the total concentration associated with mine tailings, 51.8% associated with smelter deposition, and 34.2% with background. The next most labile geochemical phase (Fe + Mn Oxides) showed similar results with as much as 85.3% associated with mine tailings, 56.8% associated with smelter deposition, and 4.2% associated with the background soil. Published by Elsevier Ltd.

Območje Ozarkov v južnem Missouriju gradijo predvsem karbonatne, morske, platformne kamnine paleozojske starosti. Teren, ki vsebuje obširen kras, predstavlja kopno že od poznega Paleozojka. Da bi bolje razumeli geološko zgodovino tega kraškega sistema, smo raziskali stratigrafske podatke ohranjene v zapolnitvi velike vrtače pri največjem izviru v okolici. Vzorci zapolnitve iz naravnih izdankov in iz vrtine so bili analizirani s termoluminiscenco (TL) in 10Be kozmogeno metodo. Fizikalno-kemijske značilnosti zapolnitve so bile določene vizualno, z rentgensko metodo in merjenjem velikosti delcev. Podatki vrtine kažejo, da je debelina alohtonega materiala, ki zapolnjuje vrtačo 36,3 m. Ta material prekriva podorne bloke in sedimente debeline vsaj 15,6 m. Glede na teksturo, strukturo in barvo delimo material, ki zapolnjuje vrtačo na 7 con. Analize 10Be koncentracij kažejo, da material za celotni stolpec zapolnitve izvira iz rezidualnega materiala iz srednjega (Illinoian) in zgornjega Pleistocena (Wisconsian). Rentgenske analize glin kažejo, da zapolnitev vrtače vsebuje enake količine kaolinita in illita, kar je skladno z zemeljskim preperevanjem. The Ozark Plateaus region of southern Missouri is underlain by dominantly carbonate marine platform rocks of Paleozoic age. The region has been sub-aerially exposed since the late Paleozoic and is characterized by extensive karst. To better understand the geologic history of this regional karst system, we examined the stratigraphic record preserved in the fill of a large doline near the largest spring in the region. Samples of fill from natural exposures and drill core were analyzed using thermoluminescence (TL) and 10Be cosmogenic techniques, and the physical/chemical characteristics of the fill material were determined by visual inspection, X-ray analyses, and grain-size measurements. Drill-hole data indicate that the allochthonous doline fill is 36.3 m thick and rests on at least 15.6 m of cave breakdown and sediment. The doline fill is divisible into 7 zones. Analysis of 10Be concentrations suggest that the entire doline fill was derived from local residuum during the middle (Illinoian) to late Pleistocene (Wisconsinan). X-ray diffraction analyses of clays throughout the doline fill indicate that they consist of nearly equal amounts of kaolinite and illite, consistent with terrestrial weathering.

Airborne particulate material collected from seventeen rural unsurfaced roads in Missouri's agricultural and resource mining areas were characterized using the BCR sequential extraction procedure and simulated in vitro body fluids to determine the phase partitioning and bioaccessibility of Pb associated with roadway dusts. Results show that dusts produced from driving over unsurfaced roads in the mining area has a substantial portion of the Pb concentration associated with the more mobile exchangeable-plus-carbonate and reducible geochemical phases. By comparison, unsurfaced road dusts outside the resource mining area have lower metal contents, as expected, and a larger portion of the total Pb concentration associated with the immobile oxidizable and non-silicate bound residual phases. SEM/EDS analysis suggests the minerals associated with the more mobile Pb components include cerussite, Pb oxides and sulfates. Compared with the coarser > 1 mu m size fraction of dust, the < 1 mu m fraction contains a substantially higher concentration of Pb in association with clay minerals. Extraction tests using simulated body fluids show that gastric fluid can mobilize as much as 69% of the total Pb concentration in mining area road dust samples after five hours. Simulated alveolar lung fluid also was an efficient extractor of Pb from the < 1 mu m sample dust fraction,dissolving up to 100% of the available Pb after 100 h. Regression analysis suggests that aqua regia total Pb concentration is a good predictor of mobility and bioaccessibility and can be used to minimize costs associated with monitoring suspended dust contamination. Published by Elsevier Ltd.

Fugitive road dust collection for chemical analysis and interpretation has been limited by the quantity and representativeness of samples. Traditional methods of fugitive dust collection generally focus on point-collections that limit data interpretation to a small area or require the investigator to make gross assumptions about the origin of the sample collected. These collection methods often produce a limited quantity of sample that may hinder efforts to characterize the samples by multiple geochemical techniques, preserve a reference archive, and provide a spatially integrated characterization of the road dust health hazard. To achieve a "better sampling" for fugitive road dust studies, a cyclonic fugitive dust (CFD) sampler was constructed and tested. Through repeated and identical sample collection routes at two collection heights (50.8 and 88.9 cm above the road surface), the products of the CFD sampler were characterized using particle size and chemical analysis. The average particle size collected by the cyclone was 17.9 μm, whereas particles collected by a secondary filter were 0.625 μm. No significant difference was observed between the two sample heights tested and duplicates collected at the same height; however, greater sample quantity was achieved at 50.8 cm above the road surface than at 88.9 cm. The cyclone effectively removed 94% of the particles >1 μm, which substantially reduced the loading on the secondary filter used to collect the finer particles; therefore, suction is maintained for longer periods of time, allowing for an average sample collection rate of about 2 g mi.

Fugitive dust from 18 unsurfaced roadways in Missouri were sampled using a novel cyclonic fugitive dust collector that was designed to obtain suspended bulk samples for analysis. The samples were analyzed for trace metals, Fe and Al, particle sizes, and mineralogy to characterize the similarities and differences between roadways. Thirteen roads were located in the Viburnum Trend (VT) mining district, where there has been a history of contaminant metal loading of local soils; while the remaining five roads were located southwest of the VT district in a similar rural setting, but without any mining or industrial process that might contribute to trace metal enrichment. Comparison of these two groups shows that trace metal concentration is higher for dusts collected in the VT district. Lead is the dominant trace metal found in VT district dusts representing on average 79% of the total trace metal concentration, and was found moderately to strongly enriched relative to unsurfaced roads in the non-VT area. Fugitive road dust concentrations calculated for the VT area substantially exceed the 2008 Federal ambient air standard of 0.15 μg m−3 for Pb. The pattern of trace metal contamination in fugitive dust from VT district roads is similar to trace metal concentrations patterns observed for soils measured more than 40 years ago indicating that Pb contamination in the region is persistent as a long-term soil contaminant.

We characterized, for the first time, submicro- and nanosized fission product-alloy particles that were extracted nondestructively from spent nuclear fuel, in terms of noble metal (Mo–Ru–Tc–Rh–Pd–Te) composition, atomic level homogeneity and lattice parameters. The evidences obtained in this work contribute to an improved understanding of the redox chemistry of radionuclides in nuclear waste repository environments and, in particular, of the catalytic properties of these unique metal alloy particles.

The Taum Sauk Dam Upper Reservoir located in southeast Missouri failed on December 14, 2005. Two days after the catastrophic failure event an aerial survey were conducted to collect Light Detection and Ranging (LiDAR) data. The LiDAR data were interpreted and evaluated to a sub-meter resolution. The data were used to quantify the extent of the damage produced by the water released into a Missouri State Park. Damage consisted of washing out trees, soil, and the reservoir embankment, and scouring the ground to bedrock in places. Additionally, the data also were used in the evaluation of the reservoir damage, which consisted of a 207.3m (680ft) wide breach and scoured slopes. This paper focuses on the multiple uses of LiDAR data to assess damage to natural resources, and hydraulic and geotechnical evaluation of the failure.

The potential effect of alteration phases on the kinetics of glass corrosion has been examined in a preliminary series of Product Consistency Tests (0.5, 1, 3, 7, 35, and 91 days). Crushed samples of a relatively simple Li-Na-Ca-K-Al-B-Si glass were reacted in the presence of a relatively high ionic strength fluid, to which various alteration phases (analcime, adularia, chabazite, or Na-montmorillonite) were added as “seed-crystals”. The release of boron and lithium were used to monitor the corrosion rate of the glass. In general, corrosion rates varied only slightly between the tests with different seed-crystals types. Boron and lithium contents in tests with analcime or adularia were slightly higher than tests with Na-montmorillonite or chabazite present. Silicon concentrations did not display any consistent variation over the testing interval, remaining relatively similar to the starting leachant value of 3.5 × 10−2 M. The concentration of aluminum, however, decreased significantly during the first 35 days of testing and could be inversely correlated to boron and lithium concentrations. The concentration of aluminum then increased between 35 and 91 days, whereas boron and lithium concentrations remained relatively static. The noted correlation between aluminum and boron (or lithium) suggests a coupling of the rate of glass corrosion with aluminum concentration.

Storage of CO 2 in saline aquifers is a viable option for reducing the amount of CO 2 released to the atmosphere. This paper provides an overall review of CO 2 sequestration in saline aquifers. First, the principles of CO 2 sequestration are presented, including CO 2 phase behavior, CO 2 -water-rock interaction, and CO 2 trapping mechanisms. Then storage capacity and CO 2 injectivity are discussed as the main determinants of the storage potential of saline aquifers. Next, a site section process is addressed considering basin characteristics, reservoir characteristics, and economic and social concerns. Three main procedures are then presented to investigate the suitability of a site for CO 2 sequestration, including site screening, detailed site characterization, and pilot field-scale test. The methods for these procedures are also presented, such as traditional site characterization methods, laboratory experiments, and numerical simulation. Finally, some operational aspects of sequestration are discussed, including well type, injection rate, CO 2 purity, and injection strategy.