The transfer capability of long-lived Chernobyl radionuclides from surface soil to river water in dissolved forms

Title: The transfer capability of long-lived Chernobyl radionuclides from surface soil to river water in dissolved forms

Author: H Amano, T Matsunaga, S Nagao, Y Hanzawa, M Watanabe, T Ueno, Y Onuma

Reference: Organic Geochemistry, Volume 30, Issue 6, June 1999, Pages 437-442

DOI:http://dx.doi.org/10.1016/S0146-6380(99)00028-5

Keywords: Sr-90; Cs-137; Transuranic elements; Speciation; Surface soil; Runoff; Dissolved organic materials; Fulvic acid; Ultrafiltration; Chernobyl 30 km zone

Abstract: Hydrologic runoff is one of the main processes in which radionuclides deposited in the surface environment migrate widely in both particulate and dissolved forms. This paper focuses on the transfer capability of long lived Chernobyl radionuclides from surface soil to river water in dissolved forms. First, concentration and speciation of radioactive Cs, Sr and transuranic isotopes, such as Pu and Am, were examined in undisturbed surface soil along the river in the exclusion zone (30 km zone) near the Chernobyl Nuclear Power Plant (NPP) in order to validate the radioactive contamination characteristics. Almost all radioactivities exist in the very top surface in the undisturbed soil layer. Sr-90 in the soil was estimated to be highest in the water soluble and exchangeable fractions, which were easily accessible to river water as a dissolved fraction. Pu isotopes and Am-241 are major radionuclides in free humic and free fulvic acid fractions. Secondly, surface soil near the Sahan River was extracted with distilled water, as an analogue of rain water, to estimate the dissolved fraction in runoff components from surface soil to river water. After a filtration procedure, extracted water was treated with ultra filtration techniques separating the molecular weight fractions of beyond and below 10,000 Da. Each fraction was measured for the radioactivity and the characteristics of organic materials including humic substances. Most Pu and Am exist in the molecular weight fractions beyond 10,000 Da, in spite of the fact that most of the dissolved organic fractions exist below 10,000 Da. This means that transuranic elements such as Pu and Am are associated with mobile high molecular weight materials like fulvic acids in water leachates.

URL: http://www.sciencedirect.com/science/article/pii/S0146638099000285

Nuclear weapon and Chernobyl debris in the troposphere and lower stratosphere

Title: Nuclear weapon and Chernobyl debris in the troposphere and lower stratosphere

Author: Ludwika Kownacka, Zbigniew Jaworowski

Reference: Science of The Total Environment, Volume 144, Issues 1–3, 29 April 1994, Pages 201-215

DOI: http://dx.doi.org/10.1016/0048-9697(94)90439-1

Keywords: Radionuclides; Troposphere; Stratosphere; Nuclear tests; Chernobyl

Abstract: High altitude aircraft sampling of aerosols has been carried out at 4–7 levels up to 15 km over Poland. From 1973 to 1991 a total of 102 vertical concentration profiles of ⁹⁰Sr, ¹³⁴Cs and ¹³⁷Cs, and 83 profiles of ¹⁴⁴Ce were determined. One year after the sub-megaton nuclear test in 1980, ¹³⁷Cs was almost completely removed from the stratosphere. The Chernobyl debris was found in the stratosphere from the third day after the accident until the end of 1991. In May 1986 the concentration of ¹³⁴Cs and ¹³⁷Cs at stratospheric altitudes reached about 0.5% of that between the ground level and 3 km. Residence times of Chernobyl radiocesium in the lower stratosphere systematically increased between 1987 and 1991, in variance with those of the debris from nuclear tests. The vertical concentration profiles and the long residence times of radiocesium indicate that the non-violent meteorological processes were transporting the Chernobyl debris into the lower stratosphere, immediately and long after the accident. We postulate that the same quiescent processes transport vast amounts of resuspended particulate organics from the surface of land and sea into high altitudes, and may thus bear on the chemistry of the stratosphere.

URL: http://www.sciencedirect.com/science/article/pii/0048969794904391

The effective source area of 90Sr for a stream near Chernobyl, Ukraine

Title: The effective source area of ⁹⁰Sr for a stream near Chernobyl, Ukraine

Author: Rina Freed, Leslie Smith, Dmitri Bugai

Reference: Journal of Contaminant Hydrology, Volume 71, Issues 1–4, July 2004, Pages 1-26

DOI: http://dx.doi.org/10.1016/j.jconhyd.2003.07.002

Keywords: Chernobyl; Hydrologic contaminant transport; Non-point source; Soil contamination; Strontium-90

Abstract: Remediation of streams impacted by non-point source contaminants requires an understanding of both the areas within a watershed that are contributing contamination to streams and the pathways of contaminant migration to streams. From 1998 to 2002, we studied the migration of ⁹⁰Sr in the Borschi watershed, a small (8.5 km²) catchment three km south of the Chernobyl Nuclear Power Plant, Ukraine. Fuel particles, distributed in a heterogeneous pattern across the watershed, are weathering and releasing ⁹⁰Sr from the fuel matrix. Depletion of ⁹⁰Sr, evaluated in comparison to the immobile fission product europium-154, is occurring in the channel and wetland sediment. Channel sediments are uniformly depleted in ⁹⁰Sr with depth. In wetland sediments, there is a zone of depletion in the top10 cm and a zone of accumulation at depths from 10 to 25 cm. Estimates of ⁹⁰Sr depletion are used to map the effective source area that has contributed ⁹⁰Sr loading to the main channel. The effective source area includes channel bottom sediments, a wetland in the central region of the watershed, and periodically flooded soils surrounding the wetland. The total depletion from the effective source area is estimated to be 36±7×10¹⁰ Bq. Based on observations of stream flow rate and water quality in 1999–2001, the annual ⁹⁰Sr removal rate from the watershed is estimated to be 1.4±0.2×10¹⁰ or 1.5% of the inventory per year. When extrapolated over a 15-year period following the Chernobyl accident, the last value is in reasonable agreement with the estimated depletion of the source area based on ⁹⁰Sr/¹⁵⁴Eu ratios. The ⁹⁰Sr yearly leaching rate considering the whole watershed is 0.2% while the ⁹⁰Sr leaching rate considering the effective source area is an order of magnitude higher. Most of the ⁹⁰Sr release in the watershed has originated from an effective source area of 0.62 km², or 7% of the watershed area.

URL: http://www.sciencedirect.com/science/article/pii/S0169772203002225

Plutonium, 137Cs and 90Sr in selected invertebrates from some areas around Chernobyl nuclear power plant

Title:Plutonium, ¹³⁷Cs and ⁹⁰Sr in selected invertebrates from some areas around Chernobyl nuclear power plant

Author: Jerzy W. Mietelski, Svetlana Maksimova, Przemysław Szwałko, Katarzyna Wnuk, Paweł Zagrodzki, Sylwia Błażej, Paweł Gaca, Ewa Tomankiewicz, Olexandr Orlov

Reference: Journal of Environmental Radioactivity, Volume 101, Issue 6, June 2010, Pages 488-493

DOI:http://dx.doi.org/10.1016/j.jenvrad.2008.04.009

Keywords: Plutonium; ⁹⁰Sr; ¹³⁷Cs; Chernobyl; Invertebrates; Radioactive contamination of biota

Abstract: Results are presented for ¹³⁷Cs, ⁹⁰Sr and plutonium activity concentrations in more than 20 samples of terrestrial invertebrates, including species of beetles, ants, spiders and millipedes, collected in the highly contaminated area of the Chernobyl exclusion zone. The majority of samples were collected in Belarus, with some also collected in the Ukraine. Three other samples were collected in an area of lower contamination. Results show that seven samples exceed an activity concentration of 100 kBq/kg (ash weight – a.w.) for ¹³⁷Cs. The maximum activity concentration for this isotope was 1.52 ± 0.08 MBq/kg (a.w.) determined in ants (Formica cynerea). Seven results for ⁹⁰Sr exceeded 100 kBq/kg (a.w.), mostly for millipedes. Relatively high plutonium activity concentrations were found in some ants and earth-boring dung beetles. Analyses of activity ratios showed differences in transfer of radionuclides between species. To reveal the correlation structure of the multivariate data set, the Partial Least-Squares method (PLS) was used. Results of the PLS model suggest that high radiocesium activity concentrations in animal bodies can be expected mainly for relatively small creatures living on the litter surface. In contrast, high strontium activity concentrations can be expected for creatures which conduct their lives within litter, having mixed trophic habits and a moderate lifespan. No clear conclusions could be made for plutonium.

URL: http://www.sciencedirect.com/science/article/pii/S0265931X08000696

Inflow of Chernobyl 90Sr to the Black Sea from the Dnepr River

Title: Inflow of Chernobyl ⁹⁰Sr to the Black Sea from the Dnepr River

Author: Gennady G. Polikarpov, Hugh D. Livingston, Ludmilla G. Kulebakina, Ken O. Buesseler, Nikolai A. Stokozov, Susan A. Casso

Reference: Estuarine, Coastal and Shelf Science, Volume 34, Issue 3, March 1992, Pages 315-320

DOI: http://dx.doi.org/10.1016/S0272-7714(05)80087-3

Keywords: Chernobyl; ⁹⁰Sr; Dnepr River; Black Sea

Abstract: Following the Chernobyl reactor accident in April 1986, studies of radionuclides in aquatic systems in general, and in the Black Sea in particular, have focused primarily on the fate and behaviour of direct fallout deposition (Buesseler et al., in press; Livingston et al., 1988; Polikarpov et al., 1991). In this paper we present an evaluation of riverine ⁹⁰Sr input and its use as a tracer for circulation studies of Chernobyl labelled shelf waters. We describe how ⁹⁰Sr measurements in the Dnepr River in the period 1986–89 can be used to determine the amount and timing of the subsequent ⁹⁰Sr inflow to the northwest Black Sea. Comparison of these data with measurements made in the Danube River in 1988 demonstrates that the Dnepr ⁹⁰Sr flux to the Black Sea is about one order of magnitude higher than that of the Danube.

URL: http://www.sciencedirect.com/science/article/pii/S0272771405800873

Soil contamination with 90Sr in the near zone of the Chernobyl accident

Title: Soil contamination with 90Sr in the near zone of the Chernobyl accident

Author: V.A Kashparov, S.M Lundin, Yu.V Khomutinin, S.P Kaminsky, S.E Levchuk, V.P Protsak, A.M Kadygrib, S.I Zvarich, V.I Yoschenko, J Tschiersch

Reference: Journal of Environmental Radioactivity, Volume 56, Issue 3, 2001, Pages 285-298

DOI: http://dx.doi.org/10.1016/S0265-931X(00)00207-1

Keywords: Soil contamination; ⁹⁰Sr; Chernobyl; 30 km exclusion zone; Map

Abstract: Representative large-scale soil sampling on a regular grid of step width about 1 km was carried out for the first time in the near zone of the Chernobyl accident (radius 36 km). An integrated map of terrestrial ⁹⁰Sr contamination density in the 30 km exclusion zone (scale 1 : 200,000) has been created from the analysed samples. Maps of the main agrochemical characteristics of the soils, which determine the fuel particle dissolution rates and the contamination of vegetation, were produced. The total contents of ⁹⁰Sr on the ground surface of the 30 km zone in Ukraine (without the reactor site and the radioactive waste storages) was about 810 TBq (8.1×10⁺¹⁴ Bq) in 1997, which corresponds to 0.4–0.5% of the Chernobyl reactor inventory at the time of the accident. This assessment is 3–4 times lower than previous estimates.

URL: http://www.sciencedirect.com/science/article/pii/S0265931X00002071

Fuel particles in the Chernobyl cooling pond: current state and prediction for remediation options

Title: Fuel particles in the Chernobyl cooling pond: current state and prediction for remediation options

Author: A. Bulgakov, A. Konoplev, J. Smith, G. Laptev, O. Voitsekhovich

Reference: Journal of Environmental Radioactivity, Volume 100, Issue 4, April 2009, Pages 329-332

DOI: http://dx.doi.org/10.1016/j.jenvrad.2008.12.012

Keywords: Chernobyl; Cooling pond; Fuel particles; ⁹⁰Sr; Dissolution; Remediation

Abstract: During the coming years, a management and remediation strategy for the Chernobyl cooling pond (CP) will be implemented. Remediation options include a controlled reduction in surface water level of the cooling pond and stabilisation of exposed sediments. In terrestrial soils, fuel particles deposited during the Chernobyl accident have now almost completely disintegrated. However, in the CP sediments the majority of ⁹⁰Sr activity is still in the form of fuel particles. Due to the low dissolved oxygen concentration and high pH, dissolution of fuel particles in the CP sediments is significantly slower than in soils. After the planned cessation of water pumping from the Pripyat River to the Pond, significant areas of sediments will be drained and exposed to the air. This will significantly enhance the dissolution rate and, correspondingly, the mobility and bioavailability of radionuclides will increase with time. The rate of acidification of exposed bottom sediments was predicted on the basis of acidification of similar soils after liming. Using empirical equations relating the fuel particle dissolution rate to soil and sediment pH allowed prediction of fuel particle dissolution and ⁹⁰Sr mobilisation for different remediation scenarios. It is shown that in exposed sediments, fuel particles will be almost completely dissolved in 15–25 years, while in parts of the cooling pond which remain flooded, fuel particle dissolution will take about a century.

URL: http://www.sciencedirect.com/science/article/pii/S0265931X08002324

90Sr migration to the geo-sphere from a waste burial in the Chernobyl exclusion zone

Title: 90Sr migration to the geo-sphere from a waste burial in the Chernobyl exclusion zone

Author: L Dewiere, D Bugai, C Grenier, V Kashparov, N Ahamdach

Reference: Journal of Environmental Radioactivity, Volume 74, Issues 1–3, 2004, Pages 139-150

DOI: http://dx.doi.org/10.1016/j.jenvrad.2004.01.019

Keywords: Chernobyl; Strontium-90; Fuel particles; Groundwater; Retardation; Sorption; Hydro-dispersion

Abstract: Results are presented from an ongoing field-scale experimental study (namely the Chernobyl Pilot Site project) aimed at characterization of processes controlling ⁹⁰Sr releases from a shallow trench containing nuclear fuel particles, and subsequent radionuclide transport in the underlying sandy aquifer at the Chernobyl nuclear power plant site. Microscopic analyses of waste material and leaching experiments have shown that 10–30% of the radioactive inventory is associated with chemically extra-stable Zr–U–O particles. The largest fraction of ⁹⁰Sr activity in the trench (≈30–60%) is currently associated with relatively slowly dissolving non-oxidized UO₂ matrix fuel particles. The ⁹⁰Sr migration velocity in the eolian sand aquifer is retarded by sorption to ≈9% of groundwater flow velocity (K_d ≈ 2 ml/g). The dispersivity values for non-reactive solute transport in the aquifer predicted by geostatistics (i.e. 0.8 6 cm) were confirmed by a natural gradient tracer test using ³⁶Cl. The observed negative correlation between hydraulic conductivity and K_d of aquifer sediments suggests that ⁹⁰Sr could be subjected to larger dispersion in the subsurface compared with ³⁶Cl.

URL: http://www.sciencedirect.com/science/article/pii/S0265931X04000244

Distribution and migration of ⁹⁰Sr in components of the Dnieper River basin and the Black Sea ecosystems after the Chernobyl NPP accident

Title: Distribution and migration of ⁹⁰Sr in components of the Dnieper River basin and the Black Sea ecosystems after the Chernobyl NPP accident
Author: N.Yu. Mirzoyeva, V.N. Egorov, G.G. Polikarpov

URL: http://www.sciencedirect.com/science/article/pii/S0265931X13000489

Kinetics of dissolution of Chernobyl fuel particles in soil in natural conditions

Keywords: Chernobyl; Fuel particles; Dissolution kinetics; Sr-90; Mobility; Soil

Abstract: Kinetic of fuel particles dissolution under natural environmental conditions has been investigated using the data on ⁹⁰Sr speciation in soils collected from 1995 to 1997 within the Chernobyl nuclear power plant 50 km zone. The dependency of fuel particles dissolution constants on the soil acidity (pH=4–7) has been obtained on the basis of large and statistically reliable experimental data. Results show that between 2 and 21% of ⁹⁰Sr activity is associated with weathering resistant fuel particles. Therefore, these particles would not influence the radiological situation in the near future. The map of the main agrochemical characteristics and the map of the fuel particles dissolution constants have been created for the 30-km zone territory. According to the prognosis of dynamics of fuel particles dissolution in the investigated zone, a radiological situation along the fuel paths of radioactive fallout in present time reached a stable state. An increasing in absolute contents of ⁹⁰Sr mobile forms in neutral soils will be observed in the next 10–20 yr. However, the difference between the maximum level of mobile forms contents and their existing contents will not exceed 20%.