This chapter deals with dissolved or miscible compounds in the flow of water in the unsaturated zone. While multiphase and immiscible transport of compounds is an important environmental problem, this topic is left to more advanced texts. Immiscible compounds are termed nonaqueous phase liquids, NAPL, in the literature and are generally organic compounds.
The primary approach will be to develop deterministic models based on conservation of mass and a Fickian transport law presented in Section 4.2.3. However, transfer function models for one-dimensional vertical soil profiles will also be explored. The emphasis will be on developing complete mathematical models.