Development of a monitoring and data analysis method for microplastic particles in Dutch marine sediments

Indicative Microplastic Number Concentrations (MNC) for 2023 (three samples per location) are presented.
A relatively high MNC was found at the location Bocht van Watum (BVW) in the Ems-Dollard estuary; which can be explained by the local very high sedimentation rate and organic carbon content. As expected, the offshore locations show lower MNCs, because they are more distant from coastal inputs. Note that no conclusions can be drawn based on these data, because three years of baseline data (N=9 per location), produced with a finalized and validated method, are needed to present results with sufficient confidence. However, we propose that these initial data provide a useful indicative picture of microplastics (MPs) in Dutch marine sediment. A clear indicative relation (N=8) was found between the sediment organic carbon (OC) content and the MNC; illustrating the importance of sedimentation rate, possibly increased by biofouling. An indicative top-list of polymers (particle number based) found in Dutch marine sediments are shown.