HR: 1340h
AN: A33A-0825    [Abstracts]
TI: The Effect of Inlet Aspiration of Aerosol Odd-nitrogen Species on NOy Budget Determination.
AU: * Knapp, D J
EM: david@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305, United States
AU: Rogers, D C
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305, United States
AU: Weinheimer, A J
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305, United States
AU: Montzka, D
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305, United States
AU: Flocke, F M
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305, United States
AU: Zheng, W
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305, United States
AU: Wennberg, P
AF: California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, United States
AU: Crounse, J
AF: California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, United States
AU: McCabe, D
AF: California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, United States
AU: DeCarlo, P
AF: University of Colorado, CIRES, Boulder, CO 80309-0216, United States
AU: Dunlea, E
AF: University of Colorado, CIRES, Boulder, CO 80309-0216, United States
AU: Aiken, A
AF: University of Colorado, CIRES, Boulder, CO 80309-0216, United States
AU: Jimenez, J
AF: University of Colorado, CIRES, Boulder, CO 80309-0216, United States
AU: Blake, D
AF: University of California, 570 Rowland Hall, Irvine, CA 92697, United States
AB: During the MILAGRO/MIRAGE-MEX campaign in March 2006, the NCAR chemiluminescence NOx, NOy, O3 instrument was flown aboard the NSF C-130 in and around the Mexico City Metropolitan Area (MCMA) to sample the urban pollution plume. The NOy instrument sampled ambient air from an aft-facing inlet extended on a pylon from the bottom of the aircraft, in a continuously aspirated flow of about 1 SLM. The sample flow entrained small aerosols which is understood from a practical perspective, but until this time had not been quantified for this inlet configuration. During flights close to MCMA, relatively high values of ammonium nitrate aerosol (5.2 ppbv equivalent mixing ratio) were measured by the University of Colorado AMS instrument coincidently with high NOy readings (5.5 ppbv) from the NCAR NOy instrument. Subsequent analysis of the NOy partitioning resulted in a component NOy deficiency of 15 - 40 percent, based on independent but concomitantly measured major NOy species: NOx, PANs, HNO3, alkyl nitrates and aerosol NH4NO3. The aspiration efficiency of small aerosols from the NOy inlet was modeled using the Fluent aerodynamic model. The amount of aerosol NH4NO3 and HNO3 on fine dust were calculated based on the determined aspiration efficiencies for a range of aerosol masses, and the potential contribution of these species to the NOy budget was determined. Systematic aspiration of an unknown amount of these aerosols may at least partially explain historic examples of missing NOy.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting