AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Measuring Dry and Wet Deposition of Atmospheric Aerosols to Surfaces in Syracuse, NY
ALEXANDER JOHNSON, Cliff Davidson, Syracuse University
Abstract Number: 378 Working Group: Urban Aerosols
Abstract Dry deposition of aerosols is a major atmospheric input to the urban environment where it can degrade natural and man-made surfaces. Surrogate surfaces are frequently used to measure dry deposition fluxes, including some that are designed to minimize atmospheric turbulence and create a thin, uniform boundary layer over the surface. These characteristics can provide a measured flux that serves as a lower limit of the dry deposition onto rougher, more complex surfaces.
Wet deposition also removes aerosols from the atmosphere, and this can occur by both washout and rainout processes. While the wet deposition flux is usually measured as a time average for one precipitation event, the flux may vary within an event depending on meteorology and influences from local emissions.
Dry deposition and wet deposition were measured on the Syracuse University campus in Syracuse, NY from 2016 to 2018. The objectives were to determine ranges of dry deposition velocities of inorganic anions and to determine variations in wet deposition fluxes within individual rainstorms. Dry deposition velocities were determined by measuring the fluxes using surrogate surfaces, 1.2 meters in diameter, and by simultaneously measuring airborne concentrations. Measured dry deposition velocities were in the range of 0.6-2.5 cm/s (fluoride), 1.9-9.2 cm/s (chloride), 0.11-1.8 cm/s (sulfate), and 0.1-1.1 cm/s (nitrate). Larger deposition velocities of sulfate and chloride were obtained during the winter, possibly due to entrainment of deicing salts into the atmosphere. Fresh precipitation was collected on Jun. 4, 2017, Oct. 9, 2017, and Jul. 25, 2018 at multiple time steps during each storm. Wet deposition fluxes of sulfate, nitrate, and chloride generally decreased over time, suggesting that washout is an important process for removing contaminants. However, fluxes sometimes increased due to changes in wind direction and precipitation intensity.