This study investigated soil development resulting from revegetation in a coal mining area in northern Henan, China. The effectiveness of six distinct revegetation methods for reclaiming mine-degraded lands was assessed. These methods employed various species such as Ulmus pumila, Amorpha fruticosa, Robinia pseudoacacia, Jerusalem artichoke, and Sea buckthorn. Over a three-year reclamation period, soil development was analyzed to identify the most suitable plant species. Soil samples were collected from different depths, encompassing the topsoil (0–20 cm) and subsoil (20–40 cm) for each method and a control group. Principal component analysis was employed to evaluate the impacts of the revegetation methods on soil development. The findings show that revegetation significantly impacted soil properties, lowering pH, electric conductivity, and density while increasing moisture, organic carbon, nitrogen, phosphorus, and potassium. The effects were more pronounced in the topsoil. Among the six revegetation methods, a mixed plantation of Sea buckthorn and Amorpha fruticosa was the most effective, delivering the highest organic carbon in the topsoil at 3.23% and the subsoil at 1.32%. This study offers insights into successful mine reclamation and the advancement of green and climate-smart mining practices.

Underground reservoir technology can mitigate water shortage and pollution problems in water shortage coal mining areas and has a good application prospect. While still a new technology, the theory and method of underground reservoirs need to be improved. This research focused on the hydrochemical characteristics of mine water and their significance for the site selection of underground reservoirs. With the Shendong coal mining area as a case study, the hydrochemical major ions, toxicological indexes, and stable isotopes of hydrogen and oxygen were tested for the mine water samples, and the water quality was quantitatively evaluated and the origins of over-limit variables were investigated by hydrogeochemical numerical simulation and ionic ratio analysis. The influencing factors of water quality were analyzed and the significance of mine water quality for the site selection of underground reservoirs was discussed. The results show that the main over-standard variables are Na⁺, F⁻, SO₄²⁻, TDS, and sodium ion adsorption ratio (SAR), and a strong positive correlation exists between F⁻ and SAR and a negative correlation exists between F⁻ and Ca²⁺. Na⁺ in mine water originates from the dissolution of halite and silicate rocks, as well as reverse cation exchange. F⁻ originates from reverse cation exchange and the displacement between OH⁻ in alkaline water and F⁻ adsorbed on the surface of minerals. On the whole, the mine water quality is better on the east than on the west of the WL River. The water–rock interactions in goaf increase the concentrations of F⁻ and Ca²⁺ and SAR. The areas where the mine water samples have low concentrations of Na⁺, F⁻, and low SAR values, such as the shallow coal seams at the SGT, DLT, and WL mines, are favorable sites for the underground reservoir. The outcomes may benefit the reasonable site selection of underground reservoirs in similar coal mining areas with water shortage.