Arabian Journal of Geosciences最新文献

Assessment of soil organic carbon (SOC) stock and identification of the factors influencing its spatial variation are crucial for adopting appropriate mitigation and adaptation strategies under changing climatic conditions. The present study aims to measure SOC content and stock and identify the factors contributing to SOC variation in India’s sub-tropical, dry sub-humid Eastern Plateau Region (EPR). It also aims to recognize the potential land uses for enhancing the C stock in the region. Soil samples were collected from two soil depth layers—0 to 10 cm and 10 to 20 cm, from locations under different soil type, land use, and topographic conditions. The Walkley-Black method was used to determine the SOC content of the samples. Ordinary kriging based on an exponential semi-variogram model was employed to analyze the spatial variability of SOC concentration and its relationship with the sampling strata. The study shows that the topsoil variation in SOC depended mainly on the land use type and the corresponding soil properties viz. pH and texture. Cultivated areas, especially those of the lowland, recorded higher SOC than other land use classes. The findings of the present study are useful for defining agricultural management practices and carbon sequestration strategies for the region in the context of climate change.

The possible seismo-ionospheric anomalies of the recent Mw 6.0 and Mw 6.4 twin earthquakes of 14 November 2021 in southern Iran were studied through Global Positioning System (GPS) and ground ionosonde observations. GPS measured total electron content observations, and ionosonde measured NmF2 and hmF2, showing ionospheric anomalies in the pre-seismic and co-seismic phases of the earthquakes. A positive increase in ΔTEC was observed at near-field stations ~ 2–7 days before the twin earthquakes. Our observations also show an increase in the estimated values of NmF2 and hmF2 in the pre-seismic phase compared to their mean values. As the “Kp” and “Dst” indices were quiet during the observation period, these anomalies are apparently generated by seismic activity. The observation of sudden co-seismic ionospheric disturbances at near-field stations immediately after the earthquakes explains the mechanism of co-seismic energy propagation through the lithosphere-atmosphere–ionosphere coupling. The estimated differential NmF2 values show a dip in the peak electron density of − 2.84 × 10¹¹ e/m³ during the time of earthquakes. Our results also show anomalous pre-seismic enhancements in all the three parameters used in this study—TEC, NmF2, and hmF2—an indication of precursory signatures of the twin events. In addition, these parameters also show similar changes in their co-seismic phases. Thus, the observed pre- and co-seismic ionospheric anomalies reveal the characteristic signatures of the preparation processes and the co-seismic energy propagation of the twin earthquakes.

Dried Athel leaves (DAL) are abundant agricultural waste that may have a detrimental effect on the environment due to improper disposal. The current paper is aimed at investigating the incorporation of DAL into lime treatment of heavy clays, presenting a novel sustainable waste management strategy. To the best of the authors’ knowledge, this topic has not been investigated in the literature. The experimental programme is designed to thoroughly assess its effects on the hydro-mechanical properties of lime-treated clay in particular strength gain, swelling pressure and permeability. Tests were conducted on the specimens treated with different ratios of lime and DAL and cured under two different temperatures (i.e. 20 and 40 °C) for various periods. Moreover, microstructural analysis was undertaken to support the results. The results indicated that adding 2% DAL to lime-treated clay specimens cured at 20 °C for 3 months remarkably increased unconfined compressive strength by about 68% compared with those attained on lime-treated clay. Stress-strain relationships suggested that the specimens modified by DAL exhibited an enhanced ductile behaviour. Moreover, the incorporation of 2% DAL further reduced clay swelling pressure by 25% compared with those treated by lime only, resulting in a total swelling pressure reduction of 93.6% compared with that recorded on untreated specimens. Permeability enhancement in the specimens treated with lime and DAL was also observed and supported by the morphological analysis. The comprehensive experimental results confirmed the suitability of using DAL as an efficient enhancer to lime-treated clay. The research outcomes can provide valuable insights into the feasibility of DAL as an eco-friendly additive for improving geotechnical engineering practises.

Microbial-induced carbonate precipitation (MICP) is a promising method for improving the properties of geotechnical engineering materials. However, little research has been conducted on the creep behavior and long-term strength of MICP-treated expansive soil. Therefore, this study performed triaxial consolidated undrained creep tests to investigate the improvement effect of MICP on the creep behavior and long-term strength of expansive soil. The results indicate that with the increase of deviatoric stress, the creep process of MICP-treated expansive soil includes four stages: instantaneous creep, decelerating creep, steady-state creep, and accelerated creep. Based on the creep test results, a calculation method has been proposed to quickly and accurately determine the long-term shear strength of MICP-treated expansive soil. Under different confining pressure conditions, the long-term shear strength of the improved expansive soil has been significantly increased, indicating that the MICP method can effectively enhance the long-term shear strength of expansive soil. Furthermore, both the long-term cohesion and the long-term internal friction angle of the MICP-improved expansive soil have been slightly reduced, with the long-term shear strength being approximately 65 to 70% of the short-term shear strength. This study confirms the positive effects of the MICP method on inhibiting the creep of expansive soil and enhancing its long-term strength.