LINKIP · Linking time domain spectral IP to hydraulic properties for environmental and engineering applications

Linking time domain spectral IP to hydraulic properties for environmental and engineering applications

Access to clean drinking water is a necessary requirement for life. With increasing difficulty in securing safe drinking water from surface waters, it is anticipated that the use of groundwater will increase. There are, however, several threats to the quality of this groundwater, such as the migration of pesticides and nitrates from agricultural applications into the water, waste leachates, and industrial contaminants (chemical industry, gasworks, impregnation plants, dry cleaning, etc.). To plan for protection, mapping of both groundwater resources and potential contaminant sources is needed. The objective of the LINKIP (link induced polarisation) project was the improvement of the geophysical induced polarisation (IP) method to characterise the underground and to provide better understanding of the subsurface and mapping properties which are essential for a long term sustainable management of groundwater resources. The aim was to evaluate how much spectral content in the direct current IP (DCIP) data can be enhanced using the newest optimised data acquisition hardware in combination with the latest developments in data processing algorithms. A further aim was also to assess the possibility to link information related to hydraulic properties (as e.g. permeability) and pollution status properties to such geoelectrical models of the subsurface. For that, also the link between time domain and frequency domain IP measurements was studied to get knowledge about to what extent these two domains can be made equivalent in practical application. The outcomes of the LINKIP project show that in theory and in a laboratory environment both IP measurement domains can reveal the same information but are limited by the gathered data quality. One link between both domains can be the transformation to a relaxation time distribution which reveal almost identical results for both domains providing very good data quality. In general, the results from our field measurements using both domain methods, yielded similar findings, but due to different measurement techniques and instrument generations, discrepancies in the phase shift results have shown up and leave room for further investigations. By using the DCIP method at a test site with known hydrogeological properties and by applying the latest processing and inversion algorithm a comparability between the spectral content of the IP method and the permeability could be found. These results suggest that the number of drillings can be reduced by using the IP method to get similar information about (e.g.) the permeability of water-bearing layers in a faster and more cost-efficient manner, supplemented by drilling followed by hydraulic tests in selected spots for verification and calibration. Using IP to monitor biological remediation processes from the surface seems also promising after serval laboratory experiments with E.coli bacteria, even though the signals from the bacteria appear to be small and, so far challenging to measure in the field.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз