Nutrient Dynamics in Stormwater Runoff from Green Roofs with Varying Substrate

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Fohner, John Michael
Health and environmental sciences; Earth sciences Environmental science; Green roofs; Runoff; Water quality; Fresh Water Studies; Hydrology; Water Resource Management
thesis / dissertation description
One major concern with urban development is the increasing amount of stormwater runoff from large expanses of impervious surfaces. These impervious surfaces reduce the ability of stormwater to infiltrate into the soil and eventually groundwater, which leads to greater amounts of surface runoff. Green technology serves as a viable solution to many of the environmental problems presented by modern development. Fifteen mock, extensive green roofs were built in the fall of 2008 at the Watershed Research and Education Center in Fayetteville, Arkansas. The goals of this project were to (1) measure the amount of stormwater runoff from varying treatments and control roofs, (2) measure the stormwater runoff quality from varying treatments, and (3) study the release of nutrients over time from the green roofs with added compost. Our results show that after an initial flush of nutrients from green roofs with added compost, many nutrient concentrations, such as total organic carbon (TOC), total nitrogen (TN), nitrate-N (NO3-N), and other physiochemical properties have been reduced. However, even after two years, P concentrations in runoff water still exceed 1 mg/L from green roofs using compost in the growing matrix. Analysis of the remaining nutrients in the compost shows that TP loads from green roofs with added compost could be elevated for a number of years. The results from this study provide a benchmark for developing green roofs in Northwest Arkansas or other similar climactic regions.