Sources and sinks of nitrous oxide (N2O) in deep lakes

As reported from marine systems, we found that also in15 prealpine lakes N2O concentrations werestrongly correlated with O2 concentrations. Inoxic waters below the mixed surface layer, N2Oconcentrations usually increased with decreasingO2 concentrations. N2O is produced in oxicepilimnia, in oxic hypolimnia and at oxic-anoxicboundaries, either in the water or at the sediment-waterinterface. It is consumed, however, incompletely anoxic layers. Anoxic water layers weretherefore N2O undersaturated. All studied lakeswere sources for atmospheric N2O, including thosewith anoxic, N2O undersaturated hypolimnia.However, compared to agriculture, lakes seem not tocontribute significantly to atmospheric N2Oemissions.