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Missouri University of Science and Technology (2013)

Green roof water quality impacts and physicochemical stability

Harper, Grace Ella

Titre : Green roof water quality impacts and physicochemical stability

Auteur : Harper, Grace Ella

Université de soutenance : Missouri University of Science and Technology

Grade : M.S. in Environmental Engineering 2013

Résumé
Green roofs can provide environmental benefits and conserve energy ; this research evaluated green roof stormwater management, nutrient loading, and erosion prevention for two green roof media. During a pilot study, the runoff quantity and composition from green roof material was evaluated continuously under field conditions for two different media, both tested under planted and unplanted conditions. Water quantity results show over a 40% reduction in runoff from just the growing media and over 60% reduction in runoff with established plants in green roof media over the eight month study. Previous studies have reported a "first flush" of excess nutrients but without evaluating the duration and intensity of this phenomenon throughout the first year of the roof’s life. Total phosphorus at 30 mg/L and nitrogen concentrations above 60 mg/L were observed in green roof runoff initially, with concentrations decreasing over time to 5 and 10 mg/L, respectively. In addition, elevated total organic carbon concentrations were observed, with concentrations of 500 mg/L initially, decreasing to below ten percent of initial concentrations. Media type and age were the largest influences on carbon and nutrient concentrations. Understanding runoff nutrient kinetics can better aid in developing procedures to minimize nutrient runoff and predict nutrient loading more accurately. In testing physical stability, both wind tunnel testing and sampling of total suspended solids in runoff were performed. The green roof drainage and filter fabric systems proved effective at preventing water-based erosion, with median total suspended solids concentrations for both below 20 mg/L. Because wind erosion can occur, surface stabilizers (i.e. adhesives) are available to secure green roof media. Green roof adhesive and plant cover were evaluated through wind tunnel testing ; both reduced wind scour down to one-tenth of observed scour without any cover, providing protection against wind erosion

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