FIELD-SCALE TRANSPORT OF NONPOLAR ORGANIC - SOLUTES IN 3-D HETEROGENEOUS AQUIFERS

Field experiments have indicated that reactive solute plumes released in natural porous media decelerate with time and undergo enhanced spre ading. To analyze these and other unresolved transport issues, a metho dology is presented to simulate the field-scale transport of dissolved nonpolar organic compounds in 3-D heterogeneous aquifers. This includ es the development of a model that couples a stochastic technique for generating 3-D flow fields with a mobile-immobile domain model to acco unt for sorption and intraparticle mass diffusion. The methodology is presented through the analysis of the transport of tetrachloroethylene (PCE) at the Borden site, and model results are compared to field dat a, analytical solutions, and other studies. The input parameters are b ased on laboratory data reported in the literature. The interpretation of these data is discussed, and the required experimental procedures are identified. The model results for the expected displacement of the plume's centroid (first spatial moment) are nearly identical to those observed in the field and capture the trends in the field data more a ccurately than previous studies. The observed second spatial moments o f the plume are within the 95% confidence intervals generated by the m odel (based on 2500 realizations). In general, the behavior of the plu me can be attributed to the large-scale heterogeneities in the subsurf ace hydraulic properties, the non-ergodic nature of the plume, the sor ption of the solute within the soil matrix, and the intraparticle mass transfer limitations.