The Fate of Microplastics in Rural Headwater Lake Catchments
Brittany Welsh, Andrew M. Paterson, Huaxia Yao, Chris McConnell, Julian Aherne
Abstract
In this study, the fluxes of microplastics (mp) were quantified during a 12-month period for three rural headwater lake catchments in Muskoka-Haliburton, south-central Ontario, Canada. A novel catchment particle balance approach was used, incorporating inputs from atmospheric deposition and stream inflows against lake outflow and sedimentation. This approach provides the first reported observation-based estimates of microplastic residence time in freshwater lakes. Atmospheric deposition had the highest daily microplastic flux (3.95–8.09 mp/m 2 /day), compared to the inflow streams (2.21–2.34 mp/m 2 /day), suggesting that it is the dominant source of microplastics to rural regions. Approximately 44–71% of the deposited microplastics were retained in the terrestrial catchments and 30–49% of the microplastics in the stream inflows were retained in the study lakes. Given that output fluxes ranged from 0.72–3.76 mp/m 2 /day in the sediment and 1.18–1.66 mp/m 2 /day in the lake outflows, the microplastic residence time was estimated to be between 3 and 12 years, suggesting that lakes are an important reservoir for microplastics. Fibers were the dominant shape in atmospheric deposition, streamwater, and lake water; however, in lake sediment, there was a higher proportion of fragments. Across all media, poly(ethylene terephthalate) was the dominant polymer identified (23%).