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| Titel |
Tropical small streams are a consistent source of methane |
| VerfasserIn |
Leena Vihermaa, Susan Waldron |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250076229
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| Zusammenfassung |
| To date only a few studies have quantified diffusive methane emissions from headwater
streams therefore the magnitude and seasonal variation of these emissions remain poorly
understood. Here we present results from two Western Amazonian small streams (first and
second order) in Tambopata National Reserve, Peru. Towards the end of wet season,
April-May 2012, the streams were sampled using a static floating chamber to accumulate
methane. Samples were drawn from the headspace twice daily over period of four days on
three separate occasions. The methane concentrations were analysed using a gas
chromatograph and the linear part of concentration increase used to calculate the flux
rates. The streams were consistently outgassing methane. The seasonally active
first order stream outgassed 6 ±2.4 nmol CH4-C m-2 s-1 and the second order
stream 20 ±4.0 nmol CH4-C m-2 s-1. The latter flux rate is comparable to fluxes
measured from seasonally flooded Amazonian forest in previous studies. The range
measured in our streams is comparable to previous results in temperate streams and the
lower end of fluxes observed in some peatland streams. The only other study on
Amazonian small streams detected methane fluxes that were 100 times greater than those
measured here. Depending on the density of small streams in Amazonian basin
and the prevalent flux rate, the fluvial methane fluxes may constitute a significant
global warming potential. Upscaling to the Amazon basin, assuming small stream
density of 0.2 %, as was found at our field site, and the flux rates detected, yields an
annual global warming potential equal to approximately 1.5 Mt of CO2 which is of
minor importance compared to aquatic CO2-C flux of 500 Mt yr-1 from the basin.
However, if the higher fluxes detected in the previous study were prevalent, the
basin wide methane flux could become significant. Further studies are needed to
establish the stream density in the Amazon basin and typical methane flux rates. |
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