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| Titel |
Yields of hydrogen peroxide from the reaction of hydroxyl radical with organic compounds in solution and ice |
| VerfasserIn |
T. Hullar, C. Anastasio |
| 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 ; 11, no. 14 ; Nr. 11, no. 14 (2011-07-22), S.7209-7222 |
| Datensatznummer |
250009941
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| Publikation (Nr.) |
 copernicus.org/acp-11-7209-2011.pdf |
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| Zusammenfassung |
| Hydrogen peroxide (HOOH) is a significant oxidant in atmospheric condensed
phases (e.g., cloud and fog drops, aqueous particles, and snow) that also
photolyzes to form hydroxyl radical (•OH). •OH can react with organics in
aqueous phases to form organic peroxyl radicals and ultimately reform HOOH,
but the efficiency of this process in atmospheric aqueous phases, as well as
snow and ice, is not well understood. We investigate HOOH formation from •OH
attack on 10 environmentally relevant organic compounds: formaldehyde,
formate, glycine, phenylalanine, benzoic acid, octanol, octanal, octanoic
acid, octanedioic acid, and 2-butoxyethanol. Liquid and ice samples with and
without nitrate (as an •OH source) were illuminated using simulated solar
light, and HOOH formation rates were measured as a function of pH and
temperature. For most compounds, the formation rate of HOOH without nitrate
was the same as the background formation rate in blank water (i.e.,
illumination of the organic species does not produce HOOH directly), while
formation rates with nitrate were greater than the water control (i.e.,
reaction of •OH with the organic species forms HOOH). Yields of HOOH, defined
as the rate of HOOH production divided by the rate of •OH production, ranged
from essentially zero (glycine) to 0.24 (octanal), with an average of 0.12 ± 0.05 (95 % CI). HOOH production rates and yields were higher at
lower pH values. There was no temperature dependence of the HOOH yield for
formaldehyde or octanedioic acid between −5 to 20 °C and ice samples had
approximately the same HOOH yield as the aqueous solutions. In contrast,
HOOH yields in formate solutions were higher at 5 and 10 °C compared to
−5 and 20 °C. Yields of HOOH in ice for solutions containing nitrate and
either phenylalanine, benzoate, octanal, or octanoic acid were
indistinguishable from zero. Our HOOH yields were approximately half those
found in previous studies conducted using γ-radiolysis, but this
difference might be due to the much lower (and more environmentally
relevant) •OH formation rates in our experiments. |
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