Technogenic radioactive waste from uranium mining and processing represents a persistent environmental challenge worldwide, yet integrated assessments of radionuclide redistribution across multiple environmental compartments at individual sites remain scarce, particularly in Central Asia. This study presents a multi-compartment investigation of a technogenic radioactive waste storage facility in the Navoi region of Uzbekistan, simultaneously characterizing 226Ra, 232Th, 40 K, 222Rn, and total uranium across soil, pore air, and groundwater. Soil 226Ra activities (mean: 5306.5 Bq/kg; CV: 103.1%) were markedly heterogeneous and exceeded control-site levels by an order of magnitude, with subsurface enrichment at 45–50 cm depth (5936.8 vs. 4676.2 Bq/kg at the surface; Wilcoxon p = 0.070), indicating downward migration driven by water-mediated transport. A statistically significant, moderately strong to strong positive correlation was found between 222Rn and 226Ra activities (r ≈ 0.67–0.70; p < 0.01) at the 99% confidence level, indicating that radon exhalation is largely controlled by the parent radium content. Pore-air radon activity at the waste site (mean: 13.77–16.79 Bq/m3) was nearly double that at control sites (7.71 Bq/m3). The equivalent activity concentration of total uranium in groundwater ranged from 2.32 to 12.25 Bq/L, with a mean value of 5.78 Bq/L, substantially exceeding the WHO guideline value for total uranium in drinking water (30 µg/L, corresponding to approximately 0.76 Bq/L for natural uranium), whereas 226Ra activity concentrations (mean: 0.177 Bq/L) remained below the recommended WHO guidance level. The absence of a significant uranium 226Ra correlation (r ≈ 0.07) suggests independent geochemical migration pathways. The ambient dose equivalent rate at the waste site (mean: 0.313 µSv/h; max: 0.85 µSv/h) was approximately three times higher than in adjacent settlements (0.104 µSv/h), reflecting substantial spatial heterogeneity associated with radionuclide accumulation and localized technogenic influence. These results provide the first integrated, multi-compartment dataset for a uranium waste repository in Uzbekistan and demonstrate that active radionuclide redistribution across the soil–water–air system necessitates sustained radioecological monitoring at this and comparable legacy sites.

Radionuclide migration and correlation in the soil–water–air environment at a radioactive waste storage site, Uzbekistan

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2026年6月16日

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Umidjon Haydarov,
Amrullo Muzafarov,
Shakhboz Khasanov

摘要

Technogenic radioactive waste from uranium mining and processing represents a persistent environmental challenge worldwide, yet integrated assessments of radionuclide redistribution across multiple environmental compartments at individual sites remain scarce, particularly in Central Asia. This study presents a multi-compartment investigation of a technogenic radioactive waste storage facility in the Navoi region of Uzbekistan, simultaneously characterizing ²²⁶Ra, ²³²Th, ⁴⁰ K, ²²²Rn, and total uranium across soil, pore air, and groundwater. Soil ²²⁶Ra activities (mean: 5306.5 Bq/kg; CV: 103.1%) were markedly heterogeneous and exceeded control-site levels by an order of magnitude, with subsurface enrichment at 45–50 cm depth (5936.8 vs. 4676.2 Bq/kg at the surface; Wilcoxon p = 0.070), indicating downward migration driven by water-mediated transport. A statistically significant, moderately strong to strong positive correlation was found between ²²²Rn and ²²⁶Ra activities (r ≈ 0.67–0.70; p < 0.01) at the 99% confidence level, indicating that radon exhalation is largely controlled by the parent radium content. Pore-air radon activity at the waste site (mean: 13.77–16.79 Bq/m³) was nearly double that at control sites (7.71 Bq/m³). The equivalent activity concentration of total uranium in groundwater ranged from 2.32 to 12.25 Bq/L, with a mean value of 5.78 Bq/L, substantially exceeding the WHO guideline value for total uranium in drinking water (30 µg/L, corresponding to approximately 0.76 Bq/L for natural uranium), whereas ²²⁶Ra activity concentrations (mean: 0.177 Bq/L) remained below the recommended WHO guidance level. The absence of a significant uranium ²²⁶Ra correlation (r ≈ 0.07) suggests independent geochemical migration pathways. The ambient dose equivalent rate at the waste site (mean: 0.313 µSv/h; max: 0.85 µSv/h) was approximately three times higher than in adjacent settlements (0.104 µSv/h), reflecting substantial spatial heterogeneity associated with radionuclide accumulation and localized technogenic influence. These results provide the first integrated, multi-compartment dataset for a uranium waste repository in Uzbekistan and demonstrate that active radionuclide redistribution across the soil–water–air system necessitates sustained radioecological monitoring at this and comparable legacy sites.