Integrated Geochemical and Spatial Assessment of Potentially Toxic Metal Contamination in Urban Soils of Turkestan, Kazakhstan: Implications for Environmental Monitoring and Sustainable Urban Development

Abstract

Urban soils are sensitive indicators of environmental quality and anthropogenic pressure, particularly in arid regions where pollutant accumulation is enhanced by limited precipitation and intense evaporation. This study aimed to assess physicochemical properties, heavy metal contamination, spatial heterogeneity, and potential pollution sources in urban soils of Turkestan, Kazakhstan. Surface soil samples were collected from 15 representative sites covering industrial, transport, residential, peripheral, and recreational land-use zones. The samples were analyzed for pH(H2O), total dissolved solids, petroleum hydrocarbons, organic matter, and total concentrations of Cu, Zn, Pb, and Cd. Spatial distribution mapping, Pearson correlation analysis, principal component analysis (PCA), and heatmap visualization were applied to identify contamination patterns and likely pollution sources.  The investigated soils exhibited stable alkaline conditions, with pH values ranging from 8.52 to 8.74, typical of arid urban environments. Zinc showed the highest variability, with concentrations ranging from 68.0 to 203 mg kg-1 and a coefficient of variation exceeding 50%, indicating localized enrichment. Cadmium displayed pronounced spatial heterogeneity (0.14-2.80 mg kg-1) and enrichment near industrial and transport-related areas. Copper concentrations ranged from below the detection limit to 61.3 mg kg-1, whereas lead exhibited comparatively lower spatial variability. Spatial distribution maps revealed contamination hotspots associated with transport corridors, industrial facilities, and fuel stations. Multivariate statistical analysis demonstrated relationships among metals, petroleum hydrocarbons, and urban infrastructure, while PCA distinguished metal-enriched sites from mixed urban and low-impact areas. Urban soils of Turkestan are influenced by localized anthropogenic activities and can serve as useful indicators of technogenic pressure in arid urban environments. The integrated application of spatial mapping and multivariate statistical approaches provides a practical framework for environmental monitoring, pollution management, and sustainable urban development in data-limited Central Asian cities.