Analytical methods to determine Po and Pb in marine samples

This paper describes the methods of sampling, preconcentration, chemical separation and final count of ²¹⁰Po and ²¹⁰Pb present in different marine matrices to determine their background levels in a marine ecosystem. Complex, time consuming and selective radioanalytical methods have been used to prepare final clear sources for alpha spectrometry and beta count; in fact, gamma spectrometry, a method direct and non destructive, cannot be taken into account because the ²¹⁰Pb activity is very low which does not allow to carry out sufficiently accurate measurements and ²¹⁰Po is not a gamma emitter but it emits only alpha particle at 5.40 MeV. The results of ²¹⁰Po and ²¹⁰Pb activity concentrations obtained in different marine samples collected in the first two campaigns are still very few to discuss about the ²¹⁰Po and ²¹⁰Pb behavior in marine environment.     

Quantification of measurement uncertainty in the sequential determination of <Superscript>210</Superscript>Pb and <Superscript>210</Superscript>Po by liquid scintillation counting and alpha-particle spectrometry

Methodologies for the quantification of measurement uncertainties associated with the determination of ²¹⁰Pb- and ²¹⁰Po-specific activities by liquid scintillation counting (LSC) and alpha-particle spectrometry are presented, and are demonstrated using the soil reference material IAEA-326. Major contributors to the combined uncertainty associated with the measurement result of ²¹⁰Pb were the uncertainties of net count rates in the ²¹⁰Pb energy region of the sample spectrum and in the ²¹⁰Bi energy region of the blank spectrum. The predominant sources of uncertainty in the measurement of ²¹⁰Po were the uncertainties of net count rates in the regions of interest of ²⁰⁹Po and ²¹⁰Po. The relative standard uncertainty of ²¹⁰Po exponentially increases with the time interval between the sampling date and the separation date of Po, and this effect is strongly dependent on the ²¹⁰Po/²¹⁰Pb activity ratio. When the specific activity of ²¹⁰Pb is much higher than that of ²¹⁰Po in the sample, the relative standard uncertainty of the ²¹⁰Po determination increases significantly within a short time interval between the sampling date (or reference date) and the separation date of Po in samples.     

The fractionation and determination procedures for the speciation of Pb and Po in soil samples

A method for speciation and determination of ²¹⁰Pb and ²¹⁰Po in soil samples was developed. The speciation was carried out by fractionating the soil samples into five fractions which are water soluble or exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter and bound to residue. After mineralisation, 10% solution of each fraction was used to spontaneously deposit polonium on a silver disk at 85-90 °C and pH 1.5, and ²¹⁰Po was measured by α-spectrometry; the remain solution was used to separate lead by anion-exchange resin and purified by precipitation as PbS and PbSO₄, and ²¹⁰Pb was determined by a low background β-counter. The IAEA-327 reference material (soil) was studied for ²¹⁰Pb and ²¹⁰Po speciation. The results show that: (1) the average yields are 88.7 ± 6.4% for ²¹⁰Pb and 93.8 ± 8.2% for ²¹⁰Po; (2) if compared to the total ²¹⁰Pb activity in the sample, ²¹⁰Pb fractions are 0.95% in exchangeable form, 10.6% bound to carbonates, 14.3% bound to Fe-Mn oxides, 7.0% bound to organic matter and 67.2% bound to residue or acid soluble, and the corresponding values for ²¹⁰Po are 0.17%, 0.97%, 21.0%, 0.47% and 77.4%, respectively; and (3) the obtained ²¹⁰Pb concentration is in good agreement with the recommended value given by the IAEA.     

Polonium-210 and lead-210 in marine organisms: Intake levels for Japanese

The concentrations of²¹⁰Po and²¹⁰Pb were determined in about 30 species of marine organisms collected mainly from the north-easterm region of Japan to know the levels and distributions of these radionuclides and to estimate their intake levels from marine foods.²¹⁰Po and²¹⁰Pb showed a wide range of concentration in species: 0.6–26 and 0.04–0.54 Bq/kg (wet wt) in fishes, 0.5–220 and 0.2–43 Bq/kg (wet wt) in molluscs, echinoderms and chordatas, and 2.8–4.3 and 0.4–1.3 Bq/kg (wet wt) in algae, respectively. Higher accumulation of²¹⁰Po relative to²¹⁰Pb was found in all of the samples analyzed. The intake levels of²¹⁰Po and²¹⁰Pb by marine foods consumption were roughly estimated to be 0.48–0.69 and 0.022–0.042 Bq/d per person, respectively, on the basis of the statistical data on the consumption of seafood and/or production rates of marine foods.     

Estimation of sedimentation rates using 210Pb and 210Po at the coastal water of Sabah, Malaysia

Sediment cores were obtained from Teluk Brunei, Sipitang, Teluk Kimanis, Kota Kinabalu and Kuala Penyu at the coastal water of Sabah and analyzed for ²¹⁰Pb and ²¹⁰Po to estimate the sedimentation rates. The calculated sedimentation rates of ²¹⁰Pb and ²¹⁰Po varied from 0.003 to 0.049 cm/y and 0.74 to 8.77 cm/y, respectively. The highest sedimentation rates were determined for ²¹⁰Pb and ²¹⁰Po at stations located at Sipitang (mean: 0.027 cm/y) and Teluk Kimanis (mean: 5.53 cm/y), respectively. The sedimentation rate estimated for ²¹⁰Pb is not fully reliable because the activity of ²²⁶Ra was higher than that of ²¹⁰Pb and bioturbation was active at the sampling stations.     

Radiochemical characterization of spring waters in Balaton Upland, Hungary, estimation of radiation dose to members of public

Hungary is rich in spring waters. A survey studying the naturally occurring alpha emitter radionuclides in 30 frequently visited and regularly consumed spring waters was conducted out in the Balaton Upland region of Hungary.²²⁶Ra, ²²⁴Ra, ²³⁴U, ²³⁸U and ²¹⁰Po activity concentrations were determined by using alpha spectrometry after separation from matrix elements. Average concentration (mBq L^{− 1}) of ²²⁶Ra, ²²⁴Ra, ²³⁴U, ²³⁸U and ²¹⁰Po in the spring waters is varied from 2.1 to 601, from < 1.1 to 65.4, from 3.9 to 741.9, from < 0.44 to 274.3 and from 2 to 15.2 respectively. In most cases radioactive disequilibrium was observed between uranium and radium isotopes. The doses for the analyzed samples of spring water are in the range 3.59–166.73 μSv y^{− 1} with an average 18.2 μSv y^{− 1} .This is well below the 100 μSv y^{− 1} reference level of the committed effective dose recommended by WHO. Only one water sample had a dose higher than 100 μSv y^{− 1}, mainly due to the contribution from radium (²²⁶Ra, ²²⁴Ra) and ²¹⁰Po isotopes. This study provides important information for consumers and authorities about their internal radiological exposure risk from spring water intake.     

Analysis of Pb in water samples with plastic scintillation resins

²¹⁰Pb is a radioactive lead isotope present in the environment as member of the ²³⁸U decay chain. Since it is a relatively long-lived radionuclide (T_1/2 = 22.2 years), its analysis is of interest in radiation protection and the geochronology of sediments and artwork. Here, we present a method for analysing ²¹⁰Pb using plastic scintillation resins (PSresins) packaged in solid-phase extraction columns (SPE cartridge). The advantages of this method are its selectivity, the low limit of detection, as well as reductions in the amount of time and reagents required for analysis and the quantity of waste generated. The PSresins used in this study were composed of a selective extractant (4′,4″(5″)-Di-tert-butyldicyclohexano-18-crown-6 in 1-octanol) covering the surface of plastic scintillation microspheres. Once the amount of extractant (1:1/4) and medium of separation (2 M HNO₃) were optimised, PSresins in SPE cartridges were calibrated with a standard solution of ²¹⁰Pb. ²¹⁰Pb could be fully separated from its daughters, ²¹⁰Bi and ²¹⁰Po, with a recovery value of 91(3)% and detection efficiency of 44(3)%. Three spiked water samples (one underground and two river water samples) were analysed in triplicates with deviations lower than 10%, demonstrating the validity of the PS resin method for ²¹⁰Pb analysis.     

A modified method for the sequential determination of 210Po and 210Pb in Ca-rich material using liquid scintillation counting

This research describes methods for the sequential determination of ²¹⁰Pb and ²¹⁰Po activity concentrations in Ca-rich ash samples collected from oil shale-fired power plants in Estonia. The procedure involves digestion of Ca-rich ash samples in a microwave digestion system, radiochemical separation of ²¹⁰Pb and ²¹⁰Po and their measurements. All samples, blanks and standards were measured by liquid scintillation counting (Quantulus 1220). The method was tested using IAEA (International Atomic Energy Agency) RGU-1 and IAEA-444 reference materials. Spectral calibration/peak identification which included the optimization of α/β discrimination system (pulse shape analyser), and recovery have been made by ²⁰⁹Po and ²¹⁰Pb standard solutions.

     

210Pb and 210Po concentrations in the Venice lagoon ecosystem (Italy) and the potential radiological impact to the local public and environment

In order to evaluate the possible radiological impact to the local public and environment from a phosphogypsum stockpile, ²¹⁰Po and ²¹⁰Pb concentrations in river water, lagoon water, suspended matter, superficial sediment, algae and bivalves samples collected in Venice lagoon area have been investigated. The results show that the mean ²¹⁰Po and ²¹⁰Pb concentrations in river water are 1.42±0.36 mBq^.l^-1 and 1.46±0.39 mBq^.l^-1 with a mean ²¹⁰Po/²¹⁰Pb ratio of 0.98±0.17 and about 60% of them are associated with the particulate; ²¹⁰Po and ²¹⁰Pb contribution from the phosphogypsum stockpile to the river water is negligible. Higher ²¹⁰Po (2.61-5.67 mBq^.l^-1) and ²¹⁰Pb (1.31-3.62 mBq^.l^-1) concentrations in the lagoon waters have been observed if compared with the literature values. About 60% of ²¹⁰Po and ²¹⁰Pb are found in the soluble form with a mean ²¹⁰Po/²¹⁰Pb ratio of 1.79±1.47. ²¹⁰Po and ²¹⁰Pb concentrations in 28 out 37 sediment samples ranged from 26 to 45 Bq^.kg^-1 (dry weight), only 9 sediments with ²¹⁰Po and ²¹⁰Pb concentrations greater than 45 Bq^.kg^-1 are found and most of them are located 1-4 km near the phosphogypsum stockpile. The elevated ²¹⁰Po and ²¹⁰Pb concentrations in the sediments may be due to the contamination from the phosphogypsum stockpile. The mean ²¹⁰Po/²¹⁰Pb ratio (0.986±0.049) in the sediments shows that ²¹⁰Po and ²¹⁰Pb exist in nearly secular equilibrium. ²¹⁰Po and ²¹⁰Pb concentrations in algae vary with different species. The mean ²¹⁰Po and ²¹⁰Pb concentrations in Gracilaria compress and Ulva laetevirens which show a similar behavior, are 3.18±1.23 Bq^.kg^-1 and 2.42±1.26 Bq^.kg^-1 (fresh weight), respectively, with a mean ²¹⁰Po/²¹⁰Pb ratio of 1.45±0.34. The mean concentration factors with respect to the filtered water are 1096±424 for ²¹⁰Po and 1299±680 for ²¹⁰Pb. The mean ²¹⁰Po and ²¹⁰Pb concentrations in the soft part of Mytilus edulis are 23.2±9.7 Bq^.kg^-1 and 0.537±0.203 Bq^.kg^-1 (fresh weight), respectively, with a mean ²¹⁰Po/²¹⁰Pb ratio of 43.6±10.0. The mean concentration factors with respect to the filtered water are 8006±3351 for ²¹⁰Po and 290±109 for ²¹⁰Pb, showing a very high accumulation effect for ²¹⁰Po. The accumulation behaviors of Cerastoderma glaucum and Tapes philippinarum for ²¹⁰Po are similar to Mytilus edulis, but that for ²¹⁰Pb seems less effective, corresponding to a relatively higher ²¹⁰Po/²¹⁰Pb ratio. The estimated committed effective doses from ²¹⁰Po for the individual local public through ingestion of bivalves are in the range of 0.050-0.231 mSv^.y^-1.     

Measurement of lead-210, bismuth-210, and polonium-210 in environmental samples

Mathematical equations governing the ratio of²¹⁰Bi/²¹⁰Pb and²¹⁰Po/²¹⁰Pb activities are used to explain the ingrowth of²¹⁰Bi and²¹⁰Po in environmental samples during post collection. Procedures are described for radiochemical separation of²¹⁰Pb,²¹⁰Bi, and²¹⁰Po in a state of radioactive disequilibrium and quantification by alpha- and beta-counting. Also, the special case is considered where²¹⁰Bi is in equilibrium with²¹⁰Pb, but both are in disequilibrium with²¹⁰Po. In this case, the activities of both²¹⁰Pb and²¹⁰Po are computed by measuring²¹⁰Po activity twice, using alpha-counting.     

Radiochemical determination of210Po and210Pb in water

A method for²¹⁰Po and²¹⁰Pb determination in water samples is described. The nuclides are concentrated, in presence of added²⁰⁸Po and lead carrier, by evaporation. Then the polonium is plated electroless from the acidic solution on a copper planchet and measured by alpha spectrometry.²¹⁰Pb separation from the other isotopes is based on the solutility of PbSO₄ in citrate.²¹⁰Pb content is determined by measuring the activity of its daughter²¹⁰Bi. The critical steps in the isolation of lead have been examined and discussed.     

Simultaneous determination of210Bi and210Po on pine needles by solvent extraction and liquid scintillation counting

A determination procedure has been developed for²¹⁰Bi and²¹⁰Po in environmental samples and was applied for pine needles. Bismuth-210 and²¹⁰Po separated from the parent nuclide²¹⁰Pb as BiOCl precipitate were extracted simultaneously by TOPO/toluene containing PPO and POPOP. The separation of²¹⁰Bi and²¹⁰Po from²¹⁰Pb was almost satisfactory. The activity of²¹⁰Bi+²¹⁰Po in the TOPO/toluene was measured periodically by liquid scintillation counting for about 20 days after separation. The time course of the decreasing pattern of the activity was determined by the initial activity ratio²¹⁰Po/²¹⁰Bi. The decreasing pattern of the activity was compared with theoretical patterns, and best estimates for²¹⁰Po and²¹⁰Bi were obtained by non-linear least-squares fitting. The activities of²¹⁰Bi and²¹⁰Po were determined for one-year and two-year old pine needles fro the same pine tree, and weathering half-time and deposition rate of these nuclides was discussed.     

Development of measurement system for adsorption of long-lived radon decay products on the leaf surface of tobacco plants

Our previous studies indicated the suitability of tobacco plants for biomonitoring remediated depositories, due to their ²¹⁰Po and ²¹⁰Pb accumulation ability. The methods and requirements of testing ²¹⁰Pb uptake by leaf-surface adsorption was investigated and implemented in the construction of a controlled environment. Uranium ore (theoretical Rn concentration 638 Bqm^?3) was the main source of radon and progeny. Rn concentrations were measured by RAD7, AlphaGUARD, EQF 3220, RTM 2100 and CR-39 SSNTDs (411–516 Bqm^?3). Activity concentrations of the attached and unattached fractions were determined by EQF 3220. The results are indicative of good measurement setup for tracking ²¹⁰Po(Pb) uptake pathways.     

The radiation dose and distribution coefficient of 210Po and 210Pb concentrations in aquatic environs of major rivers of coastal Karnataka

The activity of ²¹⁰Po and ²¹⁰Pb was measured in different matrices of aquatic ecosystem of the major rivers of Coastal Karnataka viz, Kali, Sharavathi and Netravathi. The environmental samples such as surface water, suspended particulate matter and sediment have been subjected to analyses. The activity of these two radionuclides were determined by radiochemical separation of ²¹⁰Po and counting the activity using a ZnS(Ag) alpha counter. The activity ratio of ²¹⁰Po and ²¹⁰Pb and correlation between the activity of these radionuclides were studied. From the measured concentration of ²¹⁰Po and ²¹⁰Pb, the internal Committed Effective Dose to the population for the study area was calculated. The distribution coefficient K_d between water, suspended particulate matter and sediments have been calculated to understand the distribution and accumulation of these radionuclides in different matrices of the aquatic environment.

     

Optimization of Pb determination via spontaneous deposition of Po on a silver disk

The accuracy of ²¹⁰Pb determination via spontaneous deposition of ²¹⁰Po on a silver disk and alpha spectrometric measurement was examined. The study focused on the storage conditions of the polonium-containing solutions, the tracer used in polonium analysis and the effect of storage time and acid concentration on ²¹⁰Po deposition. The intermediate precision and repeatability associated with the improved ²¹⁰Pb analysis of fresh groundwater samples was 5 and 14%, respectively. These improved values were achieved by using glass bottles as storage containers for the solution remaining from the first ²¹⁰Po deposition, by rinsing the sample container with concentrated hydrochloric acid after storage and by using different isotopes of polonium as the yield determinant tracer in the first and the second deposition. Less polonium adsorption onto the storage container walls occurred with HCl than with HNO₃. The overall uncertainty in ²¹⁰Pb analysis was (11 ± 7)% at the 95% confidence level. The minimum detectable activity concentration was 0.1 mBq l⁻¹ calculated from blank samples and 0.05 mBq l⁻¹ using the background counts of the alpha spectrometer.     

Measurements of <Superscript>210</Superscript>Po and <Superscript>210</Superscript>Pb in total diet samples: Estimate of dietary intakes of <Superscript>210</Superscript>Po and <Superscript>210</Superscript>Pb for Japanese

To estimate the dietary intakes of ²¹⁰Pb and ²¹⁰Po for the Japanese adults and their annual effective doses, ²¹⁰Pb and ²¹⁰Po were measured for 240 daily diet samples collected at two locations of Ishikawa Prefecture in Japan over three years by duplicate portion studies. No appreciable differences in intake rates of ²¹⁰Pb and ²¹⁰Po and their ²¹⁰Po/²¹⁰Pb ratios were seen among the years in each district, and between the two districts. The intake rates evaluated using 240 diet samples were 0.20 Bq/d/p for ²¹⁰Pb and 0.61 Bq/d/p for ²¹⁰Po as a median, respectively. Annual effective doses of ²¹⁰Pb and ²¹⁰Po for Japanese adults were estimated to be 0.050 and 0.053 mSv/y, respectively.     

A rapid method for the separation of 210 Po from 210 Pb by TIOA extraction

A rapid method for the separation of ²¹⁰ Po from ²¹⁰ Pb was developed utilizing extraction of triisooctylamine (TIOA)/xylenein HCl+H₂O₂ medium. Polonium in the form of PoCl ₆ ²– was extracted into TIOA phase and ²¹⁰Pb remains in the aqueous phase. Lead-²¹⁰ was determined by -countingof its granddaughter, ²¹⁰ Po ingrown from ²¹⁰ Pb forsome period of time. Distribution of ²¹⁰ Po and ²¹⁰Pb in TIOA and aqueous phases was investigated in various concentrations ofHCl media. Hydrogen peroxide was used to further decompose organic matterand to remove sulfur to prevent its deposition on the silver disc. The improvedprocedure resulted in a good chemical yield (80–95%) and a good á-resolution.     

Analysis of 210Pb and 210Po in Brazilian foods and diets

Radiochemical procedures for the analysis of ²¹⁰ Pb and ²¹⁰ Po in foods and diets are presented. Because of the low beta energy of ²¹⁰ Pb, its analysis was based on a separation of the daughter radionuclide ²¹⁰ Bi by precipitation of lead sulphate, ²¹⁰ Bi ingrowing and beta counting of this nuclide. ²¹⁰ Po analysis was based on wet dissolution of the sample, deposition onto silver disc and counting by alpha-spectrometry. Levels of these radionuclides in individual items and diets of selected university students were determined in order to evaluate the intakes of ²¹⁰ Pb and ²¹⁰ Po as well as the dose due to ingestion of foods and diets in São Paulo city.     

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.     

Activity concentration of polonium-210 and lead-210 in tobacco products and annual committed effective dose to tobacco users in Tiruchirappalli District (Tamil Nadu,India)

The present study has carried out with an objective of determining the activity concentrations of two radionuclides namely polonium-210 (²¹⁰Po) and lead-210 (²¹⁰Pb) in smoke tobacco products (cigarette, bidi and cigar) and smokeless tobacco products (chewing tobacco and snuff) consumed in Tiruchirappalli District, Tamil Nadu (India) and their annual committed effective dose to tobacco consumers. The concentration of ²¹⁰Po was always higher than that of ²¹⁰Pb in all the analyzed tobacco products. It also revealed that 79% of Annual committed effective dose comes from ²¹⁰Po and about 21% from ²¹⁰Pb. Maximum concentration (13.2 mBq g^?1) of ²¹⁰Po recorded in cigarette and lowest concentration was observed in snuff (6.4 mBq g^?1). The highest mean committed effective dose of ²¹⁰Po and ²¹⁰Pb in various tobacco products were found in cigarette followed by bidi, cigar, chewing tobacco and snuff. The study revealed that the tobacco products available in Tiruchirappalli District contain a relatively lower concentration of radionuclides when compared to other regional studies. Since this kind of study in India is fragmentary, the present study has generated a base data for the first time for entire Tiruchirappalli District.