Uptake of gas-phase ammonia. 2. Uptake by sulfuric acid surfaces
Aerosols play an important role in the atmospheric chemistry of both the stratosphere and the troposphere. Aerosols also affect the earth's climate by directly scattering radiation, and indirectly, by serving as cloud condensation nuclei (CCN). The number of cloud droplets formed is directly proportional to the number density of cloud condensation nuclei. The size, density and composition of these cloud droplets in turn determine the effect of clouds on the Earth's albedo. The uptake of gas-phase ammonia by sulfuric acid surfaces was measured as a function of temperature (248--288 K), gas-liquid interaction time (2--15 ms), and acid concentration (20--70 wt% H{sub 2}SO{sub 4}) using a droplet train apparatus. The uptake coefficient increases as a function of acid concentration and reaches unity at about 55 wt% H{sub 2}SO{sub 4}. The increased NH{sub 3} uptake in acid solution is apparently due to reaction between NH{sub 3} and H{sup +} at the gas-liquid interface. The results yielded parameters required to model the reaction of NH{sub 3} with H{sup +} at the gas-liquid interface. These uptake experiments were expanded to include a detailed study of gas transport to a moving train of droplets. An analysis of previous sulfuric acid aerosol neutralization experiments shows that the uptake of ammonia by ternary NH{sub 3}-H{sub 2}SO{sub 4}-H{sub 2}O solutions is significantly lower than that by fresh binary H{sub 2}SO{sub 4}-H{sub 2}O solutions. At typical tropospheric water and ammonia vapor concentrations, NH{sub 3} uptake coefficients need to be included in detailed microphysical models of sulfuric acid aerosols.
- Research Organization:
- Boston Coll., Chestnut Hill, MA (US)
- Sponsoring Organization:
- National Science Foundation; Environmental Protection Agency; US Department of Energy
- DOE Contract Number:
- FG02-91ER61208; FG02-94ER61854
- OSTI ID:
- 20003216
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 44 Vol. 103; ISSN JPCAFH
- Country of Publication:
- United States
- Language:
- English
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