Effective prediction of transport of chemical pollutants through a subsurface groundwater system and associated assessments of risk requires a valid “conceptual model” of the contaminant migration scenario. The classical contaminant conceptual model is one of a near- surface “leachable source zone” where chemical contaminant is leached, . dissolved/solubilised, into water infiltrating through the source (Figure ). A dissolved- phase chemical solute plume subsequently emerges in water draining from the base of the contaminant source zone and moves vertically downward through any unsaturated zone present. The dissolved solute plume ultimately penetrates below the water table to subsequently migrate laterally in the flowing.
