Artikkelit kirjoittajalta Hannu Nykänen

Jari Huttunen, Hannu Nykänen, Jukka Turunen, Olli Nenonen, Pertti Martikainen. Typpioksiduulivirrat suunnitellun Vuotoksen tekojärven alueen soilta.
English title: Fluxes of nitrous oxide on natural peatlands in Vuotos, an area projected for a hydroelectric reservoir in northern Finland.
Avainsanat: global change; Northern boreal peatlands; climate warming; flooding; greenhouse gas emission; hydro dam
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Nitrous oxide (N2O) fluxes were measured on ten natural minerotrophic peatlands in an area planned for a hydroelectric reservoir (Vuotos) in northern Finland. The mean N2O fluxes from the sites with mean water tables from –25 to 3.4 cm (negative below the peat surface) ranged from –30 to 230 µg m–2 d–1 during summer 1994. At the driest site, the herb-grass spruce mire with the mean water table at –38 cm, the mean summertime N2O emission was 940 µg m-2 d-1 in 1994, attributable to the increased N2O release at low peat temperatures in autumn. A similar increase in the N2O emissions was not found in 1995, as the measurements were finished before the peat started to freeze. The mean N2O fluxes at the sites correlated negatively with the mean water table levels. The peatlands in the northern boreal zone are unlikely important sources of atmospheric N2O in their natural state. The planned reservoir would barely have large long-term N2O emissions from the pelagic zone, but the importance of temporally flooded areas in the postflood N2O release is uncertain similar to the short-term emissions following the flooding.
  • Huttunen, Research and Development Unit of Environmental Health, Department of Environmental Sciences, Bioteknia 2, University of Kuopio, PO Box 1627, FIN-70211 Kuopio, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Nykänen, Sähköposti: ei.tietoa@nn.oo
  • Turunen, Sähköposti: ei.tietoa@nn.oo
  • Nenonen, Sähköposti: ei.tietoa@nn.oo
  • Martikainen, Sähköposti: ei.tietoa@nn.oo
Jouko Silvola, Pertti Martikainen, Hannu Nykänen. A mobile automatic gas chromatograph system to measure C02, CH4 and N2O fluxes from soil in the field.
Avainsanat: peatland; Carbon dioxide; methane; Automated measuring; nitrous oxide
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A caravan has been converted into a mobile laboratory for measuring fluxes of C02, CH4 and N2O from the soil in the field. The caravan is equipped with a gas chromatograph fitted with TC-, FI- and EC-detectors, and a PC controlled data logger. The gas collecting chambers can be used up to 50 m from the caravan. The closing and opening of the chambers, as well as the flows of sample gases from chambers to the gas chromatograph, is pneumatically regulated. Simultaneous recordings of temperature, light intensity and the depth of water table are made. The system has been used for two months in 1992, and some preliminary results are presented. Keywords: Automated measuring, carbon dioxide, methane, nitrous oxide, peatland
  • Silvola, Department of Biology, University of Joensuu, P.O. Box III, FIN-80I0I Joensuu, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Martikainen, Sähköposti: ei.tietoa@nn.oo
  • Nykänen, Sähköposti: ei.tietoa@nn.oo
Pertti J. Martikainen, Hannu Nykänen, Patrick Crill, Jouko Silvola. The effect of changing water table on methane fluxes at two Finnish mire sites.
Avainsanat: peat soil; Drainage; nutrient status; methane flux; methane oxidation
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Methane fluxes were measured using a static chamber technique on a minerotrophic fen and an ombrotrophic peat bog site located on the Lak-kasuo mire complex in central Finland. Both sites consisted of a virgin area and an area drained in 1961 by ditching. The measurements in 1991 were made biweekly from spring thaw to winter freezing. During this period, the mean CH4 emission from the virgin minerotrophic site and virgin ombrotrophic site was 98 mg m-2 d-1 and 40 mg m-2 d-1 , respectively. The mean emission of CH4 from the drained ombrotrophic site was 18 mg m-2 d-1. The drained minerotrophic site consumed methane during most of the measuring period, the average uptake was 0.13 mg m-2 d-1. Draining had lowered the average water table by 4 cm at the ombrotrophic site and by 20 cm at minerotrophic site. The possible reasons for the different development of the water table and methane fluxes at ombrotrophic and minerotrophic sites after draining are discussed. Keywords: Drainage, methane flux, methane oxidation, nutrient status, peat soil
  • Martikainen, Department of Environmental Microbiology, National Public Health Institute, P.O. Box 95, FIN-70701 Kuopio, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Nykänen, Sähköposti: ei.tietoa@nn.oo
  • Crill, Sähköposti: ei.tietoa@nn.oo
  • Silvola, Sähköposti: ei.tietoa@nn.oo
Tormod Lien, Pertti Martikainen, Hannu Nykänen, Lars Bakken. Methane oxidation and methane fluxes in two drained peat soils.
Avainsanat: bog; fen; temperature; water level
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Methane production and consumption in drained minerotrophic and ombrotrophic peat was investigated using a combination of field measurement and laboratory incubations. In the field, methane fluxes were measured at intervals over a seven (minerotrophic) and ten (ombrotrophic) month period together with measurements of methane concentrations and temperature at various depths. In the laboratory, aerobic incubations of drained peat samples from various depths were conducted over a range of temperatures to determine rates of potential methane oxidation. The maximum potential methane oxidation rate occurred at a depth close to that of the water table. The oxidation rate was much higher in the ombrotrophic peat than in the minerotrophic peat. However, field measured methane fluxes were lower in the minerotrophic peat. This is attributed to a relatively low water table. Methane oxidation increased over the temperature range 2 to 30°C and decreased at temperatures >34°C. Methane production in the aerobic incubation experiment was measured by inhibition of methane oxidation with dimethyl ether. Production rates were only 1-7% of net oxidation rates. Thus, the measured net rates of methane absorption in aerobic incubations largely reflect gross oxidation rates. Keywords: Bog, fen, temperature, water level
  • Lien, Department of Biotechnological Sciences, Agricultural University of Norway, P.O. Box 5040, N-I432 Aas, Norway Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Martikainen, Sähköposti: ei.tietoa@nn.oo
  • Nykänen, Sähköposti: ei.tietoa@nn.oo
  • Bakken, Sähköposti: ei.tietoa@nn.oo

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