Rapid method for 226Ra and 228Ra analysis in water samples

Summary The measurement of radium isotopes in natural waters is important for oceanographic studies and for public health reasons. Radium-226 (T_1/2 = 1620 y) 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 analysis of ²²⁶Ra and ²²⁸Ra in natural waters can be tedious and time-consuming. Different sample preparation methods are often required to prepare ²²⁶Ra and ²²⁸Ra for separate analyses. A rapid method has been developed at the Savannah River Environmental Laboratory that effectively separates both ²²⁶Ra and ²²⁸Ra (via ²²⁸Ac) for assay. This method uses MnO₂ Resin from Eichrom Technologies (Darien, IL, USA) to preconcentrate ²²⁶Ra and ²²⁸Ra rapidly from water samples, along with ¹³³Ba tracer. DGA Resin^ò (Eichrom) and Ln-Resin^ò (Eichrom) are employed in tandem to prepare ²²⁶Ra for assay by alpha-spectrometry and to determine ²²⁸Ra via the measurement of ²²⁸Ac by gas proportional counting. After preconcentration, the manganese dioxide is dissolved from the resin and passed through stacked Ln-Resin-DGA Resin cartridges that remove uranium and thorium interferences and retain ²²⁸Ac on DGA Resin. The eluate that passed through this column is evaporated, redissolved in a lower acidity and passed through Ln-Resin again to further remove interferences before performing a barium sulfate microprecipitation. The ²²⁸Ac is stripped from the resin, collected using cerium fluoride microprecipitation and counted by gas proportional counting. By using vacuum box cartridge technology with rapid flow rates, sample preparation time is minimized.     

Rapid method for determination of 228Ra in water samples

A new rapid method for the determination of ²²⁸Ra in natural water samples has been developed at the SRNL/EBL (Savannah River National Lab/Environmental Bioassay Laboratory) that can be used for emergency response or routine samples. While gamma spectrometry can be employed with sufficient detection limits to determine ²²⁸Ra in solid samples (via ²²⁸Ac), radiochemical methods that employ gas flow proportional counting techniques typically provide lower minimal detectable activity levels for the determination of ²²⁸Ra in water samples. Most radiochemical methods for ²²⁸Ra collect and purify ²²⁸Ra and allow for ²²⁸Ac daughter ingrowth for ~36 h. In this new SRNL/EBL approach, ²²⁸Ac is collected and purified from the water sample without waiting to eliminate this delay. The sample preparation requires only about 4 h so that ²²⁸Ra assay results on water samples can be achieved in <6 h. The method uses a rapid calcium carbonate precipitation enhanced with a small amount of phosphate added to enhance chemical yields (typically >90 %), followed by rapid cation exchange removal of calcium. Lead, bismuth, uranium, thorium and protactinium isotopes are also removed by the cation exchange separation. ²²⁸Ac is eluted from the cation resin directly onto a DGA Resin cartridge attached to the bottom of the cation column to purify ²²⁸Ac. DGA Resin also removes lead and bismuth isotopes, along with Sr isotopes and ⁹⁰Y. La is used to determine ²²⁸Ac chemical yield via ICP-MS, but ¹³³Ba can also be used instead if ICP-MS assay is not available. Unlike some older methods, no lead or strontium holdback carriers or continual readjustment of sample pH is required.     

The determination of mercury by non-flame atomic absorption and fluorescence spectrometry.

An isotopic dilution method has been developed for the determination of ²²⁶Ra and ²²⁸Ra in sea water and sediments with ²²³Ra as a yield tracer. An alternative procedure which obviates the need for ²²³Ra is demonstrated for sediments by the assay of ²²⁴Ra and ²²⁸Th which occur naturally in sediments. In addition, a direct method for β-counting ²²⁸Ra–²²⁸Ac is proposed. Radium, polonium, thorium and uranium isotopes and ²¹⁰Pb are coprecipitated from sea water with aluminum phosphate carrier. The radium and lead-210 are coprecipitated with lead nitrate in sediment leachings. All radium procedures utilize identical chemical isolation and the cathodic electrodeposition of radium. Subsequently, the α-radiation emitted by ²²⁶Ra, ²²³Ra and ²²⁴Ra is determined by pulse-height analysis: the ²²⁸Ra-²²⁸Ac and ²¹⁰Pb-²¹⁰Bi are measured by low background anticoincidence β-counting techniques. This method was used for samples containing 10^-11–0.5 · 10^-12 g of ²²⁶Ra and 10^-13–10^-15 g of ²²⁸Ra and gave a precision of 3–6% and 5–10% respectively, even though radium levels an order of magnitude less can be measured. The ²²⁶Ra method is applicable to all environmental samples, whereas ²²⁸Ra determinations are limited to applications where the ${}^{228}\text{Ra}{}^{226}\text{Ra}$ activity ratio is greater than 0.1. This method is especially attractive for studies of parent-daughter disequilibria.     

Determination of <Superscript>228</Superscript>Ra in human bone ash containing significant quantities of <Superscript>40</Superscript>K and Ca<Superscript>2+</Superscript>

The determination of ²²⁸Ra by means of γ-spectrometry, in material containing significant quantities of ⁴⁰K and Ca²⁺ such as bone ash results in increased values of counting uncertainty and lower limit of detection (LLD) because of a significant contribution from the Compton continuum of ⁴⁰K. However, ⁴⁰K is widely removed from bone ash if ²²⁸Ra is coprecipitated with barium sulfate. As a result, the counting uncertainty and LLD are significantly reduced. A method is presented for determination of very low activity concentrations of ²²⁸Ra. Impurities introduced by precipitation are negligible when applying high resolution γ-spectrometry.     

Contribution to the simultaneous determination of228Ra and226Ra by using 3M's EMPORETM radium rad disks

New method for simultaneous determination of²²⁸Ra and²²⁶Ra by using 3M's EMPORE^TM Radium Rad Disks in water has been developed. Both radionuclides²²⁶Ra and²²⁸Ra were counted through their daughter products,²²⁶Ra by conventional radon emanation techniques and²²⁸Ra through its daughter²²⁸Ac by using a proportional counter. Different molarity of diammonium hydrogen citrate were used for elution of²²⁸Ac and²²⁶Ra from EMPORE^TM Radium Rad Disks. 79% of²²⁸Ac was eluted in 10 ml of 0.0003M diammonium hydrogen citrate. The recovery of²²⁶Ra was 99% by using 40 ml of 0.2M diammonium hydrogen citrate adjusted by ammonium to pH 7.8.     

Chemometrics of the distribution and origin of <Superscript>226</Superscript>Ra, <Superscript>228</Superscript>Ra, <Superscript>40</Superscript>K and <Superscript>137</Superscript>Cs in plants near the West Macedonia Lignite Center (Greece)

Summary The distribution and origin of ⁴⁰K, ²²⁶Ra, ²²⁸Ra and ¹³⁷Cs has been investigated in trees, mosses and lichens in the basin of the West Macedonia Lignite Centre. In tree leaves ¹³⁷Cs is negligible, while the ²²⁶Ra and ²²⁸Ra concentrations are affected by the fly ash particles. Concerning ²²⁶Ra and ²²⁸Ra values of mosses and lichens, which are systematically larger than those of unpolluted areas, the application of chemometrics proved that they originate mainly from the lignite fly ash.     

Determination of228Ra in drinking water

A procedure for the analysis of²²⁸Ra in drinking water has been developed. The procedure involves separation of radium by an initial coprecipitation with lead sulfate. The isolated Pb(Ra)SO₄ is then dissolved in sodium diethylenetriamine pentaacetate (DTPA). Radium-228 is co-precipitated from this solution with barium sulfate while the DTPA supernate which contains pre-existing²²⁸Ac is discarded. The purified Ba(Ra)SO₄ precipitate is then allowed to ingrow, generating²²⁸Ac, which is then dissolved in DTPA, isolating both²²⁶Ra and²²⁸Ra in the precipitate while²²⁸ Ac remains in the aqueous supernate. The supernate is partitioned against di-(2-ethylhexyl phosphoric acid), HDEHP, dissolved in n-heptane, which retains the²²⁸Ac. Actinium-228 is then stripped from the organic phase by partitioning against 1M HNO₃. Finally, the²²⁸Ac is coprecipitated onto cerium oxalate. The precipitate is collected on a filter and counted in a low-background beta counter. Radium-228 standards with concentrations ranging from 0.044 to 1.6 Bq were used to establish the detector counting efficiency for²²⁸Ac in cerium oxalate samples, as well as monitoring the chemical yield and absorption factors. The resultant average value of 30.3±2.1 cpm/Bq (uncertainty given at 95% level of confidence) was obtained. Various²²⁸Ra cross checks from U. S. Environmental Protection Agency (EPA) with concentrations of 0.063–0.52 Bq/l were analyzed in order to assess the performance of the procedure. The minimum detectable concentration (MDC) of²²⁸Ra in water with this procedure is 0.015 Bq/l. This is based on a one liter aliquot of sample, a 100 min couting period, and a 3 hour decay interval between the end of²²⁸Ac ingrowth and midpoint of counting. Decontamination factor studies were performed to determine the extent of the carry-over of²³⁸U,²²⁶Ra,²¹⁰Po, and⁹⁰Sr into the final fraction.     

A method for the simultaneous estimation of228Th and229Th

A simple method is reported in this paper to estimate²²⁹Th in the presence of²²⁸Th. The total activity of²²⁹Th and²²⁸Th was determined by following the alpha activity growth (using a liquid scintillation counter and proportional counter) of purified thorium samples. The activity ratio of²²⁹Th/²²⁸Th was determined by alpha spectrometry. From the initial total activity and ratio, disintegration rates of²²⁹Th and²²⁸Th were calculated. The values obtained for the activities have a precision better than ±2%.     

Estimation of growth rate of hokutolite from Tamagawa hot-spring,Akita, Japan

The concentrations of radium isotopes and the progenies (²²⁶Ra; ²²⁸Ra and ²²⁸Th) in three hokutolite samples from Tamagawa hot-spring were measured. These isotopes were analyzed by a well-type HPGe γ-ray spectrometer for the 351, 911 and 583 keV γ-ray from ²¹⁴Pb, ²²⁸Ac and ²⁰⁸Tl, respectively, each being in radioactive equilibrium with precursors. Concentration of ²²⁶Ra and ²²⁸Ra were observed to be in the range of 52–85 and 7.1–85 Bq/g, respectively. The activity ratios of ²²⁸Ra/²²⁶Ra and ²²⁸Th/²²⁶Ra provided the estimation of the growth rate (0.09–0.15 mm/y). Estimated ²²⁸Ra/²²⁶Ra activity ratios in hot-spring water from surface of three hokutolite were concordant.     

The determination of radium-226 and radium-228 in soils and plants,using radium-225 as a yield tracer

Recovery of²²⁶Ra in analysis is determined using²²⁵Ra separated by anion exchange from²²⁹Th and²³³U. Radium is coprecipitated with barium, and purified by ion exchange.²²⁶Ra and²¹⁷At (decay product of²²⁵Ra) are measured by α-spectrometry.²²⁸Ra is determined both by β-counting²²⁸Ac and²²⁵Ac separated from²²⁸Ra and²²⁵Ra, and by α-counting its daughters after the decay of²²⁵Ra. Sources for α-spectrometry are prepared by electrodeposition (molecular plating).     

Development of a sequential method for the determination of238U,234U,232Th,230Th,228Th,228Ra,226Ra,and210Pb. in environmental samples

A sequential analytical method for the determination of²³⁸U,²³⁴U,²³²Th,²³⁰Th,²²⁸Th,²²⁸Ra,²²⁶Ra and²¹⁰Pb in environmental samples was developed. Uranium and thorium isotopes are first chromatographically sepaaated using tri-n-octyl phosphine oxide (TOPO) supported on silica gel. The uranium isotopes are determined by alpha-spectrometry following extraction with TOPO onto a polymeric membrane. Thorium isotopes are co-precipitated with lanthanum fluoride before counting in an alpha spectrometer. Radium isotopes and²¹⁰Pb are separated by co-precipitation/precipitation with mixed barium/lead sulphate. Radium-226 is determined by gross alpha counting of the final BaSO₄ precipitate and²²⁸Ra by gross beta counting of the same source. Lead-210 is determined through beta counting of its daughter product²¹⁰Bi.     

Thorium series disequilibrium and geochemical processes in estuarine sediments of Mandovi river

The measurements of natural radioactivity due to thorium isotopes have been carried out in estuarine sediments of Mandovi river (Goa). The geochemical behaviour of these sediments has been studied by leaching the samples with 5 % ethylenediaminetetraacetic acid at pH 3.0 in order to investigate the processes occurring on the surface of the sediment particles and the distribution of natural thorium in estuarine sediments. The²²⁸Th/²³²Th activity ratios have been found to be in the range of 2.00 to 2.12. This anomaly between²³²Th and²²⁸Th has been attributed to the preferential leaching of²²⁸Ra by water flowing over these sediments. The activities of²²⁸Ra on the surface labile layers of the sediments have also been determined. The²³⁰Th/²³²Th activity ratios have been found to be in the range of 0.94 to 1.04. These ratios are mainly dependent on the precipitation action of²³⁰Th on adjacent sediments.     

Distribution of radioisotopes in sediment cores from nearshore off Xinghua Bay mouth,Fujian, China

Two marine sediment cores were collected from nearshore off Xinghua Bay mouth in Fujian, China and the ⁴⁰K, ¹³⁷Cs, ²¹⁰Pb, ²²⁶Ra, ²²⁸Ra, ²²⁸Th and ²³⁸U in the cores were measured using γ-spectroscopy. For the core ZK6, the activities of ⁴⁰K were vertically homogeneous within measured error in the whole core and ²²⁶Ra, ²²⁸Ra and ²²⁸Th showed large vertical variations with the same tendency. The sedimentation rates were 0.400 cm·y⁻¹ above 50 cm and 0.737 cm·y⁻¹ below depth of 50 cm. The change of sedimentation rates indicates the heterotaxy, which was justified by the absence of ¹³⁷Cs in the zone of 25–50 cm. For core ZK6, the sedimentation rate was 0.179 cm·y⁻¹. Vertical distributions of ⁴⁰K, ²²⁶Ra, ²²⁸Ra, ²²⁸Th and ²³⁸U in the core ZK18 are similar to each other although there were significant large variations with depth. The large variations of radioisotopes with depth in the cores mean that the sediment cores have been disturbed largely due to marine environment change. The mean activities of radioisotopes in the core ZK6 are higher than ZK18 that may be ascribed to different hydrodynamic environments.     

Interpretation of thorium bioassay data

This study is a comparison between bioassay data of thorium-exposed workers from two different facilities. The first of these facilities is a monazite sand extraction plant. Isotopic equilibrium between²³²Th and²²⁸Th was not observed in excreta samples of these workers. The second facility is a gas mantle factory. An isotopic equilibrium between²³²Th and²²⁸Th was observed in excreta samples. Whole body counter measurements have indicated a very low intake of thorium through inhalation. As the concentration of thorium in feces was very high we concluded that the main pathway of entrance of the nuclide was ingestion, mainly via contamination through dirty hands.The comparison between the bioassay results of workers from the two facilities shows that the lack of Th isotopic equilibrium observed in the excretion from the workers at the monazite sand plant possibly occurred due to an additional Th intake by ingestion of contaminated fresh food. This is presumably because²²⁸Ra is more efficiently taken up from the soil by plants, in comparison to²²⁸Th or²³²Th, and subsequently,²²⁸Th grows in from its immediate parent,²²⁸Ra.     

A study on thorium levels in human femur bones

The incorporation of naturally occurring thorium isotopes in human femur bones was studied by analyzing 28 bone samples. The results show that the activity concentrations of ²³²Th and ²³⁰Th are in the range of the blank values resulting in an upper limit of theirs activity concentrations in human bones. The presence of ²²⁸Th can be attributed, on the basis of model calculations, to the radioactive decay of deposited ²²⁸Ra. We conclude that thorium is not detectably incorporated into human bones.     

Chemometry of the distribution and origin of 226Ra, 228Ra, 40K and 137Cs in the soil near the lignite fired plants of West Macedonia (Greece)

The distribution and origin of natural ⁴⁰K,²²⁶Ra and²²⁸Ra and artificial ¹³⁷Cs have been investigated in the surface soil of a West Macedonia basin at four lignite fired power plants. No significant increase in specific activity of soil due to natural radionuclides of coal has been found. The specific activities of ²²⁶Ra, ²²⁸Ra and ⁴⁰K are equal to those of Greek soils. Radiocesium activity is slightly higher in the first 10 cm layer. The application of chemometrical methods confirmed that the radionulides ²²⁶Ra, ²²⁸Ra and ⁴⁰K are natural components of the soil and they do not originate from fly ash. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of227Ac in geological materials through neutron activation and alpha-spectrometric assay of induced228Th

A new route has been developed for the micro-determination of²²⁷Ac in geological materials by neutron activation. The method is based on intense neutron irradiation of the analysed samples followed by separation and α-spectrometric determination of²²⁸Th, the β-decay product of the 6.1 hrs²²⁸Ac isotope formed. Two alternatives are considered for analysis related to the origin of the analysed matrix. The high sensitivity of the method is documented by the determination of 10^?17 g²²⁷Ac/g sample. The method is successfully applied for age determination of five uranium containing materials and old uranium glass from Bohemia, CSSR.     

Assessment of 226Ra and 228Ra activity concentration in west coast of India

An investigation on the distribution of ²²⁶Ra and ²²⁸Ra activity concentration in coastal surface sea water from Okha in Gujarat to Ratnagiri in Maharashtra state along the west coast of India was carried out. In-situ pre-concentration technique was used to measure radium isotopes by passing 1,000 L of seawater through MnO₂ impregnated polypropylene filter cartridges at all the locations. ²²⁶Ra was estimated using gamma ray peak of its daughter radionuclides ²¹⁴Bi and ²¹⁴Pb. ²²⁸Ra was estimated from its daughter ²²⁸Ac. In the coastal waters, ²²⁶Ra and ²²⁸Ra activity concentration were observed to be in the range of 1.5–2.9 and 2.5–8.6 Bq m^?3 with a mean of 2.2 and 4.9 Bq m^?3 respectively. The activity of ²²⁸Ra was observed to be more than ²²⁶Ra in all the locations. The variation in spatial distribution of the radium isotopes activity concentration and its ratio with respect to location is discussed in the paper. The radioactive database obtained represents reference values for coastal environment of India.     

Radikalanionen des Bis(diphenylphosphino)maleinsäureanhydrid und seiner Derivate Polarographische und ESR-Messungen Präparative Anwendungen

Die Halbstufenpotentiale der Reduktion der Titelverbindung und einiger ihrer Derivate werden polarographisch gemessen. Die gefundenen, bemerkenswert niedrigen Reduktionspotentiale werden vergleichend diskutiert. Ihre Abstufung kann nur z. T. durch induktive Substituenteneffekte erklärt werden. Zusätzlich muß eine Ausweitung der π-Elektronenzustände unter Einschluß der Phosphoratome diskutiert werden, was auch aus den Kopplungskonstanten in den ESR-Spektren der gebildeten Radikalanionen zu schließen ist. Die Kaliumsalze der Radikalanionen sind äußerst luftempfindlich. Dagegen ist das aus Cobaltocen und Bis(diphenylphosphino)-maleinsäure-thioanhydrid ( 2 ) entstehende [CoCp₂]⁺[ 2 ]^? an der Luft beständig. Aus solchen ?Salzen”? der Radikalanionen können durch Umsetzung mit Metallhalogeniden Metall(0)-Komplexe der ditertiären Phosphane erhalten werden. Radical Anions of Bis(diphenylphosphino)maleic Anhydride and its Derivatives. Polarographic and ESR Measurements. Preparative Applications Half-wave potentials of the title compound and some of its derivatives have been measured by polarography. The observed reduction potentials are remarkably low. The changes within this series cannot be explained by inductive effects only. A contribution of extended π-states has to be regarded likewise, including the phosphorus atoms. This is confirmed by the coupling constants derived from ESR spectra of the radical anions formed by the reduction. The potassium salts of the radical anions are extremly air sensitive. However the salt of the cation [CoCp₂]⁺ with the radical anion of bis(diphenylphosphino)maleic thioanhydride is stable at the air. It is prepared in excellent yields from CoCp₂ and the diphosphine in toluene. The salts of the radical anions can be used to synthesize metal(0) complexes of the corresponding ditertiary phosphines by their reaction with metal halides.     

Measurement of <Superscript>228</Superscript>Ra in the Yellow Sea and East China Sea using the radon emanation method

²²⁸Ra levels in the Yellow Sea and East China Sea were determined using the emanation method. The seawater radium was concentrated using an Mn-fiber and the ²²⁴Ra ingrowth was measured after about half a year when the initial ²²⁴Ra in the sample would have decayed. The ²²⁴Ra activity in the sample was evaluated using the decay dynamics relationship between parent ²²⁸Ra and daughter ²²⁸Th. The concentration and distribution feature of ²²⁸Ra in the Yellow Sea and East China Sea were studied and the ²²⁸Ra concentrations in the surface seawater of the Yellow Sea and the East China Sea were in the range 0.09–15.0 Bq/m³ with an average of 6.84 Bq/m³ during the summer cruise, and in the range 0.09–16.9 Bq/m³ with an average of 6.37 Bq/m³ during the winter cruise. The ²²⁸Ra distribution in the northern Yellow Sea was different from the southern Yellow Sea and East China Sea. The highest ²²⁸Ra activity of surface water was located in the middle of the northern Yellow Sea, but for the southern Yellow Sea and East China Sea, it decreased with increasing distance from China continent.