The problem of soil heavy metal pollution caused by coal gangue accumulation areas is becoming more and more serious. In situ plant remediation technology has become one of the most promising methods to solve heavy metal soil pollution due to its advantages of the green economy. In this experiment, the characteristics of heavy metal pollution in the shallow soil (vertical depth 0~20 cm) 300 m outside the square circle of a typical coal gangue accumulation area in the Fengfeng Mining Area of Hebei Province, China were used as the prototype. Alfalfa and ryegrass were selected as the test plants. Pot experiments were carried out at different heavy metal concentrations (Cu:14/64/100 mg/kg, Pb:15/38/170 mg/kg, Cd:1/4/8 mg/kg) levels to study and reveal the effects of single and compound soil heavy metal pollution on seed germination and seedling growth characteristics of alfalfa and ryegrass. The results showed that: (1) Under the condition of single Cd pollution, the germination index of alfalfa seeds and the germination potential of ryegrass seeds show a trend of “low concentration promotion and high concentration inhibition”. Under the condition of single Pb and Cu pollution in soil, the germination indices show obvious inhibition and damage effect; that is, with an increase in concentration, the germination rate, germination potential, germination potential, and vigor index show a decreasing trend. When Pb is 170 mg/kg or Cu is 100 mg/kg or Cd is 8 mg/kg, the inhibitory effect on seed germination and seedling growth of the two plants is the most harmful. (2) Due to the different concentrations of heavy metal combined pollution, there are synergistic or antagonistic effects between Cu, Pb and Cd in soil on alfalfa and ryegrass. That is to say, under low concentrations of heavy metal pollution, the inhibitory effect of combined stress is greater than that of single stress, and under high concentration of heavy metal pollution, the inhibitory effect of combined stress is less than that of single stress. (3) Whether in the single pollution or combined pollution of soil, ryegrass is always more tolerant than alfalfa, indicating that ryegrass has more potential for remediation.

The destruction of shallow aquifers by water-conducting fractures of overlying strata caused by underground coal mining is the most representative form of mining-induced damage in the Yushenfu mining area. It has become an important factor restricting the green mining of coal in the Yushenfu mining area and even the ecological protection and high-quality development of the middle reaches of the Yellow River. As the key scientific problem of water-preserved coal mining, the scientific understanding of the development law and main influencing factors of water-conducting fractures in overlying strata has attracted great attention. Taking the geological occurrence characteristics of the main coal seam in Yushenfu mining area as the prototype, 24 different types of numerical models are constructed with the key characteristics of the overburden structure, such as the number of layers of sandstone in the overburden (sand layer coefficient) and the thickness ratio of sandstone and mudstone in the overburden (sand–mud ratio), as the main variables. By means of numerical simulation experiment and theoretical calculation, combined with field measurement and comparison, the influence of the key characteristics of overburden structure on the development height of water-conducting fracture is studied and revealed. It is proposed that the effective area for the study area to achieve water-preserved coal mining by using the height-limited mining method must conform to the coal seam overburden structure characteristics of “sand–mud ratio 6:4 and sand layer coefficient less than 70%” and “sand–mud ratio 8:2 and sand layer coefficient less than 80%”. The results not only enrich and deepen the research on the influence of geological factors and the law of controlling the development of water-flowing fractures in overlying strata, but also provide theoretical support for the precise protection of groundwater resources in the Yushenfu mining area in the middle reaches of the Yellow River.

How to solve the contradiction between coal mining and soil and water conservation is a key scientific issue in the achievement of high-quality development in the middle reaches of the Yellow River. In this paper, the northern Shaanxi mining area in the middle reaches of the Yellow River is taken as the research area, and the surface loess micro-topography is taken as the entry point. The numerical simulation test and soil loss model calculation are used to reveal the different types of loess natural slope morphology (straight slope, concave slope, convex slope, and composite slope) and the natural slopes (5°, 15°, 25°, 35°, 45°). The influence characteristics and laws of the same mining on the surface loess slope morphology in the coal mining subsidence area are analyzed, and the soil erosion effect on the slope scale is analyzed. The results show that: (1) Coal mining subsidence will lead to an increase in the slope of the loess slope, and the smaller the natural slope, the greater the increase in slope. Among them, the influence of coal mining subsidence on the ‘concave loess slope with natural slope of 15°’ is the most significant, and the natural slope of 15° is the key dividing point for the transformation of the sensitive slope shape of the loess slope in the coal mining subsidence area of northern Shaanxi. (2) Coal mining subsidence will lead to the decrease in slope length of a loess natural slope, and the smaller the natural slope, the greater the decrease in slope length. Among them, coal mining subsidence has the most significant impact on the ‘concave loess slope with a natural slope of 25°’. The natural slope of 25° is the key point of the sudden change rate of the slope length of the loess slope in the coal mining subsidence area of northern Shaanxi. (3) Coal mining subsidence will lead to the increase in the soil erosion modulus on the surface loess slope under the scale of ‘annual erosion rainfall’ and ‘typical field erosion rainfall’, and the smaller the natural slope, the greater the increase in the soil erosion modulus. The natural slopes of 15° and 25° are the key points of the abrupt change in soil erosion intensity on the loess slope in the coal mining subsidence area of northern Shaanxi under the scales of ‘annual erosion rainfall’ and ‘typical erosion rainfall’, respectively. Under the scale of annual erosion rainfall, the increment of the 15° slope was 1.65 times, 1.12 times, 1.11 times, and 1.02 times that of the 5°, 25°, 35°, and 45° slopes, respectively. Under the typical erosion rainfall scale, the increment of the 25° slope was 4.22 times, 1.32 times, 1.04 times, and 1.15 times that of the 5°, 15°, 35°, and 45° slopes, respectively. (4) For the loess subsidence slope with any slope shape, the increase in slope gradient is the main factor for the increase in the soil erosion modulus. Under the annual erosion rainfall scale, the contribution of slope increase was 92.9%. Under the typical erosion rainfall scale, the contribution of slope increase was 79.1%. The research results can provide scientific guidance for soil erosion and control in the northern Shaanxi mining area in the middle reaches of the Yellow River Basin.

Background: A scientific understanding of soil erosion in coal mining subsidence areas is crucial for promoting green development and ecological restoration within the large coal bases of the Yellow River’s middle reaches. Methods: This study focused on the shallow soil layer (0–40 cm) of a loess mining subsidence area and typical slopes in northern Shaanxi. Integrating field sampling, laboratory measurements, and model-based calculations, we analyzed the impact of mining subsidence on soil anti-erodibility by examining the coupled “slope position × soil depth” effect. Results: The results indicate that: (1) Mining subsidence significantly reduced the content of water-stable aggregates (>0.25 mm) and decreased the mean weight diameter of soil aggregates on the loess slope, with the >0.25 mm aggregate content being the most affected; (2) The adverse effect of subsidence on key soil anti-erodibility indicators weakened progressively from the slope top to the slope toe. The 0–20 cm soil layer at the slope top showed the greatest sensitivity; (3) Following subsidence, the comprehensive soil anti-erodibility index decreased significantly, indicating markedly enhanced erosion susceptibility. The most pronounced reduction (97.13%) was observed in the “slope top + 0–20 cm soil layer”. Conclusion: The “slope top + 0–20 cm soil layer” should be prioritized as a key area for erosion control on subsided loess slopes. These findings provide a scientific basis for targeted soil erosion management in coal mining subsidence areas of northern Shaanxi.