 |
| Titel |
Eddy covariance flux measurements confirm extreme CH4 emissions from a Swiss hydropower reservoir and resolve their short-term variability |
| VerfasserIn |
W. Eugster, T. DelSontro, S. Sobek |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 8, no. 9 ; Nr. 8, no. 9 (2011-09-29), S.2815-2831 |
| Datensatznummer |
250006138
|
| Publikation (Nr.) |
 copernicus.org/bg-8-2815-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
| Greenhouse gas budgets quantified via land-surface eddy covariance (EC) flux
sites differ significantly from those obtained via inverse modeling. A
possible reason for the discrepancy between methods may be our gap in
quantitative knowledge of methane (CH4) fluxes. In this study we carried
out EC flux measurements during two intensive campaigns in summer 2008 to
quantify methane flux from a hydropower reservoir and link its temporal
variability to environmental driving forces: water temperature and pressure
changes (atmospheric and due to changes in lake level). Methane fluxes were
extremely high and highly variable, but consistently showed gas efflux from
the lake when the wind was approaching the EC sensors across the open water,
as confirmed by floating chamber flux measurements. The average flux was
3.8 ± 0.4 μg C m−2 s−1 (mean ± SE) with a
median of 1.4 μg C m−2 s−1, which is quite high even
compared to tropical reservoirs. Floating chamber fluxes from four selected
days confirmed such high fluxes with
7.4 ± 1.3 μg C m−2 s−1. Fluxes increased
exponentially with increasing temperatures, but were decreasing exponentially
with increasing atmospheric and/or lake level pressure. A multiple regression
using lake surface temperatures (0.1 m depth), temperature at depth (10 m
deep in front of the dam), atmospheric pressure, and lake level was able to
explain 35.4% of the overall variance. This best fit included each
variable averaged over a 9-h moving window, plus the respective short-term
residuals thereof. We estimate that an annual average of 3% of the
particulate organic matter (POM) input via the river is sufficient to sustain
these large CH4 fluxes. To compensate the global warming potential
associated with the CH4 effluxes from this hydropower reservoir a 1.3 to
3.7 times larger terrestrial area with net carbon dioxide uptake is needed if
a European-scale compilation of grasslands, croplands and forests is taken as
reference. This indicates the potential relevance of temperate reservoirs and
lakes in local and regional greenhouse gas budgets. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|