MAGNETIC SUSCEPTIBILITY MAPPING OF FOREST TOPSOILS: REPRODUCIBILITY AND IMPLICATIONS FOR ENVIRONMENTAL MONITORING

The magnetic susceptibility of soils is currently used to assess the degree of exposure to pollution dust containing magnetic particles. This study was carried out in the frame of the MagProx project, supported by the European Union, aimed to develop magnetometry as proxy method for screening and monitoring of environmental pollution. The main goal of the proposed research part was to show the reproducibility of the environmental magnetic susceptibility measurements. In a first field campaign in 2000, we investigated 298 localities in North and West Austria at a 10 x 10 km grid for a magnetic susceptibility mapping of the forest topsoils using GPS Trimble 4700 and Bartington MS2D probe sensor. The values vary in the range between -6*10^-5 SI and 86*10^-5 SI with a mean of 4.2*10^-5 SI.

In a second field campaign in 2001, we repeated measurements at 119 localities along selected West-East and North-South profiles. A careful data analyses shows that several factors have a significant impact on the reproducibility of the magnetic susceptibility readings, e.g. the water content logged in the moss cover, inhomogeneities within the investigated places, and forest work. The regression coefficient R² between the magnetic susceptibility values from two data sets is 0.906, with an average difference of 2.3*10^-5 SI, indicating a high degree of agreement between the results of two mapping campaigns.