Storm-Driven Mobilization of Urban Sewer Resistomes: From Hidden Reservoirs to Surface Exposure Interfaces

Urban sewer networks may be an underquantified source of environmental antibiotic resistance genes (ARGs), as ARG-bearing biomass, extracellular DNA, mobile genetic elements, and particle-associated material accumulate in wastewater, biofilms, and deposits before wet-weather release. Climate-driven intensification of heavy rainfall may enhance overflow, surcharging, flooding, and hydraulic connectivity between sewers and surface waters, increasing episodic ARG export. Here we synthesize current evidence using a coupled source–storage, mobilization–routing, and fate–exposure framework. Rainfall can detach biofilms, erode deposits, redistribute intracellular and extracellular ARGs between freely suspended and particle-associated states, and increase event loads even when concentrations decline through dilution. However, field studies rarely quantify antecedent stocks, release thresholds, hydrograph-resolved fluxes, source contributions, decay, or exposure dose. We therefore identify the state variables, rate functions, and measurements needed to couple sewer hydraulics, particle transport, microbial ecology, molecular surveillance, and exposure assessment. Reframing storm-associated antimicrobial resistance as a compartmental mass-balance and transport problem can move the field from occurrence mapping toward prediction of peak concentrations, event loads, deposition hotspots, persistence, and exposure likelihood in climate-stressed urban watersheds.