Americium In Soils Research Articles

Determination of uranium, plutonium and americium in soil and sediment by a sequential separation procedure using a single DGA column

A novel method has been developed for the simultaneous determination of uranium, plutonium and americium nuclides in soil and sediment samples up to 5 g. Samples are destroyed by fusion with sodium hydroxide. Pre-concentration procedure tailored to the extraction chromatography is based on co-precipitation of actinides and removal of silica, iron and calcium. For the sequential separation of actinides a single DGA resin® (containing N,N,N′,N′-tetra-n-octyldiglycol-amide) column is used. Separation of americium from lanthanides is inherently involved in the EC procedure. Alpha sources are prepared from the individual actinides strip solutions. High recoveries (above 75%) and sensitivities (about 0.1 Bq/kg) have been obtained to allow the determination of actinides of environmental levels. The whole procedure can be performed in 2 days.

Dependence of the migration ability of plutonium and americium in soils on additions of natural and modified organic compounds

The nature and content of modified humic acid derivatives influence the intensity of the recovery of Pu, Am, and Corg from soddy podzolic soil with distilled water. Under the dynamic conditions, these radionuclides are recovered more intensely in the presence of carboxylated humic acids, compared to the hydroxymethylated derivatives. When soils with the introduced modified humic acid derivatives are subjected to prolonged washing with distilled water, the radionuclides undergo redistribution within the columns, suggesting their migration. Under the action of dissolved organic substances isolated from soils (low-molecular-weight nonspecific organic compounds and fulvic acids), the radionuclide migration in soils occurs still more intensely. In the course of soil column washing with an aqueous phase containing the dissolved organic matter, Pu and Am pass into the mobile state to a greater extent than in washing the soils with distilled water.

Pu and Am determination in the environment—method development

A high resolution inductively coupled plasma mass spectrometric (HR-ICP-MS) method for the determination of plutonium isotopes, Am and the 240Pu/239Pu isotope ratio utilising modification of Pu-02-RC Plutonium in Soil Samples, Pu-03-RC Plutonium in Soil Residue—Total Dissolution Method, Pu-11-RC Plutonium Purification—Ion Exchange Technique, Pu-12-RC Plutonium and/or Americium in Soil or Sediments, HASL-300 was developed. Total plutonium concentrations (239+240Pu) measured in environmental samples by this HR-ICP-MS method were in good agreement with recommended data obtained from a-spectrometry. It was achieved the decreasing of the time to analyze the samples over than 33%.

Soil organic matter and migration properties of239,240Pu and241Am

Humus influence on mobility of plutonium and americium in soil has been investigated. To do this the entrance of radionuclides into soil water solutions with different organic matter concentration and the distribution of 239,240 Pu and 241 Am between humus fractions of soil has been analyzed. The mineral and organic soils with distinct quantitative and qualitative composition of humus, contaminated by radionuclides of Chernobyl origin have been studied. The groups of fulvic (FA) and humic acids (HA) which differ in their composition and solubility in water were extracted from soils and the content of 239,240 Pu and 241 Am in these organic fractions was detected. It was established that humus substances (HS) mainly promote the fixation of 239,240 Pu and 241 Am in solid phase of soil. The humus of organic soils promotes the fixation of plutonium and americium to a greater extent than HS of mineral soils. That is one of the reasons of lower mobility of 239,240 Pu and 241 Am in organic soils. A higher ability of plutonium to form the difficultly soluble complexes with HS compare to americium may be a factor of higher mobility of americium in soil.

Plutonium and americium behaviour in soil-vegetation cover of natural and semi-natural ecosystems

The results of investigation s of transuranic elements { H,,M0 Pu and 24 'Am) behaviour in the soil-vegetation cover of natural and semi-natural ecosystems in the regions of Belarus contaminated as a result of Chernobyl acci­ dent have been summarised. The parameters of plutonium and americium vertical migration have been estimated for typical soil varieties; the radionuclides accumulation coefficients have been defined for dominating species of meadow and forest vegetation. The dynamics of change in physico-chemi cal state of plutonium and americium (the share and geochemical stability of hot particles, the ratio between fixed and mobile forms) has been analysed in various types of soils in the post-chernobyl period. It was established that the content of exchangeable 239 - 240 Pu and MI Am does not exceed 12.5%, the largest part of radionuclides is in fixed form in composition of soil humus and or- gano-mineral components. The linear rate of vertical migration of plutonium and americium in soils is 0.14-1.25 cm/year. Simultaneous interaction of different agrochemical parameters and natural conditions masks the influence of individual soil properties on migration rate, but the correlation with humidity has been reviled. The ac­ cumulation coefficients of americium in the system soil-plant are 1.2-4 times higher that those for plutonium. The method of reduction in the bioavailability of transuranic elements has also been proposed.

Physicochemical Speciation of Americium in Soils from Rocky Flats, Colorado, USA

The objective of the research was to characterize the 241Am distribution in six operationally defined chemical and mineralogical phases of soil samples taken from the Rocky Flats Environmental Technology Site (RFETS). Soil samples were subjected to selective sequential fractionation procedures to determine 241Am association with the soluble, exchangeable, carbonate, organic, sesquioxide and silicate fractions. The highest percentage of 241Am was found to be associated with the sesquioxide (hydrous oxide) fraction (39–47%), with lesser amounts in the soluble (14–17%), exchangeable (4–9%), carbonates (4–17%), organic (3–13%), and silicate (10–21%) soil fractions. Differences between americium and plutonium association with various soil fractions were observed.

Simultaneous determination of plutonium and americium in soils by extraction chromatography

A radiochemical method is described for the determination of238Pu,239(240)Pu and241Am in a single soil sample. Plutonium is separated from a HNO3 leaching solution by a Microthene-TNOA column; amcricium is coprecipitated by oxalic acid, decontaminated from polonium by a TNOA-column in HCl medium, separated from the rare earth elements by a Microthene-HDEHP column, eluted with a 0.07M DTPA+1M lactic acid solution and finally purified by a PMBP-TOPO extraction. The method supplies a good decontamination of Am and Pu from natural alpha emitters; starting from 50 g soil, the average yields were 75.1±13.4% for plutonium and 57.7±10.8% for Am.239(240)Pu,238Pu and241Am concentrations (mBq/kg) in three different kinds of soil were the following: 255, 10.4, 81.3 (uncultivated soils); 236, 11.6, 76.7 (cultivated soils); 46, 1.9, 19.8 (river sediment). The average ratios238Pu to239(240)Pu and241Am to239(240)Pu were 0.044 and 0.350, respectively.

Investigations of interactions of transuranics and cerium with humates

239Pu and 241Am have been shown to be associated with high molecular weight components isolated from soils. Attempts to detect humates on soil particles by examination on a microscope by monitoring Raman light absorption have failed. The cerium-containing organic soil used in this study can not be used to model the short-term behaviour of americium in soils.

Investigation of solubilization of plutonium and americium in soil by natural humic compounds

An investigation was conducted under simulated natural conditions to determine the solubilization of plutonium and americium in contaminated soil by humic compounds. The results indicate that the solubilization of plutonium and americium by fulvic acid--the more soluble humic compound--is slight. In no instance did the plutonium and americium concentrations in solution approach the drinking water limits. What little solubilization that occurs is probably due to complex formation and/or colloid peptization. The resulting solutions are unstable, and over a period of a few days, most of the plutonium and americium precipitate, either as a result of colloid coagulation or hydrolysis. Two other factors appear to limit the solubilization of these elements: only a relatively small fraction of the plutonium and americium seems to be readily soluble, and there is apparently a low saturation value for these elements in both water and fulvic acid solution.