Soil moisture is key in maintaining surface energy balance and the hydrological cycle. However, the patterns of soil moisture change at different altitudes and their response to rainfall are not fully understood. The aim of this study is to analyze the changes in soil moisture at different altitudes in the Mu Us Sandy Land, assess the soil moisture response to various rainfall events, and evaluate the factors affecting this response. To achieve this, we set up two soil moisture and precipitation monitoring systems in the Ejin Horo Banner, located at the northern edge of the Mu Us Sandy Land. Results show that the annual precipitation at the site was 342.6 mm, with most rain falling between July and September. The region experiences soil drought from June to October. At the lower X1 test site, the increase in soil moisture in the 0–90 cm layer during rainfall was greater than the amount of precipitation, suggesting that lateral water flow from higher areas influences soil moisture at lower positions. This study used Grey Relational Analysis to identify the key factors influencing soil moisture changes; the result showed that the initial soil moisture and total precipitation have the strongest correlation with changes in soil moisture, making them the main factors controlling soil moisture response at the site. These findings enhance our understanding of soil moisture dynamics and provide a foundation for vegetation restoration in semi-arid sandy areas and ecosystem rehabilitation.

The impact of various modification methods on enhancing the adsorption performance of coal gangue (CG) for hazardous heavy metals has not been thoroughly investigated. In this study, three CG samples were first modified by calcination, followed by acid washing, alkali washing, and hydrothermal treatment, to obtain modified CG samples. The adsorption performance was assessed based on the adsorption capacities for Cd²⁺ and Pb²⁺ (i.e., q_e,Cd and q_e,Pb), and the kinetics of the adsorption processes were analyzed using kinetic equations. XRD, SEM-EDX, FTIR, and N₂ adsorption–desorption isotherms were used to elucidate the adsorption mechanisms. Results indicated that q_e,Cd and q_e,Pb of raw CG samples were approximately 10 and 25 mg/g, respectively, with only slight changes observed after calcination, acid washing, and alkali washing. In contrast, hydrothermal treatment yielded NaP and NaA zeolites, which significantly enhanced q_e,Cd and q_e,Pb to values of 48.5–72.7 and 214.9–247.5 mg/g, respectively. The hydrothermally treated CG samples primarily adsorbed Cd²⁺ and Pb²⁺ through ion exchange with Na⁺ within the zeolite structure, facilitating the entry of these ions into the zeolite’s pore channels. The adsorption processes were effectively described by the pseudo-second-order kinetic model. By optimizing the conditions of hydrothermal modification, the adsorption performance of CG samples is anticipated to further improve due to the creation of additional adsorption sites.

The selection of a suitable location is a crucial prerequisite for the construction of an underground reservoir in water-scarce coal-mining regions, while there are few reports related. In this research, the geological influencing factors of water storage capacity of an underground reservoir were investigated. Caved sandstone provides effective storage space for mine water and mudstone in the floor prevents the mine water in the goaf from leaking downward. The water storage capacity of coal mine underground reservoir is positively correlated with the coal thickness, sandstone ratio of the roof, water storage coefficient, and effective safety thickness, and is negatively correlated with the elevation of the main coal floor and sandstone ratio of the floor. A mathematical model of water storage coefficient was established and a geological site selection method of a coal mine underground reservoir was proposed based on an entropy weight method. With a HJT coal mine in the Shendong coal mining area of China as a case study, the implementation of this method was elaborated. For an existing underground reservoir, located in the goaf of No. 12301 fully mechanized long wall mining face of No. 1⁻² coal seam in the HJT mine field, the water storage coefficient (Q) and the site selection suitability index (SI) were 0.2194 (Q) and 0.544 (SI, at a good level). The estimated values were consistent with the actual situation, which may verify the accuracy and reliability of this method to some extent. SI was estimated for No. 2⁻² coal seams and the suitable locations for the construction of underground reservoirs were predicted in this mine field.

Coal gangue is a fine-grained mineral with nutrient content, which can be used as a potential soil amendment. Nevertheless, current research on using coal gangue to improve soil water and support plant growth is still insufficient. In this study, coal gangue powder (CGP) was added to aeolian sandy soil. We compared the soil hydraulic properties and plant growth of original aeolian sandy soil (CK) and different CGP application rates (10% and 20%). The results indicated that the application of CGP transformed the soil texture from sandy to loamy, significantly reduced soil bulk density and saturated hydraulic conductivity (Ks) values, altered the soil water characteristic curve, enhanced soil water-holding capacity, and increased plant-available water. Compared with the CK group, the emergence rate of alfalfa seeds increased from approximately 50% to over 70% after CGP application. During the growth process, CGP application significantly elevated the net photosynthetic rate, transpiration rate, and stomatal conductance of alfalfa leaves. Rapid fluorescence kinetics monitoring of leaves demonstrated that alfalfa treated with CGP had a higher efficiency in light energy utilization. However, the photosynthetic capacity of leaves did not improve as the CGP application rate increased from 10% to 20%, suggesting that excessive CGP addition did not continuously benefit plant gas exchange. In conclusion, CGP application can improve the soil hydraulic properties of aeolian sandy soil and support plant growth and development, which is conducive to reducing the accumulated amount of coal gangue, alleviating plant water stress, and promoting ecological restoration in arid mining areas. We recommend a 10% addition of coal gangue powder as the optimal amount for similar soils.

Clarifying how plants utilize water in coal mining subsidence zones is essential for grasping plant-soil dynamics and guiding ecological rehabilitation. However, current knowledge on species-specific variations in water uptake and their adaptive responses to such subsidence remains limited. This research leveraged isotopic fingerprinting (δ²H, δ¹⁸O) alongside soil water content and root distribution to explore the root water uptake sources of two predominant species (Stipa bungeana Trin. and Artemisia desertorum Spreng.) in coal mining zones and their reactions to land subsidence triggered by coal extraction. The results indicated negligible differences in soil water content and soil water isotopic composition between subsidence and non-subsidence zones, irrespective of rainfall. Before rainfall, the water sources of the two species were unaffected by subsidence; however, after rainfall, discernible changes occurred. Plants in the subsidence area absorbed more water from the top 0–10 cm soil layer, indicating a more pronounced response to rainwater infiltration. Notably, A. desertorum, in contrast to S. bungeana, tapped into deeper soil water during arid conditions and swiftly switched to shallow soil water sources following rainfall, highlighting its adaptable water usage strategy and greater ecological resilience. The findings of this study cast new light on plant-water relationships in coal mining subsidence regions, providing essential guidance for ecological restoration and management efforts.

The direct vapor equilibration-laser spectroscopy (DVE-LS) method can be used to measure the stable isotopes of soil water (δ²H and δ¹⁸O), a technique that is easier to operate and quicker for sampling compared to the traditional cryogenic vacuum distillation (CVD) method. However, the soil water isotope values thus obtained often deviate from the true value, which is affected by the equilibrium temperature during the measurement process. Therefore, this study conducted an indoor experiment on five soil samples of varying textures. The dry soil was wetted by reference water samples to four different soil water content (SWC) values and then equilibrated at five different temperatures. The soil water isotope deviation value (SWIDV) of the DVE-LS method was determined by building a correction equation between SWIDV and the influencing factors (equilibrium temperature, soil clay content (SCC), and SWC, after which the correction equation values were compared to those calculated by the CVD method for the field-collected soil samples to check the accuracy. The results shows that the Δδ²H value increased with increasing equilibrium temperature and soil clay content, but decreased with increasing SWC. The multi-factor variance analysis shows that equilibrium temperature, SCC, and SWC significantly affected the Δδ²H values and deviation values with the DVE-LS method, but insignificantly affected the Δδ¹⁸O values and deviation values. The correction equations (3) was built at different equilibrium temperatures, and the RMSE decreased from 4.07‰ to 1.24‰ and from 8.99‰ to 4.14‰, respectively, as calibrated by the isotope values of soil samples collected in Changwu and Suide counties. The correction equations under various equilibrium temperatures increased the accuracy of the DVE-LS method in obtaining soil water isotope values and promoted the application of the DVE-LS method in soil water isotope analysis.