Application of magnetic methods for assessment of soil restoration in the vicinity of metallurgical copper-processing plant in Bulgaria.

Copper ore mining and processing are among the most harmful anthropogenic influences for the environment and they are a subject of international and national law regulations. Recultivation of areas influenced by mining and processing industry is commonly applied and monitored in order to restore as much as possible the natural environment. In this study, environmental magnetic methods are applied in order to assess the degree of soil restoration in terms of soil development, after remediation of waste dump from Cu-processing plant. Soils developed under birch forest stands of different age (5, 15, and 25 years) as well as raw waste material were sampled along depth down to 20-30 cm. Variations in magnetic parameters and ratios obtained (magnetic susceptibility, frequency-dependent magnetic susceptibility, anhysteretic remanence (ARM), isothermal remanence (IRM), ARM/IRM100mT) suggest the presence of magnetic enhancement in the upper 0-15 cm, the thickness of this layer varying depending on the age of the forest stand. Magnetic mineral responsible for this enhancement is of magnetite type, while waste material contains a large amount of hematite, as evidenced by coercivity analysis of IRM acquisition curves and thermal demagnetization of composite IRM. Magnetic grain-sized proxy parameters suggest that magnetite particles are coarser, magnetically stable, while no or minor amount of superparamagnetic grains were detected at room temperature. A well-defined linear regression between the topsoil magnetic susceptibility and the approximate age of the forest stand provides an indication that the magnetic enhancement is of pedogenic origin. It is concluded that the observed magnetic enhancement of recultivated soils studied is linked to a combined effect of pedogenic contribution and possible additions of industrial ashes as a liming agent for soil restoration.

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.