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Fate of microplastics in background headwater lake catchments using a particle balance approach
Summary
This study tracked the input, output, and retention of microplastics across three background headwater lake catchments in Ontario, Canada over a full year. Atmospheric deposition was a major microplastic input even in these remote locations with no nearby urban sources. The findings show that even pristine-seeming catchments accumulate microplastics from long-range atmospheric transport.
Abstract Microplastics are pervasive contaminants of concern, yet their fate in headwater lakes, especially in background regions, remains relatively unknown. Further, few field studies have quantified the inputs, outputs, and pathways of microplastics at the catchment level. In this study, the flux of microplastics (MP) were quantified over a 12-month period for three background headwater lake catchments in Muskoka-Haliburton, Ontario, Canada. A microplastic particle balance approach was used, incorporating inputs from atmospheric deposition and stream inflows against outflows and sedimentation to lakes. Atmospheric deposition had the highest daily microplastic flux rate (3.84–8.04 MP/m 2 /day), suggesting that it is the dominant source of microplastics to lakes in background regions. Of the microplastics deposited on the catchment, 41–73% were retained in the terrestrial area. Furthermore, a large fraction of the microplastics entering the lake were retained (30–45%), suggesting that lakes are a reservoir for microplastics. The microplastic residence time for the study lakes ranged from 3.15 to 7.70 years. Fibres (> 60%) were the most common particle type, further, polyethylene terephthalate was the dominant polymer identified followed by polypropylene and polyamide.