HR: 0800h
AN: B51A-0182    [Abstracts]
TI: Dry Deposition of Fine Aerosol Nitrogen to an Agricultural Field Measured by Eddy-Correlation Mass Spectrometry
AU: * Gonzales, D A
EM: daniel.gonzales@asu.edu
AF: Arizona State University, Chemical and Materials Engineering PO Box 876006, Tempe, AZ 85287-6006 United States
AU: Allen, J O
EM: joallen@asu.edu
AF: Arizona State University, Chemical and Materials Engineering PO Box 876006, Tempe, AZ 85287-6006 United States
AU: Allen, J O
EM: joallen@asu.edu
AF: Arizona State University, Civil and Environmental Engineering PO Box 875306, Tempe, AZ 85287-5306 United States
AB: In urban areas high emissions of reactive nitrogen species cause an increase in atmospheric aerosol nitrogen formation and deposition. This nitrogen is eventually removed from the atmosphere by wet or dry deposition, with dry deposition often accounting for more than half of the total deposition of particulate nitrate. Total N deposition is not adequately characterized, in part because dry deposition is difficult to measure or model. For example measured fine particle deposition to a forest canopy differs from predicted values by an order of magnitude. The eddy-correlation technique is a micrometeorological method used to directly measure fluxes from measurements made above the surface. Eddy-correlation mass spectrometry (ECMS) has been developed to directly measure aerosol particle deposition velocities from fast response aerosol concentration and wind velocity measurements. Using an Aerodyne Aerosol Mass Spectrometer (AMS), the size and composition of ambient aerosols were measured at 10~Hz. The AMS signal is proportional to non-refractory PM_1.0 mass. Aerosol deposition fluxes for a given averaging period are then calculated directly as the covariance of the vertical wind velocity with the AMS signal (F = -\overline{w'S'}). A field study was conducted to measure aerosol nitrogen dry deposition to an agricultural field immediately downwind of the Phoenix metropolitan area using eddy-correlation mass spectrometry. The study was supplemented with aerosol composition measurements including bulk deposition collectors and filter bank samplers. Here we compare the results of the flux estimates from bulk collection with inferential measurements (filter samples and modeled deposition velocities) and direct micrometeorological measurements (ECMS) in order to improve nitrogen deposition estimates.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0368 Troposphere: constituent transport and chemistry
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0469 Nitrogen cycling
SC: Biogeosciences [B]
MN: Fall Meeting 2005