42-3 Storm- Driven Mobilization of Anthropogenic Litter in Urban Stream Systems

Abstract:

Rivers play a critical role in transporting anthropogenic litter (AL), including macroplastics (> 5mm in diameter), from land-based sources to the ocean. However, recent studies have suggested that most of this material introduced to watersheds is retained and broken down into microplastics, which can be easily ingested by aquatic organisms or enter the water supply. For example, macroplastics and other forms of AL are typically transported in streams during high-flow (e.g., storm) events and can be entangled in riparian vegetation. While some studies have used video cameras to determine the amount of AL transported in a river system during a storm event, this approach does not capture the material sequestered or dislodged from riparian zones. The Wissahickon watershed (164.92 km²) in Philadelphia, PA, experiences a disproportionately high amount of AL pollution. However, it’s currently unknown how much AL pollution is transported from the watershed during storm events. This study used a combined approach of GoPro™ cameras deployed during storm events and mass-balance sampling within the adjacent floodplains before and after to provide one of the most accurate delineations of AL transport in river systems to date. All visible debris items within each river segment, and observed during each storm event, were counted and categorized via the NOAA Marine Debris Checklist to determine the relative influence of AL sources. The results of this experiment help to inform litter intervention strategies in upstream areas and cleanup events associated with riparian areas.

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