CLEVELAND, Ohio — Plastic litters Lake Erie beaches: bottles, cigar tips, straws and bits of boldly colored microplastic that used to be who knows what.
But the mass of plastic on the surface is a sliver of the true size of plastic pollution in the lake. A new Rochester Institute of Technology study used 3D modeling to examine nine types of polymers and estimated that the lake includes 381 metric tons of plastic — more than 50 times greater than the previous estimates at the surface.
The modeling found that the three polymers with the lowest density — polyethylene, polypropylene and expanded polystyrene — accumulate on the surface of the lake while the other six polymers were concentrated in the sediment.
Unlike in the oceans, plastic does not collect in floating patches in the Great Lakes. Much of the plastic lodged near coastlines, especially on the eastern end of the lake, because of currents.
Four years ago, RIT mathematicians estimated that nearly 10,000 metric tons — or 22 million pounds — of plastic debris enter the Great Lakes every year from the United States and Canada.
The question a mathematical modeling doctoral student Juliette Daily and Professor Matthew Hoffman wanted to answer now was where that plastic ended up. Because samples of surface water show much less pollution.
“The samples taken at the surface… don’t give you good picture of what’s happening in the lake,” Daily said. “There’s all this missing plastic. The numbers are way smaller than what you’d think, based on input, so we tried to answer where the missing plastic would go.”
Much of the plastic comes flushed from city streets throughout the watershed, down storm drains and into the lake.
The modeling allows other scientists to start thinking about policies and behavior changes, Hoffman said.
“There aren’t great numbers to track how much waste is entering the water anywhere in the world. It’s not like we’ve got accurate monthly data on how this is moving. There’s a lot of work yet to be done,” Hoffman said.
Plastic over time may lose buoyancy, and even floating pieces may sink.
The problem is a big one, for the whole Great Lakes, researchers said. Plastic from Chicago could end up in Ohio.
“It’s definitely not, Cleveland’s trash is Cleveland’s problem. It’s going to move throughout the lake. It can end up in a lot of places,” Daily said. “Even if it makes it out of Erie, it becomes Ontario’s problem.”
More on plastic in the Great Lakes:
Port Clinton installs giant metal fish sculpture to collect plastic bottles
How can $2 million in U.S. EPA Trash-Free grants curb the Great Lakes plastic problem?
How to help Lake Erie beaches on International Coastal Clean-up Day
Ban balloon launches around the Great Lakes? Survey shows where litter ends up
You’re drinking plastic in your bottled water: 2018 State of the Great Lakes