Collaborative Proposal: Plastic Spiraling In River Networks (Plastic-SIReN): Determining the controls of watershed plastic fluxes using a field and modeling approach

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Plastic litter is a widespread problem. Oceans have accumulated up to 21.1 million tons of plastic, the majority of which enters via rivers. But rivers are not just pipes delivering plastic to oceans. Instead, as plastic moves downstream in rivers it may settle, break into pieces, or interact with organisms. A substantial amount of plastic is likely stored in rivers, but when and where plastic is stored vs. moved downstream remains unknown. The research combines field measurements and computer modeling across a range of stream sizes, which is novel in the field of plastic research. This research is needed to better manage plastic pollution, where to focus cleanups, and whether drinking water sources are affected. A diverse team of students will learn how to measure plastics in streams in three different watersheds. The overarching research question is: “How does spatial and temporal variation in hydrology control the proportion of plastic debris that is retained within river networks vs. transported downstream?” The project will identify the role of flow variation, plastic characteristics, and watershed characteristics on plastic movement. A coupled field and modeling approach will be applied in the watersheds of three metropolitan regions (Chicago, IL; Boston, MA; Toronto, ON). Field measurements will take place at multiple sites in each watershed. At each site we will measure macro- and microplastic at base and storm flows to quantify plastic concentrations, types, size distribution, storage in sediments, and fluxes. A hydrologic model applied to each of the three watersheds will quantify river network-scale plastic accumulation, residence time, and retention. The team will work with watershed groups to identify hotspots of plastic accumulation to prioritize plastic waste cleanups and will present at ocean science and drinking water meetings, where management of plastic pollution is a major interest.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.