Time domain induced polarisation experiments on gasoline contaminated samples

Recently environmental studies have used geophysical methods to delineate oil contaminated sites (Vanhala, 1997). Organic liquids have a high resistivity and thus induction methods are not weil adapted to fine contaminated areas. On the other hand Induction Polarisation has been widely recognised as a useful method for the detecting organic electrical response In field ( Vanhala et al, 1992) and in laboratory (Vanhala et Soininen. 1995) experiments. The later author had a frequency domain approach (SIP) to the problem. On the other hand our initial work carried out in the time domain (Sumner, 1976) and is still in a laboratory phase. In order to study the induced polarisation effect in gasoline contaminated soil samples a GPIB controlled system was developed to carry out electrical measurements as it is shown in Fig.l. This System is able 10 obtain measurements at a rate of ten samples per second. Specially developed porous ceramic electrodes were built to obtain suitable electrical current contacts. Non polarizable electrodes SilverlSilver Chloride were used to measure potential.