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a Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512
b University of Alaska, 303 IARC, Fairbanks, AK 99775
c Sonoma Technology, Inc., 1360 Redwood Way, Suite C, Petaluma, CA 94954
d Univ. of La Laguna, Tenerife, Canary Islands, Spain
* Corresponding author (johnw{at}dri.edu)
Received for publication March 31, 2000. Aerosol chemical and optical properties were measured near the Mt. Zirkel Wilderness Area in northwestern Colorado. Six-hour PM2.5 (particles with aerodynamic diameters less than 2.5 µm) mass concentrations and PM2.5 dry particle light scattering at 550 nm averaged 4.6 µg m-3 and 8.6 Mm-1, respectively. Sulfates, organic carbon, and geological material were the principle components of particle mass and light scattering. Hygroscopic growth was consistent with that expected for ammonium sulfate aerosols. Size distributions derived from three-wavelength (i.e., 450, 550, and 700 nm) nephelometer data were similar to those measured in other remote areas of the western USA. Quasi-dry chemical light scattering efficiencies derived using Mie theory were 3.6 m2 g-1 for organic carbon, 2.5 m2 g-1 for sulfates (ammonium sulfate and ammonium bisulfate), 2.6 m2 g-1 for ammonium nitrate, and 1.76 m2 g-1 for geological material. These values are lower than but consistent with previously reported results. Realistic efficiencies could not be derived using the multiple linear regression (MLR) approach.
Abbreviations: AAE, average absolute error EC, elemental carbon ELSIE, Elastic Light Scattering Interactive Efficiencies model GCVTC, Grand Canyon Visibility Transport Commission GMD, geometric mean diameter GSTD, geometric standard deviation MLR, multiple linear regression Mm-1, inverse megameter (1/106 m) MZVS, Mt. Zirkel Visibility Study OC, organic carbon PM2.5, particles with aerodynamic diameters less than 2.5 µm RH, relative humidity
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