Assessment of the concentration of rare earth elements (REEs) in industrially impacted topsoil: a case study from the Jizera Mountains and Upper Silesian Industrial Area (USIR), Poland

This study investigates heavy rare earth elements (Ho, Er, Tm, Yb, Lu) in soils from two industrially influenced regions in southern Poland: the Jizera Mountains and the Upper Silesian Industrial Region (USIR). A total of 166 soil samples were collected from different land use types, including arable, forested and mountain areas. Sampling involved collecting soil cores up to 30 cm deep using a Humax sampler, with GPS-based georeferencing. Magnetic susceptibility was measured to identify horizons enriched with technogenic magnetic particles linked to industrial pollution. Selected subsamples were analyzed for REEs concentrations using Inductively Coupled Plasma Mass Spectrometry. Elevated concentrations of heavy REEs were observed in the Jizera Mountains, an area naturally enriched in REEs due to the presence of minerals such as monazite and xenotime. Agricultural soils showed significantly higher REEs concentrations than adjacent forests, likely due to fertilizer use and soil disturbance from cultivation. The highest enrichment factor (about 3) and geoaccumulation index (about 1.5) values were observed in mountainous areas, over twice as high as in arable and forest soils. ANOVA revealed statistically significant differences (p < 0.05), with the strongest effect observed for IG Lu. Strong positive correlations (r > 0.7) among REEs suggest shared natural or anthropogenic sources. These findings highlight the combined influence of geological background and human activity on REEs accumulation in soils and demonstrate the utility of EF and IG indices for assessing soil contamination in industrially impacted regions.