5-9 Measuring Microplastic Concentrations in Long Island Sound Beach Sands: Grain Size & Coastal Geomorphology Considerations

Session: Nearshore and Estuarine Research: Dynamics and Future Resiliency in the Coastal Zone (Posters)

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Abstract:

Microplastics are now present all over the world, appearing in abundance within the atmosphere, biosphere, and hydrosphere. Recent studies have also shown MPs to be accumulating substantially in sedimentary deposits across marine and terrestrial environments. Here we present new data on microplastic concentrations in the beach sands around Long Island Sound, representing the region’s first such study. We analyze sands from more than 30 beaches on the north and south shores of Long Island Sound in Connecticut and New York, respectively. For each analyzed sand we (1) measured the microplastic abundance and type, (2) determined overall grain size distribution and mode, and (3) broadly characterized the sample collection site’s coastal geomorphology and orientation.  At each location we used a saturated NaCl solution density flotation method to separate microplastics from the mineral and organic components of the sample. Microplastics were tallied by color and type (fragments, foams, fibers, films, and pellets). Grain size analysis of each sample was done using standard dry sieve methods.  Each sample site was categorized as “protected/harbor” vs “open exposure.”

The mean microplastic concentration at the CT study sites was ~240 MPs/kg, with five samples yielding more than twice that average. North shore Long Island beaches averaged ~160 MPs/kg with no sample yielding more than twice that. Fibers were the dominant MP type, with rare fragments. In comparing microplastic concentration with grain size variance and mode, we found that generally finer grain samples in our full dataset yielded higher MP concentrations and that elevated microplastic concentration did not correlate with sites categorized as “protected/harbor” across the dataset.  Sands from beaches oriented roughly toward the region’s prevailing westerly winds did not exhibit higher concentrations of microplastics compared to those oriented generally toward the east.  Data for each location was also compared to the proximity to major population centers, such as New York City, NY and New Haven, CT with the general pattern of samples from closer to such centers exhibiting higher MP concentrations.

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