Laboratory modeling of microbial and chemical clay minerals transformations of upper aquifer soils under intensive...

Storage of nitrogen‑sulfuric acid waste from uranium ore mining and processing enterprises in sludge ponds leads to groundwater contamination by soluble components with degradation of impervious barriers. This results in a significant alteration of the geochemical environment and the mineral composition of rocks, as well as creates risks of soluble toxic components from waste entering water intakes and open hydrographic networks. Laboratory modeling of biofouling processes and subsequent alterations in soil composition from upper aquifer adjacent to the sludge repository of the Angarsk Electrolysis Chemical Plant (Angarsk, Russia) was conducted in this study. The investigation established that anthropogenic impacts resulting from elevated concentrations of nitrates, sulfates, ammonium, and bicarbonates significantly modify both the mineralogical and microbial composition of soils, consequently influencing their biogeochemical transformation characteristics. Under technogenic pollution conditions, microbial processes promote the development of more densely structured biofilms while simultaneously impeding iron reduction processes that normally facilitate more profound mineralogical alterations. The transformation of clay mineral composition plays a pivotal role in biofouling dynamics and governs subsequent mineral modification pathways. Microbial-mediated processes can induce structural reorganization of smectite minerals into tobelite-like configurations through two principal mechanisms: biologically facilitated iron dissolution and ammonium saturation of interlayer spaces resulting from dissimilatory nitrate reduction and subsequent ammonification processes.