226Ra In Environmental Samples Research Articles

Determination of 226Ra in environmental samples by alpha spectrometry: a new separation method based on the rapid co-precipitation of 226Ra with PbSO4

Determination of 226Ra in environmental samples by alpha spectrometry: a new separation method based on the rapid co-precipitation of 226Ra with PbSO4

Rapid determination of 226Ra in environmental samples

A new rapid method for the determination of 226Ra in environmental samples has been developed at the Savannah River Site Environmental Lab (Aiken, SC, USA) that can be used for emergency response or routine sample analyses. The need for rapid analyses in the event of a Radiological Dispersive Device or Improvised Nuclear Device event is well-known. In addition, the recent accident at Fukushima Nuclear Power Plant in March, 2011 reinforces the need to have rapid analyses for radionuclides in environmental samples in the event of a nuclear accident. 226Ra (T1/2 = 1,620 years) is one of the most toxic of the long-lived alpha-emitters present in the environment due to its long life and its tendency to concentrate in bones, which increases the internal radiation dose of individuals. The new method to determine 226Ra in environmental samples utilizes a rapid sodium hydroxide fusion method for solid samples, calcium carbonate precipitation to preconcentrate Ra, and rapid column separation steps to remove interferences. The column separation process uses cation exchange resin to remove large amounts of calcium, Sr Resin to remove barium and Ln Resin as a final purification step to remove 225Ac and potential interferences. The purified 226Ra sample test sources are prepared using barium sulfate microprecipitation in the presence of isopropanol for counting by alpha spectrometry. The method showed good chemical recoveries and effective removal of interferences. The determination of 226Ra in environmental samples can be performed in less than 16 h for vegetation, concrete, brick, soil, and air filter samples with excellent quality for emergency or routine analyses. The sample preparation work takes less than 6 h. 225Ra (T1/2 = 14.9 day) tracer is used and the 225Ra progeny 217At is used to determine chemical yield via alpha spectrometry. The rapid fusion technique is a rugged sample digestion method that ensures that any refractory radium particles are effectively digested. The preconcentration and column separation steps can also be applied to aqueous samples with good results.

Application of ICP-QMS for the determination of ultratrace-levels of 226Ra in geothermal water and sediment samples

A rapid, accurate and less labor intensive approach to determining 226Ra in environmental samples was examined; this utilized quadrupole-based inductively coupled plasma mass spectrometry (ICP-QMS). The procedure used chemical separation by ion exchange chromatography to remove most of the matrices after coprecipitation with BaSO4. The average chemical recovery of the NIST SRM preparation method ranged from 60.5 to 85.9% using 133Ba as internal tracer by gamma counting. This technique was capable of completing a 226Ra measurement within 3 min. It did not require an in-growth period to allow radon and its progeny to achieve secular equilibrium with the parent 226Ra as is needed for liquid scintillation analyzer (LSA). The method detection limits for the determination of 226Ra in geothermal water and sediment samples were 0.02 mBq L−1 (0.558 fg L−1) and 0.10 Bq kg−1 (2.79 fg g−1), respectively. The results obtained with various natural samples and the suitability of the method when applied to various environmental matrices such as geothermal water and sediment are discussed. When ICP-QMS was compared to double-focusing magnetic sector field inductively coupled plasma mass spectrometry (ICP-SFMS), good agreement was obtained with a correlation coefficient, r2 = 0.982.

Development of Marinelli beaker standards containing thorium oxide and application for measurements of radioactive environmental samples

Marinelli (reentrant) beakers are recommended for measurement of low-activity radioactive environmental samples, in both liquids and solid phases. The preparation of Marinelli beaker standards containing 232ThO 2 in a secular equilibrium with its daughter nuclides was studied. Standards were prepared by mixing of known amounts of solid ThO 2 and various solids (e.g. CaCO 3) to reach desired density (e.g. 1.1 g / cm 3 for CaCO 3). Measurements of calibrated Marinelli standards with HPGe detector showed that the energy dependence of the efficiency is similar to that of a point source, i.e. an almost linear dependence of log efficiency vs. log energy in the 200– 2000 keV range, however the parabolic correlation fits better. The validity of these standards was checked by comparison to three certified reference Marinelli standards containing radio-cesium, radio-potassium and 226Ra in environmental samples. Quite good agreement was obtained between our standards and the published certified data. The limit of detection for the determination of radio-cesium by γ -ray spectrometry under the prevailing experimental conditions is 0.07 Bq ( 1.9 pCi ) , for 1.0 kg of environmental samples.

Procedures for the determination of 222Rn exhalation and effective 226Ra activity in soil samples

Two methods for measuring 222Rn exhalation and effective 226Ra in soil samples were studied. In the first determination, the method employed was based on the adsorption of radon onto activated charcoal and subsequent measurement of the activity of its daughters with an HPGe (high-purity germanium) detector. In the second, vials containing an aqueous suspension of the sample, mixed with an insoluble high efficiency mineral oil scintillation cocktail, were measured using a low-level liquid scintillation counter. Studies of optimum sampling time, efficiency in both procedures, variation of 226Ra efficiency with quenching, as well as the effect of sample amount and granulometry upon the quenching parameter, were carried out. The two methods were applied to the determination of 222Rn exhalation and effective 226Ra in environmental samples.

Activity concentrations and population dose from radium-226 in food and drinking water in Taiwan

The purpose of this study was to determine the radioactivity of 226Ra in environmental samples in Taiwan. Fish, pork, rice, flour, chicken, vegetable, milk, fruit, egg and water samples were collected and pretreated by radiochemical procedure to extract the 226Ra, and the activity concentrations of 226Ra were determined using a liquid scintillation counter. The 226Ra content of groundwater was 12.0 mBq l −1. The 226Ra contents of the food ranged from 0.02 Bq kg −1 fresh to 0.17 Bg kg −1 fresh. The annual internal dose from ingestion of 226Ra from food and drinking water per caput was evaluated to be 7.5 μSv.

A sequential analytical method for the determination of U-238, Th-232, Th-230, Th-228, Ra-228 and Ra-226 in environmental samples

A sequential analytical method for the determination of 238U, 234U, 234Th, 230Th, 228Th, 228Ra and 226Ra in environmental samples has been developed. Uranium and thorium isotopes are initially separated using tri-n-octyl phosphine oxide (TOPO) supported on a column of silica gel. The uranium isotopes are determined by alpha-spectrometry following extraction with TOPO onto a polymeric membrane. Thorium isotopes are coprecipitated with lanthanum fluoride before counting in an alpha spectrometer. Radium isotopes are separated by coprecipitation with mixed barium and lead sulphate. Radium-226 is determined with the radon emanation technique on a solution of the mixed barium and lead sulphates in ethylene-diamine tetra-acetic acid. Radium-228 is measured by its daughter product 228Ac in a 2 πβγ coincidence counter.

The determination of 226Ra in environmental samples with zinc sulfide powder

The determination of 226Ra in environmental samples with zinc sulfide powder