White and wonderful? Microplastics prevail in snow from the Alps to the Arctic

Abstract

Microplastics (MPs) are ubiquitous, and considerable quantities prevail even in the Arctic; however, there are large knowledge gaps regarding pathways to the North. To assess whether atmospheric transport plays a role, we analyzed snow samples from ice floes in Fram Strait. For comparison, we investigated snow samples from remote (Swiss Alps) and populated (Bremen, Bavaria) European sites. MPs were identified by Fourier transform infrared imaging in 20 of 21 samples. The MP concentration of Arctic snow was significantly lower (0 to 14.4 × 10³ N liter^-1) than European snow (0.19 × 10³ to 154 × 10³ N liter^-1) but still substantial. Polymer composition varied strongly, but varnish, rubber, polyethylene, and polyamide dominated overall. Most particles were in the smallest size range indicating large numbers of particles below the detection limit of 11 μm. Our data highlight that atmospheric transport and deposition can be notable pathways for MPs meriting more research.

Fig. 1. Map of sampling locations for snow.

(A) Sampling sites in the Arctic (ICE, ice floes; SV, Svalbard) and (B) in Europe (HL, Heligoland; BR, Bremen; BV, Bavaria; TSCH, Tschuggen; DV, Davos). (C) Overview of all locations. Size of circles reflects MP particle quantities at log scale.

Fig. 2. Particles detected in snow samples collected at different locations from Europe to the Arctic.

(A) MP particle quantities recorded by FTIR at different locations. (B) Concentrations of microfibers detected at different locations (note that no polymers were identified). (C) Box-and-whiskers plot of proportions of MP numbers in different size classes from all snow samples. The upper and lower boundaries of the box indicate the 75th and 25th percentiles, respectively. The line within the box marks the median, error bars (in µm) indicate the 90th and 10th percentiles, and black diamonds represent outliers. (D) Relative composition of polymers identified by FTIR at different locations.

Fig. 3. Photographs of MPs detected in snow.

(A) Polystyrene fiber from Svalbard 4 (length, 1101 μm); (B) polypropylene particle from Heligoland (diameter, 256 μm); (C) polyvinyl chloride fiber from Ice Floe 8 (length, 956 μm). Note that these particular two fibers could be analyzed by FTIR as they happened to lay plane on the filter. (D to F) Aluminum oxide filter with enriched snow sample. (G to I) Corresponding polymer-dependent false-color image after FTIR measurement and automated analysis. (D and G) Bavaria 2: The sample with most MPs; (E and H) Ice Floe 9: the sample with the third most MPs; (F and I) Bremen: The sample with intermediate MP numbers but many fibers (photo credit: S. Mützel, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung).