Very tiny plastic particles of micro and nano size are difficult to measure in the environment to assess exposure risks. Researchers of Wageningen University now provide the first mechanistic modelling study on the behaviour and fate of nano- and microplastic in surface waters.

 

Plastic debris has been detected in the oceans, in soils, sediments and surface waters worldwide. Emissions are expected to increase by an order of magnitude in the coming years. Fragmentation leads to smaller and smaller particles, eventually reaching the submicron scale. At these very small sizes, plastic particles may pose unforeseen risks. Yet they are hard to measure in the environment so that exposure assessments have to rely on modelling.

 

In their recent pioneering study published in the journal Environmental Pollution, Ellen Besseling and co-workers simulate the concentrations of plastic particles between 100 nm up to 10 mm for the hydrological flow regime of a real river. The model accounted for direct transport of the particles, but also for aggregation of the particles with natural suspended solids, and the transport and settling of the resulting so-called heteroaggregates. The model also accounted for the presence of biofilm on the plastics, and model scenarios were calculated for plastics of different density.

 

Settling to the sediment for instance, was important for nano- and microplastics smaller than one micrometre due to settling of aggregates, and for plastic particles bigger than fifty micrometre due to direct settling, but much less for sizes in between. This means that these particles are expected to be exported to sea to a larger extent.

 

 

Original publication:

Besseling E., Quik J.T., Sun M., Koelmans A.A. (2016). Fate of nano- and microplastic in freshwater systems: A modeling study. Environ Pollut, DOI:10.1016/j.envpol.2016.10.001

 

 

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