Impact of soil organic matter on Pu migration in five Lithuanian surface soils.

Pu distribution coefficient K variation was experimentally determined and examined in natural soil samples considering the type of soil, particle size, pH, the concentration of macroelements and organic matter content. This research was carried out with sand, silty sand, peat, clayey sand and clayey loam samples by applying Pu tracer in flow-through column tests. Due to relatively short contact time of 0.

Experimental and modelling studies of radiocesium sorption/desorption processes in the fixed-bed moss column.

The experimental and modelling studies of the fixed-bed column filled with inanimate mosses Ptilium crista-castrensis containing background levels of Cs, flushed with the distilled water are presented. Fitting of the experimental results by Langmuir and Freundlich sorption models gave significant deviations. A more sophisticated two kinetic site model created for the case of non-equilibrium transport of the radiocesium solute through porous media was more suitable to describe the experimental data.

Cs and plutonium isotopes accumulation/retention in bottom sediments and soil in Lithuania: A case study of the activity concentration of anthropogenic radionuclides and their provenance before the start of operation of the Belarusian Nuclear Power Plant (NPP).

Knowledge of the background activity concentrations of anthropogenic radionuclides before the start of operations of the new nuclear facilities in Belarus is of great value worldwide. Inland water bodies in Lithuania (specifically the Neris River, the Nemunas River and the Curonian Lagoon) are near the site of the Belarusian NPP under construction and, for this reason, sediments and flooded soils from these sensitive areas were analysed for radiocesium and plutonium isotopes (macrophytes were analysed only for Cs) in 2011-2012. The Cs and Pu activity concentrations in bottom sediments from the Nemunas River, sampled in 1995-1996 and re-calculated to the year 2016, were compared with those of 2011-2012.

Study of the formation of the primary Cs vertical profile in the organic matter-rich sediments.

A laboratory study of the formation of the primary vertical profile of the Cs activity concentration in the anaerobic organic matter-rich sediments was carried out. The incubation was performed using sediment baths method (initial thickness of the water layer over the sediments ∼40 cm, initial radiocesium activity concentration in water ∼14.53 Bq·L).

Accumulation and translocation peculiarities of (137)Cs and (40)K in the soil--plant system.

Long-term investigations (1996-2008) were conducted into the (137)Cs and (40)K in the soil of forests, swamps and meadows in different regions of Lithuania, as well as in the plants growing in these media. The (137)Cs and (40)K activity concentrations, the (137)Cs/(40)K activity concentration ratio and accumulation, and translocation in the system, i.e.

Spatial patterns and ratios of ¹³⁷Cs, ⁹⁰Sr, and Pu isotopes in the top layer of undisturbed meadow soils as indicators for contamination origin.

Spatial distribution of activity concentrations of (137)Cs, (90)Sr, and (239,240)Pu in the top layer of undisturbed meadow soils was compared between two regional transects across Lithuania: one in the SW region, more affected by the Chernobyl radioactive fallout, and the other in the NE region. Radiochemical, γ-, α-, β-, and mass spectrometric methods were used to determine the radionuclide activity. Our results validate that higher activity concentrations in the top soil layer were present in the SW region, despite the fact that sampling was performed after 22 years of the Chernobyl Nuclear Power Plant (NPP) accident.

Anthropogenic radionuclide fluxes and distribution in bottom sediments of the cooling basin of the Ignalina Nuclear Power Plant.

Based on γ-ray emitting artificial radionuclide spectrometric measurements, an assessment of areal and vertical distribution of (137)Cs, (60)Co and (54)Mn activity concentrations in bottom sediments of Lake Drūkšiai was performed. Samples of bottom sediments from seven monitoring stations within the cooling basin were collected in 1988-1996 and 2007-2010 (in July-August). For radionuclide areal distribution analysis, samples from the surface 0-5 cm layer were used.

Behaviour of (99)Tc in aqueous solutions in the presence of iron oxides and microorganisms.

A set of experiments was performed to determine the factors that influence TcO4(-) interaction with Fe-bearing minerals and to explore the effect of microbial activity on the behaviour of Tc(VII) in solution, in the presence of iron oxides under oxidizing medium. Gradual sorption of TcO4(-) (aq) onto wustite/magnetite was observed under alkaline conditions (pH 8-9). No pronounced effect of TcO4(-) (aq) interaction with hematite was observed in the investigating alkaline systems.

Accumulation and transfer of 137Cs and 90Sr in the plants of the forest ecosystem near the Ignalina Nuclear Power Plant.

The radioecological state of the forest ecosystem in the vicinity of the Ignalina Power Plant prior to decommissioning was analysed with specific emphasis on (137)Cs and (90)Sr activity concentrations in plant species growing in two reference sampling sites (Tilze and Grikiniskes). In the period of 1996-2008 the mean contamination of plants with (137)Cs was from 45 to 119 Bq/kg and with (90)Sr - from 3 to 42 Bq/kg. Measured (137)Cs TF values for soil-root transfer mainly ranged between 1.

Distribution of artificial gamma-ray emitting radionuclide activity concentration in the top soil in the vicinity of the Ignalina Nuclear Power Plant and other regions in Lithuania.

The impact of the operating Ignalina Nuclear Power Plant (INPP) on the contamination of top soil layer with artificial radionuclides has been studied. Results of the investigation of artificial gamma-ray emitting radionuclide distribution in soil in the vicinity of the INPP and distant regions in Lithuania in 1996-2008 (INPP operational period) show that nowadays (137)Cs remains the most important artificial gamma-ray emitting radionuclide in the upper soil layer. Mean (137)Cs activity concentrations in the top soil layer in the vicinity of the INPP were found to be significantly lower compared to those in remote regions of Varėna and Plungė (~300 km from INPP).

Effect of microorganisms on the plutonium oxidation states.

Particular microbes from substrates at the low-level radioactive waste repository in the Ignalina NPP territory were exposed to (239)Pu (IV) at low pH under aerobic conditions. Pu(III) and Pu(IV) were separated and quantitatively evaluated using the modified anion exchange method and alpha spectrometry. Tested bacteria Bacillus mycoides and Serratia marcescens were more effective in Pu reduction than Rhodococcus fascians.

Assessing deposition levels of 55Fe, 60Co and 63Ni in the Ignalina NPP environment.

Two RBMK-1500 reactor units operated in Lithuania in the 1987-2004 period (one of them was stopped for decommissioning in 2004). This study presents a preliminary investigation of surface deposition density levels of (55)Fe and (63)Ni in moss samples collected in the close vicinity of the Ignalina NPP. Non-destructive analysis by the HPGe gamma-spectrometry was followed by radiochemical separation.

Study of plutonium migration and/or accumulation in soil under field and laboratory conditions.

This study investigated the dependence of Pu3+ and Pu4+ vertical distribution on the soil characteristics in soddy and forest soil. Soil samples were analysed for organic matter and pH. Special columns with contaminated (239Pu) soil surface were kept for 326 days under field conditions.

Comparative analysis of (239)Pu, (137)Cs, (210)Pb and (40)K spatial distributions in the top soil layer at the Baltic coast.

This paper presents the results of an investigation into the spatial distribution of radionuclides of artificial ((239,240)Pu, (137)Cs) and natural ((210)Pb, (40)K) origins in the upper (0-5 cm) soil layers on the Baltic coastline of Lithuania ( approximately 5 km(2) area). The samples were analysed by gamma ray spectrometry and combined radiochemical procedures. The highest (210)Pb, (239,240)Pu and (137)Cs activity concentrations were determined in the forest samples, whereas (40)K activity was rather homogeneous across the study area.

Toxicity to Tradescantia of technogenic radionuclides and their mixture with heavy metals.

The genotoxic effects on Tradescantia of (137)Cs, (90)Sr, and (236, 242)Pu, a heavy metal mixture [Cd, Cr(VI), Cu, Mn(II), Ni, Pb, Zn] and of a complex mixture of these toxicants were determined. The impact of radionuclides on plants subjected to ionizing radiation exposure was estimated. The number of somatic mutations and the quantity of nonviable stamen hairs were used as end points in the testing.