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A B S T R A C TScalar radiomagnetotelluric measurements were carried out on a contaminated test area close to the Brazi Refinery in Romania in order to detect and to monitor a 1 m thick oil layer expected at 5 m depth. Radio transmitters broadcasting in a frequency range from 10 kHz to 300 kHz were selected to observe the apparent resistivity and the phase data associated with the E-and B-polarizations. They were located parallel and perpendicular to the assumed strike direction of the contamination plume. The data were interpreted by a 2D inversion technique from which the conductivity structure of the area was derived. The 2D inversion models of all profiles on the contaminated area show a poor-conductivity zone above the groundwater table which could be associated with the oil contamination.A first attempt was also made to monitor the contaminated layer: the radiomagnetotelluric measurements were repeated on the same profiles a year later, but this time in a dry period, not in a rainy one. The 2D inversion results of the measurements in the dry period indicate that the high-resistivity layer moved closer to the surface. Additional reference measurements were then carried out on a non-contaminated area situated at a distance from the refinery, in the opposite direction to the flow of the groundwater. These reference measurements were used for the derivation of the unperturbed geology and they were also compared with the measurements of the contaminated test area. There is a significant difference in the frequency dependences of the apparent resistivities of the reference and contaminated areas, which could indicate a contamination at shallow depth. The 2D inversion results show the increase of resistivity at a depth of about 5 m beneath the contaminated area where the oil contamination is expected according to the information from the boreholes.

Three-dimensional pore structure of four samples of geological rock was obtained using serial sectioning. Their fractal and flow properties have been successfully determined through image analysis. The measured 3D box counting fractal dimension of four geological rock samples are 2.59, 2.88, 2.88 and 2.29, which are not integer dimensions. This would imply that the structure of the four geological rock samples is fractal in nature. Porosity of the four rock samples are ranged from 0.18 to 0.31 and the specific surface area is ranged from 1.57 to 2.75 mm-1. Tortuosity estimated from image analysis of the four samples is ranged from 1.11 to 5.83 and varied in each fluid flow direction. This would imply that the rock samples are not uniform in its pore structure. The fractal dimension as a representation of the isotropic level of the pore structure is not clearly clarified and it still needs further investigation.