Comparison of Atmospheric Microplastic in remote and urban locations in Norway; occurrence, composition and sources

Ocean currents originating in the south of Europe have been proposed to function as major transport routes of microplastics from the more densely populated southern areas in Europe to the Arctic. However, given the limited empirical data and lack of harmonized methodologies for sample collection, little is known about the role urban sites play as emission sources. Here we present the outcomes of a study applying passive and active air-samplers for wet and dry deposition on two remote monitoring stations, Ny Ålesund (Svalbard) in the High Norwegian Arctic, and at Birkenes in mainland Norway in 2022, 2023 and 2024. We complement the results with samples collected in three Norwegian cities (Tromsø, Trondheim and Oslo). Bi-weekly samples were collected during the period of June-December in 2022 and 2023 for the Norwegian onshore samples and during June 2021 and 2023 for the arctic offshore samples. In 2024 we sampled from January to December with the same approach. We used full metal bulk precipitation samplers and suspended air samplers (Innovation NILU’s Atmospheric Microplastic Collector).All samples were handled under strict QA/QC requirements, with all sample treatment occurring in controlled conditions of clean rooms and laminar flow cabinets. After filtration on a GF/F filter, polymer determination was performed by pyr-GC/MS (Frontier lab multi shot pyrolizer EGA/PY 3030D connected to a Frontier lab AS 1020E Auto shot sampler connected to a ThermoScience TSQ9000 GC/MS/MS). All samples were accompanied with field and procedural blanks. Results were further analysed with respect to their spatial origin and long-range transport using the Lagrangian particle dispersion model FLEXPART.MP concentrations in deposition samples were more than 10000-times higher than in active samples, and Arctic samples were in general lower than samples from the Norwegian mainland. Rubber from car tires and Nylon dominated most samples, followed by PMMA and PVC. While tire wear particles (TWP) and Nylon dominate in the Norwegian mainland samples, contribute almost every of the measured polymers to the samples from Zeppelin station, Svalbard. MP concentrations in deposition samples were more than 10-times higher than in active samples, and remote samples were lower than samples from the urban sites. The prevalence of TWP in most samples, and especially in urban samples, indicates the important role TWP play in the overall inventory of atmospheric microplastic. Seasonal variations could be observed at all sites as well, with increasing microplastic concentrations found in the fall. Results were further analysed with respect to their spatial origin and long-range transport using the Lagrangian particle dispersion model FLEXPART. Seaspray, roaddust and agricultural sources were among the main sources identified by the model.