Assessing the Impact of Urban Development on Soil Health and Nutrient Cycling Across Urban Areas

Urbanization, a hallmark of the 21st century, has significantly altered land use and environmental systems worldwide. This study aimed to bridge a critical research gap by investigating the effects of urbanization on soil properties, using Astana, Kazakhstan, as a case study to reflect broader urban soil trends. The objective was to assess soil texture, humus content, pH, and soluble salts across various land use categories, including residential, commercial, industrial, and forested areas, which served as control/reference sites. Soil samples were analyzed for nitrate nitrogen, available phosphorus, potassium, sulfur, humus, pH, and soluble salts such as calcium, magnesium, chloride, sulfate, and bicarbonate. Comparative analyses revealed notable variations in bulk density across land use categories. Residential areas exhibited lower bulk densities (topsoil: 1.24–1.32 g/cm3; subsoil: 1.41– 1.54 g/cm3), indicating lesser compaction. Conversely, commercial zones showed increased bulk densities (topsoil: 1.41–1.55 g/cm3; subsoil: 1.52–1.65 g/cm3), reflective of foot traffic and impermeable surfaces. Industrial zones recorded the highest bulk densities (topsoil: 1.55–1.62 g/cm3; subsoil: 1.63–1.76 g/cm3), largely attributed to heavy machinery and construction activities. Agricultural lands demonstrated moderate bulk densities (topsoil: 1.30–1.42 g/cm3; subsoil: 1.52–1.66 g/cm3), influenced by tillage practices, while forested areas had the lowest bulk densities (topsoil: 1.20–1.30 g/cm3; subsoil: 1.34–1.45 g/cm3), indicating minimal disturbance and higher organic content. Nutrient assessments indicated that nitrate nitrogen and phosphorus levels were generally moderate, with agricultural areas exhibited significantly higher phosphorus concentrations due to fertilizer application. Additionally, heavy metal concentrations, particularly lead and chromium, were found to be elevated in industrial zones, highlighting potential contamination risks. The study concluded that urban soils display diverse nutrient levels and physical properties, with forested areas providing a baseline for comparison. These findings emphasize the need for comprehensive soil evaluations in urban planning to address the specific conditions of different land use types. Implementing tailored management practices can enhance soil health and foster sustainable urban development on a larger scale.