Studies of the physico-chemical conditions of the sediment-water interface in Lokka and Porttipahta reservoirs

The physico-chemical conditions of the sediment-water interface in the Lokka and Porttipahta reservoirs in Northern Finland were investigated. Oxygen concentration was measured from sedimented matter and the bottom sediment with a minielectrode measurement technique. The consumption of O₂ was calculated by Fick's first law of diffusion across the sediment-water interface. Methane samples were sub-sampled from sediment cores and analysed with a gas Chromatograph equipped with FI-detector. The oxygen and methane concentrations correlated to the redox potentials. Methane concentration was high in organic rich sediments with low redox potential values. Oxygen coasumption was higher in Lokka.