Soil heterogeneity, fingered flow and macropore flow cause solutes to spread out in time and space as they move downwards from the soil surface with infiltrating water. Temporal solute spreading is characterized by the breakthrough curve (BTC), which describes the travel time distribution of solutes at a given depth. The spatial solute spreading is characterized by the spatial solute distribution curve (SSDC), which is the spatial equivalent of the BTC. Combining the BTC and the SSDC gives the leaching surface. The leaching surface thus describes both the spatial and the temporal redistribution of uniformly applied solutes at a given depth.

Currently, leaching surfaces can be constructed from multicompartment sampler data. They provide a valuable tool for a quantitative analysis of such data. However, to compare leaching surfaces from different soils or different climatological conditions, a parameterization of the leaching surfaces is highly desirable. We intend to develop such a parameterization by means of a physical analogue: heat flow through a non-homogeneous, heat-conducting strip. A heat pulse at the beginning of the strip causes a temperature wave. This temperature wave passes a cross-section of the strip. By modifying the parameters that describe the thermal conductivity of the strip and the geometry of the cross-section, this temperature wave can possibly be modified to approximate any observed leaching surface. The best-fit parameters thus provide a quantitative representation of the leaching surface.

Preliminary results will be presented. Leaching surfaces will be generated from analytical and numerical solutions of the heat flow problem.