AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Washoff of Dry Deposited Atmospheric Aerosol from a Traditional Roof and a Green Roof
ALEXANDER JOHNSON, Cliff Davidson, Syracuse University
Abstract Number: 537 Working Group: Urban Aerosols
Abstract Dry deposited aerosols accumulate onto urban surfaces such as building roofs. In a rainstorm, some of these aerosols are washed off by stormwater runoff, thereby contaminating the runoff. Wet deposition may also contribute additional contaminants to the runoff. Not much is known on the relative contributions of wet and dry deposition to stormwater runoff contamination. There is also essentially no information on the extent to which an observable “first flush effect” exists, where most of the dry deposited contaminants on building roofs are removed during the early part of a rainstorm.
Besides traditional building roofs, green roofs are also dry deposition sites for atmospheric aerosols. Falling rain can wash deposited aerosol off of the vegetation and growth medium surfaces of a green roof. Some chemicals within the growth medium may contribute additional contamination to the runoff, while other contaminants in the runoff may be filtered out by the growth medium. The complex processes influencing the chemical content of stormwater runoff on a green roof have not been well-studied.
To better understand these processes, experiments were conducted on two adjacent roofs in downtown Syracuse, New York: a 1.3 acre traditional roof on the War Memorial Sports Arena and a 1.5 acre green roof on the Onondaga County Convention Center. Runoff was collected from both roofs during several rainstorms and analyzed for sulfate and nitrate. In separate experiments, dry deposition fluxes of these two chemical species were measured using large flat disks on the Syracuse University campus approximately 1.6 km away. Airborne concentrations were simultaneously measured to obtain dry deposition velocities. These data are being used to construct mass balances to better understand the processes occurring on both roofs.