Really large systems, like ocean currents and weather, operate at very large scales. And so is your plastic waste, according to a new study by Janice Brahney of the Department of Watershed Sciences. The plastic straw you threw away in 1980 has not gone away; it shattered into pieces too small to be seen and travels through the atmosphere, seeping into soil, ocean waters and air. Microplastics are so prevalent that they now affect the way plants grow, float in the air we breathe, and permeate distant ecosystems. They can be found in places as diverse as human bloodstream to the guts of insects in Antarctica.
Understanding how microplastics move in global systems is key to solving the problem, Brahney said. His new research focuses on how these invisible pieces of plastic enter the atmosphere, how long they stay in the air, and where in our global system we can expect to find hot spots of microplastic deposition.
Plastics enter the atmosphere … not directly from garbage cans or landfills as you would expect … but from old, decomposed waste that makes its way into large-scale atmospheric models. Roads are a great source of atmospheric plastics, where vehicle tires crumble and hurl tiny pieces skyward through heavy turbulence created by vehicles. Ocean waves are also full of insoluble plastic particles that were once food wrappers, soda bottles and plastic bags. These “inherited plastic” particles float to the top layer of water and are stirred by waves and wind, then catapulted into the air.
Another major source of re-emission of plastics is dust produced by agricultural fields. Plastics are introduced into the soil when fertilizers from waste treatment operations are used (virtually all microplastics that are rinsed off with wastewater remain with bio-waste after the treatment process). Wind can also be a factor near population centers, causing decomposed plastic particles in the air.
Once in the atmosphere, plastics could stay suspended for up to 6.5 days – enough time to cross a continent, said Natalie Mahowald, co-author of the journal. The most likely location for plastic deposition from the atmosphere is above (and in) the Pacific and Mediterranean Oceans, but continents actually receive more net plastics from polluted ocean sources than they do. send, depending on the model. The United States, Europe, the Middle East, India and East Asia are also hot spots for land-based plastic deposition. Along the coasts, oceanic sources of airborne plastic become more important, including the west coast of the United States, the Mediterranean and southern Australia. Dust and agricultural sources for airborne plastics are greatest in North Africa and Eurasia, while road-generated sources have had a big impact in heavily populated regions around the world.
This study is important, said Brahney, but it’s only the beginning. Much more work is needed on this pressing issue to understand how different environments can influence the process … humid versus dry climates, mountainous versus lowland. The world has not slowed down its production or use of plastic, she said, so these issues become more pressing every year.
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Material provided by SJ and Jessie E. Quinney College of Natural Resources, Utah State University. Original written by Lael Gilbert. Note: Content can be changed for style and length.