Microbial Biomass and β-glucosidase Activity in Technosols Constructed from Iron Mining Tailings and Construction Waste

Iron mining and the construction sector are major sources of solid waste, including iron mining tailings (IMT) and construction and demolition waste (CDW), whose generation processes contribute to carbon emissions and the overloading of landfills. Soil formation and functionality are strongly governed by soil–plant–microorganism interactions, which drive carbon cycling and the development of edaphic systems. In this context, Technosols composed of IMT and CDW, respectively, in different proportions (60:40, 70:30, and 80:20), as well as 100% IMT, were evaluated and compared with a natural soil (Haplic Ferralsol). After 120 days of cultivation with Urochloa brizantha cv. Marandu, rhizosphere and bulk soil samples were collected to assess microbial biomass carbon and β-glucosidase activity. From this perspective, no significant differences were observed in rhizosphere microbial biomass carbon or enzymatic activity between the Technosols and the natural soil.  However, β-glucosidase activity in the bulk soil was lower in all treatments (3.97 𝜇g p-nitrophenol.g.soil^-1h^-1) compared with the control (13.06 𝜇g p-nitrophenol.g.soil^-1h^-1). These results elucidate the important role of the rhizosphere environment in the initial pedogenesis of soils composed of anthropogenic materials. Thus, beyond the influence of root exudates, rhizosphere microorganisms are essential for the formation and functional sustainability of Technosols, ensuring key biogeochemical functions in soils composed of anthropogenic materials. By sustaining biogeochemical functions through the soil–root interface, Technosols demonstrate potential for environmental restoration as a Nature-based Solution, contributing to the Sustainable Development Goals.