Soil Additives for Green Roof Runoff Enhanced Nutrient Management

Presenter: Isabelle C. Garand

Faculty Sponsor: Nick B. Tooker

School: UMass Amherst

Research Area: Environmental Science and Sustainability

Session: Poster Session 4, 2:15 PM - 3:00 PM, Auditorium, A32

ABSTRACT

Urban stormwater runoff rises as impervious surfaces spread, carrying pollutants, notably excess nutrients, that degrade water quality, and aquatic ecosystems. The Environmental Protection Agency (EPA) estimates that city blocks generate about 5 times more runoff than woodland areas of the same size (US EPA, 2003). As areas urbanize, effective stormwater Best Management Practices (BMPs) are essential. Green roofs, among the EPA-approved BMPs, transform rooftops into water-retaining surfaces, making them valuable for redevelopment in space-constrained urban landscapes. Along with reducing runoff volume and peak flow, green roofs provide additional benefits: enhancing biodiversity and mitigating the urban heat island effect. However, they often release high nutrient levels offsetting their environmental benefits. Prior research suggests that soil additives, especially those with high adsorptive capacities for phosphorus and nitrogen, are a promising approach to reducing nutrients leaching, but few studies have explored this. Biochar and crushed concrete have been studied as soil additives on a field scale, though not in a controlled laboratory setting where the impacts of these additives can be systematically isolated. This study evaluates biochar and crushed concrete as green roof soil additives to decrease nutrients leaching from green roofs at a laboratory scale. Experiments involve applying synthetic rainwater to soil columns with different soil compositions and analyzing runoff for pH, conductivity, temperature, and concentrations of ammonia, nitrate, and total phosphorus. Identifying effective soil additives can enhance green roofs’ role as nutrient management tools, improving their function in urban landscapes, and moving us towards a greener, more environmentally friendly world.

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