 |
| Titel |
Atmospheric chemistry of carboxylic acids: microbial implication versus photochemistry |
| VerfasserIn |
M. Vaïtilingom, T. Charbouillot, L. Deguillaume, R. Maisonobe, M. Parazols, P. Amato, M. Sancelme, A.-M. Delort |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 16 ; Nr. 11, no. 16 (2011-08-25), S.8721-8733 |
| Datensatznummer |
250010031
|
| Publikation (Nr.) |
 copernicus.org/acp-11-8721-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
The objective of this work was to compare experimentally the contribution of
photochemistry vs. microbial activity to the degradation of carboxylic acids
present in cloud water. For this, we selected 17 strains representative of
the microflora existing in real clouds and worked on two distinct artificial
cloud media that reproduce marine and continental cloud chemical
composition. Photodegradation experiments with hydrogen peroxide
(H2O2) as a source of hydroxyl radicals were performed under the
same microcosm conditions using two irradiation systems. Biodegradation and
photodegradation rates of acetate, formate, oxalate and succinate were
measured on both media at 5 °C and 17 °C and were shown to be on the
same order of magnitude (around 10−10–10−11 M s−1). The
chemical composition (marine or continental origin) had little influence on
photodegradation and biodegradation rates while the temperature shift from
17 °C to 5 °C decreased biodegradation rates of a factor 2 to 5.
In order to test other photochemical scenarios, theoretical photodegradation
rates were calculated considering hydroxyl (OH) radical concentration values
in cloud water estimated by cloud chemistry modelling studies and available
reaction rate constants of carboxylic compounds with both hydroxyl and
nitrate radicals. Considering high OH concentration ([OH] = 1 × 10−12 M) led to no significant contribution of microbial activity in
the destruction of carboxylic acids. On the contrary, for lower OH
concentration (at noon, [OH] = 1 × 10−14 M), microorganisms could
efficiently compete with photochemistry and in similar contributions than
the ones estimated by our experimental approach.
Combining these two approaches (experimental and theoretical), our results
led to the following conclusions: oxalate was only photodegraded; the
photodegradation of formate was usually more efficient than its
biodegradation; the biodegradation of acetate and succinate seemed to exceed
their photodegradation. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|