Kinetics of Reactions Between Free Radicals and Surfaces (Aerosols) Applicable to Atmospheric Chemistry

  1. David R. Schryer
  1. Daryl D. Jech,
  2. Patrick G. Easley and
  3. Barbara B. Krieger

Published Online: 21 MAR 2013

DOI: 10.1029/GM026p0107

Heterogeneous Atmospheric Chemistry

Heterogeneous Atmospheric Chemistry

How to Cite

Jech, D. D., Easley, P. G. and Krieger, B. B. (1982) Kinetics of Reactions Between Free Radicals and Surfaces (Aerosols) Applicable to Atmospheric Chemistry, in Heterogeneous Atmospheric Chemistry (ed D. R. Schryer), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM026p0107

Author Information

  1. Department of Chemical Engineering, University of Washington, Seattle, Washington 98195

Publication History

  1. Published Online: 21 MAR 2013
  2. Published Print: 1 JAN 1982

ISBN Information

Print ISBN: 9780875900513

Online ISBN: 9781118663813

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Keywords:

  • Atmospheric chemistry—Addresses, essays, lectures

Summary

The reactions between free radicals of atmospheric interest and solid surfaces were experimentally investigated using a fast-flow tubular reactor. The pure surfaces were in the form of dried aerosols and coatings. The OH radical was detected by UV resonance fluorescence. At room temperature, the scavenging rate ranged from 0.01 to 0.40 of the kinetic collision frequency. Oxygen and hydrogen atoms were reacted with actual aerosols and were detected using chemiluminescence. Rates for these atoms and HO2 were generally much slower than for OH unless the atoms reacted with the surface to form volatile products. When this occurred (e.g., O+NH4Cl), the fraction of collisions resulting in loss of the atom was nearly 1.0.

The chosen surfaces were: (1) “natural” aerosols (NH4N03, (NH4)2S04, NH4C1, Na2S04, NAN03), (2) “ma-made” surfaces typical of fly ash and auto emissions composition (FeS04-Fe0x, Zn(N03)2, Pb(N03)2, K2C03) , and (3) organic surfaces (malonic acid, glycine, sodium propionate). for OH, the second group of surfaces was somewhat more reactive than the other two; however, exceptions occurred (e.g., malonic acid).

The data were compared to results of other researchers engaged in modeling atmospheric chemistry. The present results support the concept that heterogeneous reactions of certain free radicals have rates that are composition-dependent and should be included in models of the local urban troposphere (near a specific source). for models over a larger area, it is felt that unreactive aerosols will “dilute” reactive aerosols so that heterogeneous losses of free radicals will be less important.