Patterns and mechanisms of cross-media antimicrobial resistance development in a typical reclaimed water-receiving urban river

Reclaimed water (RW) from municipal wastewater treatment plants has raised environmental concern due to its complex mixtures of organic and inorganic pollutants, including emerging contaminants (ECs) occurring at trace levels. However, the extent to which ecological replenishment with RW promotes antimicrobial resistance (AMR) development in urban rivers, together with the underlying cross-media dissemination patterns, driving factors, and mechanisms across the water-sediment continuum, remains unclear. Here, we established a six-indicator framework to assess AMR risk and characterized its distinct spatial patterns in river water and sediment along a typical RW-receiving urban river. RW input rapidly reconfigured the resistome in the water column, whereas sediment exhibited a progressive, distance-dependent shift downstream. RW-associated selection pressures intensified AMR development in the water column by increasing antimicrobial resistance gene (ARG) abundance and horizontal gene transfer (HGT) potential, while strengthened cross-media exchange of antimicrobial-resistant bacteria (ARB) between water and sediment appeared to be an important process sustaining AMR development in sediment. By integrating structural equation modeling, machine learning, and correlation analyses, we identified several candidate factors of AMR dissemination (e.g., antimicrobials triclosan and sulfapyridine, along with four per- and polyfluoroalkyl substances) and quantified their contributions. Mantel analysis further supported triclosan and total nitrogen as influential RW-derived factors of sediment AMR dissemination. These findings clarify how RW reshapes AMR dissemination across the river water-sediment continuum and provide a mechanistic basis for managing AMR risks associated with urban RW reuse.