THE IMPACTS OF RENOURISHMENT AND GRAIN SIZE ON MICROPLASTIC ABUNDANCE IN CAROLINA BEACH SANDS

Beach renourishment is common along the coast of the Carolinas, yet little is known about its impact on microplastic concentrations in beach sands. This study investigates how microplastic abundance varies with both grain size and time since beach renourishment. Samples were collected from three zones, the dunes, the high tide line, and within the intertidal zone, from 8 beaches in North Carolina and South Carolina, U.S.A. Microplastics (MP) were found at every beach in abundances ranging from 59.9 to 351.2 particles per gram (n/g) with no distinct abundance patterns associated with sampling zone.The plastics were very small, averaging just over 100 μm in width, and both fibers and particles are common morphologies. The sands analyzed, with the exception of one coarser sample, had mean grain size values in the fine to medium grain size range and there is no correlation with grain size and MP abundance. The sands were moderately to poorly sorted (sorting range from 0.52 to 1.18 ɸ) and poorly sorted samples had lower MP abundances. There is variation in MP abundance between beaches, but there is no relationship between abundance and time since beach renourishment. These results suggest that other factors have a stronger influence on concentrating MP along Carolina coasts than renourishment.