Effect Of Mineralogy Research Articles

Statistical Investigation of the Mineralogical Effect on Blastability in Granitic Rocks

Statistical Investigation of the Mineralogical Effect on Blastability in Granitic Rocks

Land use drives the distribution of free, physically protected, and chemically protected soil organic carbon storage at a global scale.

Soil organic carbon (SOC) sequestration is increasingly emphasized as a climate mitigation solution, as scientists, policy makers, and land managers prioritize enhancing belowground C storage. To identify key underlying drivers of total SOC distributions, we compiled a global dataset of soil C stocks held in three chemical forms, reflecting different mechanisms of organic C protection: free particulate organic C (fPOC), physically protected particulate organic C (oPOC), and mineral-protected soil organic C (mSOC). In our dataset, these three SOC pools were differentially sensitive to the effects of climate, soil mineralogy, and ecosystem type, emphasizing the importance of distinguishing between physical and chemical C protection mechanisms. C stocks in all three pools varied among ecosystems: cropland soils stored the least amount in each pool, with forest and grassland soils both containing significantly more fPOC (40%-60% greater in each ecosystem) than croplands. oPOC stocks did not significantly differ from zero in croplands but were substantial in forest and grassland soils. Meanwhile, mSOC stocks were the greatest in grasslands and shrublands (90%-100% greater than croplands). In cropland soils, there were no major effects of tillage on C storage in any of the three pools, while manure addition enhanced mSOC stocks, especially when added with inorganic N. Thus, the human land use intensity in croplands appears to reduce SOC storage in all major pools, depending upon management; retaining native vegetation should be emphasized to maintain current global SOC stocks.

Effect of soil pH and mineralogy on the sorption and desorption of phosphite and phosphate in Ultisols of the Southeastern Coastal Plain

AbstractThe development of transgenic crop varieties capable of utilizing phosphite (Phi) as a phosphorus (P) source is a promising strategy to increase P use efficiency while decreasing reliance on phosphate (Pi)‐based fertilizers. However, little information is available on Phi sorption and desorption in soils. We conducted batch experiments to investigate the sorption of Phi and Pi by three Ultisols from the Coastal Plain of the southeastern United States. At the soils' acidic field pH (pH 4.7–6.2), Pi had a higher affinity than Phi for soil solids, where maximum sorbed concentrations of Pi were an average of 44% greater than those of Phi. The sorption of both P species decreased when experiments were repeated adjusting soil pH to 6.5. More Phi than Pi was recovered during desorption experiments, indicating that Phi was more reversibly sorbed and, therefore, may be more plant‐available than Pi. Multiple linear regression between calculated linear distribution coefficients (KD; 10 mg P L−1 input solutions) and soil properties suggested that amorphous Al‐ and Fe‐oxides controlled Pi sorption. Alternatively, amorphous Al‐oxides and gibbsite controlled Phi sorption. Our results show that a lower affinity of Phi than Pi in Ultisols could improve P availability for plant uptake of Phi‐based fertilizers but may increase the risk of soil P buildup over time.

Leaching behaviour of limonite ores from Lapaopao, Southeast Sulawesi, Indonesia: Effect of mineralogy and acid types

An atmospheric leaching study of limonite ores from Lapaopao, Southeast Sulawesi, using hydrochloric acid (HCl), nitric acid (HNO<sub>3</sub>), and sulfuric acid (H<sub>2</sub>SO<sub>4</sub>) has been performed. The objectives of this study were to analyze the effect of ore mineralogy and acid types on the dissolution behavior of minerals and the leaching rate of Ni and Co at atmospheric pressure conditions. Mineralogical analysis was carried out using optical microscopy, scanning electron microscopy (SEM), and X-ray diffractometry (XRD), while the ore's chemical composition was determined by using X-ray fluorescence spectrometry (XRF) and atomic absorption spectrophotometry (AAS). Mineralogically, the limonite ores are dominated by goethite, followed by gibbsite, talc, and lizardite, with less amounts of hematite and quartz. Analysis results of solid residues revealed that mineral dissolution order was determined as follows: goethite > lizardite > gibbsite> hematite > talc> quartz. The results of the leaching experiment exhibited that the order of leaching rates of Ni in the three ores samples using three different acids were found as follows: Ore-1 > Ore-2 > Ore-3. Comparison of HCl, HNO<sub>3</sub>, and H<sub>2</sub>SO<sub>4</sub> as the lixiviants for the leaching of limonite ores demonstrated that HCl was the most reactive acid, followed by HNO<sub>3</sub> and then H<sub>2</sub>SO<sub>4</sub>. This might be due to the differences in mineralogical nature and reactivities of acids during the leaching process.

Mineralogical and environmental effects on the δ13C, δ18O, and clumped isotope composition of modern bryozoans

Extensive bryozoan fossil records date back to the early Ordovician, forming an important part of sedimentary archives, yet the applicability of classical 18‑oxygen thermometry to bryozoan carbonate is still a matter of debate, with mineralogical and biological issues still hindering paleoclimate reconstructions. Complementing other methods (i.e., δ18O, Mg/Ca), clumped-isotope thermometry (Δ47) could provide more accurate paleotemperature estimates and help identify potential biotic factors influencing the isotopic composition of bryozoans. Here we report on the first investigation of clumped-isotope thermometry applied to bryozoan carbonate, spanning a broad range of modern species living in different environments from two localities (Atlantic Ocean and Mediterranean Sea). We confirm that bryozoan δ13C and δ18O records are affected by biotic and abiotic factors susceptible to bias in growth condition estimates. Our Atlantic bryozoans yield Δ47 derived temperatures (T47) consistent with spring/fall seawater temperature (but only after correcting for minor mineralogical effects), reflecting seasonal growth bias or, more likely, moderate isotopic disequilibrium. By contrast, Mediterranean samples display large positive offsets from Δ47 equilibrium values. We propose that this stronger disequilibrium is related to the higher salinity at this site, decreasing Carbonic Anhydrase activity, favoring CO2 hydroxylation over hydration, and slowing down DIC (dissolved inorganic carbon) equilibration reactions at the precipitation site. Our findings highlight how “vital effects” in bryozoans is not only species-specific as often assumed for other biocalcifiers, but could also depend on mineralogy and environmental factors.

Nano structure of CO2-Brine-Kaolinite Interface: Implications for CO2 Geological Sequestration

CO2-Brine-Rock interaction has been identified to govern CO2 multiphase flow and affect the integrity of the underground reservoirs. However, limited investigations address the role of brine salinity, rock mineralogy, and organic matter in CO2 wettability at nano scale. To solve this problem, a molecular dynamics (MD) simulation is performed. The interfacial properties, including density distribution and radial distribution function (RDF, g(r)), are calculated for CO2 saturated high salinity water and CO2 saturated low salinity water. The density distribution profile shows that mineralogy is a critical parameter for CO2 wettability: lowering salinity leads to a more CO2 wet siloxane surface while the aluminol surface becomes less CO2 wet. g(r) reveals that the type of organic matter plays a critical role: base functional group (-N) renders a CO2 wet surface whereas the acid functional group (-COOH) causes a water wet surface. This investigation integrates the effects of brine salinity, mineralogy, and organic matter to evaluate CO2 wettability. This MD simulation reveals the principal factors controlling the CO2 wettability at the nano scale and provides a general paradigm to reduce the leakage risk of CO2 geological sequestration.

Freeze–Thaw Performance Trends of Short-Term Cured Cement-Stabilized Aggregate Quarry By-Product Materials

Recent research studies conducted at the Illinois Center for Transportation focused on sustainable applications of quarry-by-products (QB) as pavement foundation materials and demonstrated the superior durability performance of dolomitic aggregate materials exposed to long-term cementitious reaction and repeated freezing and thawing. This study investigated the influence of QB chemical composition on the strength of cement-stabilized samples exposed to freeze–thaw cycles. Dolomitic QB materials from different quarries in Illinois and with different magnesium oxide (MgO) content, and a control limestone sample were chemically characterized by X-ray fluorescence and X-ray diffraction techniques. The QB materials were then stabilized with 3% cement and subjected to a 7-day curing period, followed by freeze–thaw conditioning. Unconfined compressive strength and resonant frequency tests were conducted to examine how the percentage of MgO and dolomitic minerals could alter the strength/stiffness with freeze–thaw cycles. Optical microscopy analysis was also performed to observe the extent of microstructure damage with freezing and thawing. Over the course of the applied freeze–thaw cycles, no notable minerology effect on strength or stiffness characteristics was observed for the short-term curing. Instead, performance was predominantly governed by physical properties, such as the particle size distribution, which played a more significant role after short-term curing. Well-graded QB materials with optimum packing, following Talbot’s equation with a 0.45 exponent, consistently exhibited the highest strength after any freeze–thaw cycle. The next phase of research, focusing on long-term curing, is expected to provide more insights into the chemical and mineralogical effects of QB materials on durability performance.

Submillimeter-wavelength Polarimetry of IRC+10216

We present SCUBA-2/POL-2 850 μm polarimetric observations of the circumstellar envelope (CSE) of the carbon-rich asymptotic giant branch (AGB) star IRC+10216. Both far-IR (FIR) and optical polarization data indicate grains aligned with their long axis in the radial direction relative to the central star. The 850 μm polarization does not show this simple structure. The 850 μm data are indicative, albeit not conclusive, of a magnetic dipole geometry. Assuming such a simple dipole geometry, the resulting 850 μm polarization geometry is consistent with both Zeeman observations and small-scale structure in the CSE. While there is significant spectral-line polarization contained within the SCUBA-2 850 μm passband for the source, it is unlikely that our broadband polarization results are dominated by line polarization. To explain the required grain alignment, grain mineralogy effects, due to either fossil silicate grains from the earlier oxygen-rich AGB phase of the star or due to the incorporation of ferromagnetic inclusions in the largest grains, may play a role. We argue that the most likely explanation is due to a new alignment mechanism wherein a charged grain, moving relative to the magnetic field, precesses around the induced electric field and therefore aligns with the magnetic field. This mechanism is particularly attractive as the optical, FIR, and submillimeter-wave polarization of the carbon dust can then be explained in a consistent way, differing simply due to the charge state of the grains.

A review of mechanical properties and carbonation behavior evolution of lime mortar for architectural heritages restoration

Using lime mortar to connect, protect and decorate buildings was a very common technique in ancient times. Understanding the mechanical properties and carbonation mechanism of lime mortar is the basis for successful restoration and protection of architectural heritage. The compatibility and durability of lime mortar and architectural heritage promote the study of related mechanisms, so that it can adapt to the current reality. In this paper, the factors affecting the mechanical properties of lime mortar are summarized, and the carbonization principle of lime mortar is analyzed. The effects of water-binder ratio, aggregate mineralogy and particle size, inorganic additives and organic additives on the mechanical properties of lime mortar were elaborated in detail, especially the action behavior of organic additives in the carbonation process of lime mortar. Suggestions for enhancing the mechanical properties of lime mortar are put forward, which provides a theoretical basis for improving the compatibility and durability of materials in the restoration of ancient buildings.

Effects of topography, climate, mineralogy and physicochemical properties on potassium forms in various soils of Fars province, southern Iran

The relationship between potassium (K) and soil physicochemical properties can be used to understand the K cycling. Topography, as a soil forming factor, has an important effect on the soil characteristics of every region. This study was conducted to investigate K and its relationship with climate, mineralogy, and physicochemical properties in toposequences of two regions (Sepidan and Darab) in southern Iran. XRD analysing patterns showed montmorillonite, illite, chlorite, and kaolinite as diagnostic minerals of these regions. Due to being located in arid regions of Iran and lack of good rainfall, the results did not show any significant difference between the selected areas. So, climate could not be considered as an effective factor in supplying K for plants. In both regions, topography affected soil development as a soil forming factor, so that anywhere the more developed soil was observed, the more extracted K forms were found. In different physiographic units of Sepidan region, topography, by affecting soil properties through microclimate, drainage and sunshine quality, caused differences in distribution of K forms. The correlation between different K forms and soil properties in both regions because of weathering and releasing K from K-bearing minerals like illite, showed a relationship with soils finer section.

Comparison of measured versus modeled TOC in the Tuscaloosa marine shale of Southwestern Mississippi, U.S.A.

This study presents a comparison of measured versus modeled total organic carbon (TOC) in the Upper Cretaceous Tuscaloosa marine shale (TMS) of southwestern Mississippi as a case study to evaluate the effects of mineralogy on the TOC estimated from the ΔlogR method. The ΔlogR method is utilized to calculate TOC, which involves baselining sonic transit time and resistivity log curves in a non-source rock section of the formation. In our application, the well log curves were baselined in the upper TMS, which is described as a non-source rock section, and in the lower TMS above the high resistivity zone (HRZ), which is described as having a higher carbonate content. The ΔlogR calculated TOC values from these two baselining approaches show that the lower baseline results in improved agreement between measured TOC and calculated TOC. This improvement is likely to be due to the lower baseline accounting for the increase in resistivity caused by higher carbonate content, in addition to any presence of TOC. The upper baseline, which has a lower carbonate content, does not account for this resistivity increase. Additionally, sample type appears to affect the comparison of measured and ΔlogR calculated TOC. Most of the samples used in this study are legacy cuttings that were not preserved during storage, exposing the high surface area cuttings to increased rates of oxidation, whereas geophysical logs record the rock properties in situ. To account for this oxidation effect, the difference between the medians of the TMS HRZ TOC core and cuttings values was added to each TOC measurement in this study, resulting in a median measured TOC value that is similar to the median of the lower TMS-baselined ΔlogR calculated TOC value. Overall, this study demonstrates that carbonate content and sample type can affect how well measured and ΔlogR-modeled TOC values compare.

Ammonium Recovery from Synthetic Wastewaters by Using Zeolitic Mixtures: A Desorption Batch-Study

Resource recovery from wastewater is very important in view of a circular economy approach in the water field. Among the different technologies applied to realize circular economy, an attractive option is the use of nutrient-enriched media that can be utilized as slow-release fertilizers. Zeolites have been re-discovered for their key role in ammonium (NH4+) adsorption from treated wastewater. Although many studies have been carried out to assess the ability of zeolites to adsorb NH4+, only few papers concerning NH4+ desorption from zeolites are available in the literature. Therefore, this study investigated NH4+ desorption from mineralogically different zeolites, before (ZNS and ZNC) and after (ZSS and ZSC) their treatment with sodium chloride. The zeolites differed in mordenite content. The amount of the desorbed NH4+ varied from 78 to 84% of the total NH4+ adsorbed. In particular, the NaCl-treated materials showed the largest desorption (27.6 ± 0.2 mg L−1, and 27.9 ± 0.7 mg L−1, ZSS, and ZSC, respectively) as compared to the untreated zeolites (22.9 ± 0.3 mg L−1, and 24.2 ± 0.3 mg L−1, ZNS, and ZNC, respectively) because of the different affinity of the cations for the zeolite surface. A monomodal pseudo-first-order model best approximated the desorption kinetics, suggesting only one mechanism of NH4+ desorption from zeolites. Such a mechanism is based on the ion exchange between dissolved Na+ and adsorbed NH4+. The desorption kinetics also showed that NH4+ desorbed slower from the NaCl-treated zeolites than the untreated ones. This effect was explained by the different affinity of Na+ and NH4+ for the zeolite surfaces as due to the diverse sizes of the Na+ and NH4+ hydration spheres. By revealing the effect of zeolite mineralogy and surface treatments in the desorption of NH4+, this study can suggest new and effective synthetic strategies for the achievement of cheap new materials to be applied in environmental remediation within a circular economy perspective.

Microstructural analysis of slag properties associated with calcite precipitation due to passive CO2 mineralization

CO2 mineralization in slag has gained significant attention since it occurs with minimal human intervention and energy input. While the amount of theoretical CO2 that can be captured within slag has been quantified based on slag composition in several studies, the microstructural and mineralogical effects of slag on its ability to capture CO2 have not been fully addressed. In this work, the CO2 uptake within legacy slag samples is analyzed through microstructural characterization. Slag samples were collected from the former Ravenscraig steelmaking site in Lanarkshire, Scotland. The collected samples were studied using X-ray Computed Tomography (XCT) to understand the distribution and geometry of pore space, as well as with scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) to visualize the distribution of elements within the studied samples. Electron backscatter diffraction (EBSD) was used to study the minerals distribution. The samples were also characterized through X-ray diffraction (XRD) and X-ray fluorescence (XRF), and the amount of captured CO2 was quantified using thermogravimetric analysis (TGA). Our results demonstrate that CO2 uptake occurs to the extent of ∼9–30 g CO2/ kg slag. The studied samples are porous in nature, with pore space occupying up to ∼30% of their volumes, and they are dominated by åkermanite-gehlenite minerals which interact with the atmospheric CO2 slowly at ambient conditions. EDS and EBSD results illustrate that the precipitated carbonate in slag is calcite, and that the precipitation of calcite is accompanied by the formation of a Si-O-rich layer. The provided analysis concludes that the porous microstructure as well as the minerals distribution in slag should be considered in forecasting and designing large-scale solutions for passive CO2 mineralization in slag.

Atmospheric aerosol particles before, during, and after a convective dust event on the Jornada experimental range as measured using Raman hyperspectral imaging

AbstractThe effects of winds and local mineralogy on ambient aerosol composition are poorly understood. We measured the Raman spectra (RS) of ambient aerosol particles on the Jornada Experimental Range, a desert location in southern New Mexico, used these RS to group spectra by composition or spectral features, and compared the numbers of RS with the winds and minerology. An aerosol Raman hyperspectral imager was used to collect particles onto a tape and measure a hyperspectral Raman image in 15‐ or 20‐min intervals. Over a 48 h period, 6306 RS were above the thresholds used and were analyzed further. Multiple RS may originate from the same particle. Of these 6306 RS, 2567 were classified as luminescence; 2647 contained the D and G peaks of DG Carbon (DGC, which includes soots, black carbon, and similar materials); 43 exhibited peaks consistent with CH stretching; and 130, 102, and 29 RS were consistent with quartz, carbonates (calcite and dolomite), and potassium feldspar, respectively. A convective dust event was concurrent with an increase in the number of RS of luminescent particles >20X the median; numbers of DGC RS in the interquartile range of DGC for the entire measurement period; RS consistent with quartz, calcite, iron oxides, feldspar, and anatase; and no RS consistent with oxalates or nitrates. This work shows that hyperspectral Raman imaging can help understand the time‐dependent composition of ambient aerosol particles at time resolutions below an hour.

Evaluating the role of salts on wettability alteration in dolomite rocks: Possibility of water based oil mobilization application

While many low salinity studies have been conducted on chalks, calcite minerals and sandstone rocks, few research articles have explored the same for applications in dolomite rocks. To explore the effect of mineralogy, a comparative study on the wettability alteration in the presence of low salinity brines for 2 carbonate rocks of varying composition was studied. The contact-angle experiments were performed for two carbonate samples. One carbonate sample was composed of ∼100 % dolomite mineral whereas the other carbonate rock sample was composed of both dolomite and calcite mineral (5 % calcite and 95 % dolomite). The ionic solutions were composed of NaCl, MgCl2, CaCl2 and CaSO4 single salt solutions of concentration (500 ppm to 5000 ppm). The contact angle reduction was observed in the following order CaSO4 > MgCl2 > CaCl2 > NaCl for the carbonate sample containing calcite and dolomite minerals and the maximum reduction in contact angle for the carbonate sample containing dolomite and calcite minerals was observed for CaSO4 brines was 26.13 % for 1000 ppm concentration. The contact angle reduction observed for the carbonate sample containing dolomite mineral was found to be in the following order MgCl2 > CaCl2 > CaSO4 > NaCl and the maximum reduction in contact angle was observed for MgCl2 brines was 24.58 % for 3000 ppm concentration. The wettability alteration observed in the carbonate sample containing dolomite mineral was less as compared to the carbonate sample containing calcite and dolomite mineral. In the presence of MgCl2 brines, the pH of the brines dominates the mineral dissolution, thereby improving or reducing the extent of wettability alteration. However, the complete wettability reversal has not been observed in this study. An increase in temperature (from 70 to 90 °C) was found to be favourable for wettability alteration while the presence of calcites, along with dolomites has the potential to further improve oil recovery.

Machine learning models for occurrence form prediction of heavy metals in tailings

ABSTRACT Modern mining and metal ore smelting produce vast tailings, increasing heavy metal pollution. The study of heavy metal occurrence forms is a promising way to remediate contaminated tailings while minimizing environmental damage. However, laboratory measurements of heavy metal occurrence forms are complex and time-consuming, so a fast and accurate identification method is urgently needed. This study used gradient boosting regression tree (GBRT) approaches to predict heavy metal occurrence forms in tailings, with tailings mineralogy information and heavy metal properties as input variables and the percentages of seven occurrence forms as output variables. The optimum GBRT model achieved excellent performance, with R values greater than 0.92 recorded on the testing set for all seven occurrence forms. The feature importance analysis showed that electronegativity was the most critical variable across all occurrence forms, with an average feature importance of 0.442, followed closely by atomic number, which had an average feature importance of 0.211. Overall, this study proposes a reliable and efficient GBRT prediction model for heavy metal occurrence forms, providing new insights into the effects of tailings mineralogy on heavy metal occurrence forms. This approach can be applied to contamination analysis and the safe and efficient use of heavy metals.

On the modelling of stress-dilatancy behavior in weakly cemented sands

A comprehensive study on the stress-dilatancy behavior of cemented sand and its modeling is presented. The effect of confining pressure, relative density, and cement content on stress-dilatancy behavior are studied from the published experimental results and an additional series of experiments performed in this study. To facilitate a contrast and comparison of stress-dilatancy behavior between these datasets, a normalized stress ratio is proposed which removes the effect of mineralogy and morphology of parent sand. A set of key insights were obtained from this comparative study which aided in improving the stress-dilatancy relation; for example, the effect of initial conditions on stress-dilatancy behavior was found to be captured by the ratio of cohesion intercept (or tensile strength) and mean effective stress before shearing. The limitations of stress transformation, often used in modelling of cemented sand, were also systematically studied by a set of carefully designed experiments; it was found to be only applicable before gross yielding of cementation. After gross yielding, it is necessary to take in account of the breakage of bonds/cementation. The gross yield locus was identified from 70 experimental datasets and a cohesion/bond degradation model was formulated to model the stress-dilatancy behavior of cemented sand. The efficacy of stress-dilatancy relations (after including the gross yield locus and bond degradation behavior) is evaluated from the experimental results; the Rowe's stress-dilatancy relation was found to be most suitable with the proposed bond/cohesion degradation model.

Streaming and zeta potentials of basalt as a function of pressure, temperature, salinity, and pH

The electric surface charge of basalt in contact with filing fluids (e.g. water and CO2) has broad range of applications in varied fields such as gas geological storage sites, geothermal systems, and hydrocarbon reservoirs. The surface charge at the interface between a solid surface (e.g. rock) and liquid (e.g. aqueous solution) can be quantified by the zeta potential, thus zeta potential measurement is a useful technique for interpreting wetting characteristics of rock-fluid systems. However, there is no data for zeta potentials of basaltic rocks in presence of aqueous solutions or how zeta potentials may be affected by pressure, temperature, salinity, or pH. Thus, streaming potential measurements were performed to determine the zeta potential of basaltic rocks in the presence of aqueous NaCl solution at pore pressures (1.72 MPa to 6.9 MPa), temperatures (298 K and 323 K), brine salinities (1 wt% NaCl to 3.5 wt% NaCl), and pH values (4 to 10). Also, the effects of mineralogy and CO2-presence (dead and live brines) on the zeta potential were evaluated. The results showed that the zeta potential remained constant versus pressure, while it increased (became less negative) with increasing temperature and salinity, and decreased (became more negative) with increasing pH. This study provides key fundamental data and thus improves fundamental understanding of basalt-water-CO2 interactions, thereby aiding in the improvement of various industrial applications, including gas geo-storage schemes and geothermal energy production.

Differential effects of clay mineralogy on thermal maturation of sedimentary n-alkanes

Clay minerals serve as important catalysts for the degradation of a range of biomolecules during diagenesis, yet their effects are seldom considered when interpreting organic molecular and isotopic data in the context of paleoenvironmental reconstruction. We investigated the thermal maturation of immature sedimentary organic matter in the presence of two clay minerals (kaolinite and montmorillonite) using a series of laboratory-based anhydrous pyrolysis experiments. Organic matter was extracted from a modern terrestrial sediment, mixed with each clay mineral, and heated at 100–300 °C for up to 30 days – in this way, initial organic matter was identical in each system. Abundances, molecular distributions, and paired compound-specific stable isotopic compositions (δDn-alkane and δ13Cn-alkane) of n-alkanes were measured as a function of heating time. For both kaolinite and montmorillonite amended experiments, the shifts in molecular distributions are highly controlled by significant secondary production of n-alkanes from molecularly large lipid precursors, as evidenced by significant increases in the total amount of n-alkanes accompanying increased thermal maturation. Significant decreases in carbon preference index (CPI) are observed before minor decreases in average chain length (ACL), leading to behavior in CPI-ACL space that is fundamentally different from identical systems free of clay minerals. Furthermore, distinct distributions of secondary n-alkanes between the clay mineral systems indicate differential mechanisms and sites of precursor degradation. In the presence of clay minerals, δ13Cn-alkane of immature bituminous organics initially decreases with increasing thermal maturation, opposite most data reported from experimental alteration of relatively mature sedimentary matter. This shift is similarly driven by secondary production of n-alkanes, arising from kinetic fractionation associated with preferential cleavage of 12C12C bonds from parent molecules – the kinetics of this process vary per clay mineralogy but are controlled by the same process. Conversely, we see an enrichment in δDn-alkane with increasing maturation, indicating control of the two isotopic systems by separate mechanisms. Moreover, kaolinite and montmorillonite exhibit differential control on δDn-alkane, leading to separate domains in dual isotopic space. Overall, the changes in δ13Cn-alkane and δDn-alkane are relatively small over the timescales studied, even at temperatures as high as 300 °C (less than ∼0.6–1‰ for δ13Cn-alkane and ∼8–15‰ for δDn-alkane). Considering these factors on a geological timescale, variations in clay mineralogy through a buried sedimentary sequence may impart matrix effects on molecular and isotopic signatures that can bias interpretation of paleoenvironmental conditions.

Effect of salinity, mineralogy, and organic materials in hydrogen wetting and its implications for underground hydrogen storage (UHS)

Hydrogen is a green energy carrier, which appears to reshape the current energy supply chain. To develop a full-scale hydrogen supply chain, underground hydrogen storage has been proposed as a key method. However, one of the key hurdles in UHS is the fluid-rock interactions or hydrogen wetting. The interfacial reactions govern hydrogen wetting in underground reservoirs and thus determine the hydrogen flow and govern the amount of hydrogen trapping in porous media. Although the hydrogen wetting has been gaining attention, how the hydrogen wetting behaves in complicated underground circumstances remains in the shadow.To understand the nano-scale character of hydrogen wetting, a series of molecular dynamics (MD) simulations were performed to analyse the hydrogen distribution on kaolinite surface in function of salinity, mineralogy, and organic materials. We computed density distribution and the radial distribution function (RDF, g(r)) of each species. The results show that salinity can dramatically affect hydrogen distribution on the siloxane surface while negligible effects can be observed on aluminol (gibbsite) surfaces of kaolinite. Furthermore, the hydrogen distribution can be notably shaped by organic materials. Organic materials with acid functional group (–COOH) can generate a more hydrogen wetting surface than base functional group (–NH). This investigation reveals the governing mechanics of hydrogen-brine-kaolinite reactions at molecular scale, unravels the effects of hydrogen-brine-kaolinite reactions in hydrogen wetting and thus provides a paradigm to screen candidate sites for the UHS.