technogenic magnetic particles
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Solid fossil fuel power plants are the main source of energy in Poland. In 2018, the most important energy carrier was hard coal with a share of 57.9%, followed by lignite with a share of 18.1%. In addition to CO2, NOx and SOx, the combustion of fossil fuels produces dusts containing, among others, potentially toxic elements (PTEs), e.g., Pb, Zn, Cu, Cr, Cd. Although the currently operating power plants have efficient filter systems, the total dust emission in Poland in 2017 amounted to 341,000 t, of which approximately 36,000 t was from the power plants. PTEs present in the power plant dust are often accompanied by technogenic magnetic particles (TMPs)—mainly iron oxides and hydroxides formed in high-temperature technological processes as a result of the transformations of iron minerals contained in raw materials and additives. The presence of magnetic iron minerals (e.g., magnetite, hematite, maghemite, metallic iron) in the tested ashes from hard coal and lignite power plants was confirmed by scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) analysis. The sequential extraction analysis showed that most of the analyzed PTEs found in dust after hard coal combustion were mainly related to amorphous and crystalline FeOx or in the residual fraction and in dust after lignite combustion, mainly in the most mobile fractions.

The work is devoted to the study of pollution by technogenic magnetic particles and heavy metals of soils in the city of Gubakha, Middle Ural (Russia). The aim of the work is the ecological and geochemical assessment of the elemental chemical composition of the soils of the city of Gubakha, and the establishment of the geochemical role of technogenic magnetic particles (TMPs). For the first time, the regularities of the spatial distribution of magnetic susceptibility in the soils of the city of Gubakha were revealed, and the morphology, elemental and mineralogical compositions of magnetic particles in the soils of an industrial city in the Middle Urals were characterized using the methods of the chemical extraction of iron compounds, magnetic separation, ESEM/EDS, and Mössbauer spectroscopy. The magnetic phase of soils contains magnetite/maghemite, hematite, pyrrhotite, intermetallic alloys and chromite. Spherical magnetic particles are hollow, and have a magnetite shell and a varied surface texture. The crystal lattice of magnetite is characterized by low stoichiometry. The heavy metals Zn, Cu, Ni and Cr are concentrated in magnetic particles and have a high correlation coefficient with magnetic susceptibility. The level of contamination of Cu, Ni, Zn, Cr and Mn in the soils of a residential zone of Gubakha, estimated by the value of the pollution load index (PLI), was high. The Igeo index for Fe ranges from 6.2 to 12.2, for Cu–1.1 and Ni–1.1. The combination of methods for measuring magnetic susceptibility, determining the mineralogical composition of iron compounds, and determining the elemental chemical composition by X-ray fluorescence, has shown the effectiveness of an integrated approach for carrying out an ecological–geochemical assessment of the soil cover of Gubakha.

Studies on the effects of dust deposition on soils in urban-industrial areas were conducted with application of magnetic (soil magnetometry, thermomagnetic analysis) and geochemical (elements content) methods. The study area covers three different forest sites on Upper Silesian Conurbation. The purpose of the research was an estimation of soil pollution and characteristic of air derived particles. Results show magnetite and maghemite as dominant magnetic components of analyzed soil samples. The highest volume magnetic susceptibility (κ) and no correlation with potentially toxic elements (PTEs) were stated close to metallurgical plant whilst the highest correlation coefficient between κ and PTEs was stated in samples from the urban area and in a vicinity of coking plant.