Hydrogeologists have traditionally used distribution coefficients Kd to describe the rate of migration of sorbing contaminants. Recent investigations have questioned the validity of the Kd approach for contaminants governed by multicomponent ion exchange and have noted that computed Kd values in such cases are not constant across an advancing solute front. This report demonstrates that mass balance arguments can nevertheless be utilized to define a constant “effective” Kd which may then be used to calculate the contaminant front velocity. For selected cases of one‐dimensional binary and ternary exchange, front locations calculated using the effective Kd approach agree closely with concentration profiles calculated using a general numerical simulation model of ion‐exchanging solute transport. The effective Kd approach is also applied to a field problem involving the injection of advanced‐treated municipal effluent into a shallow confined aquifer. Although the effective Kd approach is sometimes a practically useful tool, it is shown to be limited to situations where dispersion can be neglected.
ASJC Scopus subject areas
- Water Science and Technology