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| Titel |
Methane dynamics in different boreal lake types |
| VerfasserIn |
S. Juutinen, M. Rantakari, P. Kortelainen, J. T. Huttunen, T. Larmola, J. Alm, J. Silvola, P. J. Martikainen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 6, no. 2 ; Nr. 6, no. 2 (2009-02-16), S.209-223 |
| Datensatznummer |
250003431
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| Publikation (Nr.) |
 copernicus.org/bg-6-209-2009.pdf |
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| Zusammenfassung |
| This study explores the variability in concentrations of dissolved CH4
and annual flux estimates in the pelagic zone in a statistically defined
sample of 207 lakes in Finland. The lakes were situated in the boreal zone,
in an area where the mean annual air temperature ranges from −2.8 to 5.9°C.
We examined how lake CH4 dynamics related to regional lake types
assessed according to the EU water framework directive. Ten lake types were
defined on the basis of water chemistry, color, and size. Lakes were sampled
for dissolved CH4 concentrations four times per year, at four different
depths at the deepest point of each lake. We found that CH4
concentrations and fluxes to the atmosphere tended to be high in nutrient
rich calcareous lakes, and that the shallow lakes had the greatest surface
water concentrations. Methane concentration in the hypolimnion was related
to oxygen and nutrient concentrations, and to lake depth or lake area. The
surface water CH4 concentration was related to the depth or area of
lake. Methane concentration close to the bottom can be viewed as proxy of
lake status in terms of frequency of anoxia and nutrient levels. The mean
pelagic CH4 release from randomly selected lakes was 49 mmol m−2 a−1. The sum CH4 flux (storage and diffusion) correlated
with lake depth, area and nutrient content, and CH4 release was
greatest from the shallow nutrient rich and humic lakes. Our results support
earlier lake studies regarding the regulating factors and also the magnitude
of global emission estimate. These results propose that in boreal region
small lakes have higher CH4 fluxes per unit area than larger lakes, and
that the small lakes have a disproportionate significance regarding to the
CH4 release. |
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