Distribution patterns and origin of potentially toxic elements in soils of the Vanadzor urban area (Armenia)

Urban soils preserve important information about the processes conditioning the pollution levels of urban areas. Thus, geochemical characterization of the urban areas is essential for improving environmental quality and reducing potential risks. The results of this study showed that Cu, Pb, Zn and Cr in soils of Vanadzor city exhibited similar spatial distribution patterns. The higher contents of these elements were located close to industrial and residential areas suggesting their predominant anthropogenic origin. In addition, these elements display EF above moderate level. Three geochemical associations unveiled by k-means clustering and the interrelationship of the studied elements within these geochemical associations revealed by the hierarchical clustering showed that Cr, Cu, Zn, Pb are linked to Ca minerals or Fe oxy/hydroxides. The results of the hierarchical clustering of the subdataset (upper 25th quartile (> 75%) of the Ca database) revealed that the contents of Cr, Zn, Cu, Pb are lined to Fe, whereas the clustering of soil samples having > 75% contents of Cr, Zn, Cu, Pb revealed a link between these elements and Ca suggesting their fixation by Ca minerals. These findings inferred the existing differences in behavior of Cr, Zn, Cu, and Pb sorption by Ca minerals and Fe oxide-hydroxide in various areas of the city territory. Non-carcinogenic health risks to children were detected for Fe (three sites) and Cu (one site). For Pb, adverse health effects to children were observed in the main residential part of the city, whereas for adults, a precautionary risk level was identified in these areas.