Atmospheric Chemistry and Physics Discussions
www.atmos-chem-phys-discuss.net
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4
2
2004
10.5194/acpd-4-1311-2004
http://www.atmos-chem-phys-discuss.net/4/1311/2004/
http://www.atmos-chem-phys-discuss.net/4/1311/2004/acpd-4-1311-2004.html
http://www.atmos-chem-phys-discuss.net/4/1311/2004/acpd-4-1311-2004.pdf
1311
1337
2004-03-02
Uptake study of ClONO<sub>2</sub> and BrONO<sub>2</sub> by water droplets
G. Deiber
Ch. George
S. Le Calvé
F. Schweitzer
Ph. Mirabel
Centre de Géochimie de la Surface/UMR 7517, CNRS and Université Louis Pasteur, 1 rue Blessig, F-67084 Strasbourg, France
Laboratoire d’Application de la Chimie à l’Environnement (LACE), 43 boulevard du 11 Novembre 1918, F-69622 Villeurbanne, France
The uptake kinetics of gaseous ClONO<sub>2</sub> and BrONO<sub>2</sub> on aqueous
surfaces were measured, using the droplet train technique coupled to a mass
spectrometer, as a function of temperature and liquid composition (pure
water and NaCl or NaBr containing solutions). The uptake kinetics are driven
by the reactivity of these gases and, for both compounds, the uptake rates
on pure water or on NaCl solutions (0.1 M) are comparable. The uptake
coefficient γ of ClONO<sub>2</sub> does not depend on the temperature
while that of BrONO<sub>2</sub> increases slightly when the temperature is raised
from 272 to 280 K. For ClONO<sub>2</sub> and BrONO<sub>2</sub>, the uptake rates
increase on NaBr-doped droplets, enabling the estimation of the mass
accommodation coefficient α. The corresponding values for α
are 0.108±0.001 for ClONO<sub>2</sub> and 0.063±0.009 for
BrONO<sub>2</sub>.
<br><br>
The reactions of ClONO<sub>2</sub> and BrONO<sub>2</sub> on NaCl solutions lead,
respectively to the formation of Cl<sub>2</sub> and BrCl. The uptake of
ClONO<sub>2</sub> on NaBr solutions generates BrCl as primary product, which in
turn can react with NaBr to produce Br<sub>2</sub>. As expected, the only product
of BrONO<sub>2</sub> reaction on NaBr solution is Br<sub>2</sub>.