Microplastics in the Delaware River Estuary: Mapping the Distribution And Modeling Hydrodynamic Transport

Microplastic pollution poses a significant threat to the ecosystem, encompassing not only aquatic organisms but also plants and human health due to their capacity for bioaccumulation, driven by their minute size and persistence. Although previous research predominantly centered on the effects of microplastics in ocean environments, it is vital to recognize that their ultimate destination is often rivers and estuaries, serving as more precise point sources for analysis. This research focuses on a comprehensive investigation involving the monitoring and modeling of microplastic distribution and concentration within the Delaware estuary. Grab and net sampling methods were employed across Philadelphia, Camden, and Wilmington, Delaware, to examine the distribution, concentration, and characteristics of these pollutants. The findings indicate that microplastic's diameters varied from 90 µm to 1000 µm along the Delaware River, with 71% of particles in grab samples under 500 µm. In contrast, 66% of particles in net samples exceeded 500 µm. Moreover, concentrations in grab samples ranged from 0.24072 to 7.08 particles/m3, whereas net samples showed significantly lower concentrations, ranging from 0.000059 to 0.00268 particles/m3. The investigation discovered a range of plastic compounds, most notably polyester, polypropylene, and polyethylene, with fibers being the most common shape. Furthermore, the concentration and composition of microplastics were closely linked to urbanization, population density, and industrial activities. Analysis using the Delaware River Basin Commission's 3D hydrodynamics model revealed that microplastics predominantly stayed in upper water layers for up to 20 days and moved toward the opposite bank from their release point, influenced by current dynamics. These findings not only enhance our comprehension of microplastic pollution in freshwater ecosystems but also establish a foundational framework for future research aimed at developing effective management and remediation strategies, particularly for ecosystems near to the Delaware estuary. This study provides essential data that can inform policy decisions and conservation initiatives designed to reduce the environmental impact of microplastics.