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International Conference 2011

Uranium, Mining and Hydrogeology VI

Workshops UMH I

Workshop 3: Reactive Transport Modelling

Chair: David Blowes, Heino Nitsche, David Read

The discussion began with the statement that already a number of coupled models exist, i.e. models where hydrogeological and thermodynamical (geochemical) processes are linked. Therefore some questions resulted:

How can we use the available possibilities meaningfully?
To what extent can we solve real problems with the existing models?

For clarifying these questions the interdisplinary cooperation of geologists, hydrogeologists, chemists and physicists is necessary. For the meaningful use of models they must be tested first on laboratory and then on field scale. Therefore sufficient data basis, precisely defined laboratory conditions and "personal" empirical values are necessary. For the further technical conversion of the model also the natural field conditions must be examined in detail. Sometimes one only recognizes after beginning with the modelling, which parameter is really necessary and how large the influence of boundary conditions is.

There must be the possibility to regard possible contamination paths and risks in the models. On the one hand groundwater flowpaths, but also migration of gases, not only in the unsaturated zone, are of great importance. On the other hand climatic influences, e.g. precipitation and geological processes, e.g. erosion, are to be examined. Furthermore one would have to consider perhaps also situations, which could lead to human failure. With the discussion of different scenarios these factors are not only to be regarded as single events but also in their complexicity in order to detect possible interactions and consequences.

For the creation of models hydrodynamical and geochemical processes must be considered together. For the hydrodynamic component an exact knowledge about hydrogeological parameters or conditions (permeability, transmissivity, porosity, ground-water level) and hydrochemical and geological influences (dispersion, chemistry, viscosity, geothermal conditions) is necessary. For the geochemical part of a model a series of aspects play an important role, which are not investigated sufficiently yet, respectively for which still no sufficient experience exists.

The thermodynamic and kinetic processes are already considered in many models very exactly. Problematic are however partly results, which were obtained in laboratory scale. To what extent are they realistic for natural conditions? For example the behavior of colloids is not yet sufficiently known, in order to be able to interpret the material transfer bound to it. First model investigations already exist and can serve as base for the further research. Furthermore it is necessary to examine biological processses triggered by biological interactions, but also by anthropogenic influences more intensively.

Hydrodynamics and geochemistry can be differently weighted depending upon the question. Considering e.g. the mine "Königstein" groundwater regime or flow behavior is of great importance due to the special characteristics of the aquifer as "double porosity aquifer". On the other hand special geochemical parameters are more important within the tailings in Aue, described as "anthropogenic influenced chemistry".

A difficult question directs to the accessibility of the data necessary for modellings. How can a sufficient database be arranged?

In the future better communication and cooperation of different working groups should be aimed at. A better interdisplinary cooperation between the workgroups, who have databases, and those who execute the technical conversion of models has to be achieved. A dynamic cooperation should be considered as taken for granted, i.e. an intensive exchange of continued data collection and model results should be ensured.

Unsolved in the discussion remained the question about expectations of governments and authorities and also from the Federal Office for Radiation Protection. As a result it remains to state hat for successful solutions in the future a interdisplinary cooperation between scientists from the different fields involved and between government, authorities, the "owners" of the available database and scientists must be intensified.

© A. Berger <umh@geo.tu-freiberg.de>, 17.05.2010, http://www.geo.tu-freiberg.de/umh/UMHI_Workshop3e.htm