The thought of pollution tends to conjure images of some fairly tangible threats: tall stacks spewing dark smoke into the sky, smoggy cityscapes, beaches slicked with oil, animals stuck in plastic bags or six-pack rings.
The list of pollutants extends well into the less-visible range, also. And among those “hidden” pollutants of concern is a group known collectively as microplastics. These tiny contaminants are no larger than 5 millimeters long and are often much smaller. They’re basically ubiquitous, and have been found everywhere from soil to rain and even our bodies.
Microplastics also pervade the Great Lakes—the largest group of freshwater lakes on Earth—and two University of Wisconsin-Madison environmental engineers are studying how they proliferate in these big and important bodies of water.
Haoran Wei and Mohan Qin, both assistant professors of civil and environmental engineering, are focusing on incredibly small microplastics less than 50 micrometers across.
“There’s a real need to study this in the Great Lakes,” Wei says. “We know that there are 22 million tons of plastic flowing through the Great Lakes every year. They will slowly disappear, but it’s not like they are completely degrading. They release a lot of invisible plastic particles, and we currently don’t know how much of that stuff there is.”
To do this, they’ll create and use specialized membranes to separate microplastics of differing sizes for observation. Then, they’ll use surface-enhanced Raman spectroscopy—which uses scattered light to detect and identify materials—to detect the plastics.
“We’ll collect water samples from Lake Michigan and Madison’s Lake Mendota and put them in a rooftop tank along with some consumer-grade plastic products,” Wei says. “We’ll leave that out to study how sunlight and radiation promote the release of microplastic particles when these sorts of larger plastic products are floating on the water’s surface.”
Qin and Wei are working on the project, which began in February 2022, with funding from the Wisconsin Sea Grant at UW-Madison. Through the course of the project’s two-year duration, they hope to refine their technique to reliably detect microplastics and also to shed light on how they proliferate. They ultimately hope to build a standardized technique that researchers or environmental agencies in other locales can use to monitor water-borne microplastics.
That’s all the more important because, while microplastics are an area of growing concern, there’s a lot we don’t yet know about them. The Environmental Protection Agency has noted a “critical need” to develop methods to determine the contaminants’ environmental and human health risks.
“We can detect this in human blood or even in the poop of babies, so these plastics are getting into children before they’re even born,” Qin says. “There’s no study yet that definitively shows how they impact human health, but they’re everywhere, so we need to know more about them.”
Photo caption: Assistant professors Mohan Qin and Haoran Wei work with Ziyan Wu (fore) as she pours water for testing. Qin and Wei are leading a project to study the presence of microplastics in the Great Lakes.