Petromagnetic parameters of urban soils as an indicator of pollution (the case of Ufa city, Russia)

Abstract The article examines the petromagnetic parameters of soils within the urbanized area of Ufa (Republic of Bashkortostan, Russia), with additional comparison to data on elemental composition and particle morphology. According to statistical analysis, background values of magnetic susceptibility (χ) are estimated at 83 x 10− 8 m3/kg for the southern (residential) part of the city and 140 x 10− 8 m3/kg for the northern (industrial) zone. The relative contributions of the ferromagnetic, dia-/paramagnetic, and superparamagnetic components to the total magnetic susceptibility were 95%, 4%, and 1%, respectively. Comparison with previously obtained elemental composition data for the study area revealed correlations between magnetic susceptibility and the concentrations of Cu, Cr, S, Ni, As, Pb, Sb, and Zn. Spatial analysis of magnetic susceptibility distribution revealed localized zones of elevated values in industrial areas associated with petrochemical and metalworking enterprises. Scanning electron microscopy of micromineral phases contained in the soil cover revealed the presence of magnetic particles with both spherical and irregular morphologies, ranging in size from 20 to 120 µm. In areas subjected to intense anthropogenic impact, intermetallic Fe-Cr alloys (10 to 60 µm in size) were identified, along with alloying elements such as tungsten (W) and combustion-related indicator elements including barium (Ba) and sulfur (S). The Day-Dunlop diagram reflects the differentiation between samples subjected to varying degrees of anthropogenic impact. In industrial areas, a predominance of multidomain particles over single-domain particles is observed, indicating the accumulation of technogenic magnetic components. In residential zones, their concentrations remain lower, which can be attributed to the reduced intensity of local pollution sources.