Microplastic particles in North Sea sediments 2015

Blue microplastic particles are dominant in the North Sea

2016.02.16 | Nina Marie Bram Nielsen

The presence of microplastic particles in the size range of 20-5000 µm have been studied in sediment collected at ten stations in August 2015 in the Danish part of the open North Sea. The contents and composition of microplastic particles in all samples with volume of 50 ml were determined by visual identification using microscopy after the samples had been chemically digested to remove natural organic matter, density fractionated with saturated saline solution and size fractionated in six size classes using test sieves.

The study showed that particles identified as microplastic particles occurred in all ten sediment samples. 90–100 % of all identified microplastic particles were fibres, i.e. elongated filaments, and they were thereby the dominating type of microplastics followed by plastic films/fragments that contributed with up to 8 %. The contents of microplastic particles were in the range 192-675 particles per kg dry weight and 260-980 particles per litre wet sediment. In addition, another significant group of the particles was characterised as of “uncertain origin”, because they most likely consisted of remains from natural organic matter, but it could not be fully excluded that they consisted of synthetic polymers.

Microplastic particles in the size range of 20-300 µm dominated with 69-97 % in the sediment samples. The smallest particles in the size fraction 20-38 µm contributed with 5-44 % of the particles identified as microplastic in the different samples. Particle sizes > 1000 mm only contributed with 0-5 % of the identified microplastic particles. No plastic particles > 5 mm were found in the samples.

Regarding colour composition, blue microplastic particles were with 44 % on average the most frequent group, followed by black particles with 25 % on average. Some particles with other colours of e.g. white, red, grey, brown, green, pink and violet were also identified as microplastic.

No clear spatial trends west-east or north-south were found when all the samples from the North Sea were compared.

Strand, J. & Tairova, Z. 2016. Microplastic particles in North Sea sediments 2015. Aarhus University, DCE – Danish Centre for Environment and Energy, 20 pp. Scientific Report from DCE – Danish Centre for Environment and Energy No. 178. View full report here.

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