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| Titel |
Comparison of labeled tracer methods to measure methane oxidation rates in the water column |
| VerfasserIn |
Susan Mau, Monica Heintz, Jan Blees |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034272
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| Zusammenfassung |
| The ocean is generally considered a minor source of methane (CH4) to the atmosphere.
Macro-seepage from geological sources at the seafloor is suggested to contribute the most
from all of the oceanic sources, about 25 Tg CH4/yr to the atmospheric CH4 budget (4% of
total sources), whereas the open ocean contributes only 0.4 Tg CH4/yr (0.07% of total
sources). However, most source estimates lack certainty due to a limited knowledge of the
fate of CH4 in the water column. CH4 in the water column is mainly influenced by turbulent
mixing, a process that spreads and dilutes CH4, and microbial oxidation, the only
process that limits the fraction of CH4 in the water column and thus the fraction of
CH4 escaping into the atmosphere. Unfortunately, measurements of the rate of
microbial oxidation are still rare. Only a few attempts have been made to quantify CH4
oxidation in the water column. CH4 oxidation rates were either measured indirectly by
correlation with tracers such as 3He, 222Rn, CFC11 or directly by using 14CH4 or
C3H4-labeling/incubation techniques. A comparison of the two labeling/incubation
techniques will be presented. The ease of use, time series experiments, kinetic experiments,
and the effect of incubation temperature will be discussed and water column profiles
compared. Our results indicate similar depth-profiles of turnover times using the two
different labeled tracers. However, the data sets are offset. More rapid turnover times
were measured using C3H4 and slower turnover of CH4 was found using 14CH4. |
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