Rock magnetic indicators for heavy metal concentrations in soils and sediment

Magnetic parameters are sensitive indicators for variations in the type, grain size and concentration of magnetic particles in soils and rocks. An essential advantage of the geophysical method is the possibility of a cost-efficient extension and condensation of information on environmental pollution.

Many heavy metal emissions are highly magnetic particles which can be quickly and clearly detected with the help of magnetic susceptibility and other parameters. Anthropogenic influence can increase the magnetic susceptibility of sediments and soils by a multiple of the natural magnitude. Examinations of soils and sediments show statistically significant connections between the magnetic susceptibility and certain heavy metal concentrations, in each case depending on the size and chemical composition of the particles responsible for the heavy metal anomaly. Especially in the case of particulate heavy metal input (dust, ashes, sludge) magnetic susceptibility can be used as an indicator for heavy metal contamination.

The measurement of magnetic susceptibility can be performed on any sample material in the laboratory as well as also directly on site. These examination methods have been successfully used for decades in interdisciplinary environmental research. With their help, contaminated horizons can be isolated and the extent of the accumulation can be estimated with relative ease.

We determined magnetic parameters of samples of structural material, sewage sludge and compost from the sewage plant Leoben to examine their possible application as indicators for heavy metals which are environmentally relevant in the area of Leoben. The results of the magnetic examinations are in good agreement with those of the chemical analyses. We were able to discover a pronounced correlation between the analysed heavy metals and the magnetic parameters.

Magnetic measuring methods cannot replace chemical analyses and mineralogical examinations, but as an indicator for heavy metal emissions they constitute a quick and economic basis for evaluation.

Magnetic measurements of soil samples of Austrian soil status inventories for the provinces of Carinthia, Styria, Burgenland, Lower and Upper Austria were used for the mapping of the magnetisability at different soil depths. The soils are not only influenced by emissions but also by natural magnetic minerals. The determination of natural normal values enables a transregional interpretation of such maps, which to date has only been possible with detailed knowledge of the geology and soil types of a research site.

Download Poster: Hanesch 2004 (pdf)

In cooperation with three partner institutes in Germany, Poland and the Czech Republic we created transregional maps of the magnetic susceptibility of forest soil locations and examined the remote transportation of magnetic particles.

Partners:

• Geophysics Working Group, Institute of Geology and Paleontology, University of Tuebingen, Germany
• Geophysical Institute, Academy of Sciences of the Czech Republic, Prague, Czech Republic
• Institute of Environmental Engineering, Polish Academy of Sciences, Zabrze, Poland

Research network within the framework of the EU mobility programme for the investigation of the potential of mineral magnetic methods for environmental and climate research.

Partners:

• Lancaster University,  UNITED KINGDOM
• University of Liverpool, UNITED KINGDOM
• Universidad Complutense Madrid, SPAIN
• CEREGE, Aix en Provence, FRANCE
• Ludwig-Maximilians-Universität München, GERMANY
• Istituto Nazionale di Geofisica, Roma, ITALY
• Utrecht University, THE NETHERLANDS
• Southampton Oceanography Centre, UNITED KINGDOM
• ETH Zürich, SWITZERLAND

In cooperation with the Landwirtschaftlichen Versuchszentrum Steiermark, the aim of the project was to gain basic insights on the applicability of geophysical measurement methods for the planar detection of heavy metal accumulation in soils. The basis for the mapping of magnetic susceptibility were the measurements of all samples of the soil status inventories of the provinces of Styria, Lower Austria and Burgenland. The data pool contains 1254 sites with surface soil and subsoil samples, as well as 760 additional sites with surface soil samples.
The volume susceptibility was determined in the sample archives without opening the sample containers. For special laboratory measurements of the mass specific susceptibility, a representative number of test portions were retrieved. The determination of the characteristic magnetic parameters was carried out in the Magnetics Laboratory of the Montanuniversität. Virtually all anomalies of the susceptibility in the surface soil are simultaneously also areas with demonstrably increased heavy metal content. The difference in susceptibility between surface soil and subsoil is a measure for the accumulation of magnetic phases in certain horizons. The application of the method in the field was tried out in two test fields.
The anomaly patterns of the magnetic susceptibility show a general agreement with the prevailing wind direction and the valley axis. Based on the results from the test fields Veitsch and Leoben we were able to show that magnetic susceptibility mapping can be used as an economic method for the planar detection of industrial immissions.