Enhanced microbial degradation of fomesafen in anoxic conditions by glucose: Degradation characteristics under different redox conditions

Fomesafen (FSA), a widely applied diphenyl ether herbicide, frequently contaminates surface and subsurface environments, yet its environmental fate under anoxic conditions remains poorly resolved. This study systematically evaluated FSA anaerobic biodegradation under five environmentally relevant redox conditions—nitrate, MnO 2 , Fe(III), sulfate, and bicarbonate (methanogenic)—using microcosm experiment. Parallel treatments with and without glucose (1 mM) assessed the extent of co-substrate stimulation. We found that FSA degradation was strongly redox-dependent, with Fe(III)-reducing conditions supported complete FSA removal within 140 days, and glucose addition accelerated transformation dramatically, achieving full removal within 18 days, with rate constant increased from 0.01876 to 0.27276 d −1 with glucose, reducing the half-life from 36.9 to 2.5 days. Microbial community analyses revealed distinct structural variations across different redox conditions, highlighting the important roles of electron acceptors and glucose in shaping microbial community assembly. Syntrophic interactions likely played a crucial role in FSA degradation across all conditions. This study provides critical insights into the natural attenuation potential of FSA in anoxic matrices, and offers scientific guidance for the development of targeted redox-based bioremediation strategies for FSA contaminated anoxic soil-groundwater.