Atmospheric deposition drives microplastic contamination in remote lakes of Newfoundland, Canada

Microplastics (MPs) have been identified in virtually all environments around the globe, posing a threat to both humans and nature. Though there have been numerous studies on MPs in aquatic environments, there is still a lack of knowledge on MPs in freshwater lakes, especially small endorheic lakes in remote high-latitude regions. In this study, we present evidence of MP pollution in sediments from lakes across Newfoundland, Canada. We found between 6000 and 24,000 MP kg-1 wet weight in lake sediments, with most MP particles between 2 and 10 μm in size. Polyvinyl chloride and polyurethane were the most commonly identified polymers, and they were also found in atmospheric samples collected during a hurricane that made landfall in Newfoundland in 2021. Given that lakes were located in sparsely populated areas and were either endorheic or had minimal inflow and outflow, local sources of MPs are negligible. Therefore, the observed MPs likely originate from atmospheric transport, delivered via rain, snow, or wind from distant sources. Once deposited, the lakes' closed-basin hydrology promotes particle retention, allowing MPs to accumulate in sediments over time. This study provides a baseline of MP pollution in the lakes of Newfoundland, which can support future studies investigating how atmospheric events may redistribute microplastics across the globe, especially in remote regions.