Figure 3. Factors influencing transfer processes between solids and water

ERDC TN-DOER-C16

July 2000

in detail in the following sections on the source, CDF and vadose zone considerations, and saturated

zone and receptor factors. Discussion of the evaluations is focused on upland CDFs but most of

the considerations apply as well to all CDFs.

SOURCE: In order for contaminants to cross the interface between dredged material solids and

water, a difference in chemical potentials must exist. Chemicals flow from a region of high chemical

potential to a region of low chemical potential just as electric current flows from a region of high

electrical potential to one of lower electrical potential or as mass flows from a position of high

gravitational potential to one of low gravitational potential. When chemical potentials are equal,

the net transfer of contaminant across the solid-water interface is zero, and the mass of contaminant

in each phase is constant, but not necessarily equal. The processes shown in Figure 3 control the

rate at which equilibrium is reached and the equilibrium distribution of contaminant between solid

and aqueous phases. Once equilibrium is reached, the ratio of contaminant mass in the solid phase

to the contaminant mass in the aqueous phases does not change.

Figure 3. Factors influencing transfer processes between solids and water