Partitioning and transformation of diuron in water-sediment systems: Influence of Eichhornia crassipes on contaminant redistribution and metabolite formation.

Aquatic macrophytes can actively reshape contaminant fate in aquatic systems by redistributing chemicals across environmental compartments rather than promoting removal. Herbicides frequently enter aquatic systems through agricultural runoff, leading to accumulation in sediments and interactions with biota. Diuron, a persistent photosystem II inhibitor with strong affinity for organic matrices, is widely detected in aquatic environments and forms transformation products. However, the role of aquatic macrophytes in modulating its environmental fate remains insufficiently understood. Here, water-sediment microcosms were used to evaluate the influence of Eichhornia crassipes on diuron fate under environmentally relevant concentrations (2.5, 10, 25 µg L⁻¹) over 45 days. In unvegetated systems, diuron accumulated predominantly in sediments, accompanied by progressive formation of DCPMU. In contrast, the presence of E. crassipes reduced sediment retention and promoted redistribution toward plant biomass, with preferential accumulation in roots. Plant biomass accounted for up to 71% of the total applied diuron at 2.5 µg L⁻¹ , whereas sediment dominated at 10 and 25 µg L⁻¹ (67-68%). This redistribution coincided with higher bacterial abundance and greater occurrence of DCPMU in vegetated systems, suggesting that biologically active compartments may influence contaminant fate within the system. Mass balance analysis demonstrated that vegetation regulates contaminant fluxes within aquatic systems. Although no oxidative damage was detected, physiological responses indicated effective antioxidant regulation, maintaining redox homeostasis. Importantly, E. crassipes did not promote contaminant removal but instead altered its environmental fate by redirecting its distribution. These findings highlight the importance of metabolite formation and biomass accumulation for phytoremediation strategies and environmental risk assessment.