Accession Number:

ADA522779

Title:

Molecular Beams Studies of Gas Transport and Reactions at the Surface of Surfactant-Coated Sulfuric Acid

Descriptive Note:

Final rept. 1 Feb 2007-30 Nov 2009

Corporate Author:

WISCONSIN UNIV-MADISON BOARD OF REGENTS/RESEARCH SPONSORED PROGRAMS

Report Date:

2009-11-01

Pagination or Media Count:

8.0

Abstract:

Sulfuric acid particles in the atmosphere are tiny chemical reactors that convert benign gases such as HCl and HBr into Cl2, ClBr, and Br2, which catalytically destroy ozone. These aerosol droplets may also contain organic molecules emanating from the ocean and land, which may and coat the surface of the aerosol particles. Gas-liquid scattering experiments show that these surfactant coatings can suppress ozone destruction by inhibiting the uptake of HCl into the acid droplets if the organic molecules pack tightly enough at the surface to impede gas transport. Remarkably, the scattering experiments indicate that these organic molecules more often enhance gas uptake because they do not pack tightly but contain functional groups that act as interfacial dissociation sites for HCl and HBr. Short-chain alcohols such as butanol always enhance HCl uptake because HCl and HBr protonate ROH groups, forcing the halide and hydrogen ions into the acid. Pentanoic acid also enhances uptake because HCl can protonate the -COOH group, but butyl and hexyl amine always suppress HCl uptake because the -NH2 group is already protonated by the acid. These studies provide a rich picture of the surface organic chemistry of sulfuric acid and how it controls the uptake of ozone-destroying gases.

Subject Categories:

  • Atmospheric Physics
  • Organic Chemistry
  • Test Facilities, Equipment and Methods
  • Atomic and Molecular Physics and Spectroscopy
  • Ecology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE