Modeling the transport of solutes influenced by multiprocess nonequilibrium

A model that explicitly accounts for multiple sources of nonequilibrium is presented. The multiprocess nonequilibrium (MPNE) model is specifically formulated for cases where nonequilibrium is caused by a combination of transport‐ and sorption‐related processes. Sensitivity analyses were performed to delineate the conditions under which the MPNE model reduces to the bicontinuum and to the local equilibrium models. These conditions are strongly controlled by the magnitude of the dimensionless rate parameters. Performance of the MPNE model was evaluated with several published data sets. An empirical regression equation was successfully used to estimate values for sorption rate constants required in the MPNE model. The MPNE model, with values for all parameters obtained from independent sources, predicted behavior exhibited by the data. This provides support for the validity of the conceptualization upon which the model is based.