The fragmentation of plastic materials is of key importance to the European Strategy for Plastics in a Circular Economy, the EU Marine Strategy Framework Directive and the UN Regional Seas Programmes. The fate and effects of the estimated 500,000 tonnes of plastic litter in the marine environment today [1] is greatly dependent on the dynamic processes involved in the fragmentation of the plastic materials. Once plastic waste has started to fragment it is not only still harmful, it also becomes increasingly infeasible to clean up or recycle.

To study plastic fragmentation in a controlled experimental setting, we selected a set of conventional thermoplastics and compostable plastics and followed them for in excess of one year in a laboratory seawater microcosm. A novel method to quantify electrical resistances through plastic items was used to measure plastic degradation as function of plastic item residence time in the microcosm. Microbial taxa in the seawater microcosm, such as Cyanobacteria, Proteobacteria, Planctomycetes and Bacteriodetes, formed biofilms on the plastic items, causing some buoyant plastic types like polyethylene to become dense enough to sink. Microplastics were released from some of the plastic items, contributing to part of the weight loss over the course of the experiment. The mass of the plastic items measured before and after their residence in the microcosm showed a ≤1% weight loss per year for polyethylene, polystyrene and polypropylene, 3–5% for latex, polyethylene terephthalate and polyurethane, 15% for cellulose acetate, and 7–27% for polyester and polylactic acid (compostable plastic).

The results of this VU-Deltares-ILVO-VLIZ collaborative study are published with open access:

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Gerritse, J., Leslie, H.A., de Tender, C.A., Devries, L.A., Vethaak, A.D. Fragmentation of plastic objects in a laboratory seawater microcosm. Sci Rep 10, 10945 (2020).

Contact: Dr. Heather Leslie,