Monitoring of microplastics in the Norwegian environment (MIKRONOR) 2023

Summary

The MIKRONOR monitoring program aims to establish baseline levels of microplastics in the Norwegian environment and to identify potential sources and sinks. This third MIKRONOR report focuses mainly on results from air samples, including data on tyre wear particles (TWP), as well as river and fjord surface water samples, and their correlation to rainfall and river discharge levels. Additionally, it presents data from sand samples taken from an OSPAR beach in the outer Oslofjord. The results for 2023 provide evidence of the omnipresence of microplastics in the environment. However, levels were higher near cities and populated areas, with decreasing levels further from human activities. This trend was observed in both air and surface water samples. Sand samples from the OSPAR beach in the Oslofjord showed levels of microplastics comparable to, or slightly higher than studied beaches at Svalbard. Since no other beach studies have been conducted in the MIKRONOR program, it is difficult to determine typical microplastic levels on a beach in the outer Oslofjord. Determined levels of microplastics in the beach samples were comparable to levels in marine bottom sediment at remote areas along the coast and lower than levels in sediments from the Oslofjord. Main conclusions of this report highlight the need for further research into the processes that control the levels and variations of microplastics and TWPs, such as weather conditions, river discharge, and air mass movement. Sampling of different matrices should, where possible, be conducted using similar strategies and equipment to improve the comparability of results. Additionally, the high spatial and temporal variability between samples must be considered to determine the appropriate number of analyses needed to obtain reliable results.