Experimental Investigation On Dynamic Contaminant Release From Permeable Sediment Layer Under Oscillating Flow

The dynamic contaminant release properties for the permeable sediment layer under different flow conditions, including steady flow, periodic unidirectional unsteady flow and bidirectional oscillating (reciprocating) flow, were investigated by means of water channel flume experiment, and the hydrodynamic influencing mechanism of the unsteady flow feature on the contaminant transport process in interfacial exchange zone was further analyzed. The experimental results indicate that the interfacial contaminant dynamic release rate under the bidirectional oscillating flow is shown to be a notable increase as comparing to that in the case of unidirectional steady or unsteady flows. The interfacial contaminant release rate tends to increase with the increasing average flow velocity, decreasing period and augmenting amplitude for the case of the considered oscillating flow. And the hydrodynamic influencing mechanism by which the substantially enhanced direct mass exchange between the overlying water and the pore water within the permeable sediment layer occurs, which becomes a dominant mass transport process in the interfacial exchange zone, is predominantly attributed to the flow reversal during each period under the oscillating flow condition.