Aeolian transport of microplastics from the sub-tidal beach surface into coastal dunes

Microplastics impact marine and terrestrial ecology as vectors of chemical pollution and are widespread contaminants in beach sediment. Wind tunnel studies suggest that microplastics are more easily transported by wind than mineral sand grains, and hence coastal dunes ought to be relatively enriched as a local accumulation sink of microplastics blown in from the beach, relative to the sub-tidal marine environment.

To test this hypothesis, concentrations and polymer assemblage of sand-sized microplastics in surface sediment were compared between intertidal beach and coastal dune samples at two different UK coasts (Wales and SE England), using FT-IR microscopy.

Results show no differences in polymer composition, diversity, or abundance between beach (marine) and dune (aeolian) sediments. Average concentrations reached 100s of MPs/kg and their composition was dominated by rayon and polyester fibres. The lack of expected microplastics enrichment of the coastal dunes by preferential aeolian transport from the adjacent beach is attributed to the severe supply-limitation of these particles at the sediment surface interface, compared with the transport-limited movement of the wind-blown mineral sand.