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Investigation of the photolysis reactions of nitrate, hydrogen peroxide, and formaldehyde in artificial snow

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Jacobi, H. W. , Annor, T. and Quansah, E. (2004): Investigation of the photolysis reactions of nitrate, hydrogen peroxide, and formaldehyde in artificial snow , 8th International Global Atmospheric Chemistry Conference, 4-9 Sept., Christchurch, New Zealand. .
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Abstract:

Photochemical reactions in snow are important processes generating or consuming reactive trace compounds in natural snow covers. Therefore, we performed laboratory studies to investigate photochemical reactions in snow. For these experiments we used artificial snow made from purified water containing only traces of one or two compounds. Samples of the snow were irradiated for extended periods with intense UV and visible light and remaining concentrations of the trace compounds were determined after each experiment. We performed series of experiments under identical conditions to compare the photochemical reactions of nitrate (NO3-), hydrogen peroxide (H2O2), and formaldehyde (HCHO) in snow. In all cases, we found that the impurities were effectively decomposed during the experiments. Since the decay followed first-order reaction rates we concluded that the direct photolysis of the compounds were responsible for the decomposition. For our experimental conditions, we obtained comparable photolysis rates for NO3- and H2O2 and a significantly smaller rate for HCHO. In the case of NO3-, only a small fraction of the decomposed NO3- was converted into nitrite (NO2-), which remained in the snow. Further experiments with formate (HCOO-) added, which acts as an efficient sink for hydroxy radical (OH), were performed to examine the importance of the OH production channel in of the photolysis reactions. The results of these experiments will be presented.

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