Soluble release mass transfer coefficient

The overall mass-transfer coefficient. As shown above the resistance-in-series concept provides a means for combining transport processes on either side of the interface. Defined as the ratio of the flux to the concentration on particles, Ks, the overall sediment soluble release mass-transfer coefficient (L/t) is... 

The dispersion term is absent since dividing the reach into Ax completely mixed segments accomplishes dispersion numerically. In equation 1 t is time (t), Ct is soluble, particulate, and colloidal, concentration (M/L ), U is average water velocity (M/t), Ds is particle deposition flux (M/L t), h is water column depth (L), m v is suspended solids concentration (M/L ), fp and fd are fractions chemical on particles and in solution, kf is the soluble fraction bed release mass-transfer coefficient (L/t), Cs is the total, soluble and colloidal, concentration at the sediment-water interface (M/L ), Rs is particle resuspension flux (M/L t), ms is the particulate chemical concentration in the surface sediment (M/L ), fps Cts is the fraction on particles and total chemical concentration in the surface sediment (M/L ), Kl is the evaporation mass-transfer coefficient (L/t), Ca is chemical vapor concentration in air (M/L ), H is Henry s constant (L / L ) and Sx is the chemical lost by reaction (M/L t). It is conventional to use the local or instantaneous equilibrium theory to quantify the dissolved fraction, fd, particulate fraction, fp, and colloidal fraction, fooM in both the water column and bed. The equations needed to quantify these fractions appear elsewhere (4, 5, 6) and are omitted here for brevity. 

When an insoluble bubble rises in a deep pool of liquid, its volume increases according to the ideal gas law. However, when a soluble bubble rises from deep submersion, there is a competing action of dissolution that tends to reduce size. Under practical conditions, it has been proved (Rice 1982) that the mass transfer coefficient ikj for spherical particles (or bubbles) in free-fall (or free-rise) is substantially constant. Thus, for sparingly soluble bubbles released from rest, the following material balance is applicable... 

CFaT riverine models were presented for both the water column and bed sediment. They were then simplified to focus onto the non-flow resuspension soluble fraction using the quasi-steady state assumption to isolate the key water-side and sediment-side process elements. Field evidence of soluble release based on CFaT model derived data was reviewed for three rivers. Both the traditional particle background resuspension process and more recent soluble fraction process algorithms data interpretation were covered. Numerical field calibrated resuspension velocities and soluble mass-transfer coefficients were presented. Candidate water-side and sediment-side transport processes, selected from the literature were reviewed. Those that provided the best theoretical explanation and contained laboratory and/or field data support were selected. Finally, the flux and the overall transport coefficient which captures the essential features of the framework were presented. Following this the theoretical mass-transfer coefficients were applied to a site on the Fox River below De Pere Dam. Numerical calculations were made for the transport coefficients for both individual and combined processes. 

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