MEASURING MICROPLASTICS IN BEACH SANDS FROM WESTERN IRELAND: GRAIN SIZE AND COASTAL GEOMORPHOLOGY COMPARISONS

Microplastics (MPs; <5mm) in the world’s oceans are a growing concern and increasingly well -studied in the water column, in marine biota, and in marine sediments in shallow to deep depositional environments. Microplastic deposition in beach sands have received much attention recent years as well with an increasing number of studies measuring beach sand microplastic concentrations using a variety of extraction methods. Here we present new data from beach sands collected at 15 separate localities from the Aran Islands, County Clare, and County Kerry on the west coast of Ireland.

In this study we employ a simple flotation method to evaluate MP concentrations in our study sands. Our method starts with three separate ~50g aliquots of sand from each collection locality which were stirred in saturated NaCl solution (~1.21 g/cc) for floated MPs. This was repeated five times with each float decanted and vacuum sieved through 47 micron filter paper. Isolated contaminant MPs were counted by type (fiber, foam, film, fragment, or pellet) and color (blue, black, red, clear/white as the most common). All study sands yielded microplastics, with most localities having concentrations between ~150-300 MP’s per kg of beach sand. More than 90% of MPs in all collections were fibers.

For all of our study sands, we conducted control experiments with “spike and recovery” analysis to estimate the viability of the saturated NaCl flotation method. In these experiments we added a known quantity of brightly colored microplastics to the dry sand before the flotation method and measured a ~90% recovery rate of these spiked microplastic particles.

Our overall MP concentration and type results are consistent with, or slightly higher than, recent reports from other coastal marine settings analyzing beach sands. Across our samples, we note no significant differences between the MP concentrations and types in comparing beaches facing open ocean conditions versus those in protected harbors or natural inlets. We also observe that while the beach sands with the finest overall grain size in our collections tended to have higher MP concentrations, there is no clear grain-size to MP concentration relationship in our data, a finding consistent with other recent studies. Beach sand collections from the east and south coast of Ireland will allow comparisons of our dataset to those from shorelines facing the Irish and Celtic Seas.