Kurzfassung
Die grundlegende Idee des virtuellen Aquifers ist, durch numerische Modellierung von typischen Schadensfällen Erkundungsstrategien zu simulieren und zu bewerten. In diesem Beitrag wird die Bestimmung von Abbauraten erster Ordnung untersucht. Eine Schadensquelle wird dabei in einen virtuellen Aquifer eingebracht und die stationäre Schadstofffahne unter der Annahme einer Abbaukinetik erster Ordnung simuliert. Diese Fahne wird dann durch Beobachtungspegel entlang der Zentrallinie der Fahne untersucht. Anhand von vier typischen Methoden werden Abbauraten erster Ordnung berechnet und mit dem vorgegebenen Wert verglichen. Dieser Vergleich wird für unterschiedlich stark ausgeprägte hydraulische Heterogenitäten durchgeführt. Dabei zeigt sich, dass mit zunehmender Heterogenität die ermittelten Abbauraten die tatsächliche Abbaurate um Größenordnungen überschätzen können und sie somit sehr unsicher sind. Bei der Untersuchung der Messfehler wurden Abweichungen bei der Bestimmung der Piezometerhöhe und der Konzentration angenommen. Hierbei ergibt sich, dass Messfehler ebenfalls zu einer hohen Unsicherheit der Ratenkonstante führen können, wobei Messfehler der Piezometerhöhe einen stärkeren Einfluss haben.
Abstract
The principal idea of the Virtual Aquifer is to simulate and evaluate monitoring strategies and remediation options for contaminated sites by modelling typical contamination scenarios. Here the determination of first order degradation rates is studied. A virtual reality is generated by simulating the spreading of a plume, originating from a defined source and subject to first order degradation. This plume is investigated using monitoring wells placed along the plume center line. From the information thus obtained, first order degradation rates are calculated by typically used methods and are then compared to the predefined value. This comparison is conducted for different degrees of heterogeneity. It is found that with increasing heterogeneity, the calculated degradation rates can overestimate the real degradation rate by several orders of magnitude and show a high uncertainty. Measurement errors are then introduced for piezometric head and concentration measurements. It is found that up to several orders of magnitude deviations can occur between the estimated first order rate constant and the true rate, with errors of the piezometric head measurement causing the dominant uncertainty.
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Bauer, S., Beyer, C. & Kolditz, O. Einfluss von Heterogenität und Messfehler auf die Bestimmung von Abbauraten erster Ordnung – eine Virtueller-Aquifer-Szenarioanalyse. Grundwasser 12, 3–14 (2007). https://doi.org/10.1007/s00767-007-0019-8
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DOI: https://doi.org/10.1007/s00767-007-0019-8