Microplastic pollution in Canada’s capital region

Examples of microplastics recovered during sampling. Photos (a) and (b) show examples of secondary plastic fragments found in the Manta net sampling, and photos (c) and (d) show examples of the plastic particles recovered from the sediment samples. Plastic microfibers as shown in photos (c) and (d) were the most common plastic particles observed in the samples.

Plastic pollution is evident around the globe from the “great Pacific garbage patch” to empty water bottles littering riverbanks. However, another form of plastic pollution has surfaced. Microplastics are plastic particles smaller than 5 mm and microplastic pollution is an emerging environmental problem in aquatic ecosystems. Evidence for microplastic pollution in Earth’s oceans is abundant, and evidence is growing for microplastic pollution in fresh water.

We sampled water and sediment from the Ottawa River, Ottawa, Canada, to determine if microplastic pollution was occurring in this Canadian Heritage River that supports a remarkable diversity of fauna and flora and a thriving tourism industry, as well as provides drinking water to Ottawa’s residents. In the summer of 2016, water samples were collected upstream and downstream of the City of Ottawa’s wastewater treatment plant using two methods. The first method used a handheld filter and sampled 100 L of river water for plastics. The second method used a trawl net slowly pulled behind a boat for 20 minutes. These trawl samples filtered over 100,000 L of river water. We also collected river sediment samples downstream of the wastewater treatment plant. All water and sediment samples were treated with hydrogen peroxide in the lab to make the plastic particles easier to see under a microscope.

We found that plastic pollution is common in the Ottawa River and its tributaries with all 62 water samples and 10 sediment samples containing microplastics; concentrations of plastic were almost 3 times greater downstream of the wastewater treatment plant compared with upstream. We also found that the most common type of microplastics found in the river were small thread-like microfibers; microfibers are thought to originate from synthetic clothing or rope. Microbeads and plastic fragments from the breakdown of larger plastic pieces were also found. Overall, our study shows that plastic pollution seems to be everywhere in the Ottawa River and its tributaries, and the effluent from the wastewater treatment plant could be one pathway for plastics into the river. The Ottawa River tends to have greater plastic concentrations than those reported in the Great Lakes but less than what has been reported in more urbanized rivers in the United States and Europe. We still need to know more about where these plastics are coming from and what impact they may be having on the ecosystem to help reduce plastic pollution in lakes and rivers and to mitigate adverse effects on those who depend on aquatic natural resources.

Read the full paper — Microplastic abundance and distribution in the open water and sediment of the Ottawa River, Canada, and its tributaries by Jesse C. Vermaire, Carrington Pomeroy, Sofia M. Herczegh, Owen Haggart, and Meaghan Murphy on the FACETS website.