A new tool for in situ measurements of the vertical distribution of magnetic susceptibility in soils as basis for mapping deposited dust.

In situ measurements of magnetic susceptibility of topsoils are commonly used for mapping the spatial distribution of atmospherically deposited ferrimagnetic particles. However, the surface measurements integrate signal from certain soil volume and, thus, it is not evident how deep is the magnetically enhanced layer, if there is such. This information is often required for detailed sampling. Furthermore, fast estimate of the significance of lithogenic contribution is needed for the proper interpretation of the surface data. This can be reliably done on the basis of vertical distribution of magnetic susceptibility of a soil column. Until now, there was practically no reliable, fast and sensitive enough tool to carry out these measurements in real time, directly in field. In this paper, we report on a new soil-profile kappameter SM400, which enables continuous real-time measurements, performed directly in the field. We describe its basic measurement principles. Performance parameters are discussed, showing that sensitivity is high enough to depict the soil layers with different susceptibility and a data density of 6 points per 1 mm of depth, which results in smooth curves of susceptibility, unlike field or laboratory probes used until now. Profiles acquired using different probes and instruments are compared in order to demonstrate advantages of the new approach.