Source apportionment of soil pollution in industrial cities of Kazakhstan

Soils in industrial cities act as long-term sinks for anthropogenic contaminants and can provide valuable information on emission sources. This study identifies and compares the dominant pollution sources in soils of two industrial cities in Kazakhstan, Pavlodar and Ust-Kamenogorsk, using source apportionment of polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs). Ust-Kamenogorsk exhibits a robust technogenic footprint. Surface soils are highly enriched in Zn (up to ~600 mg kg^-1), Pb (~208 mg kg^-1), Cu (~74 mg kg^-1), Cd (up to 6.4 mg kg^-1), and As (~20 mg kg^-1), forming a persistent geochemical anomaly. Source apportionment revealed four major contributors. The dominant factor is non-ferrous metallurgy, clearly associated with elevated Cd-Pb-Zn-Cu loadings in topsoil. A second factor is linked to coal combustion and fly ash deposition, characterized by Fe-Al-Cr-V associations. The natural mineralogical background was distinguished as a separate source dominated by carbonate and oxide-related elements (Ca, Mn, Ba). A fourth source, marked by strong As-Se coupling, is attributed to emissions from pyrometallurgical processing.

In contrast, Pavlodar soils demonstrated lower contamination levels and a more diffuse anthropogenic signal. Three integrated factors were identified: 1) a mixed lithogenic-industrial source combining Al, Fe, Cr, Ni, and V, reflecting both parent material and refining-related activities; 2) a traffic- and construction-related source defined by Cu, Zn, Pb, Ca, and Na, indicative of abrasion products, cement dust and historical lead residues; and 3) a minor geochemical factor dominated by Co-Se, likely attributable to local lithological heterogeneity. Total PAH concentrations range from 0.82 to 3.53 µg g^-1 in Pavlodar and 0.18 to 11.31 µg g^-1 in Ust-Kamenogorsk. In Pavlodar, the prevalence of indeno[1,2,3-cd]pyrene and naphthalene indicates road materials and traffic emissions, while medium-molecular-weight PAHs, contributing up to one-third of the PAH burden, are consistent with coal combustion. Ust-Kamenogorsk shows elevated PAHs levels with distinct spatial hotspots, confirming intense industrial influence. These results demonstrate that industrial specialization controls soil pollution regimes, with Ust-Kamenogorsk representing an extreme case of metallurgy-driven contamination and Pavlodar reflecting mixed urban–industrial loading. These findings highlight the need for targeted remediation and prioritized urban environmental management.