Spatial zoning of the territory of Almaty City based on the concentration and level of heavy metal contamination of soils

Document Type : Research Paper

Authors

1 UNESCO Chair for Sustainable Development, Faculty of Geography and Environmental Sciences University, Al-Farabi Kazakh National University, Almaty, Kazakhstan

2 Department of Cartography and Geoinformatics, Faculty of Geography and Environmental Sciences, Al-Farabi Kazakh National University, Almaty, Kazakhstan

10.22124/cjes.2026.9790

Abstract

Almaty, the largest city in Kazakhstan, has a long history of industrial activity and heavy traffic, yet no systematic assessment of soil heavy metal contamination has ever been conducted across the entire urban territory. To fill this gap, we collected 412 soil samples from the top 0–10 cm layer between April and September 2025, covering all administrative districts of Almaty on a 1 km × 1 km grid. Concentrations of lead (Pb), cadmium (Cd), zinc (Zn), copper (Cu), and chromium (Cr) were measured using ICP‑OES after aqua regia digestion. Background values were established from 25 reference sites outside the city. The results show wide spatial heterogeneity: Pb ranged from 4.2 to 347.8 mg kg-1 (mean 48.6), and Cd from 0.05 to 3.92 mg kg-1 (mean 0.64). Strong positive correlations among Pb, Cd, Zn, and Cu (r = 0.69–0.84, p < 0.001) indicate common anthropogenic sources, while Cr showed only moderate enrichment (median enrichment factor 1.2). Using the threshold of background mean + 2SD, we classified the city into four zones: Class I (clean, 33% of area), Class II (moderate, 38%), Class III (high, 22%), and Class IV (very high, 7%). Very high zones are concentrated in the northern industrial belt and near the former battery plant, where Pb averaged 124.5 mg kg-1 and Cd 1.92 mg kg-1, close to Kazakh maximum allowable concentrations. Industrial areas and old residential districts displayed significantly higher contamination than new residential zones (p < 0.001). This study provides the first evidence‑based soil contamination map for Almaty, enabling targeted remediation, urban planning, and public health interventions.

Keywords

References

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Caspian Journal of Environmental Sciences
Volume 24, Issue 3
July 2026
Pages 773-782

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