Wehrer, Markus
(2009)
Mapping regions of equifinality in the parameter space: A method to evaluate inverse estimates and to plan experimental boundary conditions.
In: Jahrestagung der DBG 2009: Böden - eine endliche Ressource, September 2009, Bonn.
Kurzfassung
Breakthrough curves of column outflow experiments are frequently used to identify parameters of reactive transport in porous media. However, inverse techniques coincide often with uniqueness problems, i.e. more than a single parameter set can reproduce the breakthrough curve equally well – a problem, which is termed equifinality. In this study, maps of regions with reliable parameter estimates were created applying numerical case studies with systematically varied parameters and boundary conditions. This was carried out by comparing the numerically produced breakthrough curves from forward simulations of the advection dispersion equation including equilibrium and non-equilibrium sorption (two-site/two-region model). Mapping of regions of uniqueness in the parameter space can help to improve the reliability of inverse simulations in two ways. On the one hand, regions of uniqueness depend on the boundary conditions of the experiment. Consequently, if the correct experimental boundary conditions – such as flow velocity, number and duration of percolation intervals and flow interruptions – are chosen, uniqueness problems can be avoided a priori. All what is required are some a priori information on the target compounds and materials and maps of regions of uniqueness for different experimental designs. On the other hand parameter estimates can be plotted into such maps a posteriori, to be able to evaluate whether equifinal solutions exist. are required, then an appropriate experimental design can be selected using maps of uniqueness.
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