ZEROCD and PROFCD, Description of Two Programs to Supply Quick Information with respect to the Penetration of Tracers into the Soil

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For a variety of environmental studies it is useful to get a quick impression of how certain tracers penetrate the soil. Under some restrictive assumptions, it is possible to predict the concentration and the amount of material which has passed, and which is present, below some level without the detailed knowledge of the structure of the soil matrix. In this report a survey is given of formulas describing the behaviour of a tracer without or with decay with linear adsorption in a one-dimensional semi-infinite medium with various boundary conditions. These boundary conditions are: instantaneous injection or exposure, continuous injection or exposure, or block pulse injection or exposure. Interest is focussed on the questions at what time a specified amount of material is present below or has passed a givin depth. A computer program is described which supplies an answer to this question (ZEROCD). Another computer program (PROFCD) visualizes all relevant results (resident and flux concentration, resident and transported mass, fraction of resident (or transported) mass to total injected amount). Although the underlying assumptions may be too simple for realistic situations, yet, by varying the input parameters, the user can find upper and lower bounds for various unknowns (e.g. concentration, time of arrival and so on), without much modelling effort, because the time of calculation of both programs is very short. The latter may also facilitate the performance of a formal uncertainty analysis. Furthermore, its very short calculation time makes this software package pre-eminently useful to produce a first, rapid assessment of the evolution of pollution in a wide range of typical soil profiles within the framework of large scale environmental studies. Another application of the programs is the possibility to serve as a reference for verification of numerical computer codes, a key element of the INTRAVEL project.