ABSTRACT
Solutes applied onto the soil surface travel through a dramatically heterogeneous transport region. The heterogeneities of the flow field vary with water saturation and therefore depend on the rate of infiltration. Surface applied solutes do, in many situations, not obey the convection-dispersion equation (CDE). Flow and transport in formations of a double (or multiple) porosity is described with two (or multi-) region models that allow for variable degrees of mass transfer between the flow regions. Solutes applied onto the soil surface travel through a dramatically heterogeneous transport region. The heterogeneities of the flow field vary with water saturation and therefore depend on the rate of infiltration. Surface applied solutes do, in many situations, not obey the CDE. Solute tracer experiments can provide much more information if not only one tracer but several tracers of very different reactivity can be simultaneously visualized at excavated profile cuts.
