Pre-concentration of short-lived radionuclides using manganese dioxide precipitation from surface waters

Rapid determination of ²²²Rn and ²²⁰Rn progeny (²¹⁴Pb, ²¹²Pb, ²¹⁴Bi, ²¹²Bi) is achievable using manganese dioxide (MnO₂) precipitation with analysis by γ-spectrometry. This is of interest to environmental monitoring programmes that utilise gross activity methods to screen for anthropogenic radionuclides. The contribution from these naturally occurring radionuclides (NOR) varies, and is difficult to experimentally measure due to short half-lives (t _½ = 19.9 m–10.64 h) and low environmental activity (<0.1 Bq L^?1). The extraction efficiency of the technique is above 90%, and above 80% for other nuclides (²³²Th, ²³⁸U, ²³⁵U, ²²⁸Ac, ²²⁶Ra, ²²⁴Ra, ²¹⁰Pb, ⁵⁴Mn). Short-lived NOR have been measured at two surface water locations, and indicates elevated ²¹⁴Bi activity of 4.0 ± 1.1 Bq L^?1.     

Wavelet based spectrum processing for reduction of counting duration for quantitative estimation of ultra-trace activity in environmental matrices

A simple wavelet transformation based pre-processing method is employed to minimize the duration of counting for gamma spectrometric measurements of samples from environmental matrices. Among the various forms of analyzing wavelets, a suitable one is chosen for this purpose. Measurements with 55 different counting durations were subjected to the wavelet based processing and results were compared with long duration counting time measurements of ⁴⁰K, ¹³⁷Cs, radionuclide from ²³⁸U series (²¹⁴Bi, ²¹⁴Pb) and ²³²Th series (²²⁸Ac, ²¹²Bi, ²¹²Pb, ²⁰⁸Tl). It is observed that with a proper choice of the wavelet function a tenfold reduction in counting duration can be achieved with errors <5 %.     

Radioactivity in coffee

This research was dedicated to the study of the background levels of ²¹⁰Po and natural gamma emitters as ⁴⁰K, ²¹⁴Pb, ²¹⁴Bi, ²²⁸Ac, ²¹²Pb and ²¹²Bi in coffee powder and in coffee beverage; also the artificial ¹³⁷Cs was determined. In the coffee powder the mean ²¹⁰Po activity resulted 7.25 ± 2.25 × 10^?2 Bq kg^?1. ⁴⁰K showed a mean activity of 907.4 ± 115.6 Bq kg^?1. The mean activity concentration of ²¹⁴Pb and ²¹⁴Bi, indicators of ²²⁶Ra, given as mean value of the two radionuclides, resulted 10.61 ± 4.02 Bq kg^?1. ²²⁸Ac, ²²⁸Ra indicator, showed a mean activity concentration of 13.73 ± 3.20 Bq kg^?1. The mean activity concentration of ²¹²Pb, ²²⁴Ra indicator, was 8.28 ± 2.88 Bq kg^?1. ²⁰⁸Tl, ²²⁴Ra indicator, presented a mean activity concentration of 11.03 ± 4.34 Bq kg^?1. In all samples, the artifical ¹³⁷Cs resulted below the detection limit (2.0 Bq kg^?1). The arithmetical mean value of percentage of ²¹⁰Po extraction in coffee beverage resulted 20.5 ± 6.9. The percentage of transfer of gamma emitters,⁴⁰K, ²¹⁴Pb, ²¹⁴Bi, ²²⁸Ac, ²¹²Pb, ²⁰⁸Tl resulted of 80.0, 33.5, 24.7, 30.0, 35.1 and 53.5 % for ⁴⁰K, ²¹⁴Pb, ²¹⁴Bi, ²²⁸Ac, ²¹²Pb and ²⁰⁸Tl respectively.     

Natural radionuclide-free phosphoric acid production

High-uranium phosphate rock from Itataia, Brazil, was milled for wet-process phosphoric acid production using the dihydrate method. Uranium contained in the phosphoric acid was recovered by solvent extraction. The distribution of long-lived natural radionuclides of the ²³⁸U and ²³²Th decay series involved in these operations was evaluated. ²²⁶Ra, ²²⁸Ra and ²¹⁰Pb were found to predominate in the phosphogypsum, while ²²⁸Th, ²³⁰Th and ²³²Th in the uranium-free phosphoric acid. Thorium is removed from the phosphoric acid by solvent extraction to produce a NORM-free phosphoric acid.     

Lichen specie Canoparmelia texana as bioindicator of environmental impact from the phosphate fertilizer industry of São Paulo,Brazil

The Brazilian phosphate industry is the sixth worldwide producer of phosphate rock concentrate generating phosphoric acid, fertilizers, intermediates for fertilizers and other products. Two of the most important of these industries are both located in the city of Cubatão—São Paulo, Brazil, and they are responsible for the production of P₂O₅, generating a residue known as phosphogypsum. The raw material, phosphate rock and products are commonly transported to the industrial complex by a railroad line and present in their composition natural radionuclides from the U and Th series and rare earth elements. Lichens have been used for monitoring atmospheric pollution and radiological contamination for a long time and have proven to be an important tool. This paper aims to highlight the use of the lichen specie Canoparmelia texana (family Parmeliacea) as a bioindicator of atmospheric pollution by the natural radionuclides from the U and Th series and RREs due to the operation of these industries and the storage of their residue in the open air. Samples of these lichen specie were collected in the vicinity of the industries and the railroad. The radionuclides ²²⁶Ra, ²²⁸Ra and ²¹⁰Pb were measured by alpha and beta counting, after radiochemical separation, and ²³⁸U, ²³²Th as well as REEs were determined by instrumental neutron activation analysis. The results showed that the lichens present the same fingerprint as the phosphate rock and phosphogypsum, furthermore the cluster analysis of the results showed that the lichen samples collected near to the railroad line presented the highest values for all the elements studied.     

Radiochemical separation of bismuth activities using Dalzin,and its application to geological problems

A radiochemical method has been devised for the separation of bismuth activities of the natural series,viz.²¹⁴Bi,²¹⁰Bi and²¹²Bi, and applied to the indirect estimation of their corresponding precursors,²²²Rn,²¹⁰Pb and²¹²Pb, in a wide variety of geological materials. The method consists of the solvent extraction of bismuth in radiochemically pure form from the sample solution atpH 2 with diallyldithiocarbamido-hydrazine (Dalzin) in chloroform, and back extraction with 2M acid. The advantages of this method over the dithizone extraction system are discussed.     

Study of natural radionuclides and its radiation hazard index in Malaysian building materials

The main component of most building materials in Malaysia is rock. All rocks are known to contain natural radionuclides such as ²³⁸U and ²³²Th series as well as ⁴⁰K. In order to estimate the radiological impact to the dweller, the level of radionuclides present in various building materials available in Malaysia were analyzed using γ-spectrometry. The radiation hazard indexes were calculated based on the above results. The results showed that the activity concentration of natural radionculides ²³⁸U, ²³²Th, ⁴⁰K was between 19.0–42.2 Bq/kg, 16.5–28.8 Bq/kg and 243.3–614.2 Bq/kg, respectively. On the whole, the radionuclides concentration was still below the global average of 50 Bq/kg, 50 Bq/kg and 500 Bq/kg for ²³⁸U, ²³²Th, and ⁴⁰K, respectively The radiation hazard indexes of the building materials were also lower than the maximum value suggested.     

Development of a 212Pb and 212Bi generator for homolog studies of flerovium and moscovium

A simple generator using AG 50Wx8 cation exchange resin has been developed for continual elution of ²¹²Pb and ²¹²Bi from the parent radionuclide ²²⁸Th, derived from ²³²U. Using 0.4 M HCl as an eluent will elute ²¹²Bi while ²¹²Pb is eluted with 2 M HCl. The generator has shown good reproducibility of elution bands. A generator set-up in 2013 has been in continual use over 4 years demonstrating that this generator system has a long and stable lifetime. The generator system presented here has served as a long-term method for attaining no-carrier-added ²¹²Pb and ²¹²Bi radionuclides for homolog studies of flerovium and moscovium.

     

A 228Ra-212Pb tandem generator for potential application in biomedical studies

A new tandem generator system (cation-exchange generator column coupled to anion-exchange), based on the ²²⁸Ra as starting radionuclide, for ²¹²Pb/²¹²Bi production in the solutions suitable to direct application in biomedical investigations has been developed. Optimum conditions have been found for retention of Ra, Th and Ac parent radionuclides on the cation-exchange column and repeated elution of Pb with subsequent concentration on anion-exchange column using HBr and mixed HBr/CH₃OH solutions. It was shown that Pb/Bi could be eluted from anion — exchange column with a small volume of EDTA, DTPA, NaCl solutions or heated H₂O. The advantages of the tandem generator system for production of short-lived Pb/Bi radionuclides and their application for biomedical studies are discussed.     

The natural radioactivity of Brazilian phosphogypsum

Phosphogypsum is a high volume by-product from the phosphoric acidindustries containing naturally occurring radionuclides. Envisaging the usesof phosphogypsum, a characterization of this material in terms of spatialdistribution of radionuclides was carried out by core samples taken from stacksof two important Brazilian phosphoric acid facilities. Samples were analyzedfor ²³⁸U, ²³⁴U, ²³²Th, ²²⁶Ra, ²²⁸Ra, ²¹⁰Pb and ²¹⁰Po using alpha- and gamma-spectrometryand UV-VIS spectrophotometry. Specific activities of ²³⁸U, ²³⁴U, ²²⁶ Ra and ²¹⁰Po obtained were comparablewith data reported in the phosphogypsum literature, while higher values werefound for ²³² Th and ²²⁸Ra.     

A new method for determination of222Rn and220Rn in geothermal steam

The radionuclides²²²Rn and²²⁰Rn are measured by incorporating their daughters²¹⁴Pb and²¹²Pb in a very thin layer of PbS and accumulating the alpha spectrum of their daughter products²¹⁴Po and²¹²Po. The median yield was measured as 88% using a known amount of²¹⁰Pb tracer. A single fumarole and all 23 geothermal wells tested were found to contain²²⁰Rn. As isotopes of Th, Bi, Po and Ra, are also absorbed in the PbS layer, the method can be used for determinations of these in tap-water.     

The NIST natural-matrix radionuclide standard reference material program for ocean studies

In 1977, the Low-level Working Group of the International Committee on Radionuclide Metrology met in Boston, MA (USA) to define the characteristics of a new set of environmental radioactivity reference materials. These reference materials were to provide the radiochemist with the same analytical challenges faced when assaying environmental samples. It was decided that radionuclide bearing natural materials should be collected from sites where there had been sufficient time for natural processes to redistribute the various chemically different species of the radionuclides. Over the succeeding years, the National Institute of Standards and Technology (NIST), in cooperation with other highly experienced laboratories, certified and issued a number of these as low-level radioactivity Standard Reference Materials (SRMs) for fission and activation product and actinide concentrations. The experience of certifying these SRMs has given NIST the opportunity to compare radioanalytical methods and learn of their limitations. NIST convened an international workshop in 1994 to define the natural-matrix radionuclide SRM needs for ocean studies. The highest priorities proposed at the workshop were for sediment, shellfish, seaweed, fish flesh and water matrix SRMs certified for mBq per sample concentrations of ⁹⁰ Sr, ¹³⁷ Cs and ²³⁹ Pu + ²⁴⁰ Pu. The most recent low-level environmental radionuclide SRM issued by NIST, Ocean Sediment (SRM 4357) has certified and uncertified values for the following 22 radionuclides: ⁴⁰ K, ⁹⁰ Sr, ¹²⁹ I, ¹³⁷ Cs, ¹⁵⁵ Eu, ²¹⁰ Pb, ²¹⁰ Po, ²¹² Pb, ²¹⁴ Bi, ²²⁶ Ra, ²²⁸ Ra, ²²⁸ Th, ²³⁰ Th, ²³² Th, ²³⁴ U, ²³⁵ U, ²³⁷ Np, ²³⁸ U, ²³⁸ Pu, ²³⁹ Pu + ²⁴⁰ Pu, and ²⁴¹ Am. The uncertainties for a number of the certified radionuclides are non-symmetrical and relatively large because of the non-normal distribution of reported values. NIST is continuing its efforts to provide the ocean studies community with additional natural matrix radionuclide SRMs. The freeze-dried shellfish flesh matrix has been prepared and recently sent to participating laboratories for analysis and we anticipate receiving radioanalytical results in 2000. The research and development work at NIST produce well characterized SRMs that provide the world's environment-studies community with an important foundation component for radionuclide metrology.     

Alpha and gamma spectrometry for determination of natural and artificial radionuclides in tea, herbal tea and camomile marketed in Italy

Several kinds of tea, camomile and herbal tea were analysed to determine natural and artificial radioactivity. The radionuclides were determined by alpha (²¹⁰Po) and gamma (²²⁸Ac, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb, ⁴⁰K and ¹³⁷Cs) spectrometry. ²²⁸Ac ranged between 0.6 and 9.0 Bq kg⁻¹_dry; ²¹⁰Po between 1.90 and 36.1 Bq kg⁻¹_dry; ²¹⁴Pb and ²¹⁴Bi between 0.7 and 4.9 Bq kg⁻¹_dry; ²¹⁰Pb between < 10.0 and 58.9 Bq kg⁻¹_dry; ⁴⁰K between 463 and 936 Bq kg⁻¹_dry; ¹³⁷Cs between < 0.3 and 2.6 Bq kg⁻¹_dry. The percentage of ²¹⁰Po extraction in infusion was also determined; the arithmetical mean value of percentage of ²¹⁰Po extraction resulted 20.7 ± 7.50.     

Analysis of natural radionuclides from uranium and thorium series in briney groundwaters

Analytical procedures for measuring various radionuclides in the²³⁸U and²³²Th chains in briney waters are described. Using methods such as mass spectrometry, and alpha, beta and gamma spectrometry, the desired measurement sensitivity required for each of the radionuclides is achieved.²³³U,²²⁸Th,²⁰⁸Po,²¹²Pb, and¹³³Ba are used as tracers for chemical yield recoveries. Typical precision of the results range from 5–20%.     

Fast procedure for self-absorption correction for low γ energy radionuclide 210Pb determination in solid environmental samples

Low-energy X and γ radiations (for example of ²¹⁰Pb: E _γ = 46.5 keV) are effectively self-absorbed even in thin environmental samples, including air filters with captured dust or contaminated soil, as well as in bottom sediment matrixes with limited quantities of the samples. In this paper, a simple method for the direct analysis of ²¹⁰Pb (T _1/2 = 22.3 years) by gamma-ray spectrometry in environmental samples with self-absorption correction is described. The method is based on the comparison of two γ peak activities coming from other natural radionuclides, usually present in environmental samples. We have analyzed the dependence of the self-absorption correction factor for the ²¹⁰Pb activity on the activity ratios of 911 and 209 keV peaks and 609 and 295 keV peaks coming from nuclides of ²³⁸U or ²³²Th rows, present in typical environmental samples.     

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.     

Comparative temporal behavior of radon- and thoron-progeny in surface air over the midwestern U.S.

Temporal variations in airborne²¹⁰Pb,²¹²Pb,²¹⁴Pb,²¹⁸Po, and²¹⁴Bi concentrations at Springfield, Missouri, USA, are compared with each other and with results reported from studies performed in other parts of the world. At Springfield diurnal concentration patterns of²¹⁰Pb are similar to those of²¹²Pb, but seasonal concentration patterns differ markedly. Additionally, abnormal disequilibrium conditions are sometimes found to exist in Springfield among²¹⁸Po,²¹⁴Pb, and²¹⁴Bi in which progeny/parent ratios are greater than 1. Findings similar to those presented here have been reported at some sites throughout the world, but different temporal patterns have been reported at others. Examination of concentration dependence on meteorological conditions at Springfield indicates that some of these differences are correlated with temperature and ground snow cover. Implications of these findings for use of thoron- and radon-progeny as atmospheric tracers are discussed.     

Neutron activation analysis and radioactivity measurements of Australian coals and fly ashes

Forty elements were determined by instrumental neutron activation analysis in a wide range of Australian coals and fly ash to update and extend earlier measurements. The natural radioactivity content of selected samples were analysed by high resolution gamma-ray spectrometry and low level radiochemistry. The results indicated a marked disequilibrium of the²³²Th decay series in some samples while a general enrichment of²¹⁰Pb in most fly ash samples disrupted the²³⁸U equilibrium.     

Radioactivity of coal and ashes from Figueira coal power plant in Brazil

Summary The Figueira coal-fired power plant (CFPP) is among the Brazilian CFPP which presents higher uranium concentration. Gamma-ray spectrometry was used to determine ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³² Th and ⁴⁰K contents in pulverized coal, furnace bottom ash and fly ash samples. The natural radionuclide concentrations in pulverized coal ranged from 813 to 2609 Bq ^. kg^-1 for U series and from 22 to 40 Bq ^. kg^-1 for ²³² Th. The fly ash fraction gave concentrations ranging from 1442 to 14641 Bq ^. kg^-1, for uranium series. The same enrichment factor was observed for ²³⁸U, ²²⁶Ra and ²³² Th. Only ²¹⁰Pb and stable Pb presented a high enrichment factor for the last stage filter fly ash. The concentration of the uranium series found in the ashes is close to the limit adopted by the Brazilian guideline (CNEN-NN-4.01).²² Therefore, it is advisable to evaluate the environmental impact of the installation.     

Distribution and mean residence time of natural radionuclides in the forest ecosystem

Activity concentrations of radionuclides,⁷Be,²¹⁰Pb and²¹⁰Po, in precipitation (rain, throughfall and stemflow), wood and soil were determined by using gamma-ray and alpha-ray spectrometry to estimate the migration behavior of these radionuclides in the forest canopy. The activity ratios between output and input precipitations for the forest canopy were 0.53 of⁷Be, 0.79 of²¹⁰Pb and 1.5 of²¹⁰Po for Pasania edulis forest. A dynamic model of the transport and fate of radionuclides in the forest ecosystem was constructed. Mean residence times of radionuclides were 56 days for⁷Be, 765 days for²¹⁰Pb and 653 days for²¹⁰Po for Pasania edulis forest.