Origin of critical raw materials in technogenically disturbed soils from the territory of a steel metallurgical plant in Southeastern Europe

Abstract

Six soil profiles with metamorphic and weakly developed structure, formed on old and young Quaternary proluvial and colluvial deposits, were studied. A comprehensive dataset was obtained for over 50 elements (including more than two-thirds of the CRMs), across 20 genetic horizons of various types - metamorphic, gleyed, and contaminated with agglomeration dust, coke, and other materials. Due to the growing interest and knowledge of these raw materials, this study has derived statistical relationships between many of them in the context of increased values of most. The soils are geochemically and technogenically enriched, reflecting both natural and anthropogenic influences. Three genetic and one technogenic geochemical associations were identified through XRD, LA-ICP-MS, statistical and geochemical analyses (PCA, Pearson’s correlation, Concentration coefficients - CC). The plutonogenic association Hf–P–W–Nb–Ce/LREE–Sr–Bi–Ge+Ta–Th–Rb–Cs–Au, derived from the potassic-alkaline Buhovo–Seslavtsi pluton, shows strong correlations (r (P) = 0.46–0.86; r (W) = 0.50–0.98; r (Th) = 0.55–0.98). The ore-related association As–Mo–Co–Ni–Ga–Mn–Sb–Cu–Zn–U–V (r = 0.45–0.94) reflects proluvial material enriched with sulfide and uranyl-phosphate minerals. The lithophillyc association Ga–Y/HREE–Ce/LREE–Al–Ti–Sc–Si (r(Sc) = 0.63–0.88) represents a stable Al–Si–oxide-controlled system, while the technogenic Ba–Mn–Pb–Ag–Sr–Sb–Cu association (r(Ba) = 0.51–0.75; r(Pb) = 0.41–0.91) records up to 11-fold Pb and 4-fold Ba enrichment in surface horizons due to persistent metallurgical impact.