Effect of flow velocity on sediment oxygen demand: Experiments

Sedimentary oxygen demand (SOD) is the uptake of dissolved oxygen by sediments. The oxygen is removed from the water column by chemical oxidation and by the respiration of microbes in the sediments. In 1994, Nakamura and Stefan published a theory relating SOD to dow velocity using boundary layer concepts. This paper is an experimental validation and extension of those results. In this study, SOD is investigated in laboratory experiments in which sediments are exposed to water flowing at different velocities. The experiments were performed in a recirculating channel with well defined flow characteristics. The results verify that SOD increases linearly with the velocity of the water above the sediments when the velocities are low. As the velocity is increased, the SOD reaches an upper bound. Both the rate of increase with velocity as well as the upper bound of SOD were found to depend strongly on the sediment material, the benthic biology, and the temperature. Characterization of the highly variable benthic biology proved to be particularly difficult. SOD is approximated by linear and Michaelis-Menten type equations with velocity being the independent variable.