Reduced Graphene Oxide Modulates Bioaccumulation, Persistence, and Metabolic Transformation of 14C-Triclosan in a Soil-Radish System

The application of reduced graphene oxide (RGO) is increasing, but its impact on the behavior of co-contaminants like triclosan—a pervasive antimicrobial agent—in soil-plant systems remains unclear. This study aimed to investigate the effect of nano-sized RGO on the residues, uptake, and metabolism of triclosan in a soil-radish plant system using ¹⁴C-labeled triclosan and high-resolution mass spectrometry techniques. At RGO concentrations of 50–500 mg kg^–1, triclosan accumulation in radish decreased by 13.5–75.2%, likely due to adsorption-driven reduction in bioavailability. RGO also exhibited dose-dependent inhibitory effects on triclosan in radish roots, leaves, skins, and kernels, with edible parts showing an 11.0% reduction at 500 mg kg^–1 RGO. RGO extended triclosan’s half-life by 9.3% in soil. The parent triclosan was only detected in soils and roots. Three radish metabolites—sulfate-glucose triclosan, sulfate triclosan, and dechlorinated triclosan—were identified, with concentrations being altered by RGO exposure. Soil analysis revealed a 27.1% decrease in methyl-triclosan (the dominant metabolite) under RGO treatment, indicating modified degradation pathways. These results demonstrate RGO’s dual role in suppressing plant uptake while enhancing triclosan persistence in soil. The findings highlight RGO’s capacity to modulate organic pollutant bioavailability and transformation in soil-plant systems, emphasizing the need to assess nanomaterial co-contaminant risks in agroecosystems.