annually
Microplastic particles and fibers spiral through the Earth system, accumulating even in protected wilderness areas and national parks in the western US

Date:
June 11, 2020
Source:
Utah State University
Summary:
Watershed researchers estimate more than 1000 tons of microplastics
(equal to more than 123 million plastic water bottles) are deposited
in national parks and wilderness areas each year. Researchers
used high- resolution atmospheric deposition data and identified
samples of microplastics and other particulates collected over 14
months in 11 western U.S. national parks and wilderness areas. They
identified plastic and polymers' composition to identify sources
of plastic emitted into the atmosphere and tracked its movement.



FULL STORY ==========================================================================
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. The researchers identified plastic
and polymers' composition to identify sources of plastic emitted into the atmosphere and track its movement and fallout. The findings are reported
in the June 12 issue of Science Magazine in the article, Plastic Rain
in Protected Areas of the United States.


==========================================================================
"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." The world produced 348 million metric tons of
plastic in 2017 and global production shows no sign of slowing down. In
the United States, the per capita production of plastic waste is 340
grams per day. 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.

"Several studies have attempted to quantify the global plastic cycle
but were unaware of the atmospheric limb," Brahney said. "Our data
show the plastic cycle is reminiscent of the global water cycle, having atmospheric, oceanic, and terrestrial lifetimes." 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.

The team's field and lab personnel used sterile sampling
equipment, personal protection, and protocols to minimize particle contamination. Most of the plastics deposited in both wet and dry
samples were microfibers sourced from both clothing and industrial
materials. Approximately 30% of the particles were brightly colored
microbeads, but not those commonly associated with personal care
products, these microbeads were acrylic and likely derived from
industrial paints and coatings. Other particles were fragments of
larger pieces of plastic. The report notes, "This result, combined with
the size distribution of identified plastics, and the relationship to global-scale climate patterns, suggest that plastic emission sources
have extended well beyond our population centers and, through their
longevity, spiral through the Earth system." Results from this study
highlight the source, transport, and fate of plastics on Earth surfaces
as well as the contamination of US protected environments.

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. A staggering 4% of the atmospheric particulates identified collected from remote locations
were plastic polymers. The paper also notes that clear and white
particles were not included because they did not meet the researchers'
criteria for visual counting under magnification, ." ..suggesting our estimates of plastic deposition rates based on counts are conservative."
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.

"This ubiquity of microplastics in the atmosphere and the subsequent
deposition to remote terrestrial and aquatic environments raise widespread ecological and societal concerns," Brahney said. "Identifying the key mechanisms of plastic emission to the atmosphere is a first step in
developing global-scale solutions."

========================================================================== Story Source: Materials provided by Utah_State_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Janice Brahney, Margaret Hallerud, Eric Heim, Maura Hahnenberger,
Suja
Sukumaran. Plastic rain in protected areas of the United
States. Science, 2020; 368 (6496): 1257 DOI: 10.1126/science.aaz5819 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200611151417.htm

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