oa Reliability of Time Domain Induced Polarization Data

The Time Domain Induced Polarization technique can be really useful in environmental geophysics, e.g. in study of aquifers for clay identification or in the characterization of landfills, but often the noise content and the consequent difficulty to assess data reliability completely overcome its potential benefits.<br>therefore a time lapse DC/IP experiment has been curried out at Hørløkke landfill (Denmark), in order to discriminate among the factors that influence data repeatability and to recognize critical aspects in DC/IP survey design.<br>Two profiles crossing the landfill (410 m long, electrode spacing being 5 m) have been acquired, the time lapse test being conducted with one, two and thirty days of delay. Furthermore different arrays have been tested, to compare the effect of varying quadrapoles sequences on noise content, electrode polarization, gate sampling and stacking. Moreover the effect of the current waveform settings (On and off time length and stacking) has been investigated, in conjunction to IP time gates selection.<br>the Syscal Pro equipment from Iris instruments has been used to acquire data, but a comparison with the Terrameter SAS 4000 (Abem instrument AB) has also been carried out.<br>the results of the study suggest that the driving factor in data repeatability is the voltage level of the IP signal, electrode polarization being a second order effect: from the acquired data set it has also been possible to extract safe thresholds for the signal level. We conclude the presentation by showing the results form the comprehensive Investigation of the landfill.