EFFECT OF FLOW VELOCITY ON SEDIMENT OXYGEN-DEMAND - EXPERIMENTS

Sedimentary oxygen demand (SOD) is the uptake of dissolved oxygen by s ediments. The oxygen is removed from the water column by chemical oxid ation and by the respiration of microbes in the sediments. In 1994, Na kamura and Stefan published a theory relating SOD to dow velocity usin g boundary layer concepts. This paper is an experimental validation an d extension of those results. In this study, SOD is investigated in la boratory experiments in which sediments are exposed to water flowing a t different velocities. The experiments were performed in a recirculat ing 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, t he 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 th e sediment material, the benthic biology, and the temperature. Charact erization of the highly variable benthic biology proved to be particul arly difficult. SOD is approximated by linear and Michaelis-Menten typ e equations with velocity being the independent variable.