Urban environments, with their vast swaths of impervious surfaces, increase the amount of non-point pollution that enter receiving freshwater bodies. This increase of pollution leads to concerning ecological management problems such as the urban stream syndrome. Green stormwater infrastructure (GSI), specifically ecoroofs, are increasingly being seen as a potential mitigator of these concerns in urban planning strategies. However, the literature suggests that ecoroofs might be sources of certain metals and nutrients, such as lead, copper, iron, total phosphorus and nitrogen. The goal of our study was to investigate and observe if these concerns hold true by the collection and analysis of metal and nutrient loading and dynamics of the run-off from an aged extensive ecoroof and the environmental variables that affect them. From August 2018 to present, the runoff events from the ecoroof and conventional roof have been collected with autosamplers and flow was measured with a flow meter. About 83 samples have been collected from the ecoroof and 127 samples have been collected from the conventional roof. Bulk deposition was collected every 2 weeks and environmental data was collected from a weather station located on the roof.
Results/Conclusions
The ecoroof had about 60 percent less discharge then conventional roof. However, the ecoroof was a source of aluminum, iron, and phosphorus. The conventional roof is a source of zinc. More research needs to be done to improve ecoroof technologies including things like water treatment residuals, biochar, and mycorrhizae inoculation.