Microplastics as vectors for virus transport in saturated quartz sand: Reduced PRD1 bacteriophage infectivity and enhanced mobility

Microplastics originating from pellets, paints, fragmented macroplastics, textiles, tire wear, and personal care products enter sewage and can aggregate with viruses during treatment. After sludge application, these aggregates may infiltrate soils and enter groundwater, yet their aggregation mechanisms and effects on virus survival and transport remain unclear. To address this gap, we conducted a laboratory study to examine the effect of microplastics on virus persistence and transport in groundwater. Batch experiments were conducted by mixing the PRD1 bacteriophage (a surrogate for adenovirus) with microplastics in groundwater at various temperatures. Column experiments using saturated quartz sand were performed to evaluate the effect of microplastics on virus transport in groundwater. Microplastic particles were quantified using solid-phase cytometry, while PRD1 was enumerated using both molecular and culture-based methods. Experimental data were analyzed using the HYDRUS-1D 2-site attachment-detachment model and colloid filtration theory. Our experimental findings suggest that microplastics significantly influence viral stability and transport in groundwater. Batch experiments revealed a marked decrease in the persistence of infective viruses in the presence of microplastics, reducing viral longevity in the environment. On the other hand, co-transport experiments showed that microplastics promoted the transport of both total and infective viruses through saturated quartz sand. This dual role underscores the complex influence of microplastics in groundwater: while they may reduce virus viability, their ability to enhance viral mobility represents a significant pathway for virus dissemination. These findings highlight the need to consider microplastics not only as pollutants but also as vectors that can potentially increase the risk of waterborne transmission and compromise groundwater safety.