Properties of Urban Soils after Decontamination Measures on the Radioactively Contaminated Territory of the City of Elektrostal

Abstract

We studied the morphological properties, pH, organic carbon content, and specific activity of ¹³⁷Cs and natural radionuclides (⁴⁰K, ²²⁶Ra, ²³²Th) in the upper horizons of soils in deactivated and slightly damaged areas of the city. The studies were carried out in the urban ecosystems of the city of Elektrostal (Moscow oblast) in 2019, i.e., 6 years after local precipitation of ¹³⁷Cs due to a radiation incident. The morphological features of the upper horizons of urban soils were the following: brownish-gray color, light-loamy composition, and small-lumpy and lumpy structure, with inclusions of construction and household waste. In the upper horizons of urban quasizems and urban soils, a low carbon content (less than 1%) with high coefficients of variation were detected. In the studied urban soils, a wide range of water pH values was noted: from an acidic (4.6–5.5) to highly alkaline (>8.0) reaction. Correlation analysis showed that, in the upper horizons of UR, the content of organic carbon was reduced and alkalinization of the soil environment was observed. The accumulative type of distribution of ¹³⁷Cs was recorded for soil profiles of polluted urban ecosystems in which decontamination measures were not carried out. The profiles of urban soils that were subjected to decontamination revealed low values of the specific activity of ¹³⁷Cs in surface bulk layers and maxima in buried contaminated horizons. In the bulk horizons of UR, which include a large amount of crushed stone, there was an increase in the specific activity of ²²⁶Ra. Some technogenic horizons of UR and TCH, consisting mainly of quartz sand, are characterized by very low values of specific activities ²²⁶Ra and ⁴⁰K. Correlations of chemical and radiation indicators in the profiles of urban soils reflect the different compositions and properties of upper horizons formed as a result of excavation and decontamination work.