Natural attenuation processes control groundwater contamination in the Chernobyl exclusion zone: evidence from 35 years of radiological monitoring

Ultrasensitive optical detection of strontium ions by specific nanosensor with ultrahigh binding affinity

The release and escape of radioactive materials has posed tremendous threats to the global environment. Among various radioactive elements, 90Sr has attracted growing attention due to its long half-life and its tendency to accumulate in bone tissue. Nonetheless, the concentration of 90Sr in radioactive waste is exceedingly low, far below the detection limits of currently available strontium-targeting chemical sensors. Herein, we propose an optical nanosensor (Sr2+-nanosensor) that exhibits an ultra-low detection limit of 0.5 nM, surpassing the 90Sr in the treated radioactive water from the Fukushima. The sensor offers wide sensing range of eight orders of magnitude, rapid response of less than 10 s, and high selectivity against 31 common ions. These excellent performances are attributed to a specific ligand (Sr2+-ligand) for Sr2+ recognition. The Sr2+ is found to be bound by six oxygen atoms from the Sr2+-ligand with a stability constant at least two orders higher than that of other traditional ligands. This study offers invaluable insights for the design of Sr2+-sensing methodologies as well as a technique for detecting trace amounts of environmental radioactive pollution.

A predictive assessment of the uranium ore tailings impact on surface water contamination: Case study of the city of Kamianske, Ukraine

In this study, we present an assessment of the uranium ore tailings impact on groundwater and surface water contamination. The radioactive materials were deposited in the tailings storage facility "Dniprovske" (the city of Kamianske, Ukraine) from 1954 to 1968; now it contains about 5.85·106 m3 of hazardous waste on the area of about 76 ha in the floodplain of the Dnipro river. The lack of a proper waterproof screen below deposited tailings and in the earthen dam led to permanent watering of radioactive materials, their leaching and migration in groundwater into the nearest small Konoplianka river. We used the reports on previous site-specific studies conducted in 1999-2016, monitoring results, and the field studies conducted in 2022 with the authors' team participation. The calculations performed with the advection-dispersion model to simulate transport of radionuclides 238U, 230Th, 226Ra and 210Pb through the embankment to the Konoplianka river and dilution relations were compared to the monitoring data of the surface water quality. Among four radionuclides, uranium poses the greatest risks today; the subsurface runoff increases its concentration in the Konoplianka river water by several times over the background value. It is estimated that due to much more intensive sorption in the shallow aquifer, the contribution of 226Ra and 210Pb to the increase in radioactivity of Konoplianka river water is insignificant compared to uranium, whereas the migration front of 230Th has probably not yet reached the riverbank. In the next 50 years the radionuclide fluxes will increase by 1.3-3.7 times for different isotopes, with the uranium subsurface runoff growing at a slower rate than nowadays. These results are of high significance for improving hydrological, hydrogeological, and geotechnical monitoring on this hazardous facility to maintain its radiation safety.

Evaluating changes in radionuclide concentrations and groundwater levels before and after the cooling pond drawdown in the Chornobyl Nuclear Power Plant vicinity

In the vicinity of the Chornobyl Nuclear Power Plant (ChNPP), the cooling pond (CP) was an artificially maintained reservoir with water levels regulated to 7 m above the Pripyat River until May 2014, when its pumps stopped operating, resulting in a natural drawdown. To investigate the surface-groundwater system before and after the drawdown, we evaluated the spatial and temporal changes in ⁹⁰Sr and ¹³⁷Cs radionuclide concentrations and groundwater levels in the shallow unconfined aquifer near the ChNPP from 2010 to 2019. Additionally, we compared water levels and ⁹⁰Sr concentrations in Azbuchin Lake, wetlands inside the CP, and the Pripyat River. Using three-year averages before (2011-2013) and after (2017-2019) the drawdown period, we found that ⁹⁰Sr concentrations significantly increased up to 10² kBq/m³ in the Pripyat River floodplain, north of ChNPP, exceeding the WHO drinking water guideline of 10 kBq/m³. In contrast ¹³⁷Cs concentrations ranged consistently between 10 and 100 Bq/m³. The groundwater levels decreased over 50 cm at approximately 65 % of shallow monitoring wells and up to 6 m near the CP. The ⁹⁰Sr concentration increases in some wells at the Pripyat River floodplain were associated with decreased dilution rates from the CP due to the reduced CP leakage, causing changes in groundwater flow direction and decreases in groundwater velocity. From the new finding of this study that the drawdown increased ⁹⁰Sr concentrations near the floodplain, we estimated the ⁹⁰Sr flux and contribution to the Pripyat River and the ⁹⁰Sr contribution did not change significantly after the drawdown. However, radionuclides may accumulate more at the floodplain in the future; therefore, additional monitoring is required to verify ⁹⁰Sr transport from areas of elevated concentrations and its impact on groundwater in the aquifer.