MICROPLASTICS IN DUNE SANDS FROM OUTER CAPE COD, MASSACHUSETTS

Twenty samples from ten beaches along the Atlantic coast of the “Outer Cape” region of Cape Cod, Massachusetts were collected and evaluated for the presence of microplastics—by definition, plastic particles less than 5mm in size. Two samples, one at the surface and one from the subsurface, were taken at each location from a 1m² area. Wind speed was measured at each site. Samples were acquired at or near the landward edge of the beach in areas where prominent scarps marked the limit of the beach system. Some sample sites included dune fields located landward of the scarps. We took no samples from designated nesting areas of endangered piping plovers and least terns or the sites of dune grass planted as part of dune restoration efforts. Also, we sampled only locations that showed no signs of bioturbation caused by human beings. Samples were treated via standard sieve analysis and then examined for the presence of microplastics using a binocular microscope.

Filamentous microplastic fibers were ubiquitous in sediments from the following size fractions: 3 phi (.125 mm) and smaller, 2.5 phi (.178 mm), and 2 phi (.250 mm). Microplastic filaments in the smaller size fractions formed tumbleweeds as large as 5 mm made up of tangled microplastic fibers. These formed during operation of the sieve shaker. In contrast, even after shaking, microplastic fibers were dispersed as individual strands between grains in the 2 phi fraction. Microplastic filaments appearing as tumbleweeds and single strands were observed in surface samples as much as 1 km landward of the beach on the leeward side of dunes suggesting that aeolian transport is a significant factor in the introduction of microplastics into the terrestrial realm.

Future work entails examination of sediment samples taken along transects perpendicular to the coast as well evaluation of sediments from previously sampled sites taken in the autumn after tourist season, during the winter storm season, and in the spring after storms have subsided in order to assess the effects of seasonal variations in conditions such as wind speed in the abundance of these microplastics.