Pistia stratiotes alters diuron partitioning and metabolite formation: evidence from plant-mediated processes

Herbicide contamination in aquatic systems is commonly assessed through changes in water concentrations, potentially overlooking redistribution among environmental compartments and metabolite formation. Here, we investigated the environmental fate of diuron in aquatic microcosms with and without Pistia stratiotes , integrating diuron partitioning among water, sediment, and plant tissues with DCPMU formation, bacterial abundance, and plant physiological responses under environmentally relevant and elevated exposure levels (2.5, 10.0, and 25.0 μg L −1 ). In non-vegetated systems, diuron rapidly partitioned into sediment, which represented the main reservoir and was associated with progressive DCPMU formation. In contrast, the presence of P. stratiotes substantially altered diuron partitioning, reducing sediment retention and increasing accumulation in plant tissues, particularly roots, while bacterial abundance increased in water and sediment. These findings indicate that macrophytes can modify contaminant distribution and create alternative compartments for diuron retention and associated transformation processes. Despite physiological stress, P. stratiotes maintained diuron accumulation with limited translocation to shoots. Overall, reductions in water concentrations did not necessarily indicate contaminant attenuation, as diuron was redistributed among sediment and plant compartments and remained associated with metabolite formation. These findings highlight the importance of considering contaminant partitioning, plant accumulation, and transformation processes when assessing herbicide fate and persistence in vegetated aquatic systems.