HR: 16:45h
AN: A24B-04    [Abstracts]
TI: In-Situ Measurements of Aerosols from Motor Vehicles in the Caldecott Tunnel
AU: * Hallar, A G
EM: ahallar@mail.arc.nasa.gov
AF: NASA Ames Research Center/ NRC, National Research Council Assoicate Mail Stop 245-4, Moffett Field, CA 94035 United States
AU: Strawa, A
EM: astrawa@mail.arc.nasa.gov
AF: NASA Ames Research Center, Mail Stop 245-4 , Moffett Field, CA 94035 United States
AU: Kirchstetter, T W
EM: twkirchstetter@lbl.gov
AF: Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, MS70-108B, Berkeley, CA 94720 United States
AU: Bokarius, K
EM: kostya@aerosol.arc.nasa.gov
AF: San Jose State University, NASA Ames Research Center, Moffett Field, CA 94025 United States
AU: Harley, R
EM: harley@ce.berkeley.edu
AF: University of California, Department of Civil and Environmental Engineering, Berkeley, CA 94720-1710 United States
AB: A study was recently conducted in the Caldecott Tunnel, a heavily-used tunnel located east of San Francisco, CA. The aerosol sampled in this study was characterized by fresh automobile and diesel exhaust. Roadway tunnel studies have some strong advantages over traditional dynamometer studies. For instance this study captured the aggregate emissions of a fleet of vehicles (4000 cars/hr in the center bore) operating under real-world, in-use conditions. This experiment involved two separate test-beds, one week of measurements within a light duty (gasoline) vehicle bore and one week within a mixed light duty (gasoline cars)/ heavy duty (diesel trucks) vehicle bore. Furthermore, within the framework of this study, the relative humidity was adjusted within the sample line to test the possible hydroscopic nature of the emissions. In the heavy duty bore, an increase of RH ( from 45 percent to 80 percent) did not have an observable effect on the aerosol optical properties. A new cavity ring-down (CRD) instrument, called Cadenza (NASA-ARC), measures the aerosol extinction coefficient for 675 nm and 1550 nm light, and simultaneously measures the scattering coefficient at 675 nm. The absorption coefficient is obtained from the difference of measured extinction and scattering within the instrument. Measurements from Cadenza, a standard aethalometer, and a Scanning Mobility Particle Sizer (SMPS, TSI Inc.) are presented. The aethalometer is a filter-based photometer and the near infrared channel is calibrated to produce a measure of BC mass loading. The SMPS system measures submicrometer aerosols in the range from 3 to 1000 nm in diameter. It employs an electrostatic classifier to determine the particle size, and a Condensation Particle Counter (CPC) to determine particle concentration. A majority of particles, approximately 90 percent, measured were "ultra-fine" with sizes below 100 nm.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005