Let it glow! Adapting a method to detect microplastics in snow and evaluate the potential for long-range transport

Harmonization of methods in microplastics research is lacking; this is affecting the comparability of results and hindering reproducibility. Investigating microplastics in snow is a relatively new field of research, and it can be used to answer questions about long-range atmospheric transport of microplastics. In this thesis, snow sampling methods were combined with the dye, Nile Red, to develop a method to identify and quantify microplastics in snow. There was an emphasis on quality control (QC) and quality assurance (QA), and blank samples were taken throughout the sampling and laboratory procedures. To test and validate the method, a study was performed in northern Norway to compare urban and rural locations. In addition to the field samples, laboratory testing was done by staining know plastic polymers and excluding possible staining of different organic material occurring in snow. We found that the urban locations contained a significantly higher mean number of microplastics per liter of snow compared to rural locations, 694 ± 375 (mean ± S.E.) particles L-1 snow vs. 432 ± 386 particles L-1 snow, respectively. The most substantial proportion of microplastics was in the lowest size class (22-50 µm) for both rural and urban locations. This protocol provides a simple and effective method that can be applied anywhere and could increase the comparability of results.