Sponsor
Portland State University. Department of Environmental Science and Management
First Advisor
Jennifer L. Morse
Date of Publication
Winter 3-26-2018
Document Type
Thesis
Degree Name
Master of Science (M.S.) in Environmental Science and Management
Department
Environmental Science and Management
Language
English
Subjects
Soils -- Phosphorus content, Soil infiltration rate, Storm water retention basins, Urban runoff
DOI
10.15760/etd.6247
Physical Description
1 online resource (vii, 57 pages)
Abstract
Modern urban stormwater infrastructure includes vegetated bioretention facilities (BRFs) that are designed to detain water and pollutants. Phosphorus (P) is a pollutant in stormwater which can be retained in BRF soils in mineral, plant, and microbial pools. We explored soil properties and phosphorus forms in the soils of 16 operational BRFs in Portland, OR. Since soil hydrology can significantly impact P retention, we selected BRFs along an infiltration rate (IR) gradient. We conducted sequential fractionation and tests of P pools and measured P release in a subset of soils after drying and flooding samples for ten days. We hypothesized that mineral or organic soil P forms would be correlated with IR, and that vulnerability to P release would depend on the interaction of drying and flooding treatments with P forms and pools. IR did not significantly explain differences in P forms. Soil TP was elevated across all sites, compared with TP in agriculturally-impacted wetlands and was substantially composed of soil organic matter (OM)-associated P. Phosphorus sorbed to mineral Fe and Al oxides- was variable but positively correlated with water-extractable P. The concentration gradient of water-extractable P was primarily controlled by overall P pools. Experimentally induced P releases were seen in 5 of 6 soils exposed to drying conditions, presumably released through microbial mineralization of OM. Only one site showed significant P release following the flooding treatment. Our measurements supported the idea that Fe and Al oxides provide P sorption capacity in these BRF soils. Variable inputs of P to BRFs through stormwater and litterfall may contribute to variability in P profiles and P release vulnerability across sites. Design specifications and management decisions relating to bioretention soils (e.g. establishment of acceptable soil test P levels, focusing on P forms known to influence vulnerability of P release) may benefit from detailed biogeochemical investigations.
Rights
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Persistent Identifier
https://archives.pdx.edu/ds/psu/25519
Recommended Citation
Shetterly, Benjamin James, "Soil Phosphorus Characterization and Vulnerability to Release in Urban Stormwater Bioretention Facilities" (2018). Dissertations and Theses. Paper 4354.
https://doi.org/10.15760/etd.6247