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| Titel |
Study of the heterogeneous reaction of O3 with CH3SCH3 using the wetted-wall flowtube technique |
| VerfasserIn |
M. Barcellos da Rosa, W. Behnke, C. Zetzsch |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 3, no. 5 ; Nr. 3, no. 5 (2003-10-10), S.1665-1673 |
| Datensatznummer |
250001269
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| Publikation (Nr.) |
 copernicus.org/acp-3-1665-2003.pdf |
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| Zusammenfassung |
| This work presents the heterogeneous kinetics of the reaction of
CH3SCH3 (dimethyl sulphide, DMS) with O3 (ozone) in aqueous solutions of different ionic strengths (0, 0.1
and 1.0M NaCl) using the wetted-wall flowtube (WWFT) technique. Henry's law
coefficients of DMS on pure water and on different concentrations of NaCl (0.1M
- 4.0M) in the WWFT from UV spectrophotometric measurements of DMS in the gas
phase, using a numerical transport model of phase exchange, were determined to be H
±s (M
atm-1) = 2.16±0.5 at
274.4 K, 1.47±0.3 at
283.4 K, 0.72±0.2 at
291 K, 0.57±0.1
at 303.4 K and 0.33±0.1 at 313.4 K on water, on 1.0M NaCl to be H = 1.57±0.4 at
275.7 K, 0.8±0.2 at 291 K and on 4.0M NaCl to be H = 0.44±0.1 at 275.7 K and
0.16±0.04 at 291 K, showing a significant effect of ionic strength, m, on the solubility of
DMS according to the equation ln (H/M atm-1) = 4061 T-1 - 0.052
m2 - 50.9
m
T-1
- 14.0. At concentrations of DMS(liq) above 50
mM, UV spectrophotometry of both
O3(gas) and DMS(gas) enables us to observe simultaneously the reactive uptake of
O3 on DMS solution and the gas-liquid equilibration of DMS along the WWFT. The uptake
coefficient, g
(gamma), of O3 on aqueous solutions of DMS, varying between 1 and
15·10-6, showed a square root-dependence on the aqueous DMS concentration (as expected
for diffusive penetration into the surface film, where the reaction takes place in
aqueous solution). The uptake coefficient was smaller on NaCl solution in accord with the lower
solubility of O3. The heterogeneous reaction of O3(gas) with
DMS(liq) was evaluated from the observations of the second order rate constant
(kII) for the homogeneous aqueous reaction O3(liq) +
DMS(liq) using a numerical model of radial diffusion and reactive
penetration, leading to kII ±
D
kII
(in units of 108 M-1
s-1) =
4.1±1.2 at
291.0 K, 2.15±0.65
at 283.4 K and 1.8±0.5 at 274.4 K. Aside from the expected influence on solubility and
aqueous-phase diffusion coefficient of both gases there was no significant effect of
ionic strength on kII, that was determined for 0.1M NaCl, leading to
kII ± D
kII
(108
M-1
s-1)
= 3.2±1.0 at 288 K, 1.7±0.5 at 282 K and 1.3±0.4 at 276 K, and for 1.0M NaCl, leading to
3.2±1.0 at 288 K, 1.3±0.4 at 282 K and 1.2±0.4 at 276 K, where the error limits are
estimated from the output of the model calculations, taking the variability of individual
runs at various DMS levels into account. |
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