Natural radionuclides and cesium-137 content in Arabian Gulf bottom sediments

The activity concentration of natural radionuclides and¹³⁷Cs in the bottom sediment samples from the coastal area of Kuwait on the Arabian Gulf have been determined by -ray spectrometry with REGe detector. The data for the samples are very similar to those obtained for surface soil samples in Kuwait.¹ Two parent-progeny ratios for:^23$Th–²²⁶Ra and²²⁸Ac–²⁰⁸Tl to evaluate the geochemical behavior of the radionuclides have been estimated. The existence of a serious disequilibrium between²³⁴Th and²²⁶Ra for samples taken from the vicinity of Kuwait islands and the Ras Al-Zoor area was found. The strait between the coast of Kuwait and Bubiyan island is proposed for the future sedimentation rate determinations on the basis of²¹⁰Pb measurements. No serious contamination by technogenic radionuclides for this region of Arabian Gulf was observed.     

True coincidence summing correction determination for 214Bi principal gamma lines in NORM samples

The gamma lines 609.3 and 1,120.3 keV are two of the most intensive γ emissions of ²¹⁴Bi, but they have serious true coincidence summing (TCS) effects due to the complex decay schemes with multi-cascading transitions. TCS effects cause inaccurate count rate and hence erroneous results. A simple and easy experimental method for determination of TCS correction of ²¹⁴Bi gamma lines was developed in this work using naturally occurring radioactive material samples. Height efficiency and self attenuation corrections were determined as well. The developed method has been formulated theoretically and validated experimentally. The corrections problems were solved simply with neither additional standard source nor simulation skills.     

A comparison of two nuclear analytical techniques for determination of 210Pb-specific activity in solid environmental samples

Two nuclear analytical techniques for determination of ²¹⁰Pb-specific activity in solid environmental samples have been validated and compared. The first technique depends on determination of ²¹⁰Pb via its alpha emitting daughter ²¹⁰Po using alpha-particle spectrometry, while the second technique is based on direct determination of ²¹⁰Pb by measuring its activity at the 46-keV gamma line by low-energy gamma-ray spectrometry. Detection limits, repeatability, reproducibility, and surrogate recovery were the main validation parameters. Measurement uncertainties were estimated and compared for both techniques. Results of this study have shown that the expected activity of ²¹⁰Pb in the environmental samples and the required measurement uncertainty are the main factors influencing a selection of the appropriate method for the application.     

Simultaneous determination of 226Ra and 238U in soil and environmental materials by gamma-spectrometry in the absence of radium progeny equilibrium

The determination of ²²⁶Ra and ²³⁸U in environmental samples by gamma-spectrometry is most often carried out by hermetic sealing of the sample in a suitable container, waiting until secular equilibrium that has been established in the ²³⁸U decay chain below ²²⁶Ra and counting of the high intensity emissions of ²¹⁴Pb and ²¹⁴Bi. The 186 keV multiplet can then be corrected to provide a measure of ²³⁵U and hence, ²³⁸U. The work presented in this paper involves a critical examination of the analysis of ²³⁸U and ²²⁶Ra in environmental materials without secular equilibrium established between ²¹⁴Pb, ²¹⁴Bi and their progenitor. Results indicate that the correction of the 186 keV doublet via ²³⁴Th determination is possible, even for low-level samples but careful consideration of both experimental conditions and the composition of the sample matrix is required. This revised version was published online in July 2006 with corrections to the Cover Date.     

Direct determination of 226Ra in NORM/TENORM matrices by gamma-spectrometry

Summary The main shortcoming with the procedure to determine ²²⁶Ra in a gamma spectrum of an environmental sample by means of the ²¹⁴Bi and ²¹⁴Pb photopeaks is the likelihood of ²²²Rn leakage from the sample counting vial. An option to make such determination is to disregard the ²²⁶Ra gamma-contributions to the spectrum, other than 186.2 keV (3.5%), subtracting the ²³⁵U contribution to the ²²⁶Ra+²³⁵U peak at 186 keV. The use of this option to determine directly ²²⁶Ra activity concentrations in environmental samples and in NORM/TENORM matrices will be presented and discussed.     

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 %.     

Characterization of marine sediments using analytical techniques

This study deals with the characterization of a marine sediments profile from the Gulf of Tehuantepec, Mexico. Ten sediment samples obtained from a core of 18.3 m of length were analysed. Although there have been numerous marine sediments studies carried out in Mexico, more are needed to better understand the sea floor formation. Crystallographic, morphologic, physical, chemical and gamma ray activity analysis were carried out on the samples. The analysis results showed a decrease in organic matter content as a function of sea depth; this value is related to the specific surface area. Some hazardous materials as Cr, Mn, Ni, Sr and Hg were also identified by PIXE in some samples, probably due to anthropogenic activity. The presence of uranium a naturally occurring element was found in all the samples, suggesting a migration through all materials of strata, radioactive elements such as ²²⁶Ra, ²³⁵U, ²¹²Pb, ²¹⁴Pb, ²²⁸Ac, ²⁰⁸Ti, ²¹⁴Bi, ²²⁸Ac and ⁴⁰K were detected.     

Nondestructive determination of lead-210 and radium-226 in sediments by direct photon analysis

A method is described for the non-destructive determination of²¹⁰Pb and²²⁶Ra in sediments. The procedure is based on the direct counting of the 46.5-keV -ray of²¹⁰Pb and the 351.9-keV -emission of²¹⁴Pb. The self-absorption of the 46.5-KeV -ray is corrected using a technique involving direct gamma transmission measurements on sample and efficiency calibration standard. Several reference materials when assayed by the described method yielded results in general agreement with the certified values. The application of the method is illustrated through the analysis of the excess²¹⁰Pb profile of a Lake Ontario sediment core.     

Natural radionuclides and 137Cs activity concentration in the bottom sediment cores from Kuwait Bay

Summary The activity concentration of natural radionuclides and ¹³⁷Cs in the bottom sediments cores from Kuwait Bay have been determined by γ-ray spectrometry. Particular attention was devoted to the exact determination of two uranium isotopes: ²³⁵U and ²³⁸U in order to find any presence of depleted uranium dispersed during the 1991 Gulf War. The calculated ²³⁸U/²³⁵U activity ratios for all the surface (15 cm) as well as the core profile (up to 70 cm in depth) samples were within the limit of one standard deviation close to the value of 21.5 for natural uranium. Simultaneous instrumental determination of the unsupported ²¹⁰Pb and ²²⁶Ra in a few sediment core profiles was used for quantification of sediment accumulation rates. The calculated sedimentation rates (for the constant atmospheric ²¹⁰Pb flux rate - CRS model) ranged from 0.2 to 0.6 cm ^. y^-1 and were close to the data calculated by the Weibull distribution of ¹³⁷Cs in undisturbed sediment cores.     

Matrix materials for proficiency testing: optimization of a procedure for spiking soil with gamma-emitting radionuclides

The IAEA Reference Materials Group of the Chemistry Unit, Agency’s Laboratories Seibersdorf, has developed and optimized a procedure for spiking some environmental matrices with gamma-emitting radionuclides. This paper describes the spiking procedure, homogeneity testing of the spiked material, and assignment of property values and their associated uncertainties for the radionuclides ⁵⁴Mn, ⁶⁵Zn, ⁶⁰Co, ¹⁰⁹Cd, ¹³⁴Cs, ¹³⁷Cs, ²¹⁰Pb, and ²⁴¹Am. This procedure has already been successfully used in an IAEA proficiency test on the determination of ¹³⁷Cs and ²¹⁰Pb in spiked soil and has been found to be appropriate for production of soil materials for proficiency testing and internal quality control samples. The main advantage of this procedure is a low uncertainty arising from heterogeneity, which was found to be less than 1.2% for all the analytes studied.      

Radiometric dating of sediment records in Kuwait’s marine area

Six sediment cores collected from the Northwestern Arabian/Persian Gulf have been radiometrically dated by ²¹⁰Pb. Three cores were collected from stations within the Kuwait Bay, and three others were collected from stations outside the bay. Two models have been used for ²¹⁰Pb dating of sediment cores, i.e. Constant Flux: Constant Sedimentation (CF:CS) Model and the Constant Rate of Supply (CRS) Model. The average rates were found to vary significantly between 0.16 and 1.00 cm y^?1 for stations outside and within the bay respectively. The variability of the sedimentation rate was essentially physiographic characteristics and variable hydrodynamic condition. In this study, ¹³⁷Cs fallout radiotracer was also used to construct a realistic chronology. It was observed that the ¹³⁷Cs in the entire vertical profile has been continuously contributed by fluvial and atmospheric deposition.     

Field measurement of the <Superscript>218</Superscript>Po, <Superscript>214</Superscript>Pb and <Superscript>214</Superscript>Bi concentrations in typical indoor and outdoor environments in Beijing

The activity concentrations of ²¹⁸Po, ²¹⁴Pb and ²¹⁴Bi [i.e. C(²¹⁸Po), C(²¹⁴Pb), and C(²¹⁴Bi)] and the calculated concentration ratios [i.e. 1:C(²¹⁴Pb)/C(²¹⁸Po):C(²¹⁴Bi)/C(²¹⁸Po)] are necessary for assessing radon and its progenies exposure. In this study, a measurement method of radon progenies concentrations with both high sensitivity and low uncertainty, was developed based on the Kerr method. The field measurement results of radon progeny concentrations and calculated concentration ratios in both typical indoor and outdoor environments in Beijing, China, were reported. The effects of air exchange rate on concentration ratios of radon progenies in indoor environments were discussed.     

Temporal evolution of radionuclides in sludge from wastewater treatment plants

22 sludge samples were analyzed from three municipal wastewater treatment plants to assess both the occurrence and the temporal behavior of radioactivity during 8 sampling campaigns carried out over the period 2007–2009. As regards natural gamma emitters radionuclides from the natural ²³⁸U series (such as ²³⁴Th, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb) and the ²³²Th series (such as ²²⁸Ac, ²¹²Pb, ²¹²Bi and ²⁰⁸Tl) and other natural gamma emitters such as ⁷Be, ²¹⁰Pb_u or ⁴⁰K were measured. In the case of man-made radionuclides small amounts of ¹³⁷Cs were found, while significant amounts of ¹³¹I were detected in some samples. Correlations were found between radionuclides with the same origin. No seasonal variation for the ²³⁸U and ²³²Th series was found in the studied period but ⁷Be and ²¹⁰Pb_u showed seasonal variation that was explained by the monthly rainfall. The internal and external hazard indices were calculated and the results indicate that the radiological characteristics of the sludge do not present a significant radiological risk and make them suitable for future applications.     

Determination of 210Pb and 210Po in mineral and biological environmental samples

The paper deals with the determination of ²¹⁰ Pb and ²¹⁰ Po in mineral and biological environmental samples. ²¹⁰ Pb and ²¹⁰ Po were preconcentrated from filtered water samples by coprecipitation with iron(III) hydroxide at pH 9-10 using ammonia solution and the precipitate was dissolved with HCl and mineralized with H2O2. ²¹⁰ Pb and ²¹⁰ Po in soil or sediment, algae and mussel samples were sequentially leached out at 250 °C with HNO₃ +HF, HClO₄ and HCl. About 10-20% of the leaching solution was used for ²¹⁰ Po determination which was carried out at 85-90 °C for 4 hours by suspending a silver disk in a HCl solution of pH 1.5 and containing some hydroxylamine hydrochloride and sodium citrate. No preliminary separation was required and essentially quantitative recoveries were obtained by using standard ²⁰⁹ Po tracer. The remains of the leaching solution were used for the determination of ²¹⁰ Pb which was first separated by a BIO-RAD-AG 1-X4 resin column, then purified by using Na2S to precipitate as PbS and finally precipitated as PbSO₄ for source preparation. Starting from 3 g sediment (30 liter water), the lower limits of detection of the method were 0.73 Bq.kg^-1 (0.078 mBq.l^-1 ) for ²¹⁰ Pb and 0.25 Bq.kg^-1 (0.016 mBq.l^-1 ) for ²¹⁰ Po. The procedure has been checked with two certified samples supplied by the International Atomic Energy Agency (IAEA) and reliable results were obtained. Most of the analyzed samples were sediments, showing average yields of 84.2±5.2% for ²¹⁰ Pb and 96.4±4.1% for ²¹⁰ Po.     

Method study for the preparation of a wet sediment quality control material

Quality control materials (QCMs) to be used in daily quality control in environmental laboratories are required to be similar to real samples in terms both of composition and of physical state. The present paper describes in detail the procedure of preparation and the results of homogeneity and stability studies performed on wet sediments QCMs. For this purpose, two sediments with different matrix composition were selected and the main factors involved in the preparation of the material were carefully studied and established with the aim of guaranteeing long-term stability of the QCM: pre-treatment steps, homogenisation, bottling and storage. The results obtained from the homogeneity and from 12 months of stability studies for Cd, Cr, Cu, Ni, Pb and Zn following the aqua regia extraction procedure (ISO 11466), showed that the wet sediment QCMs we have developed are feasible, constituting a new and useful material among the aquatic sediments for quality control purposes in monitoring.     

Time sequence determination of parent–daughter radionuclides using gamma-spectrometry

The acquisition of time-stamped list data provides additional information useful to gamma-spectrometry analysis. A novel technique is described that uses non-linear least-squares fitting and the Levenberg–Marquardt algorithm to simultaneously determine parent-daughter atoms from time sequence measurements of only the daughter radionuclide. This has been demonstrated for the radioactive decay of short-lived radon progeny (²¹⁴Pb/²¹⁴Bi, ²¹²Pb/²¹²Bi) described using the Bateman first-order differential equation. The calculated atoms are in excellent agreement with measured atoms, with a difference of 1.3–4.8% for parent atoms and 2.4–10.4% for daughter atoms. Measurements are also reported with reduced uncertainty. The technique has potential to redefine gamma-spectrometry analysis.

     

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.     

Study of matrix effects and spectral interferences in the determination of lead in sediments, sludges and soils by SR-ETAAS using slurry sampling

An interference-free, fast, and simple method is proposed for Pb determination in environmental solid samples combining slurry sampling and electrothermal atomic absorption spectrometry. Samples were ground to an adequate particle size and slurries were prepared by weighing from 0.05 g to 0.20 g of dry sediment, adding nitric acid, and a solution containing 0.1% Triton X-100. Ultrasonic agitation was employed for slurries homogenization. Analytical variables including acid pre-treatment conditions, particle size, slurry stability, temperature program of the graphite furnace, and type and concentration of the chemical modifier were studied. The undesirable effects of potential non-specific and spectral interferences on Pb signal were also taken into account. Continuum source and self-reversal methods for background correction were evaluated and compared. For calibration, synthetic acid solutions of Pb were employed. Calibration was linear within the range 1-30 μg L⁻¹ and 5-30 μg L⁻¹ when the 217.0 nm and 283.3 nm analytical lines were used. Correlation coefficients of 0.9992 and 0.9997 were obtained. Using optimized conditions, limits of detection (3σ) of 0.025 μg g⁻¹ and 0.1 μg g⁻¹ were achieved for the 217.0 nm and 283.3 nm analytical lines, respectively. The method was successfully applied to the determination of lead in soil, contaminated soil, municipal sludge, and sediment samples. The accuracy was assessed by the analysis of two certified reference materials: municipal sludge (QC MUNICIPAL SLUDGE A) and lake sediment (TRAP-LRM from IJS).     

Simple collection and direct alpha-spectrometric determination of214Pb and214Bi in natural water

A rapid method has been developed for the de termination of²¹⁴Pb and²¹⁴Bi in natural waters by alpha-spectrometric measurement of²¹⁴Po. Well water was filtered on a membrane filter impregnated with manganese oxide and followed by direct alpha-spectrometric analysis. A prominent alpha peak was assigned to²¹⁴Po, which should be supported by the longer lived parents²¹⁴Pb and²¹⁴Bi. The activity ratios between²¹⁴Pb and²¹⁴Bi adsorbed on the filter were determined by using the change of activity of²¹⁴Po as a function of counting period after the filtration. The adsorbed yield of²¹⁴Pb was also determined from the growth of the alpha-peak due to²¹⁰Po from a²¹⁰Pb tracer added in the original water. The results indicated that the amount of²¹⁴Pb was in radioactive non-equilibrium state with the Rn-222 dissolved, while the activity ratios of²¹⁴Bi/²¹⁴Pb showed on increasing tendency with the storage period of the water.     

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.