AbstractThe oxygen demand of the fine sediments behind the hydroelectric dam at Altenwörth, on the Austrian Danube, was investigated using a simple Biological Oxygen Demand (BOD) method. The demand was fractionated into biological and chemical uptake and the variation with depth was studied. Chemical uptake was fast, being 90% complete within 15 minutes. Biological uptake was slower and fairly constant for some hours. The kinetics was examined and the chemical uptake found to correspond quite well with a first order rate equation