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Evaluation of Runoff Quality from an Extensive Green Roof System
This study focuses on the analysis of rainwater runoff from an extensive green roof system. Over time, space that was formally available for rainwater to properly infiltrate to the ground is being taken up by impervious built surfaces. Green roof technologies could be very beneficial in urban development, therefore the evaluation of the runoff quality is necessary to know if green roof systems act as a source of pollutants to receiving water bodies, or if they help mitigate contaminants that are washed off from the atmosphere and transfer to water bodies during rain events. The performance of green roof systems is highly dependent upon the season, temperature, wind condition, humidity, duration, and intensity of rainfall. The design of the green roof also plays an important part in the performance of the green roof, for which, material type, soil thickness, and maintenance influence the runoff quality. The green roof was analyzed for nutrients concentrations, pH, and conductivity of rainwater runoff. It was found that the green roof’s runoff had concentrations of nitrate, phosphate, and chloride ions. To investigate the amount of nutrients found in rainwater collected from different types of roofs, the green roof’s runoff nutrient concentrations were compared to those of a shingled roof. The pH and electrical conductivity of the rainwater runoff of the green roof were compared to those measured on a shingled roof as well.
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