Decades of weathering improves coal waste biogeochemical properties by altering dissolved organic matter and microbial communities: A case-study of a coal waste pile

The spatial heterogeneity of vegetation cover in coal waste pile suggests that the geochemical and biological properties of coal waste are spatially heterogeneous, which contributes to vegetation colonization on tailings. However, whether and how altering the organic matter components and microbial community of coal waste via weathering affects biogeochemical characteristics and vegetation establishment mechanisms remain unclear. Thus, we explored the characterization of dissolved organic matter in coal waste and its biogeochemical implications. Our results highlight coal waste as primary succession for bacterial communities and provide new insights into the bacterial community assembly response to dissolved organic matter and geochemical properties at such sites. Biogeochemical parameters including pH, EC, nutrients, particle size, and enzymatic activities were affected differently by organic components. The electrical conductivity (EC) decreased after decades of natural weathering, whereas pH, moisture, available N and P, urease, phosphatase, soluble microbial byproduct-like material, humic acid-like organics, bacterial diversity, and richness increased significantly. Further taxonomical and co-occurrence network analyses indicated that the primary succession of bacterial communities was strongly influenced by biogenically formed organic components, particle size, and available nutrients. Our results revealed that the humic-like components facilitated the improved biogeochemical properties and succession of composition and structure of the bacterial community. It demonstrated that weathering-induced organic matter degradation trigger biogeochemical property improvement and bacterial community succession, and further facilitate the transformation of coal waste into a plant growth substrate. Our results provide a reference for engineering and application practice of utilization and in-situ remediation ecological reconstruction in coal waste deposits.