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.     

The role of Cherenkov and liquid scintilation counting in evaluating the anion-exchange separation of210Pb−210Bi−210Po

Using as eluent a sequence of 3M HCl, 12M HCl, and 8M HNO₃, a mixture of²¹⁰Pb,²¹⁰Bi, and²¹⁰Po may be clearly separated on a column of Dowex 1×2−100 anion exchange resin. A Cherenkov count in H₂O and the variation in count rate with time confirm that the nuclides emerge in the order²¹⁰Pb→²¹⁰Bi→²¹⁰Po. If 12M HCl is replaced by 1.5M H₂SO₄/2.3 M Na₂SO₄, a clean separation also results, but recovery of²¹⁰Po becomes considerably more difficult. All three nuclides are readily detectable by liquid scintillation counting, with the efficiency for²¹⁰Pb in the 60–70% range. The Cherenkov aqueous counting efficiency for²¹⁰Bi is ∼14–15%.     

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.     

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.

     

Atmospheric deposition of 210Po and 210Pb in Malaysian waters during haze events

Biogenic burning as forest fire phenomena occurring from April to August each year in the Sumatra and Borneo islands are major sources of biogenic uranium–thorium decay series in marine systems. 30 samples were collected during the Ekspedisi Pelayaran Saintifik Perdana 2009 cruise (EPSP 2009 cruise) between 12th June and 1st August 2009 from the Straits of Malacca to the Sulu and Sulawesi Seas to study the effect of haze and the monsoon season on the deposition rate of ²¹⁰Po and ²¹⁰Pb in Malaysian waters. All samples were spiked with 1 ml of lead [Pb(NO₃)₂; 25 mg ml^?1] and 0.05 ml of Polonium-209 tracer (26.08 dpm ml^?1). ²¹⁰Po activity was determined by auto plating onto silver foil and counting using an alpha spectrometry system (Canberra model Alpha Analyst with a silicon-surface barrier detector). Lead that was collected via electrodeposition, formed lead sulphate (PbSO₄) precipitation. This precipitate was wrapped onto plastic discs and counted for ²¹⁰Pb beta activity using a gross alpha–beta counting system (Tennelec model LB-5100 low background gas-flowing anti-coincidence alpha/beta counter) after 1 month to allow bismuth ingrowths. The range of ²¹⁰Po activities varied between 51.08 ± 15.1 and 742.08 ± 220.34 Bq/kg, whereas the activity of ²¹⁰Pb ranged from 31.10 ± 4.20 to 880.23 ± 123.86 Bq/kg and ²¹⁰Po/²¹⁰Pb ratio value varied between sampling stations from 0.19 to 13.77. The contents of ²¹⁰Po were also statistically positively correlated with the amount of total suspended particulate especially those recorded during heavy haze period events.     

Mutual separation of210Po,210Bi,and210Pb with solvent extraction using copper dithizonate −CCl4 and dithizone −CCl4 solutions

Displacement-extraction of tracer concentrations of²¹⁰Po in 1.0M (H, Na)NO₃ solutions has been studied by using copper dithizonate–CCl₄ solutions. Furthermore, based on the results of the displacement-extraction of polonium, a mixture of²¹⁰Po,²¹⁰Bi, and²¹⁰Pb of tracer concentrations in 1.0M (H, Na)NO₃ solutions could be satisfactorily separated with successive extractions by copper dithizonate–CCl₄ and dithizone–CCl₄ solutions in acidic conditions.     

Separation of carrier-free210Bi and UX1 from210Pb and U,respectively, using silica gel as ion exchanger

Radiochemical separations of carrier-free²¹⁰Bi and UX₁ activities from²¹⁰Pb and U, respectively, have been carried out using a silica gel column.²¹⁰Pb was adsorbed in the column as molybdate and²¹⁰Bi passed unadsorbed. Lead activity was next removed with 25 ml of 0.1 M HNO₃. In the case of separation of UX₁, the coloured carbonate complex of U was removed from the silica surface by washing with saturated sodium carbonate solution, keeping UX₁ retained, and finally UX₁ was washed out with 25 ml of conc. HNO₃. Studies of the beta decay of²¹⁰Bi and the γ-spectrum analysis of UX₁ has shown that the separated products in both cases are of high radiochemical purity. The processes in each case took less than one hour and the yield was satisfactory.     

137Cs and 210Pb radionuclides in open and closed water ecosystems

The aim of this study was to determine the level of radionuclide concentration in sediment cores in two different water ecosystems; one closed and one open. Based on this data the changes in these ecosystems were interpreted. Two sediment cores from the Dobczyce reservoir and the Smreczynski Staw Lake were collected and divided into 1 cm thick sub-samples. The samples were air dried and homogenized. The ¹³⁷Cs and ²¹⁰Pb (²¹⁰Pb_sup, ²¹⁰Pb_total, ²¹⁰Pb_uns) concentrations were measured using gamma and alpha spectrometry. Results showed that the ¹³⁷Cs concentration in the Dobczyce reservoir is lower than in the Smreczynski Staw Lake. Total ²¹⁰Pb concentration in the Dobczyce reservoir was around 70 Bq kg^?1 and in the Smreczynski Staw Lake was about 500 or 1,200 Bq kg^?1 with the decreasing tendency in the sediment core. Sediments are very important constituents of water ecosystems. In spite of the young age of the Dobczyce reservoir, the ¹³⁷Cs and ²¹⁰Pb radionuclides were very useful in understanding of the processes which have taken place in these ecosystems. The estimated sedimentation rate indicated such processes as regular sedimentation, mixing of sediments or floods. In the Smreczynski Staw Lake the changes have reflected the changes which took place in the Tatra Mountains.     

Rapid determination of 210Po in water samples

A new rapid method for the determination of ²¹⁰Po in water samples has been developed at the Savannah River National Laboratory (SRNL) that can be used for emergency response or routine water analyses. If a radiological dispersive device event or a radiological attack associated with drinking water supplies occurs, there will be an urgent need for rapid analyses of water samples, including drinking water, ground water and other water effluents. Current analytical methods for the assay of ²¹⁰Po in water samples have typically involved spontaneous auto-deposition of ²¹⁰Po onto silver or other metal disks followed by counting by alpha spectrometry. The auto-deposition times range from 90 min to 24 h or more, at times with yields that may be less than desirable. If sample interferences are present, decreased yields and degraded alpha spectrums can occur due to unpredictable thickening in the deposited layer. Separation methods have focused on the use of Sr Resin?, often in combination with ²¹⁰Pb analysis. A new rapid method for ²¹⁰Po in water samples has been developed at the SRNL that utilizes a rapid calcium phosphate co-precipitation method, separation using DGA Resin^® (N,N,N′,N′ tetraoctyldiglycolamide extractant-coated resin, Eichrom Technologies or Triskem-International), followed by rapid microprecipitation of ²¹⁰Po using bismuth phosphate for counting by alpha spectrometry. This new method can be performed quickly with excellent removal of interferences, high chemical yields and very good alpha peak resolution, eliminating any potential problems with the alpha source preparation for emergency or routine samples. A rapid sequential separation method to separate ²¹⁰Po and actinide isotopes was also developed. This new approach, rapid separation with DGA resin plus microprecipitation for alpha source preparation, is a significant advance in radiochemistry for the rapid determination of ²¹⁰Po.     

Ceric phosphate as ion exchanger in the separation of carrier-free210Bi from210Pb,90Y from90Sr and UX1 from u

Separations of tracer cations in parent daughter systems such as carrier-free²¹⁰Bi from²¹⁰Pb,⁹⁰Y from⁹⁰Sr and UX₁ from U have been carried out in a column of ceric phosphate as ion exchanger. The exchanger has been prepared by mixing ceric sulfate in hot 10M orthophosphoric acid at 80°C and keeping for overnight. A pale yellow coloured precipitate was formed which was washed, dried at 70°C for 48 hours when a hard, granular variety suitable for column use, with a cerium to phosphate ratio of 1∶2 was obtained. 0.1M H₃PO₄ was used as medium in each of the systems studied. The β-decay curves of the separated²¹⁰Bi and⁹⁰Y and the γ-spectrum of UX₁ show that all these activities are radiochemically pure. The separation procedures adopted in each case were very clean and simple, gave quantitative yields and took less than half an hour.     

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.     

Determination of 210Po and uranium in high salinity water samples

A method for the determination of uranium and ²¹⁰Po in high salinity water samples has been elaborated. Both radionuclides are preconcentrated from 0.5 dm³ saline media by co-precipitation with hydrated manganese dioxide, followed by dissolution of the precipitate in 200 mL of 1 M HCl. Uranium isotopes ²³⁵U and ²³⁸U can be directly determined by ICP MS method with a detection limit of 0.01 ppb for ²³⁸U. Prior to a selective determination of ²¹⁰Po, the majority of other naturally occurring α-emitting radionuclides (uranium, thorium and protactinium) can be stripped from this solution by their extraction with a 50% solution of HDEHP in toluene. Finally, ²¹⁰Po is simply separated by direct transfer to an extractive scintillator containing 5% of trioctylphosphine oxide in Ultima Gold F cocktail and determined by an α/β separation liquid scintillation technique with detection limit below 0.1 mBq/dm³.     

Effective doses due to intake of radiotoxic radionuclides 226Ra, 210Po and 210Pb through drinking water of coastal Karnataka

The concentrations of ²²⁶Ra, ²¹⁰Po and ²¹⁰Pb have been measured, by high efficiency 5″ × 5″ NaI(Tl) gamma ray spectrometer and chemical deposition method, in surface water samples from major rivers Kali, Sharavathi and Netravathi of coastal Karnataka. Measurements of ²²⁶Ra, ²¹⁰Po and ²¹⁰Pb in surface water from these rivers are important because the river water is main source of potable water in this region due to inadequate supply of treated water. The mean activity of ²²⁶Ra, ²¹⁰Po and ²¹⁰Pb in the surface water of the river Kali was found to be 5.13 mBq L⁻¹, 1.28 and 1.37 Bq L⁻¹, for Sharavathi River the mean activity was found to be 3.37 mBq L⁻¹, 1.30 and 1.44 Bq L⁻¹. In Netravathi River the mean activity of ²²⁶Ra, ²¹⁰Po and ²¹⁰Pb was found to be 3.30 mBq L⁻¹, 1.00 and 1.20 Bq L⁻¹. From the measured concentration of ²²⁶Ra, ²¹⁰Po and ²¹⁰Pb, the Effective dose to the population of the region was computed. The results of these systematic studies are presented and discussed in the paper.     

Determination of 90Sr and 210Pb in deer bone samples by liquid scintillation counting after ion-exchange procedures

This work describes a procedure for the isolation of ⁹⁰Sr and ²¹⁰Pb from deer bones by anion exchange methods and their sequential measurement by LSC. To prevent collection of Pb on the Sr·Spec^® resin we first separated Pb on a Dowex anion exchange column. Sr, which is not held back on the Dowex column, was then purified using Sr·Spec^® resin: first Ca and the Ra isotopes were eluted with 3 M HNO₃ and then Sr was eluted with distilled water. With this 2-steps procedure pure ²¹⁰Pb and ⁹⁰Sr spectra can be achieved. The chemical yield of both steps was determined by ICP-MS. Our ⁹⁰Sr results show satisfying agreement with data obtained by a shorter Sr·Spec^® method and also by the “classical” ⁹⁰Sr determination using fuming nitric acid. Also ²¹⁰Pb results were checked by re-measuring bone samples with already known ²¹⁰Pb activities. Further our method was verified on the reference sample IAEA-A-12.     

Determination of environmental actinide nuclides and210Pb(210Po) by low-energy photon spectrometry with alpha-spectrometry

Low-energy photon spectrometry with -spectrometry was used to determine the environmental concentrations of low-level actinides and other nuclides, especially²¹⁰Pb and²¹⁰Po. The isotopic ratio of²⁴⁰Pu/²³⁹Pu was successfully determined by measuring L_x-ray/-ray counting ratio. A reliable method has been developed for the determination of extremely low-level²³⁷Np global fallout in environmental samples. The non-destructive determination by Ge-LEPS for natural²¹⁰Pb in various samples (tobacco leaves, commercially available tobacco, etc.) was also carried out with the determination of²¹⁰Po by -spectrometry using²⁰⁹Po as a yield tracer.     

Presence and forms of210Pb,210Bi and210Po in ground level aerosols

A scheme of fractionation of²¹⁰Pb,²¹⁰Bi,²¹⁰Po forms present in air aerosols based on the combination of methods of radiochemical analysis and radiometric deteemination with leaching by different agents has been developed. The ratio between the²¹⁰Pb,²¹⁰Bi,²¹⁰Po present in the aerosol samples was determined experimentally. Carbonate of²¹⁰Pb, and²¹⁰Po and²¹⁰Bi forms connected with oxides prevai in the aerosol component of atmospheric air.     

Determination of 210Po in Reagent Samples by Alpha-Ray Spectrometry Using Extraction Chromatographic Resin

The determination of ²¹⁰Po in phosphoric acid reagent by alpha-ray spectrometry using extraction chromatographic resin is presented. The decontamination factors of interference elements were measured. It was observed that HCl, HNO₃, ascorbic acid, thioacetamide and Cu were free from ²¹⁰Po but Pb contain small amounts of ²¹⁰Po. ²¹⁰Po in phosphoric acid samples was ranged from <8 to 2.4 Bq/l. The detection limit of ²¹⁰Po in 50 ml of phosphoric acid is 8 mBq/l with a counting time of 1 day undercounting efficiency of 30%.     

Volatility of 210Po in the gross alpha determination

Gross alpha and beta activity screening methods have been developed to determine whether specific analysis of radionuclides is required to further characterize water. Our contribution aims at the validation of possible losses of ²¹⁰Po related to underestimation of the gross alpha activity. The tap water samples likewise the selected samples of surface, underground, and mineral water were processed. These samples were treated in solutions containing both HNO₃ (recommended by ISO standards) and HCl (which could cause significant loses of volatile polonium chloride form during the sample ignition). Results of several experiments determining the recovery of polonium during the ignition of sample are discussed. Conditions which can lead to significant losses of polonium are partly demarcated.     

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.