Mechanistic elucidation of citric acid-modified biochar-mediated atrazine degradation and drift risk mitigation in maize rhizosphere soil

Atrazine (ATR), a widely used herbicide in agricultural weed management, poses significant risks to plant health and environmental safety due to its persistence and bioaccumulation. Citric acid-modified biochar (CABC) has emerged as a promising amendment for enhancing ATR removal from soil. However, CABC degradation mechanisms and capacity to mitigate ATR uptake by crops remain inadequately understood. This study investigated the efficacy of CABC in ATR degradation, elucidated associated metabolic pathways, and assessed its effect on ATR bioavailability and maize physiological responses. Application of CABC increased ATR degradation efficiency from 28.8 % (control) to 80.1 %, and significantly reduced ATR bioavailability in maize roots, stems, and leaves by 19.7∼53.1 %. CABC notably promoted dechlorination, dealkylation, and deamination of ATR, mediated by functional microbial taxa including Proteobacteria, Actinobacteria, Rhodanobacteraceae, Bradyrhizobiaceae, Nocardiaceae, Streptomycetaceae, Acetobacteraceae, and Micromonosporaceae, through gene pathways involving atzA , atzB , atzC , atzF , and triA , ultimately leading to mineralization into carbon dioxide (CO 2 ). Additionally, CABC improved soil pH, organic matter content, humus (HU) composition, and enzymatic activities, thereby enhancing maize growth, physiological resilience, and resistance to ATR-induced stress. Structural equation modeling (SEM) identified microbial activity as the principal driver of ATR degradation. These results highlight the potential of CABC as a sustainable and multifunctional strategy for bioremediation of ATR-contaminated soils and for safeguarding crop health. • Citric acid modified biochar (CABC) boosts atrazine degradation efficiency. • CABC reduces atrazine bioavailability in maize roots, stalks and leaves. • Dechlorination/dealkylation/deamination drives complete atrazine mineralization to CO₂. • Structural equation modeling confirms microbial activity dominates atrazine degradation.