Mechanical alterations in shale formations due to exposure to water-based fracturing fluids and supercritical carbon dioxide (ScCO2) significantly affect the performance of shale gas exploration and CO2 geo-sequestration. In this study, a hydrothermal (HT) reaction system was set up to treat Longmaxi shale samples of varying mineralogies (carbonate-, clay-, and quartz-rich) with different fluids, i.e. deionized (DI) water, 2% potassium chloride (KCl) solution, and ScCO2 under HT conditions expected in shale formation. Statistical micro-indentation was conducted to characterize the mechanical property alterations caused by the shale-fluid interactions. An in situ morphological and mineralogical identification technique that combines scanning electron microscopy (SEM) and backscattered electron (BSE) imaging with energy-dispersive X-ray spectroscopy (EDS) was used to analyze the microstructural and mineralogical changes of the treated shale samples. Results show no apparent changes in the Young's modulus, E, and hardness, H, after treatment with DI water under room temperature (20 degrees C) and atmospheric pressure for 7 d. In contrast, E and H were decreased by 31.2% and 37.5% at elevated temperature (80 degrees C) and pressure (8 MPa), respectively. The addition of 2% KCl into DI water mitigated degradation of the mechanical properties. Quartz-rich shale specimens are the least sensitive to the water-based fracturing fluids, followed by the clay-rich and carbonate-rich shale formations. Based on in situ morphological and mineralogical identification, the primary factors for the mechanical degradation induced by water-based fluids include carbonate dissolution, clay swelling, and pyrite oxidation. Slight increases in the measured E and H and compression of porous clay aggregates were observed after treatment with ScCO2. The major factor contributing to the mechanical changes resulting from the exposure to scCO2 appears to be the competition between swelling caused by adsorption and compression of shale matrix. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Vulnerability of peat plateaus to global warming was analyzed in northeastern European Russia. A laboratory experiment on artificial incubation of peat was carried out to analyze the resilience of organic matter of frozen peat bogs (palsas) to decomposition. The rate of mineralization of peat organic matter was calculated from data on the CO2 and CH4 emissions from the peat incubated at a temperature of +4 degrees C under artificial aerobic and anaerobic conditions during 1300 days. Peat samples were taken from the active layer (AL), transitional layer (TL), and permafrost layer (PL). The delta 13C and delta 15N isotopes and the C/N, O/C, and H/C ratios were determined as indicators of change in the decomposition rate of organic matter. By the 1300th day of the experiment under aerobic conditions, the total CO2 amount released from the analyzed samples (per 1 g of carbon) was 10.24-37.4 mg C g-1 (on average, 25.76 mg C g-1), while under anaerobic conditions, it was only 2.1-3.38 mg C g-1 (on average, 3.15 mg C g-1). The CH4 emission was detected only in the peat from the transitional layer in very small quantities. The incubation experiment results support the hypothesis that peat plateaus are resilient, especially under anaerobic conditions, regardless the ongoing climate warming.

Chemical stabilization--the mixing of additives like cement, lime, or fly-ash with soil to improve its mechanical properties-- conventionally relies on hydration reactions to generate a binder. Accelerated soil carbonation is a nascent alternative method, whereby carbon dioxide is intentionally introduced in soil mixed with alkali additives to generate a carbonate binder and sequester carbon dioxide. Non-plastic sand and silt specimens mixed with hydrated lime were carbonated for varying amounts of time at different water contents and densities to evaluate the index properties influencing the rate of carbonation and degree of mechanical improvement. It was demonstrated that volumetric air and water contents primarily govern the rate of binder formation and that mechanical properties are influenced by the carbonate binder content and density. Under optimum conditions, soil specimens could be fully carbonated within 3-24 h and unconfined compressive strengths as great as 3-4 MPa were achieved. The degree of strength improvement is comparable to cement-stabilized materials and has a similar dependence on soil type, density, and binder content. If techniques are developed that enable carbonation at scale, the sequestration of carbon dioxide would offset emissions associated with production of chemical additives used for chemical stabilization.

Terrestrial enhanced rock weathering (ERW) is a promising carbon dioxide removal technology that consists in applying ground silicate rock such as basalt on agricultural soils. On top of carbon sequestration, ERW has the potential to raise the soil pH and release nutrients, thereby improving soil fertility. Despite these possible co-benefits, concerns such as heavy metal pollution or soil structure damage have also been raised. To our knowledge, these contrasted potential effects of ERW on soil fertility have not yet been simultaneously investigated. This field trial aimed at assessing the impact of ERW on biological, physical, and chemical soil properties in a temperate agricultural context. To do so, three vineyard fields in Switzerland were selected for their distinct geochemical properties and were amended with basaltic rock powder at a dose of 20 tons per hectare (2 kg.m(-2)). On each field, basaltic rock powder was either applied one year before the sampling campaign, one month before the sampling campaign, or not applied (control) for a total of 27 plots with 9 repetitions of each level. Overall, basaltic rock powder addition had a predominantly positive to neutral effect on soil fertility. Most soil properties showed no significant change either 1 month or 1 year post application. Nevertheless, our study highlighted a significant increase in earthworm abundance (+71 % on average), soil respiration (+50 %) and extractable sodium concentration (+23 %) as early as 1 month post application. The higher soil respiration raises the question of CO2 losses from organic matter mineralization that could limit ERW's efficiency. The increase in sodium raises concerns about a sodification risk potentially damaging soil fertility. These elements now require further investigation before enhanced rock weathering can be considered a viable and secure carbon dioxide removal technology.

Climate change in the northern circumpolar regions is rapidly thawing organic-rich permafrost soils, leading to the substantial release of dissolved CO2 and CH4 into river systems. This mobilization impacts local ecosystems and regional climate feedback loops, playing a crucial role in the Arctic carbon cycle. Here, we analyze the stable carbon (delta 13C) and radiocarbon (F14C) isotopic compositions of dissolved CO2 and CH4 in the Sagavanirktok and Kuparuk River watersheds on the North Slope, Alaska. By examining spatial and seasonal variations in these isotopic signatures, we identify patterns of carbon release and transport across the river continuum. We find consistent CO2 isotopic values along the geomorphological gradient, reflecting a mixture of geogenic and biogenic sources integrated throughout the watershed. Bayesian mixing models further demonstrate a systematic depletion in 13C and 14C signatures of dissolved CO2 sources from spring to fall, indicating increasing contributions of aged carbon as the active layer deepens. This seasonal deepening allows percolating groundwater to access deeper, older soil horizons, transporting CO2 produced by aerobic and anaerobic soil respiration to streams and rivers. In contrast, we observe no clear relationships between the 13C and 14C compositions of dissolved CH4 and landscape properties. Given the reduced solubility of CH4, which facilitates outgassing and limits its transport in aquatic systems, the isotopic signatures are likely indicative of localized contributions from streambeds, adjacent water saturated soils, and lake outflows. Our study illustrates that dissolved greenhouse gases are sensitive indicators of old carbon release from thawing permafrost and serve as early warning signals for permafrost carbon feedbacks. It establishes a crucial baseline for understanding the role of CO2 and CH4 in regional carbon cycling and Arctic environmental change.

Chemical stabilization via hydration reactions with cement or lime is a universally applied method to improve the mechanical properties of shallow soils. Accelerated soil carbonation is a nascent approach intended to bypass this reaction. Carbon dioxide gas is deliberately introduced at high concentrations to react with the alkali additives and precipitate a carbonate binder that permanently sequesters carbon dioxide in the process. A large soil box experiment was performed to examine the efficacy of an accelerated surface carbonation approach, which has the potential to be applied over large areas. High concentrations of carbon dioxide gas were introduced at grade beneath a seal to facilitate vertical penetration into lime-mixed silt. The real-time progression of accelerated soil carbonation was captured with a gas flowmeter and a distributed array of embedded thermocouples and bender elements for the first time. Post-carbonation measurements of binder content and California Bearing Ratio (CBR) verified the degree of carbonation and associated mechanical improvement. Synthesis of real-time monitoring data and post-carbonation measurements indicate carbonation progressed top-down 150 to 200 mm below grade within 5 h, resulting in a substantial increase in strength and stiffness. Potential challenges and benefits associated with adoption of accelerated surface carbonation are discussed.

Climate change mitigation requires creative solutions to reduce greenhouse gases (GHG). Little research has been performed on GHG emissions from shaded turfgrass systems, resulting in a lack of best management practice (BMP) development. The aim of this research was to investigate the soil flux of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) as impacted by shade [shade (98.8%) versus sun (100%)] and differing sources (fast- versus slow-release) and rates (147 versus 294 kg ha-1 yr-1) of nitrogen (N) fertilizers on creeping bentgrass putting greens. The results show that emissions of soil CO2 and soil N2O are significantly lower in shaded plots versus sunny plots. The presence of N fertilizer significantly increased soil CO2 emissions over unfertilized plots. Quick-release N fertilizer fluxed significantly more soil N2O than the slow-release N fertilizers. Turfgrass color was significantly higher on the sunny green versus the shaded green except in late summer. Turfgrass quality was significantly higher for the shaded green versus the sunny green. Milorganite improved turfgrass quality whereas urea decreased turfgrass quality due to fertilizer burn. When N is needed to improve turfgrass color and quality, the use of slow-release N sources should be a BMP for shaded greens.

The formation of pores due to the spontaneous combustion of coal in the goaf, as well as the damage to the surrounding rock caused by high-temperature roasting, can lead to surface subsidence and even collapse. In addition, incomplete combustion of coal can result in the production of various harmful gases, which may escape into the atmosphere through these cracks and seriously pollute the air. This pollution can exacerbate topsoil subsidence, degrade soil properties, harm surface vegetation, and contaminate surface water and groundwater. As a solution to these issues, liquid carbon dioxide fire prevention and extinguishing technology are being utilized for theoretical analysis of overburden movement in goaf. A three-dimensional distribution model of porosity in caving areas has been constructed. Based on this model, dynamic changes in temperature field and oxygen concentration field during liquid carbon dioxide perfusion are being explored. The rapid vaporization of liquid carbon dioxide into inert gas within the goaf inhibits coal oxidation and heating by forming an inert belt within its diffusion range. Simulation results indicate that injecting liquid carbon dioxide at a 90 degrees angle into the oxidation zone (where oxygen concentration is 7-12%) at a volume of 750 m3h-1 best balances cost considerations with effective injection in mining goafs. Industrial testing has shown that after 65 h of perfusion, CO gas concentration decreased from 790ppm to 41ppm - proving significant fire prevention effects from liquid carbon dioxide application.

The present study aims to evaluate the possibility of perpetual pavement design with stabilized black cotton soil and polymer-modified bitumen for the major highways in India. Ground granulated blast slag (GGBS) was proposed as a potential material for use in pavements on weak subgrades, with proportions of 10%, 20%, 30%, and 40% added to the black cotton soil. Modified proctor compaction and California bearing ratio tests were conducted to determine the engineering properties of the soil and GGBS mixture. The study also aimed to design a high modulus bituminous concrete mixture for perpetual pavements using a combination of styrene-butadiene-styrene (SBS) polymer and viscosity grade 30 (VG 30) bitumen, with SBS added to the bitumen in amounts ranging from 1 to 4% by total weight. The physical and mechanical properties of both SBS-modified bitumen and neat bitumen were determined. Based on these results, 16 combinations of perpetual pavements were designed using the mechanistic-empirical methodology and according to Indian Road Congress (IRC 37: 2018) guidelines, with the aid of the IITPAVE software. These pavements included both treated and non-treated subgrades, as well as modified and unmodified mixes. The study found that the use of a sturdy foundation, treated subgrade, and high stiffness base materials is crucial in reducing the significant cost associated with using bitumen in a developing and oil-importing country like India. The designed pavements were also compared in terms of cost assessment and carbon dioxide emissions to determine the best option among the proposed combinations.

Many studies have reported modification in the degree of O3 damage to photosynthesis by elevated CO2 and soil N supply. However, the mechanism underlying the modification is unclear. To clarify the important determinants in the degree of O3 damage to net photosynthetic rate (A) in the leaves of Fagus crenata (Siebold's beech) under elevated CO2 and with different soil N supply, F. crenata seedlings were grown for two growing seasons under combinations of two O3 levels (low concentration at approximately 4 nmol mol-1 and two times the ambient concentration), two CO2 levels (ambient and 700 mu mol mol-1), and three levels of soil N supply (0, 50 and 100 kg N ha- 1 year -1). During the second growing season, we determined A, stomatal conductance for calculating phytotoxic O3 dose (POD), antioxidant concentrations, and antioxidative enzyme activities in the leaves for evaluating O3 detoxification capacity. We calculated the O3-induced reduction in mean A (Delta Amean) during the second growing season using the data reported in our previous study and plotted it against mean daily POD without flux threshold (POD0). There was no significant linear nor non-linear relationship, suggesting that not only POD0 but also O3 detoxification capacity are important determinants of Delta Amean under elevated CO2 and N supply. We found significant negative linear relationships of Delta Amean per unit POD0 (Delta Amean/POD0) with reduced ascorbate concentration in the low O3 treatment, and with percentage of O3-induced change in activity of monodehydroascorbate reductase (MDAR). In addition, the Delta Amean/POD0 was positively and significantly correlated with the activity ratio of ascorbate peroxidase to MDAR. These results suggest that reduced ascorbate pool and its maintenance through the action of MDAR could be important determinants in the degree of O3 damage to net photosynthesis under elevated CO2 and soil N supply.