Tao Peng

Identifying the causes and mechanisms of heat hazards in mining operations is essential for effective heat hazard prevention and control. In recent years, hydrothermal phenomena have frequently occurred in the eastern part of the Chenghe Mining Area, located in the central Weibei Coalfield. However, research on the geothermal fluid migration patterns and heat generation mechanisms in this region remains limited. This study comprehensively explores the geothermal field characteristics in the area, based on well temperature logging data, rock thermal conductivity, temperature control models, temperature curve analysis, and numerical simulations. It reveals the key controlling factors and mechanisms behind the formation of geothermal anomalies in the region. The results show that the overall geothermal heat flow trend in the area is characterized by low heat in the northwest and high heat in the southeast. The formation of geothermal anomalies is primarily influenced by water-conducting faults and coal seams. Based on this, the temperature control models are classified into two types: the fault + deep circulating thermal water uplift model and the coal seam heat-resistant-folded temperature control model. Heat transfer occurs through groundwater convection along the F1 fault and its secondary faults, which transport heat. The heat generation mechanism in the study area involves the heating of groundwater during deep circulation, followed by the upward migration of the heated water along the F1 fault, which adds an additional heat source to the surrounding rock of the fault, creating localized thermal anomalies. The findings of this study provide direct guidance for safe production in the Chenghe Mining Area and offer a universal theoretical framework for understanding the causes of heat hazards in mining areas with strong tectonic activity in northwestern China.

As an ideal carrier for the spread of pollutants in the aquatic environment, microplastics (MPs) can adsorb pharmaceutical β-blockers, which can affect their migration and lead to some unpredictable adverse consequences. In this paper, the sorption behaviors and mechanism of MPs (polyvinyl chloride (PVC) and polypropylene (PP)) for typical β-blocker metoprolol (MTL) were investigated. The effects of pH, salinity and humic acids (HAs) on the sorption were studied, which proved that the sorption behavior was different under different environmental conditions. Both low pH and high salinity inhibited the sorption of MTL by the MPs. Specifically, the sorption capacity of MTL increased, with pH increase from 3 to 10. When pH = 10, the sorption capacities of MTL on PVC (1.75 mg/g) and PP (3.34 mg/g) reached the maximum. After pH > 10, the amount of MTL adsorbed on PVC was slightly decreased, while that on PP was essentially the same. The addition of salt ions inhibited the sorption in the concentration range of 5–250 mg/g for both NaCl and CaCl₂, with the inhibitory effect of Ca²⁺ being stronger than that of Na⁺. Moreover, the presence of HAs promoted the sorption of MPs for MTL. In the absence of HAs, the sorption capacities of PP and PVC for MTL were 0.34 mg/g and 0.79 mg/g, respectively. When HA concentration was 100 mg/L, the highest sorption capacities of PP and PVC reached 0.79 mg/g and 1.37 mg/g, respectively. This indicated that the promoting effect of HAs on PP was stronger than that on PVC. In general, based on the study of the sorption behavior of MTL and the characterization of the MPs, the sorption mechanism was speculated to consist mainly of electrostatic interactions, cation exchange, hydrophobic interaction and halogen bonding. The sorption kinetics of MTL on the two MPs were well-fitted by the pseudo-second-order model with R² > 0.99. The sorption isotherms both fitted the Freundlich model, which substantiated that the sorption of MTL on the MPs (PVC and PP) was multilayered and heterogeneous. Collectively, these findings provided a theoretical basis for revealing the complex interactions between MPs and MTL in natural water and a new insight into the fate and migration of MPs and β-blockers in the environment.

In this study, a random subspace-based function tree (RSFT) was developed for landslide susceptibility modeling, and by comparing with a bagging-based function tree (BFT), classification regression tree (CART), and Naïve-Bayes tree (NBTree) Classifier, to judge the performance difference between the hybrid model and the single models. In the first step, according to the characteristics of the geological environment and previous literature, 12 landslide conditioning factors were selected, including aspect, slope, profile curvature, plan curvature, elevation, topographic wetness index (TWI), lithology, and normalized difference vegetation index (NDVI), land use, soil, distance to river and distance to the road. Secondly, 328 historical landslides were randomly divided into a training group and a validation group in a ratio of 70/30, and the important analysis of landslide points and conditional factors was carried out using the functional tree (FT) model. In the third step, all data are loaded into FT, RSFT, BFT, CART, and NBTree models for the generation of landslide susceptibility maps (LSM). Comparisons were made by the area under the receiver operating characteristic curve (AUC) to determine efficiency and effectiveness. According to the verification results, the five models selected this time all perform reasonably, but the RSFT model has the highest prediction rate (AUC = 0.838), which is better than the other three single machine learning models. The results of this study also demonstrated that the hybrid model generally improves the predictive power of the benchmark landslide susceptibility models.

Geothermal anomaly has gradually become a prominent issue affecting the efficient mining of coal with the depth of coal mining increasing in eastern Chenghe mining area of Weibei coalfield. Here, we comprehensively investigated the distribution characteristics of the present geothermal field, analyzed the main controlling factors, and constructed forming mode of geothermal anomaly by the temperature measurement in surface borehole and underground water, combined with coal-rock thermal conductivity test. The results show that the geothermal gradient ranged from 25.7C/km to 54.3C/km. The areas with geothermal gradient greater than 30C/km accounted for 88.31, and there was the highest gradient value in the southeast F₁ fault zone. The heat flow was between 66.81mW/m² to 128.49mW/m², which belonged to the obvious high heat flow area. Under the action of the main controlling factors such as fault, fold, coal-rock thermal conductivity, and groundwater activity in the region, the geothermal gradient and geothermal heat flow values showed an increasing trend from northwest to southeast. According to the distribution characteristics of heat flow and the action mechanism of main controlling factors, the geothermal anomaly in the study area was finally divided into two forming modes, i.e., fault-deep circulating hot water uplifting type and coal seam heat resistance-fold type. The research provides guidance for the geothermal hazard prevention of coal mine and the rational development and utilization of geothermal resources.

Water content and water–coal interface wettability are always the difficult issues of coalbed methane adsorption/desorption. In order to study the effects of the pore structure and wettability of different macro coal components on methane adsorption and desorption, we compared and analyzed the wettability difference between vitrain and durain, and revealed the influence of wettability on methane adsorption and desorption through a pore structure analysis, wettability measurements, an adsorption–desorption experiment and adsorption heat calculations under different conditions, taking the No. 4 coal in Dafosi Coal Mine of the Huanglong coalfield as the research object. The results show that both vitrain and durain are relatively hydrophilic substances. However, vitrain has a low ash content, high volatility, and less oxygen, and the pores are mainly semi-closed pores compared with dark coal. Vitrain also has poor connectivity, poor sorting, a small pore diameter, and a coarser surface, resulting in poor surface wettability. The large specific surface area (SSA) and relatively poor wettability of vitrain leads to more adsorption sites in methane, which makes the adsorption capacity of vitrain greater than that of durain, but the good pore connectivity of durain causes the strong desorption capacity of durain. The isosteric adsorption heat of the adsorption process is greater than that of the desorption process, indicating that there is a desorption hysteresis phenomenon which is essentially due to the lack of energy in desorption. Surfactants change the wettability of the coal surface, and different surfactants have different effects on methane adsorption and desorption. Relatively speaking, the methane desorption of coal samples treated with G502 and 6501 are better. The research results provide scientific reference for the study of gas–water transport in the desorption process of low-rank CBM, and provide evidence for the methane desorption model of vitrain and durain.