Researchers Are Uncovering a Plastic Cycle in the Atmosphere
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(Inside Science) -- Janice Brahney never set out to look for plastics in the atmosphere. Brahney studies the atmosphere as a vector to move elements through the environment -- for example, how phosphorus moves through the atmosphere and ends up in water bodies. But when she was setting up a network of dust sampling, she was surprised to find plastic in her dust samples.
People don't usually monitor particles bigger than 10 microns, she said. "Most particles are bigger than that, so we don’t necessarily know what’s in the dust."
That was a few years ago, and since then the understanding of plastics in the atmosphere has developed. A new paper, published today in the journal Proceedings of the National Academy of Sciences, looks at the ways plastic is getting into the atmosphere, both in urban centers and in remote locations.
"If you ask most plastic researchers they will say, 'Urban centers -- that is where our waste is generated,'" said Brahney, who works at Utah State University and is one of the researchers who conducted the study. She and her colleagues combined atmospheric models with microplastic samples taken in the western U.S. over 14 months.
Surprisingly, the data don’t suggest that cities are responsible for atmospheric plastics. Instead, the researchers found roads and the marine environment were far more important -- 84% of atmospheric microplastics came from road dust, whereas 11% came from sea spray and 5% came from agricultural soil dust.
The cars on fast-moving roads -- often outside of urban centers -- provide mechanical energy to move plastic into the atmosphere when they kick up dust. And the marine environment has accumulated so much plastic that it acts like a warehouse where microscopic particles are lifted up and brought back to land environments, Brahney said. "The ocean is spitting plastic back at us."
This type of research is helping scientists understand the plastic cycle in the environment as they do other cycles like phosphorus and carbon. Plastics are so tenacious that they’re just breaking down into smaller pieces to be carried around the globe.
For example, tiny plastic particles could get transported to a glacier, become frozen there, then melt out and flow down a river to a lake, where strong winds could come along and carry them back into the atmosphere, said Brahney. The particles could eventually get consumed by a person and then eliminated into the wastewater stream, and from there they could be applied to an agricultural field.
Some people figure that plastic pollution doesn’t impact them because they don’t live in the ocean -- but everyone breathes air, said Brahney. "There’s no escaping this. You can’t go anywhere on the earth where it isn’t."