PNNL

Abstract

Microplastic pollution is an escalating environmental concern, particularly in densely populated estuary regions, where it poses significant threats to aquatic life and human health. The dispersion patterns of various microplastic particles along the estuaries are influenced and complicated by multiple environmental factors such as river flow, tidal stirring, salt intrusion and estuarine circulation. This study examines the accumulation and dispersion patterns by modeling three typical classes of microplastics in the Delaware River Estuary: synthetic fibers, sinking plastic films, and rising plastic pellets. Our findings reveal specific areas with high microplastic accumulation for each type. Notably, the upper estuary regions exhibit significant retention of rising microplastics, associated with a region with reduced along-channel velocities at downstream of Trenton and upstream of Philadelphia. Conversely, in the lower estuary, the synthetic fibers as well as sinking plastic films accumulate at the flow convergence zone near the salinity front. All of the microplastic accumulation hotspot locations are relating river discharge, and salinity intrusion. During the dry season the microplastics are going to intrude to the upstream of the estuary, while during the wet season the strong river discharge flushes the microplastics to the downstream. On the other hand, tidal stirring, settling and resuspension processes strongly impact the spreading of the microplastics along the river.