Deterministic Analysis and Upscaling of Bromide Transport in a Heterogeneous Vadose Zone

ConservaƟ ve solute transport experiments were conducted at a fi eld plot and on an undisturbed soil core from the same site. The hydraulic and solute transport properƟ es were extensively characterized so that the data could be analyzed from a determinisƟ c perspecƟ ve. To invesƟ gate the infl uence of scale and conceptual model on solute transport in the relaƟ vely homogeneous upper soil profi le of the fi eld site, breakthrough curves that were collected at diff erent depths in the undisturbed column and in the fi eld experiments were compared and analyzed. The mobile-immobile model provided a physically realisƟ c descripƟ on of the column data that was largely independent of the transport distance, and upscaling from the undisturbed core to the fi eld plot was relaƟ vely successful. Mean and variance of the Br − travel Ɵ mes were controlled by plot-scale variability in soil water content and heterogeneity, which was overcome by averaging the concentraƟ on values from four locaƟ ons at the same depth and Ɵ me, and analyzing the Br − transport behavior as a one-dimensional process. Diff erences between the measured and simulated mass balances, average concentraƟ on, and the variaƟ ons in concentraƟ on were predicted reasonably well across depth and Ɵ me. Although predicƟ on of the exact concentraƟ on informaƟ on at a given point was not achieved, this study demonstrates that areaaverage Br − transport in a heterogeneous vadose zone can be determinisƟ cally quanƟ fi ed.