NTRS - NASA Technical Reports Server

Back to Results
Black Carbon (Soot) Aerosol in the Lower Stratosphere and Upper TroposphereWe have used two approaches to measure BCA in the stratosphere. The first method consists of collecting aerosols by impaction on quartz rods, upon which are mounted strips of polystyrene filter material. Each 25 mm by 0.5 mm filter strip is alternately masked and exposed in 5 mm long sections. After sampling, the optical density of the exposed sections is measured and compared with the optical density of the masked (unexposed) sections. The filter strip is a Lambertian collector, the scattering property of which is not affected by the deposition of liquid sulfuric acid droplets which dominate the stratospheric aerosol. Hence, all attenuation greater in the exposed than in the non-exposed sections is due to absorption by BCA or rare opaque materials such as meteoritic iron. In a second approach we expose carbon-coated gold or palladium wires to air outside the aircraft boundary layer [Farlow et al., 1979; Pueschel et al., 1989]. With a field emission scanning electron microscope we are able to characterize BCA particles in addition to the dominant sulfuric acid droplets. Typically, soot is comprised of 20 nm diameter spheres linked together as branching chains or loosely packed aggregates (Figure 1a). The microscope has a lateral image resolution of 1.5 nm and can clearly resolve individual spheres making up BCA aggregates. Their morphology is uniquely different from that of the liquid sulfuric acid-water aerosol (Figure 1b). We approximate the size of each BCA particle by that of a sphere of equivalent volume and fit a lognormal size distribution to both the BCA and H2SO4/H2O aerosols. Both sampler types have been mounted on NASA's ER-2 high-altitude research aircraft (altitude ceiling of 70,000 feet), and on NASA's DC-8 (40,000 feet ceiling) aircraft to sample aerosols from a significant portion of the atmosphere.
Document ID
Document Type
Reprint (Version printed in journal)
Pueschel, R. F.
Black, D. F.
Snetsinger, K. G.
Hansen, A. D. A.
Verna, S.
Kato, K.
Date Acquired
August 19, 2013
Publication Date
October 23, 1992
Publication Information
Publication: Geophysical Research Letters
Volume: 19
Issue: 20
ISSN: 0094-8534
Subject Category
Report/Patent Number
Paper 92GL02478
Distribution Limits

Available Downloads

There are no available downloads for this record.
No Preview Available