Sulfate in the Atmospheric Boundary Layer: Concentration and Mechanisms of Formation
- David R. Schryer
Published Online: 21 MAR 2013
Copyright 1982 by the American Geophysical Union.
Heterogeneous Atmospheric Chemistry
How to Cite
Pueschel, R. F. and Barrett, E. W. (1982) Sulfate in the Atmospheric Boundary Layer: Concentration and Mechanisms of Formation, in Heterogeneous Atmospheric Chemistry (ed D. R. Schryer), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM026p0241
- Published Online: 21 MAR 2013
- Published Print: 1 JAN 1982
Print ISBN: 9780875900513
Online ISBN: 9781118663813
- Atmospheric chemistry—Addresses, essays, lectures
Data on particulate sulfur in a coalfired power plant plume and on its long-range transport are presented in relation to the total aerosol. The primary plume aerosol that could provide potential catalytic surfaces for sulfate generation is fly ash. Its surface area was determined in situ by Knollenberg optical particle counters. Surface features and the spatial distribution of elements in individual fly ash particles were determined by scanning electron microscopy and X-ray energy dispersive analysis of airborne samples.
The results provide evidence of a selective accumulation of sulfate on the surface on some fly ash particles. The amount of sulfate thus formed, however, is only about 2 percent of the total mass. Hence, fly ash has little catalytic effect on the heterogeneous conversion of SO2 to SO4= above currently accepted rates of 1 percent per hour. Homogeneous nucleation at low rates appears to be equally important for the generation of small sulfate particles that are subject to long-range transport. This finding was confirmed by measurements in east-central Utah, a region of the contiguous U.S. that historically is characterized by excellent atmospheric clarity. Although the total particle mass of the background aerosol in Utah is 2 orders of magnitude less than in the Four Corners area, the small-particle mode is dominated by silicon and sulfur. The spherical shape of these silicon- and sulfur-containing particles indicates that a phase transition was involved in the mechanism of their formation. The increase in sulfur aerosols with height suggests their advection from remote sources. It appears that silicon is as good a tracer for a primary combustion aerosol as is sulfur for a secondary aerosol.