Transport of rate‐limited sorbing solutes in heterogeneous porous media: Application of a one‐dimensional multifactor nonideality model to field data

Abstract

The results of several experiments reported in the literature indicate that the assumptions of porous media homogeneity and instantaneous sorption are generally invalid for transport of sorbing solute at the field scale. In addition, it is probable that the “nonideal” transport observed is caused by more than one factor. The purpose of this work was to evaluate the ability of a one‐dimensional, multifactor nonideality model to represent the nonideal transport of sorbing solutes at the field scale. For this model the two‐domain approach is used to represent heterogeneity, and sorption is represented as being essentially instantaneous for a portion of the sorbent and rate limited for the remainder. Data (breakthrough curves) obtained from four field experiments reported in the literature were used to test the performance of the model. With one exception, data from laboratory or field experiments were used to identify values for input parameters; the exception concerned an assumption of a uniform distribution of sorbent between the advective and nonadvective pore water domains. Specification of input parameters independent of the data being simulated allowed the model to be used in a predictive mode. On the basis of the good match between predictions produced with the model and the data, it appears that the model provides a valid representation of sorption dynamics and solute transport for field‐scale systems influenced by heterogeneity and rate‐limited sorption. The model should be useful in situations where the extensive input data required for more complex models (e.g., stochastic) are not available.