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Microplastic on Baltic Sea beaches stems mainly from the land

According to a study from the Geomar Helmholtz Centre for Ocean Research Kiel (GEOMAR) and the Christian-Albrecht University of Kiel, microplastic on the Baltic Sea beaches of Schleswig-Holstein in northern Germany evidently stems predominantly from the beach, and is probably not caused by plastic litter in the seawater.

How much microplastic occurs on the Baltic Sea coast of Schleswig-Holstein and where it comes from has been researched by GEOMAR, together with the research workshop of the Christian-Albrecht University of Kiel. The results of the study, which, it says, documented for the first time in the region plastic litter in the micro and macro spectrum, were published in May 2023 in the technical journal "Marine Pollution Bulletin".
For the study, the research team examined, in the spring and autumn of 2018, ten beaches along the Baltic Sea coast of Schleswig-Holstein from Flensburg to the Bay of Lübeck. On sections of the beach 100 metres long, all pieces of litter were systematically collected and allocated to predetermined categories. To document the macro-litter, the scientists followed the standardised protocol of the Convention for the Protection of the Marine Environment of the North-East Atlantic (Oslo-Paris Convention, OSPAR), in order to be able to compare the measurements with the results of other studies. In the spring, the researchers found between 38 and 251 pieces of litter on the beaches. A good 40 percent of this was plastic, just under 35 percent paper, cardboard and cigarette ends, and 15 percent glass. In the autumn, the result ranged from 27 to 713 pieces, with paper, cardboard and cigarette ends accounting for more than 60 percent, plastic for a good 25 percent, and glass for 4 percent. In addition, the team took sediment specimens and analysed the microplastic and type of plastic contained in them. The microplastic from the sediment specimens was extracted by means of density separation and subsequently identified with raman spectroscopy, a method that can identify microplastic down to a size of one micrometre. The spectroscope linked to a microscope first counts the particles, and then points a raman laser onto the particle surface, records the scattered light and converts it into a spectrum that is compared with a database. On average, the team found, in both the spring and the autumn specimens, four microplastic particles in one kilogram of sand from the tested beach sediments. On average, six different polymers (PE, PP, PS, PET, PVC, POM) were identified. A correlation between the frequency of beach litter and microplastic was not found. The research scientists regard the study as a database for comparisons with the results of future studies.
Commenting on the results of the study, Mark Lenz from GEOMAR says: "We have the impression that the microplastic comes above all from the litter that is here on the beaches." The large pieces of beach litter degrade, and from this the microplastic is then formed. Only a small amount of plastic litter is washed up from the sea to the land. Overall, the Baltic Sea beaches can be described as moderately polluted. This is due above all to the westerly winds that predominate in Schleswig-Holstein and also to the fact that the Baltic Sea has only few connections to the world's seas, says Lenz.

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