The role of the SO2 oxidation for the background stratospheric sulfate layer in the light of new reaction rate data |
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Authors: | G K Moortgat C E Junge |
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Institution: | 1. Max-Planck-Institut für Chemie (Otto-Hahn-Institut), D-6500, Mainz, Germany
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Abstract: | Presently available data on the reaction of SO2 with OH radicals (OH + SO2 + \(M\xrightarrow{k_1 }]{}\) HSO3 +M) are critically reviewed in light of recent stratospheric sulfur budget calculations. These calculations impose that the net oxidation ratek of SO2 within the stratosphere should fall within the range 10?7≤k≤10?9, if the SO2 oxidation model for the stratospheric sulfate layer is assumed to be correct. The effective reaction rate constantk 1 * =k 1M] at the stratospheric temperature is estimated as $$k_1^* = \frac{{(8.2 \pm 2.2) \times 10^{ - 13} \times M]}}{{(0.79 \mp 0.34) \times 10^{ - 13} + M]}}cm^3 /molecules sec$$ where M] refers to the total number density (molecules/cm3). Using the above limiting values ofk 1 * , and the estimated OH density concentrations, the net oxidation rate is calculated as 3.6×10?7≤k≤1.3×10?8 at 17 km altitude. This indicates that the upper limit of thesek values exceeds the tolerable range imposed by the model by a factor of about four. Obviously the uncertainty of thek 1 * values and of the OH concentrations in the stratosphere is still too large to make definite conclusions on the validity of the SO2 model. |
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