Magnetic enhancement of soils attracts for decades attention in environmental magnetism. Mechanisms of this enhancement have been discussed since sixties of the last century, when this effect was recognized mainly in archeological surveying. At present, the attention is paid mostly to topsoil magnetic enhancement. Except for rare cases when iron-rich lithology may play significant role, the enhancement is attributed to iron oxides produced by pedogenic processes, ash resulting from wildfires, or atmospheric deposition of industrial emissions. Last but not least, human activities may play role, such as fertilizing forest soils by ash resulting from biomass combustion. Due to possible interplay of these sources and similarity in magnetic properties of the neoformed iron oxides, reference values of the “end members” are needed. In our contribution, we will review the available data on magnetic properties of these substances, complemented by our data on fireplace ash produced by burning wood of four different leave trees (oak, rowan-berry, birch, and cherry, ordered in ascending order of mass-specific susceptibility). For comparison, fly ash from a brown-coal burning power plant showed susceptibility about five times higher than the cherry-ash values. Our mass-specific magnetic susceptibility data of wood ash are of the same order as the data on fireplace ashes produced by unknown tree wood, reported earlier. However, other authors reported on wood ash susceptibilities that were comparable to our fly-ash sample. In our contribution, more magnetic properties will be presented and their implications will be discussed.

The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)