Application of magnetometry to assess distribution of dust pollution in topsoil of under-crown area of Norway spruce (Picea abies Karst.) and European beech (Fagus sylvatica L.)

•Dense grid magnetic susceptibility measurements were applied under tree canopy area.•Variability of κ values in forest soils is tree species-dependent.•Humus horizons in forest soils play a crucial role in storage of magnetic particles.•Topsoil's magnetic susceptibility was higher under beech in comparison to spruce.

Measurements of magnetic susceptibility (MS) of topsoil are used as an indicator of air derived pollutants containing magnetic particles and heavy metals. Here, we focused on the role of a single tree in the distribution of dust pollutants to topsoil under-crown area. Novelty is a dense grid (1 m × 1 m) for magnetic susceptibility measurements, performed in under two pairs of individual Norway spruce and European beech trees located in urban forests of industrial regions. The MS measurements and chemical analyses (pH, heavy metal contents, soil C and N) were conducted on 312 soil cores. Results show differences in storage of magnetic particles and heavy metals with respect to humus type and thickness of the humic horizon. Higher MS values were measured under beech trees where stem flow was observed. Vertical and horizontal distribution of volume magnetic susceptibility values (κ) can be affected by pedogenesis and animal activity. We found high positive correlations between heavy metal contents and MS values in soil samples.

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