the Expedition ARKTIS-XIX/4 of the research vessel POLARSTERN ...

Fig. 6.4-2: Methane
emission measurement
site 2, at Duck Lake
(see Tab. 6.4-3).
In general, the dry conditions in northeastern Greenland characterize the soil and
vegetation. The landscape of the investigated areas is dominated by polar desert
soils. The vegetation cover is scarce, leading to a low content of humus in a thin
upper layer of the soil. However, along streams and near the lakes there were also
areas with water saturated soils and a better-developed vegetation cover. The
analyses carried out later in the laboratory will indicate, if these conditions are
suitable for some methane producing microorganisms.
Lakes:
The amount of methane emission from aquatic ecosystems is the result of microbial
production and consumption by oxidation. Microbial production of methane is one of
the major pathways of degradation of organic matter in the anaerobic sediment
horizons. The produced methane can be oxidised in the upper, oxygen rich surface
sediments or in the water column.
The measurement of methane emissions from the sediment and water column was
performed at Melles, Duck and Fox Lake near the shore (c. 10 to 15 m distance) at
sites relatively close to the sites, where the soil investigations were carried out at the
lake shores. The system used for measuring the gas emission of the lakes was the
same which was used for the soil (Fig. 6.4-1). The chamber was placed directly on
the water surface. It was kept horizontally floating by eight floating bodies, sinking
about 6 cm into the water. The minimum time to collect the emitted gas at each spot
was half an hour.
In addition to the measurements of the methane emissions from the lakes, also the
methane concentrations in the water columns and the sediments were examined. For
a better understanding of the variables that potentially affect the methane emission
from a lake, the water depth, sediment and water temperature, pH-value was
67