The migration of elements from the processing waste of copper smelting slags into the ombrotrophic peat and plants

Abstract

Research subject. The processing waste of the slag from the Sredneuralsk copper smelter (“SUMZ technical sand”) is a finely dispersed (particle size less than 0.05 mm) material, mechanically activated by crushing cast slag and containing high concentrations of copper, zinc and other chalcophilic elements. Fayalite and ferrous glass predominate in its phase composition.Materials and methods. An outdoor experiment to study the elemental migration from waste into the soilplant system was conducted on the territory of the Institute of Geology and Geochemistry, Ural Branch of RAS (southwestern part of the Ekaterinburg, Sverdlovsk region). The soil substrate was prepared from lime-neutralised ombrotrophic peat (pH 6.6) with the addition of “technical sand” of 5, 10 and 20% by weight. Lawn grass mixture was grown on trial plots (1 m2). The samples of lawn grass (without separation by species), together with the root part and peat, were collected after the growing season by the “envelope” method, dried at room temperature until constant weight, and powdered. The chemical analysis of the samples was performed at the “Geoanalitik” shared research facilities of the Institute of Geology and Geochemistry, Ural Branch of RAS. The analyses were performed by inductively coupled plasma massspectrometry using the NexION-300S ICP mass-spectrometer.Results. The mobilisation of elements from the “SUMZ technical sand” into ombrotrophic peat during the summer was investigated, the distribution of elements in the underground and aboveground parts of lawn grasses was demonstrated, and accumulation coefficients were calculated. The content of most elements in all soil substrates containing waste decreased by autumn, for example, 2–3 times for Zn, Cu, Co, S, As, Pb, and Mo. The aboveground part of lawn grass had a lower concentration of the elements considered as compared to the roots, the greatest difference was observed for Co, Cd, Cu, and W. The lawn grasses grown on soil substrates with the different ratios of “SUMZ technical sand” had lower coefficients of accumulation of heavy metals compared to plants grown on the peat. The coefficients of Na, Ba, Mo, As, Cd, and Pb decreased with an increase in the proportion of waste, and for Li and Rb increased.Conclusion. The results of the research contribute to the study of the migration of elements from non-ferrous metallurgical waste into soil and plant systems.