Reactive Halogen Species Boost Fungal Spore Inactivation in Seawater during UV/PMS Treatment

With the growing prevalence of seawater-related activities (e.g., marine sports), human exposure to fungal infections through seawater contact poses a rising public health concern. The UV/peroxymonosulfate (UV/PMS) process represents a promising disinfection strategy, as UV radiation, PMS, and radicals generated from PMS synergistically inactivate pathogens. In this study, we demonstrate that halide ions at seawater-level concentrations markedly enhance the inactivation efficiency of Aspergillus niger spores by the UV/PMS process. Under seawater conditions, the UV/PMS process (50-μM PMS and 84-mJ cm^-2 UV fluence) achieved complete inactivation of 5.11-log Aspergillus niger spores, compared to only 2.45-log inactivation in deionized water under identical conditions. Through quenching experiments and kinetic modeling, we identify reactive halogen species (RHS, e.g., BrO^•, Br₂^•-, BrCl^•-) as the primary contributors to the enhanced inactivation of spores in seawater via the UV/PMS process. Microbial characterization further confirms that RHS compromise cellular integrity by causing disruption of membrane structures and damage to internal organelles. Additionally, RHS effectively suppress fungal spore photoreactivation, a critical mechanism for pathogen regrowth. These findings advance our understanding of RHS generation in saline environments and clarify their role in the mechanisms of fungal spore inactivation.