Application of magnetic susceptibility in assessment of heavy metal contamination of Saxonian soil (Germany) caused by industrial dust deposition

Magnetic susceptibility is used worldwide as a measure of concentration of (ferri)magnetic minerals in soil, sediment and dust. In soils, these minerals are of various origins: air-derived particulate pollution, parent rocks or pedogenesis. Human activity causes different changes in the content of magnetic minerals as well as their spatial and vertical distribution in soil profiles. Magnetic minerals are characterised by an affinity to other elements occurring in the soil, e.g. heavy metals. Therefore magnetic susceptibility has been widely applied as approximation of soil contamination by heavy metals.The archival soil samples collected from different soil horizons in the territory of the Free State of Saxony (Germany) were subjected to magnetic susceptibility measurements using Bartington MS2B. Additionally, samples were chemically analysed in order to determine the content of Fe, Mn, Ni, Cu, Zn, Cd, Pb and As using a method of atomic absorption spectroscopy (AAS). The contamination factor (CF) and geoaccumulation index (Igeo) were applied for assessment of soil contamination with particular potentially toxic elements (PTE), while the more general pollution load index (PLI) was used for comparison between different geographic sites.Values of magnetic susceptibility varied from 16.6 to 1382×10−8m3kg−1 in organic soil horizons and from 0.1 to 1580×10−8m3kg−1 in deeper layers. Significant and relatively high correlation coefficients between soil magnetic susceptibility and the content of some heavy metals indicated that they were of the similar origin as (ferri)magnetic minerals occurring in soil (viz. industrial pollution, parent rocks or pedogenic processes). PLI distribution over the entire area of Saxony corresponds well with the magnetic susceptibility distribution, especially in the organic soil horizon. The indices qualify the northeastern part of Saxony as extremely heavily polluted in the organic soil horizon (under forests) with decreasing contamination in deeper layers, being classified as non-polluted to moderately polluted. However, the prevailing Saxony area is characterised by low and moderate contamination by potentially toxic elements, such as heavy metals.