Huge watery plastic packages – made from flotsam from soda bottles and jetsam from shopping bags – appear as large floating islands in our oceans. On streets, plastic is often thrown, broken into smaller pieces, and churned up until it is microscopic. At that point it is washed into the atmosphere and travels the world.
By sea or on land, these tiny shards of plastic are more ubiquitous than science had known, according to a new study by researchers at Cornell and Utah State University. The research was published in the Proceedings of the National Academy of Science on April 12.
A blue piece of microplastic sits between dust and fibers on a filter under a microscope.
Natalie MahowaldCornell’s Irving Porter Church professor of engineering and lead author Janice Brahney, assistant professor of natural resources at Utah State University, found that plastics circulate through the oceans and roads and, when small enough, can become microplastic aerosols that carry the Jetstream propel across continents.
“We found a lot of plastic pollution everywhere we looked. It moves in the atmosphere and deposits all over the world, ”Brahney said. “As of this year, this plastic is not new. It is from what we have already thrown into the environment over several decades. “
Results of their study “Limitation of the atmospheric limb of the plastic cycle, ”Suggest that atmospheric microplastics in the western United States come primarily from secondary reemission sources.
From December 2017 to January 2019, the researchers collected atmospheric microplastic data from the western United States, where 84% of the microscopic shards came from road dust – cars and trucks moving the plastic. About 11% was released into the atmosphere from sea spray and 5% was from agricultural soil dust.
While large groups of waste plastic melt into shells on plastic islands on the oceans, the oceanic action grinds them into particles only micrometers in size, where the winds carry them into the atmosphere – for as little as an hour or up to six days.
While doing other scientific research, Brahney had discovered pieces of microplastic everywhere. Marje Prank, a postdoctoral fellow who worked with Mahowald, developed a microplastic transport model to determine the origin of the tiny plastics. Together they used the model to infer the sources of this microplastic.
“We did the modeling to find out the sources without knowing what the sources might be,” said Mahowald, an associate of the Cornell Atkinson Center for Sustainability. “It is amazing that there is so much plastic in the atmosphere at this level and unfortunately it accumulates in the oceans and on land and moves and moves everywhere, even in remote places.
“By our best guess of plastic sources and modeled transport routes, most continents are net importers of microplastics from the marine environment,” she said. “This underscores the cumulative role of old pollution in plastic atmospheric pollution.”
Microplastic ends up and accumulates in all sorts of places, Mahowald said. “It’s not just in the cities or the oceans,” she said. “We find microplastics in national parks.”
In addition to Mahowald, Brahney, and Prank, who now works at the Finnish Meteorological Institute in Helsinki, Finland, other authors include Gavin Cornwell, Pacific Northwest National Laboratory, Richland, Washington; Zbigniew Klimont, International Institute for Applied Systems Analysis, Laxenburg, Austria; Hitoshi Matsui, Nagoya University, Nagoya, Japan; and Kim Prather, University of California, San Diego.
The research was supported by the National Science Foundation and its National Center for Atmospheric Research. the US Department of Agriculture Forest Service; and Cornell Atkinson.
