Background value of magnetic susceptibility in forest topsoil: Assessment on the basis of studies conducted in forest preserves of Poland

• The background value of magnetic susceptibility for forest topsoil is defined.
• A similar mean value of χ was stated for topsoil organic and mineral horizons.
• Background value of χ equals to 23 × 10− 8 m3·kg− 1 for Poland area.
• Sand content is good inverse predictor for magnetic susceptibility value.

Magnetic susceptibility measurement helps detect the presence of natural and anthropogenic ferro/ferrimagnetic minerals in the soil. In this study, the topsoil horizons were studied for magnetic susceptibility and heavy metal (HM) contents. The samples were collected from 171 soil profiles located in forest preserves equally distributed over an area of Poland. The investigated soils represented a broad range of distinctive soil types. The magnetic susceptibility values (mean χ = 23 × 10− 8 m3·kg− 1) and heavy metal contents were relatively low, for both the upper organic and mineral horizons. These findings suggest that the forest preserve soils were only slightly polluted because of urban and industrial dust depositions. Due to the origin of the soil samples, the obtained results helped determine the background value for the magnetic susceptibility of the forest topsoil in Polish lowlands and uplands.