Local Monitoring Should Inform Local Solutions: Morphological Assemblages of Microplastics Are Similar within a Pathway, But Relative Total Concentrations Vary Regionally.

Pathways for microplastics to aquatic ecosystems include agricultural runoff, urban runoff, and treated or untreated wastewater. To better understand the importance of each pathway as a vector for microplastics into waterbodies and for mitigation, we sampled agricultural runoff, urban stormwater runoff, treated wastewater effluent, and the waterbodies downstream in four regions across North America: the Sacramento Delta, the Mississippi River, Lake Ontario, and Chesapeake Bay. The highest concentrations of microplastics in each pathway varied by region: agricultural runoff in the Sacramento Delta and Mississippi River, urban stormwater runoff in Lake Ontario, and treated wastewater effluent in Chesapeake Bay. Material types were diverse and not unique across pathways. However, a PERMANOVA found significant differences in morphological assemblages among pathways (p < 0.005), suggesting fibers as a signature of agricultural runoff and treated wastewater effluent and rubbery fragments as a signature of stormwater. Moreover, the relationship between watershed characteristics and particle concentrations varied across watersheds (e.g., with agricultural parameters only being important in the Sacramento Delta). Overall, our results suggest that local monitoring is essential to inform effective mitigation strategies and that assessing the assemblages of morphologies should be prioritized in monitoring programs to identify important pathways of contamination.

ASPECTS OF TOPOLOGICAL APPROACHES FOR DATA SCIENCE.

We establish a new theory which unifies various aspects of topological approaches for data science, by being applicable both to point cloud data and to graph data, including networks beyond pairwise interactions. We generalize simplicial complexes and hypergraphs to super-hypergraphs and establish super-hypergraph homology as an extension of simplicial homology. Driven by applications, we also introduce super-persistent homology.

Microplastics entering northwestern Lake Ontario are diverse and linked to urban sources.

The sources of microplastics and other anthropogenic particles in freshwater are not well understood. The Greater Toronto Area, Canada's most populous urban area, offers a great study area for understanding the sources and pathways for microplastics to enter freshwater ecosystems. Here, we quantified and characterized microplastics and other anthropogenic particles from Lake Ontario surface waters and source waters (including stormwater runoff, agricultural runoff, and treated wastewater effluent) to better understand sources to the Great Lakes. Anthropogenic particle concentrations in lake samples were 0.8 particles L-1. In source waters, average concentrations were relatively higher in stormwater and wastewater, with 15.4 particles L-1 and 13.3 particles L-1, respectively, compared to 0.9 particles L-1 on average in agricultural runoff. Source waters revealed distinct signatures related to the morphologies of anthropogenic particles, e.g., fibers in wastewater. In addition, many upstream watershed characteristics were found to be significant predictors of anthropogenic particle concentration. Proximity to urban areas were positively correlated to anthropogenic particle concentrations. Future studies should focus on local source-apportionment to inform management and prevent further contamination of microplastics to freshwater ecosystems.