JOURNALOF Contaminant Hydrology ELSEVIER Journal of Contaminant Hydrology 19 (1995) 261-267 Dispersive-diffusive transport of non-sorbed solute in multicomponent solutions Qinhong Hu, Mark L. Brusseau * 429 Shantz, Departmentof Soil and WaterScience, University of Arizona, Tucson,AZ 85721, USA Received 6 December 1994; accepted after revision 14 March 1995 Abstract The composition of fuels, mixed-solvent wastes and other contaminants that find their way into the subsurface are frequently chemically complex. The dispersion and diffusion characteristics of multicomponent solutions in soil have rarely been compared to equivalent single-solute systems. The purpose of this work was to examine the diffusive and dispersive transport of single- and multi-component solutions in homogeneous porous media. The miscible displacement technique was used to investigate the transport behavior of 14C-labelled 2,4-dichlorophenoxyacetic acid (2,4-D) in two materials for which sorption of 2,4-D was minimal. Comparison of breakthrough curves collected for 2,4-D in single- and multi-component solutions shows that there is little, if any, difference in transport behavior over a wide range of pore-water velocities (70, 7, 0.66 and 0.06 cm h-1). Thus, dispersivities measured with a non-sorbing single-solute solution should be applicable to multicomponent systems. 1. Introduction The composition of fuels, mixed-solvent wastes, landfill leachate and other contami- nants that find their way into the subsurface are frequently chemically complex. Thus, many contaminated sites have multiple contaminants in the aqueous phase. When multiple components are present in solution, a primary question to be addressed is the occurrence of antagonistic or synergistic interactions within the system (Brusseau, 1994). As such, it is important to understand the transport dynamics of multicomponent solutions. The behavior of multicomponent solutions has been widely investigated in chemical engineering. However, the dispersion and diffusion characteristics of multi- * Corresponding author. 0169-7722/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0169-7722(95)00019-4