The title of this publication („Use of models on contaminant transport”) is short – as it is supposed to be - and therefore a little too general. As a matter of fact this handbook is about the mathematical modelling of contamination processes in the underground space, i. e. of soil and groundwater. For simplicity we use the expression “modelling” which always means “mathematical modelling” in the context of this handbook (in reality modelling is a more general expression, including also analogue models and small sample analyses in laboratories). General parts of the handbook dealing with the role of modelling and the modelling activity are also true for air and surface waters, but the theoretical background and the applicable software are only described related to the underground space.
The explanation for this arbitrary selection lays in the fact that the remediation program deals with cases causing permanent contamination, which cannot be solved by the elimination of the polluting activity only and which characteristically affect the underground space. Contamination of soil and groundwater does not pass off before one’s face as opposed to surface waters and air: we cannot see its colour, cannot smell it, and the underground processes are significantly slower. These evident differences have important consequences in the investigation and evaluation processes of contaminations, because – except the cases of soil contamination caused by definite pollution sources - a priori the extent of the underground space affected by the contamination is unknown and it is hard to predict what will happen in the future.
In the course of site investigations the number of drillings should be kept as low as possible because drilling costs, together with those of sampling and laboratory analyses amount to heavy expenditure. At the same time due to the slowness of processes there is generally enough time left for the mitigation and remediation of damage. Unfortunately – as the processes will take place in the future - no measurement data are available on their impact in the planning phase. All these characteristics add significantly to the importance of calculations. The aim of modelling is to derive all information possible from the available data and to use them in calculations in the course of the planning of investigation and intervention works. In any case calculation methods, which are applicable to the spatial and temporal extrapolation of instantaneous point data, like f. e. contaminant transport models, are needed.
This handbook has been prepared for a large scale of experts: experts, who carry out or plan potentially polluting activities, who plan potentially polluting facilities, who do the licensing and inspection of such activities at the institutions of municipal and state administration and last those, who plan the investigative and the necessary intervention measures in the case of pollution. In the course of editing we tried to take into consideration the significant differences in the field of interest and professional background of these experts.
The chapter “Use of contaminant transport models in remediation” provides mainly information on the possible role of modelling in the different phases of remediation (or in the planning of polluting activities in the case of technological modelling): how can models help, and what can we expect of them?
The chapter “Creating contaminant transport models” describes the work phases of modelling with details adjusted to the needs of customers (i. e. technological experts of industrial units) and of the experts who grant the establishing permit (i. e. experts of municipalities and authorities): it supports decision making - whether the model used is appropriate for the modelling of the given problem, whether a resolution adequate to the complexity of the given problem has been chosen for the modelling, and finally: does the work carried out provide reliable results?
For the needs of the experts doing the modelling three annexes have been compiled summing up the theoretical basis of modelling, data requirements of the different types of models and software recommendations for practical use.