Microplastics and plastic additives in the St. Lawrence River and Estuary: occurrence, fate and impacts

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Microplastics (MPs) are defined as plastic fragments with a diameter less than 5 mm, which are known to be ingested by wildlife and humans. Ingestion of and exposure to microplastics may lead to adverse effects, including physical damage and toxicity related to plastics-associated chemicals (e.g., plastic additives). However, our knowledge about how MPs and plastic additives distribute, move, react and behave in the environment is very limited. Therefore, MPs pollution has been identified as a research priority by the Canadian government's Draft Science Assessment of Plastic Pollution. In Canada, the existing monitoring activities for MPs and plastic additives have centred on the Laurentian Great Lakes and the Arctic, and the status of these contaminants in other ecosystems remains largely unknown. The St. Lawrence River and Estuary (SLRE) host a suite of unique ecosystems but also constitute a vector of contaminants to the Atlantic Ocean. Given that the SLRE is one of Canada's priority ecosystems, is downstream from the Laurentian Great Lakes, and is home to more than 5 million Canadians, the lack of data on plastic pollution in the region impedes understanding effects on this important system and prioritization of management strategies. To address these knowledge gaps, this project will investigate (1) the occurrence and characteristics of MPs and plastic additives in atmospheric depositions, air particles, surface water, and biota (fish and bird) from the SLRE; (2) emissions of greenhouse gases and leaching of plastic additives during the photodegradation of MPs in water; (3) the inherent optical properties of MPs and their remote sensing applications; and (4) wildlife ecotoxicology of chemicals associated with MPs. Since the various plastics have different applications in industrial and commercial products, understanding the composition of MPs could help identify major sources and develop rational approaches for their management. Thus, the results obtained in this research will be highly valuable for the Canada-wide strategy on zero plastic waste to identify risks and provide effective countermeasures.