Abstract View
Estimating Dry Deposition of Atmospheric Aerosols by Rain Washoff from Urban Surfaces
ALEXANDER JOHNSON, Cliff Davidson, Syracuse University
Abstract Number: 323
Working Group: Urban Aerosols
Abstract
Building roofs comprise a major fraction of the overall horizontal surface area in urban environments and therefore are large receptors of dry deposited aerosols. After a long dry period, rainwater will wash the material from the surface and into stormwater runoff. Measuring the amount of suspended material in runoff from a building roof during a rainstorm could therefore potentially be used to estimate dry deposition to that surface during the antecedent dry period.
The objectives of this study were to experimentally estimate dry deposition to horizontal urban surfaces and to measure washoff of dry deposited material from the surfaces by rain. Two flat disks used previously to estimate dry deposition to horizontal surfaces were used along with two two bowl-shaped disks of similar size.
Experiments were conducted using the surrogate surfaces on the roof of Hinds Hall on the Syracuse University campus. For each experiment, the flat disks and bowl-shaped disks were exposed to collect dry deposition, and airborne concentrations were simultaneously be measured. Samples were then collected from the flat disks at the end of the exposure. In the subsequent rainstorm, fresh precipitation was collected, and runoff from the bowl-shaped disks was collected in sequential samples.
Samples were analyzed to estimate and compare the dry deposition fluxes and dry deposition velocities of fluoride, chloride, sulfate, and nitrate to the flat disks and bowl-shaped disks. The efficiencies of the washoff process for the same chemical species were also calculated using the samples from the bowl-shaped disks.
The results of this research are the first experimental data on rain washoff of dry deposited aerosols for carefully controlled surrogate surfaces. This information will be used to estimate dry deposition to actual building roofs and other flat urban surfaces.