Microplastics Found in Every Sierra Nevada Snowfall Sample, Threatening California's Water
Written by AI from phys.org's report. Not checked by a person.
UC Riverside scientists discovered plastic particles at all seven Sierra Nevada sampling sites during active snowstorms, raising concern about contamination of the snowpack that supplies 30% of California's fresh water.
Environmental toxicologist Aleksandra Karapetrova and colleagues at UC Riverside collected fresh snowfall at seven locations across the Sierra Nevada during active storms. The sites were so remote that only one could be reached by chairlift; Karapetrova had to ski to all the others. Despite the isolation, microplastic particles were found at every single site, with deposition rates of 270 to 3,200 particles per square metre per day at remote locations and 2,600 to 7,500 at Mammoth Mountain's ski area — roughly three times higher, likely due to nearby human activity and greater snowfall accumulation. The particles were identified using infrared spectroscopy as polyethylene, polypropylene, polyester/PET, and cellulose derivatives — materials shed from packaging, clothing, and other consumer products. Snow acts as an atmospheric scavenger: as snowflakes fall, they collect suspended plastic particles from the air and carry them to the ground. Air-mass tracing pointed to California's Central Valley, particularly Fresno and Madera counties, as a likely major source, though computer models could not rule out plastics arriving from even farther away. The findings carry outsized significance because the Sierra Nevada snowpack supplies roughly 30% of California's fresh water, though the study did not determine how much of the deposited plastic ultimately reaches drinking water. The research was published in the journal Environmental Science and Technology.
