The contaminant introduced into the soil-rock-groundwater system will spreadwithin the system only if a transport mechanism is available, for example, aflowing liquid. As soon as the contaminant reaches the subsurface water in the unsaturated or saturated zone, various processes (physical, geochemical and bio- chemical) determine its fate . The physical processes include advection, dis- persion,evaporation, filtration, and degassing while those of geochemical are ac-id-base reactions, adsorption-desorption, ion exchange, oxidation-reduction, pre-cipitation-dissolution, retardation and complexation. The biochemical processesinclude amongst others transpiration, bacterial respiration, decay and cell syn- thesis .