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

Fresh snow samples (50mL) were collected from 3 sites in the ski area and from 2 sites in the ski resort, all exposed to different levels of traffic of people. We performed epifluorescence imaging to detect small microplastics that are comprised between 1-100microns in size. Small microparticles concentrations ranged from 1,000-4,000/50mL in the ski resort, whereas these numbers ranged from 30 to 3,000/50mL 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 degrading air quality. As for microfibers concentrations, they ranged from 100 to 3,000/50mL in the ski resort while these numbers were lower in the ski areas, ranging from 5 to 300/50mL. 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 fluorescence) and showing weathered surface in scanning electron microscopy, suggesting their far-away source.