Effects of Hydrodynamic Conditions on Sediment Oxygen Demand: Experimental Study Based on Three Methods

The quantitative effects of hydrodynamic conditions on sediment oxygen demand (SOD) under smooth surface conditions were investigated using the following three practical and compact experimental systems: (1) a continuous flow system containing sediment core samples; (2) a rectangular flume system; and (3) a system combining the first two. Experimental results demonstrated that SOD showed a monotonically increasing tendency as the flow velocity increased with reduction of the thickness of the diffusive boundary layer. The experimental results were compared with numerical models theoretically relating SOD and flow velocity under smooth surface conditions. The features of each experimental system are discussed. The continuous flow system is advantageous because it simultaneously produces a steady state and different dissolved oxygen (DO) conditions. The rectangular flume system is suitable for fundamental studies of hydrodynamic effects on SOD because it makes controlling hydrodynamic conditions easy, while the combined system is appropriate for studying the effect of microscopic phenomena on exchange rates, as it can reproduce natural microscopic physicochemical processes.