This research was supported by a Faculty Enhancement Grant at Portland State University and National Science Foundation (CBET 2115447 & SMB 1935028). Additional supports were provided by the City of Gresham, City of Portland, Clackamas River Water Providers, East Multnomah County Soil and Water District, and Sigma Xi.
Science of The Total Environment
Microplastics -- Environmental aspects, Microplastics -- Measurement, Microplastics -- Oregon -- Analysis
While microplastics are a pollutant of growing concern in various environmental compartments, less is known regarding the sources and delivery pathways of microplastics in urban rivers. We investigated the relationship between microplastic concentrations and various spatiotemporal factors (e.g., land use, arterial road length, water velocity, precipitation) in two watersheds along an urban-rural gradient in the Portland metropolitan area. Samples were collected in August, September, and February and were analyzed for total microplastic count and type. Nonparametric statistics were used to evaluate potential relationships with the explanatory variables, derived at both the subwatershed and near stream scales. In August, microplastic concentrations were significantly higher than in February. August concentrations also negatively correlated with flow rate, suggesting that lower flow rates may have facilitated the accumulation of microplastics. Smaller size microplastic particles (< 100 μm) were found more in August than September and February, while larger size particles were more dominant in February than the other months. Microplastic concentrations were positively related to 24-h antecedent precipitation in February. Negative correlations existed between wet season microplastic concentrations and agricultural lands at the near streamlevel. The results indicate that near stream variables may more strongly influence the presence and abundance of microplastics in Portland's waterways than subwatershed-scale variables. Fragments were the most commonly observed microplastic morphology, with a dominance of gray particles and the polymer polyethylene. The findings of this study can informmanagement decisions regarding microplastic waste and identify hotspots of microplastic pollution that may benefit from remediation.
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Talbot, R., Granek, E., Chang, H., Wood, R., & Brander, S. (2022). Spatial and temporal variations of microplastic concentrations in Portland's freshwater ecosystems. Science of The Total Environment, 155143.