SOURCES AND SINKS OF NITROUS-OXIDE (N2O) IN DEEP LAKES

As reported from marine systems, we found that also in 15 prealpine la kes N2O concentrations were strongly correlated with O-2 concentration s. In oxic waters below the mixed surface layer, N2O concentrations us ually increased with decreasing O-2 concentrations. N2O is produced in oxic epilimnia, in oxic hypolimnia and at oxic-anoxic boundaries, eit her in the water or at the sediment-water interface. It is consumed, h owever, in completely anoxic layers. Anoxic water layers were therefor e N2O undersaturated. All studied lakes were sources for atmospheric N 2O, including those with anoxic, N2O undersaturated hypolimnia. Howeve r, compared to agriculture, lakes seem not to contribute significantly to atmospheric N2O emissions.