More than 1,000 tons of plastic rains into U.S. protected lands annually

In the United States, the per capita production of plastic waste is 340 grams per day. New research now estimates that more than 1,000 tons of microplastics are deposited onto protected lands in the western U.S. each year, equivalent to more than 123 million plastic water bottles.

Utah State University Assistant Professor Janice Brahney and her team used high-resolution atmospheric deposition data and identified samples of microplastics and other particulates collected over 14 months in 11 national parks and wilderness areas, according to a statement.

“We were shocked at the estimated deposition rates and kept trying to figure out where our calculations went wrong,” Brahney said. “We then confirmed through 32 different particle scans that roughly 4% of the atmospheric particles analyzed from these remote locations were synthetic polymers.”

High resilience and longevity make plastics particularly useful in everyday life, but these same properties lead to progressive fragmentation instead of degradation in the environment. These “microplastics” are known to accumulate in wastewaters, rivers, and ultimately the worlds’ oceans – and as Brahney’s team shows, they also accumulate in the atmosphere, explains the statement.

The study examined the source and life history of both wet (rain) and dry microplastic deposition. Cities and population centers were found to serve as the initial source of plastics associated with wet deposition, but secondary sources included the redistribution of microplastics re-entrained from soils or surface waters.

In contrast, dry deposition of plastics showed indicators of long-range transport and was associated with large-scale atmospheric patterns. This suggests that microplastics are small enough to be entrained in the atmosphere for cross-continental transport.

Examination of weekly wet and monthly dry samples from 11 sites allowed the authors to estimate that more than 1000 tons of microplastics are deposited onto protected lands in the western U.S. each year, equivalent to more than 123 million plastic water bottles, according to the statement.

A staggering 4 per cent of the atmospheric particulates identified collected from remote locations were plastic polymers. The ubiquity of microplastics in the atmosphere has unknown consequences for organismal health but size ranges observed were well within that which accumulate in lung tissue. Moreover, the ongoing deposition of plastic in wilderness areas and national parks has the potential to influence these ecosystems from community composition to food web dynamics.

Image credit: UN Photo/Martine Perret

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