Risk-based assessment of soil pollution by potentially toxic elements in the industrialized urban and peri-urban areas of Ahvaz metropolis, southwest of Iran

The main purpose of this research was to assess the level of contamination, source identification, geochemical fractionation, and health risk of potentially toxic elements (PTEs) in industrial soils from urban and pen-urban areas of Ahvaz city. A total of 92 surface soil samples were gathered and concentrations of sixteen PTEs were measured using aqua regia digestion by an inductively coupled plasma mass spectrometry (ICP-MS). Possible sources of PTEs were quantitatively determined by positive matrix factorization (PMF) receptor model combined with geostatistical analyses and geochemical methods. The results showed that long-term industrial activities have enhanced the levels of some PTEs particularly Pb, Hg, Zn, Mo, Sb, Fe, Cu, and Cd to different extents. Contamination indices including geoaccumulation index, pollution index, and Nemerov integrated pollution index along with multivariate statistical analyses confirmed that steel and iron industries are the most contaminating industries in the study area. The outcomes attained from Kruskal-Wallis test affirmed that there was a significant difference among the concentrations of As, Hg, Mn, Cu, Fe, Pb, Mo, Cd, V, Zn, and Sb in soils around different industrial clusters. Among the studied elements, the highest mobility factors belonged to Zn (81.49%), Pb (76.71%), Cu (71.65%), Hg (66.23%), Mn (62.48%), and Mo (59.27%), respectively. Also, the PMF model showed that steel and iron industries (51.2%) and natural sources (23.4%) are the main sources of PTEs, followed by industrial towns (16.7%) and power plants (8.7%). This is in line with the results of principal component analysis (PCA). Majority of the measured PTEs showed the highest bioavailability in surface soils collected from around the steel and iron industries. Also, based on the outcomes of the health risk assessment model, particular attention should be paid to Hg, Pb, Zn, and Cu in industrial soils of Ahvaz.