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Spatial distribution and risk assessment of microplastics in surface waters of the St. Lawrence Estuary
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This study measured microplastic pollution in the St. Lawrence Estuary in eastern Canada, finding an average of 120 particles per cubic meter of surface water. Concentrations were highest near wastewater treatment plant outflows and agricultural areas. The research highlights that estuaries serve as major conduits for microplastic pollution moving from rivers to the ocean, affecting ecosystems and potentially the seafood that communities depend on.
Development of effective prevention and mitigation strategies for marine plastic pollution requires a better understanding of the pathways and transport mechanisms of plastic waste. Yet the role of estuaries as a key interface between riverine inputs of plastic pollution and delivery to receiving marine environments remains poorly understood. This study quantified the concentration and distribution of microplastics (MPs) (50-3200 μm) in surface waters of the St. Lawrence Estuary (SLE) in eastern Canada. Microplastics were identified and enumerated based on particle morphology, colour, and size class. Fourier Transform Infrared (FTIR) spectroscopy was used on a subset of particles to identify polymers. Generalized linear models (Gamma distribution with log-link) examined the relationship between MP concentrations and oceanographic variables and anthropogenic sources. Finally, a risk assessment model, using MP concentrations and chemical hazards based on polymer types, estimated the MP pollution risk to ecosystem health. Mean surface MP concentration in the SLE was 120 ± 42 SD particles m-3; MP concentrations were highest in the fluvial section and lowest in the Northwest Gulf of St. Lawrence. However, MP concentrations exhibited high heterogeneity along the length and width of the SLE. Microplastics were elevated at stations located closer to wastewater treatment plant outflows and downstream sites with more agricultural land. Black, blue, and transparent fibers and fragments ≤250 μm were most commonly encountered. Predominant polymer types included polyethylene terephthalate, regenerated cellulose, polyethylene, and alkyds. While the overall risk to ecosystem health in the entire estuary was considered low, several stations, particularly near urban centres were at high or very high risk. This study provides new insights into the quantification and distribution of MPs and first estimates of the risk of MP pollution to ecosystem health in one of the world's largest estuaries.
More Papers Like This
Surface Water Microplastics in the St. Lawrence River and Estuary in Canada
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Researchers sampled the top 40 centimeters of surface water at 11 sites across the St. Lawrence River and Estuary in Canada, finding microplastics at every single site. Fibers were the most abundant type, followed by fragments, with polyester, polyethylene, polypropylene, nylon, and polystyrene the dominant materials. The study also observed that microplastics tended to aggregate more as water salinity increased toward the estuary mouth. The St. Lawrence is a major drinking water source and commercial fishery, making these baseline contamination data important for public health and ecosystem management.
The largest estuary on the planet is not spared from plastic pollution: Case of the St. Lawrence River Estuary
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Researchers conducted the first macroplastic survey along the St. Lawrence Estuary shorelines, finding ubiquitous contamination dominated by single-use polypropylene, polyethylene, and polystyrene items at an average density of 0.17 items/m², with abundance declining with distance from the Montreal metropolitan area.
From freshwaters to bivalves: Microplastic distribution along the Saint-Lawrence river-to-sea continuum
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Researchers traced microplastic distribution along the Saint-Lawrence River-to-sea continuum, finding both large and small microplastics in surface water and marine bivalves, with concentrations and polymer types varying between freshwater and estuarine environments.
Microplastic pollution in St. Lawrence River sediments
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Researchers found polyethylene microbeads in sediments of the St. Lawrence River at concentrations that increased downstream toward the heavily populated Quebec City area. The study is one of the first to document microplastics in the sediments of a major North American freshwater system and confirms that urban wastewater is a primary source.
Distribution, abundance, and diversity of microplastics in the upper St. Lawrence River
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This study quantified the abundance, distribution, and diversity of microplastics in sediments of the St. Lawrence River, Canada, extending previous work on large polyethylene microbeads to a broader range of particle sizes and types. The results revealed widespread microplastic contamination across the river system, with urban areas showing the highest concentrations.
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When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.