Heavy metals accumulate in high water table coal mining subsidence ponds, resulting in heavy metal enrichment and destruction of the ecological environment. In this study, subsidence ponds with different resource reutilization methods were used as study subjects, and non-remediated subsidence ponds were collectively used as the control region to analyze the heavy metal distributions in water bodies, sediment, and vegetation. The results revealed the arsenic content in the water bodies slightly exceeded Class III of China’s Environmental Quality Standards for Surface Water. The lead content in water inlet vegetation of the control region and the Anguo wetland severely exceeded limits. Pearson’s correlation, PCA, and HCA analysis results indicated that the heavy metals at the study site could be divided into two categories: Category 1 is the most prevalent in aquaculture pond B and mainly originate from aquaculture. Category 2 predominates in control region D and mainly originates from atmospheric deposition, coal mining, and leaching. In general, the degree of heavy metal contamination in the Anguo wetland, aquaculture pond, and fishery–solar hybrid project regions is lower than that in the control region. Therefore, these models should be considered during resource reutilization of subsidence ponds based on the actual conditions.

Resource-exhausted cities are cities where the ratio of exploited reserves to recoverable reserves exceeds 70%. Long-term energy extraction and consumption lead to weak economic growth, idle industrial land, and ecological imbalances. It is imperative to explore sustainable development paths that are green and low-carbon. The spatial characteristics of cities and the structure of energy networks are crucial foundations for low-carbon development and energy security in cities. The main research content includes three aspects: (1) The first involves the identification of the distribution characteristics of typical resource- exhausted cities worldwide. This mainly includes coal, oil, metallurgy, forestry, and non-metallic minerals. Among them, coal resource-exhausted cities are the most numerous, mainly distributed in China, Australia, the United States, etc. (2) The second includes an analysis of the spatial characteristics of resource-exhausted cities in China. This involves taking 24 resource-exhausted prefecture-level cities in China as the research objects, integrating geographic data such as Points of Interest (POIs), and using machine learning for accurate quantitative identification and spatial delineation of urban functions. The production space and ecological space of cities show an aggregated distribution pattern, while the living space is randomly distributed. (3) The third is based on urban energy consumption data, utilizing the modified gravity model and social network analysis (SNA), and analyzing the centrality/relevance, relationship density and frequency, and accessibility. The average degree of centrality of the 17 coal-related industries is 5.529, demonstrating the energy network structure of resource-exhausted cities. This paper provides data foundations and technical methods for achieving urban energy renewal, ecosystem stability, and optimized spatial structures.

Under the background of ecological restoration and soil structure improvement in coal mining subsidence areas, understanding the impact of land use on soil organic carbon pools and aggregate characteristics is of great significance to evaluate the quality change and ecological effect of reclaimed soil and guide the improvement of reclaimed soil. Although the dynamics of soil organic carbon under land use changes have been studied, the mechanism of aggregate carbon protection in reclaimed mining soil is still unclear. Taking the reclaimed soils of farmland, woodland, and wasteland in the Dongtan mining area of Zoucheng City in Shandong Province as the research object, by comparing the particle size composition of soil aggregates, the distribution characteristics of organic carbon in 0–20 cm and 20–40 cm soil layers, and analyzing the differences of different organic carbon components, it was found that the organic carbon content of aggregates in the 0–20 cm soil layer was higher than that in the 20–40 cm soil layer; In topsoil, the contribution of fine aggregates to total organic carbon was the largest; the contents of free light fraction (free LF) organic carbon in fine aggregates, micro-aggregates, and total free light fraction organic carbon in forest soil were significantly higher than those in farmland and wasteland. These results suggest that fine aggregates may serve as primary carriers of reclaimed soil organic carbon. The study on the surface soil aggregate organic carbon helps reveal the transformation and accumulation process of reclaimed soil organic carbon. The study found that woodland reclamation may enhance microbial-driven soil organic carbon storage, suggesting that targeted land-use strategies have the potential to maximize the carbon sequestration capacity in degraded ecosystems. Findings are specific to the 7-year reclamation period and Dongtan mining area, requiring long-term regional validation.

Hexavalent chromium Cr(VI) contamination poses a significant risk to soil ecosystems because of its high mobility and toxicity. Identifying plant species capable of surviving under Cr stress and translocating Cr to harvestable aboveground tissues is a key step in developing phytoremediation strategies. Chromium (Cr) contamination, particularly hexavalent chromium Cr(VI), poses a substantial risk to soil ecosystems. This study evaluated the tolerance, Cr distribution, and antioxidant responses of Neyraudia reynaudiana grown in soil amended with K₂Cr₂O₇. Seedlings were exposed to five nominal Cr treatments (200, 400, 600, 800, and 1000 mg kg⁻¹) and sampled at 30, 60, 90, 120, and 150 days. Total Cr concentrations were determined in soil, roots, and shoots; translocation factor (TF) and shoot bioconcentration factor (BCF) were calculated. The activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were also measured. N. reynaudiana remained viable throughout the 150 d exposure period, including under the highest nominal Cr treatment. At 150 d, TF exceeded 1.0 in the Cr400–Cr1000 treatments and reached a maximum of 1.50 in the Cr600 treatment, indicating substantial root-to-shoot Cr translocation under these conditions. In contrast, shoot BCF values remained below 0.30 (0.20–0.29 at 150 d), indicating limited concentration-based Cr enrichment in aboveground tissues. Soil total Cr concentrations declined during cultivation; however, biomass-based Cr mass balance is required to quantify net plant-associated Cr removal. The activities of SOD, POD, CAT, APX, and GR showed distinct Cr-concentration- and growth-stage-dependent responses, with the overall antioxidant response generally strongest at intermediate Cr concentrations and attenuated under the highest treatment. These findings indicate that N. reynaudiana has tolerance to Cr(VI) stress and the capacity for root-to-shoot Cr translocation in a controlled pot experiment. Its practical phytoremediation efficiency requires further evaluation using biomass-based Cr accumulation, Cr speciation, and field validation. By characterizing the Cr tolerance and translocation responses of a native slope-restoration species, this study provides a physiological basis for evaluating N. reynaudiana as a candidate plant for integrated stabilization and phytoextraction-oriented remediation strategies at Cr-contaminated sites. It also identifies the key evidence needed to translate pot-scale responses into reliable site-specific remediation assessments.

Regional resource and environmental carrying capacity (RECC) is a crucial foundation for sustainable development. This paper analyzes the spatiotemporal evolution, geographical disparities, and contributing factors of Xuzhou’s RECC from 2011 to 2023, and projects its development trend by 2030. A comprehensive evaluation index system was developed, incorporating water resource development intensity and RECC, and using the entropy weight method, the Dagum Gini coefficient, Panel Vector Autoregression (PVAR), Monte Carlo simulation, and the Grey Wolf Optimizer-Support Vector Machine (GWO-SVM) for analysis. The findings indicate that Xuzhou's RECC had a variable upward trajectory with accelerated improvement post-2016; spatially, its capacity ranked as follows: Coordinated Development Zone > Core Urban Area > Revitalization Support Zone. Inter-regional disparities were the principal source of overall regional differences, accounting for 68.55% of the total regional disparities. The primary factors associated with were prioritized as the magnitude and intensity of water resource development, Ecological Buffer and Resilience Capacity, socio-economic pressure, water usage structure and efficiency, and resource base support capacity, all of which contribute comparably. The GWO-SVM model forecasts that by 2030, Pizhou and Xinyi county-level cities will reach the maximum level of RECC, while Feng County will remain at the lowest level. These findings establish a solid foundation for developing tailored methods to promote the coordinated and high-quality advancement of Xuzhou.

Background: Trees in natural forests are a major contributor to atmospheric methane (CH₄), yet these emissions have never been investigated in reclaimed forests. Our study aimed to assess the magnitude, seasonality, drivers, and contributions of tree CH₄ emissions to ecosystem CH₄ flux in the reclaimed forests. We measured CH₄ emissions from different emission pathways, including the stems of trees (Populus euramericana, Metasequoia glyptostroboides, and Camphora officinarum), shoots of herbs (Carex breviculmis and Carex dispalata), and soils in the two reclaimed forests with reclamation periods of 12 and 5 years. We identified factors controlling seasonal tree CH₄ emissions and measured tree morphological variables (diameter at breast height, wood density, and lenticel density) to determine species differences in emissions. Results: CH₄ emissions from trees in the 12-year-old reclaimed forest were significantly higher than those in the 5-year-old forest. Seasonal variations in tree CH₄ emissions were primarily driven by growth stage and soil parameters, including soil CH₄ flux, temperature, and moisture. Conclusion: In the reclaimed forests, tree-mediated CH₄ emissions could be an important contributor to ecosystem CH₄ flux, with contributions varying by season. As these forests mature and become ecologically restored, they may significantly impact regional and global CH₄ emissions.