Self-limiting stibnite weathering in suboxic humic sediments triggers Sb2O3-like-dominated passivation and decoupled genotoxic-phytotoxic damage in Elodea canadensis.

Antimony (Sb) is a priority pollutant whose mobility and toxicity are linked to the environmental weathering of stibnite (Sb2S3). This study combined a 10-week hydrochemical investigation (SbT, SO42-, pH, Redox) with surface (AFM, SEM, Raman, XPS, Zeta-potential (ζ)), electrochemical (EIS, CV, CA, Tafel plots), and ecotoxicological (genotoxicity, phytotoxicity) analyses to elucidate weathering mechanisms under suboxic humic sedimentary conditions. A critical Sb release pulse peaked at 2 weeks (∼60 μg·L-1), followed by progressive passivation. Raman and XPS confirmed the formation of an Sb2O3-dominated layer, while Electrochemical Impedance Spectroscopy showed charge-transfer resistance (Rct1) increasing from 782.8 to 20,069 Ω2. Negative surface charge (-33 to -53 mV) indicated that OH- (and SO42-) ions competitively occupied reactive surface sites, electrostatically repelling humic polyanions and confining Sb species to the solution. Ecotoxicological assays on Elodea canadensis (1-2000 mg·kg-1 Sb2S3) revealed an asynchronous recovery phenomenon: while chlorophyll a exhibited physiological recovery after 21 days (3.05 μg·g⁻¹ at 50 mg·kg-1), comet assays demonstrated cumulative genotoxicity (35.66 ± 16.63-244.50 ± 5.92 A.U. at 2000 mg·kg-1 Sb2S3). This decoupling proves that physiological recovery can mask persistent genomic damage, highlighting the limitations of single photosynthetic biomarkers for evaluating long-term ecological risks.