ABSTRACT
Contaminants dissolved in the mobile pore water of the unsaturated zone. The process of air/water partitioning is discussed in detail in locus no. 3. Locus no. 12 concerns the movement of contaminants dissolved in the mobile water of the unsaturated zone. The definition of mobile water in the unsaturated zone and the influences on its movement in the unsaturated zone are discussed in this chapter. Water, held at gravity moves freely downward through the unsaturated zone; water held by high capillary tension is relatively immobile. The flow of water and transport of solutes in the unsaturated zone is governed by Darcy's law. Hysteresis is most pronounced in coarse-grained soils at low capillary tensions and has been attributed to several possible causes. Although the discussion of the causes of hysteresis is beyond the scope of this report, the phenomenon is important because it affects unsaturated hydraulic conductivity as well as the moisture content of the soil.
