BACKGROUND AND OBJECTIVES: Urban soils serve as important reservoirs for microbiological and helminthological contaminants, with their abundance and spatial distribution strongly influenced by soil physical properties, particularly clay content. Understanding these relationships is essential for managing public health risks in rapidly urbanizing environments. This study aims to investigate the relationship between soil granulometric composition and biological contamination in Astana, Kazakhstan, by integrating microbiological data with Geographic Information System based spatial analysis.METHODS: A total of 50 soil samples were collected from recreational areas, residential zones, and multi-storey residential districts with adjacent streets. Microbiological analyses quantified Escherichia coli, nitrifying bacteria, Clostridium perfringens, and thermophilic bacteria in Colony forming units per gram. Clay content ranged from 30 percent to 55 percent, and contamination metrics were analyzed in relation to soil texture. Using geographic information system version 3.2, microbial and helminthological data were georeferenced, interpolated, and combined with clay fraction layers through a weighted overlay model to generate a contamination risk index map highlighting spatial variability.FINDINGS: Results showed a strong positive association between clay content and both microbial abundance and helminth presence. Escherichia coli counts ranged from (1.0 ± 0.3) × 10³ colony forming units per gram in soils with 35–40 percent clay to (2.5 ± 0.6) × 10³ colony forming units per gram in 40–45 percent clay soils. Nitrifying bacteria reached up to 7.7 × 10³ colony forming units per gram in the same clay range, while Clostridium perfringens densities varied from 2.2 × 10² to 7.0 × 10² colony forming units per gram, peaking in moderately clayey soils. Thermophilic bacteria abundance increased sharply with clay content, from 10² colony forming units per gram in coarse soils to 1.7 × 10⁷ colony forming units per gram in soils with 45–50 percent clay. Helminth eggs were detected most frequently in soils containing 40–50 percent clay. CONCLUSION: The integration of microbiological, helminthological, and soil granulometric data within a Geographic Information System framework effectively characterized contamination patterns across the urban landscape of Astana. The findings highlight that soil texture, particularly clay content, plays a critical role in shaping microbial and helminth distributions.
Zandybay et al. (Thu,) studied this question.