Oxygen-supplemented organic matter significantly enhanced microbial antimony mobility in hydrologically dynamic groundwater of a typical mining area

Microbial-mediated antimony (Sb) release from stibnite (Sb 2 S 3 ) threatens groundwater safety, yet how hydrological fluctuations regulate this biogenic process and its mechanism remain poorly understood. This study explored how hydrodynamic variations (simulating organic-oxygen recharge into anoxic aquifers) govern stibnite bio-weathering in Xikuangshan shallow groundwater through microcosms. The results revealed bacterial communities exhibit dual functionality under redox fluctuations: driving biofilm formation in anoxic phases and accelerating Sb release during oxic transitions. The AnH system (Anoxic-oxic-anoxic-oxic cycles with Na-lactate for Heterotrophs) demonstrated a maximum of Sb concentration at 0.63 mM after 16 days, primarily driven by Dechloromonas, Ferribacterium , and Thauera . Microbial metabolic byproduct nitrite activates oxygen to produce H 2 O 2 (maximum of 14.7 μM), which also contributes to the release and oxidation of antimony. Moreover, carbon source affects the pathway of bacterial antimony release. Na-lactate stimulated the expression of aioA (Sb-oxidation) in heterotrophs, while inorganic carbon (Na-bicarbonate) favored soxB (sulfur-oxidation) in autotrophic Thiobacillus and mixotrophic sulfur-oxidizers. In summary, oxygen and carbon sources regulate biofilm formation, aioA and soxB expression, and H₂O₂ generation, subsequently affecting Sb release/oxidation. This study deciphered how oxygen-carbon regimes govern microbial Sb mobilization, elucidating antimony biogeochemical dynamics under hydrological fluctuations.