Researchers discover harmful microplastics in Lake Tahoe
Special to the Tribune
On a recent day at Lake Tahoe, paddle boarders glide along cobalt blue waters, sunbathers lay out their chairs for the day, and Katie Senft is leaning over, staring intently at the sand.
Senft is a staff researcher at the University of California, Davis Tahoe Environmental Research Center. She and three interns are looking for microplastics — tiny fragments of plastic smaller than a grain of rice — along the shoreline.
From the infamous “Garbage Patch” islands of floating plastic to the guts of fish and bellies of birds, plastics of all sizes are ubiquitous and well-documented in the ocean. But little data exists on microplastics in lakes.
If Senft’s preliminary research at one of the clearest, cleanest lakes in the world is any indication, the problem is widespread in freshwater systems, as well.
“The ocean gets a lot of attention about plastic in the water, and our freshwater lakes don’t,” Senft said. “This issue has flown under the radar in the Tahoe Basin. When plastics enter the environment, be it terrestrial or aquatic, they stick around for a long time. We don’t know the long-term implications of having plastics in our water and in our soil.”
Senft began sampling four beaches last summer as part of the first study of microplastics in Lake Tahoe. Largely unfunded, she’s sampling Incline Beach and Hidden Beach twice this summer.
Incline Beach is a private one, with litter picked up regularly. Still, a red bead, a fish hook with a plastic worm and part of a toy truck find their way into the research team’s bag. Often they’ll find bottle caps, plastic film from food packaging, golf balls, and beach toys buried by a wave or forgotten by a child. Once Senft even found pieces of artificial turf. Too big to be considered microplastic, which are 5 millimeters or less, the team collects these pieces for proper disposal.
But to research microplastics, the team scoops sand into glass mason jars at defined distances across the shoreline. The samples will be weighed, processed and analyzed under a microscope for plastics.
Separating sand and plastic
At the lab, the researchers appear to be making a pie more so than conducting scientific analysis.
To ensure that no external plastic disrupts their results, Senft’s team has foregone conventional plastic scientific tools in favor of the following: a wooden spoon, glass mixing bowl, glass measuring cup and aluminum pan.
Senft pours the sand into an aluminum pie plate, weighs it and places it into a drying oven to remove excess moisture. After baking it overnight, she will stir the sand with a high-density liquid solution in the mixing bowl to separate the plastic from the sediment. The plastic pieces will be further scrutinized and photographed under the microscope.
A solvable problem
Eventually, Senft would like to sample at least four beaches every quarter, looking not only at trash but also atmospheric deposition and stormwater runoff sources of plastic. In the meantime, she hopes the baseline data she’s collecting from this and last year will help bring attention to the issue, lay the groundwork for measures Lake Tahoe can take, and establish methods scientists can apply when researching microplastics in other lake systems.
Unlike many freshwater systems, the wastewater produced in the Tahoe Basin is piped out and does not return to the lake. Wastewater is the main source of microplastics in most freshwater systems, with microfibers — small bits of fiber from laundered clothes that find their way back to water systems — being the primary plastic pollutant.
“That means the microplastics we’re finding at Lake Tahoe are most likely from improperly disposed trash,” Senft said.
Residents and visitors can help by reducing the amount of plastic brought to the beach from the beginning. Lake Tahoe has some of the nation’s cleanest drinking water, so forgoing the packs of small plastic water bottles for a reusable one is an easy place to start.
For other plastic items, make sure to throw away or pack out whatever is brought in.
“The problem of plastics in Tahoe is, I believe, very solvable,” Senft said. “People think everyone can’t make a difference, but we’re actually really powerful. If everyone picked up their trash, it would make a huge difference.”
Kat Kerlin is a staff member for the UC Davis News and Media Relations department.
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