2025-10-24 トロント大学(U of T)
＜関連情報＞
- https://www.utoronto.ca/news/toronto-s-don-river-carries-36000-kg-microplastics-lake-ontario-each-year-study
- https://royalsocietypublishing.org/doi/10.1098/rsta.2023.0023
都市河川におけるプラスチック汚染物質の量、残留、損失に対する流量の影響 The influence of flow on the amount, retention and loss of plastic pollution in an urban river
Jacob Haney,Xia Zhu,Mary Long,Bailey A. Schwenk,Timothy J. Hoellein,Wilfred M. Wollheim,Richard B. Lammers,Shan ZuidemaandChelsea M. Rochman
Philosophical Transactions of The Royal Society A Published:23 October 2025
DOI:https://doi.org/10.1098/rsta.2023.0023
Abstract
Urban rivers are hypothesized to be major transporters of plastic pollution into lakes and oceans, with storm events playing a pivotal role. However, few studies investigate microplastic and macroplastic contamination and transport across a river basin, and how it varies with flow. Here, we sampled microplastic (less than 5 mm) and macroplastic (greater than 5 mm) from four sites along an urban river in Ontario, Canada, during baseflow and stormflow. To contextualize their fate and transport through river reaches, we sampled macroplastic stored in the riparian zone, overhanging vegetation, floating in surface water and riverbed and sampled microplastic from the surface water, water column and sediment. At baseflow, most macroplastic was found in the riparian zone (ranging from 0.1 to 4.7 pieces per m2). During stormflow, concentrations (micro and macro) rise and fall with discharge. Moreover, the composition of microplastics in the water column shifts from fibre- to rubber-dominated during higher flows. The mobilization of denser (e.g. rubber) particles during flow is consistent with greater water velocities during storms. Finally, using our data and flow patterns from 2022 to 2023, we estimate that approximately 522 billion microplastic particles and 20 754 macroplastic items, equalling approximately 36 000 and 160 kg by mass, respectively, are transported to Lake Ontario annually.
