Experiment on washing procedures to extract positively buoyant microplastics (> 500 µm) from beach wrack

The "beach wrack - plastic separator" is the prototype of a simple construction that we used to assess two methods for washing beach wrack. Its main component is a polypropylene container that is 40 x 30 x 22 cm in size and has a volume of 20.8 l. Furthermore, we used two grids (39.5 cm x 25.5 cm) that could be inserted horizontally into the container and between which a beach wrack sample of 500 g could be placed. The grids were made of aluminium and had a mesh size of 1 cm x 1 cm. Two handles were attached to the lower of the two grids that allowed to move the grids vertically inside the container. As soon as the container was filled with 10 litres of tap water, the upper grid prevented the beach wrack from floating to the surface, while the lower kept it from settling on the bottom of the container. The separation of the plastic particles from the sample material was induced by moving the grids up and down manually or by bubbling pressured air, which was supplied through air inlets, through the beach wrack material.For assessing the extraction efficiency of the two washing procedures, 48 kg of beach wrack were collected at the beach of Falckenstein, which is located at the western shore of the outer Kiel Fjord, Germany, (N 54.391250, E 10.190728) from May to August 2018.