Detection of hydrocarbon contaminated soil with radiomagnetotellurics

SoH contamination caused by hydrocarbons is a problem for the reorganisation of closed factories and tank farms. It is necessary to determine the kind and content of the contaminants. Soil samples lead to reliable results but the detailed investigation of an area requires a large number of boreholes, which are usually quite expensive. Radiomagnetotellurics (RMT) is comparable to the known VLF-R method but uses a broader frequency range (10-240 kHz). Electromagnetic sounding is possible by using several radio transmitters with different frequencies. The horizontal electric field in the direction of the radio transmitter and the horizontal magnetic field perpendicular to this direction are observed. From the ratio of the amplitudes of these fields the apparent resistivity is derived. The phase between the two fields yields the second measured value.