MEASUREMENT OF EFFECTIVE SATURATION CONCENTRATION FOR GAS TRANSFER

Bubbles entrained in the plunge pools of hydraulic structures are subj ected to the hydrostatic pressure of the water column. The hydrostatic pressure increases the saturation concentration of gases within the b ubbles and correspondingly alters the rates of gas transfer. An ''effe ctive saturation concentration'' is introduced to account for the elev ated pressure within the bubbles. The effective saturation concentrati on must be incorporated into gas-transfer calculations to accurately p redict downstream concentrations of dissolved gases. A method of measu ring the effective saturation concentration from simultaneous measurem ents of dissolved oxygen and methane is presented. The method is verif ied through similar measurements of dissolved nitrogen and methane. Ap plications demonstrate the use of the effective saturation concentrati on in the prediction of dissolved-gas levels downstream of hydraulic s tructures and the use of dissolved-gas measurements in the determinati on of the effective saturation concentration.