Soil enrichment, physicochemical controls, and source apportionment of potentially toxic elements in arid soils of the abarghoo–sirjan basin, central Iran

Enrichment of soils by potentially toxic elements (PTEs) is one of the major environmental concerns in many regions, particularly in arid environments. This study provides the first integrated assessment of PTE enrichment in the dust-prone area of the Abarghoo-Sirjan Basin (covering 12% of the basin) in central Iran, using an approach that combines three multi-element pollution indices (Nemerow pollution index (NPI), modified pollution index (MPI), and improved weighted index (IWI) with multivariate statistical analysis (Spearman correlation and principal component analysis). This study aimed to (i) investigate the relationships between the concentrations of 13 PTEs and soil physicochemical properties, (ii) assess the level of soil enrichment, and (iii) identify the possible sources of these elements in the study area. Concentrations of PTEs were measured in 63 surface soil samples (0-5 cm) using inductively coupled plasma optical emission spectrometry. Mean concentrations of Al, As, Cd, Cr, Ni, and Zn exceeded local background values, whereas the concentrations of Co, Cu, Fe, Mn, Pb, Sb, and V were lower than their background levels. Significant correlations were observed among most PTEs and between PTEs and soil properties (|p| = 0.25-0.95). A key finding is that the enrichment hotspot in the northeastern part is not associated with any local industrial source. The spatial coincidence of this hotspot with downwind areas relative to industrial zones in the northwest and south, together with prevailing wind directions, is suggestive of aeolian transport as a possible contributing mechanism. Multi-element indices revealed an increasing enrichment trend from the southern to the northeastern parts of the study area. Cd, Pb, and Zn were interpreted as having dominant anthropogenic sources, whereas Al, Co, Cr, Cu, Fe, Mn, Ni, Sb, and V were primarily geogenic. Although the multi-element indices indicate relative enrichment compared to local background values, comparison with Iranian DOE standards confirmed that all PTEs remain below permissible limits, indicating early-stage enrichment rather than acute contamination. These results provide a scientific basis for designing targeted pollution control strategies in dust-prone areas. Furthermore, they suggest that wind-driven particle transport may create enrichment hotspots far from their emission sources.