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Start Date

8-3-2022 12:20 PM

End Date

8-3-2022 12:30 PM

Abstract

Microplastics are a pollutant of growing concern and are ubiquitous in a variety of environmental compartments. The majority of microplastics research to date has been conducted in marine waters, and less is known regarding the sources and delivery pathways of microplastics in urban rivers. Two watersheds in the Portland metropolitan area were selected to assess microplastic concentrations and potential links with a variety of spatiotemporal factors. Samples were collected from four sites in the Clackamas River watershed and from six sites in the Johnson Creek watershed, with one sampling event in the dry season and two in the wet season. Samples were analyzed for total microplastic count and type, and spatial analyses were conducted at both the subwatershed and nearstream scale.

Microplastic concentrations in August were significantly higher than in February. August concentrations also negatively correlated with flow rate, suggesting that lower flow rates present in the dry season may have facilitated the accumulation of microplastics. Only one correlation was noted regarding antecedent precipitation amount and microplastics. Additionally, negative correlations were found between wet season microplastic concentrations and agricultural lands at the nearstream level. While additional research is needed, results indicate that the presence and abundance of microplastics in Portland’s waterways may be most strongly influenced by nearstream variables. Fragments were the most commonly observed morphology, with a dominance of the polymer polyethylene. The findings of this research can be used to inform management decisions regarding microplastic waste and identify hotspots of microplastic pollution that may benefit from remediation.

Subjects

Water quality

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Mar 8th, 12:20 PM Mar 8th, 12:30 PM

Spatial and Seasonal Variations of Microplastic Concentrations in Portland’s Freshwater Ecosystems

Microplastics are a pollutant of growing concern and are ubiquitous in a variety of environmental compartments. The majority of microplastics research to date has been conducted in marine waters, and less is known regarding the sources and delivery pathways of microplastics in urban rivers. Two watersheds in the Portland metropolitan area were selected to assess microplastic concentrations and potential links with a variety of spatiotemporal factors. Samples were collected from four sites in the Clackamas River watershed and from six sites in the Johnson Creek watershed, with one sampling event in the dry season and two in the wet season. Samples were analyzed for total microplastic count and type, and spatial analyses were conducted at both the subwatershed and nearstream scale.

Microplastic concentrations in August were significantly higher than in February. August concentrations also negatively correlated with flow rate, suggesting that lower flow rates present in the dry season may have facilitated the accumulation of microplastics. Only one correlation was noted regarding antecedent precipitation amount and microplastics. Additionally, negative correlations were found between wet season microplastic concentrations and agricultural lands at the nearstream level. While additional research is needed, results indicate that the presence and abundance of microplastics in Portland’s waterways may be most strongly influenced by nearstream variables. Fragments were the most commonly observed morphology, with a dominance of the polymer polyethylene. The findings of this research can be used to inform management decisions regarding microplastic waste and identify hotspots of microplastic pollution that may benefit from remediation.