Technogenic magnetic particles in topsoil: Characteristic features for different emission sources

Variations in mineralogical composition, grain size internal structure and stoichiometry of technogenic magnetic particles (TMPs) deposited in topsoil may provide crucial information necessary to trace main pollution sources and recognize various technological processes. The aim of the study was to characterize, by means of magnetic parameters and Mössbauer spectra, the TMPs from non-ferrous metallurgy, cement, coke, glass production as well as long range transport (LRT) and compare the obtained data with previous results focused on iron mining and metallurgy. This research shows that only certain pollution sources (e.g. mainly iron mining, iron metallurgy, LRT and partly glass production) can be successfully distinguished by the applied parameters. The main features characteristic for TMPs produced by Fe-mining are: high values of concentration-dependent magnetic parameters, low values of coercivity, significant contribution from coarse MD (multi-domain) grains and a relatively high stoichiometry of magnetite. The most discriminative feature for TMPs generated by the glass industry is the abundance of goethite in the topsoil samples, which is confirmed by magnetic and Mössbauer techniques. The TMPs released by the Ni-Cu smelter and the Pb-Zn waste exhibit significant differences in the Mössbauer parameters, indicating different stoichiometry of magnetite for each group. Such variations are due to replacement of Fe by other elements at tetrahedral sites in the case of TMPs released from the Ni-Cu smelter. TMPs characteristic for the LRT emissions contain higher amount of finer fraction of low-stoichiometry magnetite (mostly single-domain SD particles) than those originating from other sources. The TMPs accumulated in the topsoils around the coking plants cannot be clearly discriminated by the applied methodology due to strong influence of the local pollution sources. Magnetic studies of the TMPs generated by cement production are complicated, since their properties mainly depend on individual technology (e.g. additives) used by the local cement plants.