Topsoil magnetic susceptibility mapping as a tool for pollution monitoring: repeatability of in situ measurements

Many recent studies applied magnetic susceptibility mapping as a tool for preliminary pollution monitoring using the Bartington MS2 Meter. In a previous paper, we introduced a standard procedure for which the compatibility of different instrument set-ups and subjective (human) influences were tested (Stud. Geophys. Geod. 46 2002 43). In this study, we test the long-term reproducibility of this procedure. For this purpose, magnetic susceptibility was measured in two field campaigns on 129 sites located in North and West Austria on a regular grid of 10 X 10 km. The differences between the results from the two measurement series were normally distributed; their magnitudes lie within the instrument biases in 94% of all cases. Susceptibility was found to be temporally very constant for sites located far away from the pollution source. The following factors have been found to affect repeatability: inhomogeneities within the place measured, positional precision of navigation, different equipment sets used, plant cover and anthropogenic activity. Magnetic susceptibilities of soil reference materials, which have been taken at the in situ measured sites, correlated significantly with readings obtained in the field. The proposed method has both high sensitivity and repeatability and can be applied for large data set acquisition for delineating polluted areas. (C) 2004 Elsevier B.V. All rights reserved.