Lake Erie Microplastics, July 2020

Microplastics are small pieces or fragments of plastic debris. Microplastics come from a wide array of sources - namely industrial waste, wastewater discharge from laundry, and other products.

Something as simple as washing a pair of socks can introduce microplastics into the watershed. Loose plastic fibers (polyester, nylon, acrylic, etc) leave the clothing, and enter the watershed through wastewater discharge. Microplastics uptake then occurs for everything in the ecosystem. The small strands enter the ecosystem after mixing into the water plants and animals drink, absorption into the root caps of plants, and biomagnification from aquatic species. There, the plastics will remain for an estimated 400+ years. However, the breakdown of microplastics often causes them to split and fragment into smaller pieces, creating even smaller microplastics that have an easier time entering the ecosystem.  [1] 

Lake Erie itself is 25,700 km² in area, with a volume of 484 km³. The total area of the Lake Erie + Lake St. Clair drainage system is 78,000km², with more than 12 million inhabitants calling the watershed home between the United States and Canada.  [2] 

Below is an interactive map of the watershed. Take a look at various rivers, streams, cities, farms, and forests that call Lake Erie home.

The trip would be about 1,250 km (760 mi) in total, covering 40 points along the entire American coast of Lake Erie that appeared to be accessible. Grant funding secured through the Maine Space Grant Consortium covered the expenses and supplies necessary. In the days leading up to the trip, routes were planned, spreadsheets created, and supplies were gathered. Below is a photo map tour of the trip!

With the samples collected, the next step of a microplastics analysis is to filter the samples. This involves weighing the samples for volume (1g H₂O= 1mL H₂O), and then filtering through a 47mm filter with 0.45 µm (0.00045 mm) pore size.

After,  Fenton's reagent  is created by heating (for each sample) 2 mL FeSO₄ + 20 mL of 0.1 M HCl to 75°C. 5 mL 30% H₂O₂ is added to the heated solution, which is then added to the flask containing each filter. Each flask is then covered with parafilm, and left for a few days to oxidize and break down most organic material. This primarily leaves just rocks, sand, glass, and microplastics behind.

Once oxidation is complete, the samples are filtered again with a new 47mm filter with a 0.45 µm pore size. After spending a few days in the Fenton's reagent, the old filters are too brittle to be used again. The samples are then counted for microplastics using a microscope between 10-12x magnification. This count is then divided by the volume of each sample, giving the final comparable measurement of microplastics particles per liter.

The samples yielded an average of 46.5 ± 23.93 microplastics particles per liter.

Looking at the above map, the microplastics concentration appears to increase closer to larger population centers and in areas with larger industries. The cluster east of Ashtabula, OH may be related to the industrial activities in the area. Further statistical analysis is needed to determine if relationships between population and industrial activity exist.

In the below map, watersheds are created from the sample points. There does not seem to be a strong relationship between the area of the watershed and the amount of microplastics found in the samples. However, looking at the land cover of each watershed, it is observed that microplastics originated more from areas with a higher density (population and industry) than more agricultural or forested areas.