Analysis of small microparticles from snow in Park City, Utah (USA): How much of it is plastic?

Abstract Microplastics (fragments < 5 mm) are increasingly studied around the world in a diversity of ecosystems. In contrast, small microplastics (1-100 microns in size) are subject to much less studies because of their small size, which makes them challenging to detect, and their ability to be both airborne and waterborne. Here, we performed epifluorescence imaging to detect small microplastics from fresh snow samples (50 mL) that were collected from 3 sites in the ski area and from 2 sites in the ski resort of Park City, UT, all exposed to different levels of traffic of people. Small microparticles concentrations ranged from 1,000–4,000/50 mL in the ski resort, whereas these numbers ranged from 30 to 3,000/50 mL in the ski area. Against expectations, the higher and most remote site contained the greatest concentrations of microparticles, which increased over the years for each site, as a possible sign to growing airborne sources, both at the local and global levels. As for microfibers concentrations, they ranged from 100 to 3,000/50 mL in the ski resort while these numbers were lower in the ski areas, ranging from 5 to 300/50 mL. These ranges remain similar across years for microfibers in the ski area as these concentrations in the snow seem to be dictated by the amount of snow fall. All the sites showed a percentage of different polymers, such as cotton (23%) and lyocell (20%), but also a variety of synthetic polymers, such as cellulose acetate (11%), nylon (11%), polyester and polyethylene terephthalate (11%), PVC (10%), polyethylene (8%), and tire wear rubber crumb (6%). In most cases, the small microparticles and microfibers were discolored in bright field (but they were seen in epifluorescence) and showing weathered surfaces in scanning electron microscopy, suggesting their far-away source.