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| Titel |
N2O concentrations in boreal lakes are linked to nitrate and temperature |
| VerfasserIn |
Pirkko Kortelainen, Miitta Rantakari, Jukka Alm, Tuula Larmola, Sari Juutinen, Irina Bergström, Jari T. Huttunen, Jouko Silvola, Pertti J. Martikainen |
| 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 |
250078135
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| Zusammenfassung |
| While regional and global estimates for carbon dioxide (CO2) and methane (CH4) emission
from lakes are presently available, nitrous oxide (N2O) evasion from lakes and streams and
the primary drivers regulating the fluxes have remained poorly studied. Freshwater N2O data
are scarce and mostly based on short term measurements from a few lakes/rivers. The largest
N2O data was collected by Whitfield et al. (2011) focusing on 121 small, polymictic
headwater lakes in Ireland in spring 2008.
We gathered the so-far largest seasonal/annual N2O data from boreal lakes. A
subpopulation of 112 lakes from the boreal zone in Finland (from 60oN to 69oN) was
randomly selected from the Nordic Lake Survey (NLS) data base. Water chemistry,
catchment land use, climatic drivers and variables linked to catchment topography (e.g. max
depth of the lake) were determined for each lake. The lakes were sampled four times per year
(before and after ice melt, at the end of a summer stratification and during a fall overturn)
from four depths (1 m from the surface, middle of the lake, 1 m from the sediment and 20 cm
from the sediment) at the deepest point of the lake for N2O concentrations and physical and
chemical characteristics. Finnish lakes are predominantly dimictic and the average length of
the ice cover period ranges from about 5 months in the south to over 7 months in the
north.
The variability in N2O concentrations in the lake population was large in each season and
depth. Although highest N2O concentrations were often found in bottom water samples, N2O
and oxygen were poorly linked to each other (weak correlation only in winter samples).
This is in contrast to CO2 concentrations in the study lakes, which were strongly
linked to oxygen concentrations (r2= 0.79, n = 2740, p < 0.0001; Kortelainen et al.
2006).
In contrast, nitrate and temperature were strong predictors for N2O concentrations in our
data despite the large variability in lake area (from 0.04 to 63 km2), maximum depth (from 2
m to 84 m), latitude (from 60oC to 69oC) and land use, which represents typical patterns
in the boreal zone: lakes are predominantly surrounded by forests and peatlands
with a lower proportion of agricultural land. Our N2O data from randomly selected
lakes can be used to estimate the role of freshwater ecosystems to landscape N2O
emission in boreal zone and the most important drivers contributing to freshwater N2O
concentrations.
References
Kortelainen, P., Rantakari, M., Huttunen, J.T., Mattsson, T., Alm, J., Juutinen, S.,
Larmola, T., Silvola, J. & Martikainen, P.J. 2006. Sediment respiration and lake trophic state
are important predictors of large CO2 evasion from small boreal lakes. Global Change
Biology 12, 1554-1567.
Whitfield, C.J., Aherne, J. & Baulch, H.M. 2011. Controls on greenhouse gas
concentrations in polymictic headwater lakes in Ireland. Science of the Total Environment
410-411: 217-225.
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