Observation of Sulfate Compounds on Filter Substrates by Means of X-Ray Diffraction
- David R. Schryer
Published Online: 21 MAR 2013
Copyright 1982 by the American Geophysical Union.
Heterogeneous Atmospheric Chemistry
How to Cite
Davis, B. L., Johnson, L. R., Stevens, R. K., Gatz, D. F. and Stensland, G. J. (1982) Observation of Sulfate Compounds on Filter Substrates by Means of X-Ray Diffraction, in Heterogeneous Atmospheric Chemistry (ed D. R. Schryer), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM026p0149
- Published Online: 21 MAR 2013
- Published Print: 1 JAN 1982
Print ISBN: 9780875900513
Online ISBN: 9781118663813
- Atmospheric chemistry—Addresses, essays, lectures
Nearly 200 quantitative compound analyses of airborne particulates have been completed over the past several years using the reference intensity X-ray diffraction technique. This technique combined with direct beam transmission measurements provides quantitative evaluation of both crystalline and amorphous components. Some of the important features of these analyses include the dominance of the minerals calcite and quartz in particulates of the more arid regions of the United States, especially in the coarse (>2.5 μm diameter) particulate fraction, whereas clay minerals and several sulfate compounds dominate the fine fraction (<2.5 μm diameter), especially in midwestern and eastern urban areas. A number of simple and complex sulfate compounds have been observed by this means in the ambient particulate matter of major urban areas. These include mascagnite (NH4)2SO4, gypsum CaSO4·2H2, thenardite Na2SO4, and the “double salt” compounds (NH4)2Ca(SO4)2·H2O, (NH4)2Fe(SO4)2·6H2O, and (NH4)2Pb(SO4)2. Although evidence suggests that some sulfate compounds actually form as atmospheric reaction products, it is also possible that some sulfate compounds, especially CaSO4·2H2O, occur primarily as a reaction artifact on the filter substrate.