Determination of 210Pb, 210Bi and 210Po in natural drinking water

A new method for the radioanalytical determination of the ²²²Rn progenies ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Powill be presented, which has been improved for analyses of water samples fromdifferent regions in Austria. 1–2 liter samples were taken in polyethylenebottles prefilled with conc. HNO₃ to obtain 0.2M acidic solutions,thus avoiding adsorption effects. After adding 1.6 mg of inactive lead carrier,the water sample was evaporated to dryness, converted to the chloride formand dissolved in 1M HCl.     

Determination of (210)Pb, (210)Bi and (210)Po in natural waters and other materials by electrochemical separation

An improved method for determination of (210)Pb, (210)Bi and (210)Po in both natural waters and solid materials has been developed. Polonium-210 is spontaneously plated onto a silver disc from dilute hydrochloric acid medium. Bismuth-210 is then electro-deposited onto a platinum gauze cathode directly from the same solution, with a graphite rod as anode. Finally, (210)Pb is electro-deposited from a fluoroborate medium onto the same platinum gauze, used as the anode. All three nuclides are subsequently measured by standard low-level alpha and beta counting techniques. The speed of this method (approximately 6 hr per sample after pretreatment) is a distinct advantage over existing techniques, as (210)Bi must be quickly separated from (210)Pb because of its 5.02-day half-life. Another advantage of this method is that the chemical form of the sample solution is suitable for use of established separation schemes for determining other decay-series isotopes (U, Th, Pa, etc.) after the three short-lived nuclides have been processed.     

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.     

210Po、210Bi和210Pb测试技术研究进展与现状

铀系核素210Po、210Bi和210Pb的测试在铀矿地质勘查与核废物安全处置研究、沉积年代学与同位素地球化学研究、大气环境学与辐射卫生学研究等诸多领域具有重要意义。重点总结了近些年来210Pb、210Bi和210Po三核素各种测试技术的研究进展与现状,评述了存在的主要问题及未来发展趋势。     

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.     

226Ra, 210Pb, 210Bi and 210Po deposition and removal from surfaces and liquids

Deposition of ²²⁶Ra from water on nylon was investigated. Measurements performed for different pH and different radium concentrations in the water gave similar absolute activities deposited on the foil surface. Obtained results were used to estimate the amount of ²²⁶Ra plated-out on the nylon scintillator vessel in the solar neutrino experiment BOREXINO during filling of the detector. Another problem studied in the frame of BOREXINO was the removal of ²¹⁰Pb from its organic liquid scintillator by applying distillation and water extraction. After several tests had been performed for both methods it was found that after the water extraction the initial lead content in the scintillator sample was reduced only accordingly to the ratio of the volumes of the applied liquids (simple dilution). In contrast to this, distillation was very effective providing in the best case a ²¹⁰Pb reduction factor higher than 100. Removal efficiencies of the long-lived ²²²Rn daughters during etching from surfaces of standard and high purity germanium were investigated in the frame of the GERDA experiment, which aims to search for neutrino-less double beta decay of ⁷⁶Ge. The standard etching procedure of Canberra used during production of high purity n-type germanium diodes was applied to germanium discs, which had been exposed earlier to a strong ²²²Rn source for its progenies deposition. In contrast to copper and stainless steel, ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po was removed from germanium very efficiently. An evidence of a reverse process was also observed—the isotopes were transferred from the etchant to the clean germanium surface.     

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.     

210Pb and210Po in tobacco-with a special focus on estimating the doses of210Po to man

Studies have been carried out on the solubility of Pu(III) oxalate by precipitation of Pu(III) oxalate from varying concentrations of HNO₃/HCl (0.5–2.0M) solutions and also by equilibrating freshly prepared Pu(III) oxalate with solutions containing varying concentrations of HNO₃/HCl, oxalic acid and ascorbic acid. Pu(III) solutions in HNO₃ and HCl media were prepared by reduction of Pu(IV) with ascorbic acid. 0.01–0.10M ascorbic acid concentration in the aqueous solution was maintained as holding reductant. The solubility of Pu(III) oxalate was found to be a minimum in 0.5M–1M HNO₃/HCl solutions containing 0.05M ascorbic acid and 0.2M excess oxalic acid in the supernatant.     

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%.     

Sequential and rapid determination of Po-210, Bi-210 and Pb-210 in natural waters

A sequential and rapid separation method for the determination of radon daughter nuclides, Pb-210, Bi-210 and Po-210 has been developed for application to natural waters. Rapid separation is attained by the use of the same hydrochloric acid solution. After isolation of the three radionuclides from the sample by co-precipitation with added Fe³⁺, polonium isotopes are first spontaneously deposited onto a silver disc from a 0.5N hydrochloric acid solution. Next, bismuth isotopes are electrodeposited onto a platinum net cathode coupled with a platinum coil anode at 1.2 V. Finally, lead isotopes are electrodeposited onto a platinum net cathode at 1.8 V from the remaining solution by adding hydroxylamine hydrochloride as an anodic depolarizer. This method can be applied to meteorological precipitation samples where these three nuclides are separated within 10 hr after the sampling with chemical yields of more than 80% for Po-210 and Bi-210 and more than 70% for Pb-210. This method is applicable to other environmental water samples.     

Levels of 210Po and 210Pb in cigars

²¹⁰Po and ²¹⁰Pb concentrations have been determined in 58 cigar brands manufactured in 11 countries. Cuban and American cigars showed the lowest ²¹⁰Po content. The mean levels of ²¹⁰Po in Brazilian, European and Dominican cigars were almost identical and somewhat lower than the levels observed for cigars from other Latin American countries. Cuban, American and European cigars contained low levels of ²¹⁰Pb. Cigars from the remaining countries contained twice as much ²¹⁰Pb. The mean ²¹⁰Po/²¹⁰Pb ratio showed an excess of polonium. In the case of a one cigar-a-day smoker, the calculated annual absorbed dose due to ²¹⁰Po is -16 mGy.     

Radiochemical analysis of210Po in coal gasification samples

The concentrations of²¹⁰Po in samples from a coal gasifier were determined by -pulse height analysis following separations from complex organic matrices. Samples were dissolved using wet acid digestion and persulfate fusion techniques and then extracted with trilaurylamine. Polonium was auto-deposited onto silver disks using²⁰⁹Po as a tracer for yield determination. The precision of the experimental method, determined on coal, was ±6% at the 95% confidence level. Excellent agreement was attained with published data on an EPA coal sample.This work was sponsored by the Office of Health and Environment, Office of Environmental Programs, and the Office of Coal Processing, U.S. Department of Energy, under contract DE-AC05-840R21400, with Martin Marietta Energy Systems, Inc.     

210Pb and210Po analysis in sediments and soils by microwave acid digestion

A microwave acid digestion method prior to the determination of²¹⁰Pb and²¹⁰Po in sediments and soils is described. It involves an acid (HNO₃, HCl, HF and H₃BO₃ mixture) digestion with microwave heating in closed vessels at high pressures. Analyses carried out for various reference materials showed that the results were statistically equal to certified values and reproducibility was also assured. The advantage of the microwave technique compared to the traditional leaching procedures is that the solid materials are completely dissolved and, therefore, ca. 100% efficiency is achieved in the extraction of²¹⁰Po and²¹⁰Pb, even though a fraction is associated to the silica net. Moreover, time of analysis is drastically reduced, as are the risks associated to vapour inhalation and material corrosion.     

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.     

Inorganic complexation of nickel and cobalt in natural waters

The distribution of nickel and cobalt species has been computed, based on the pH-dependent model of Zirino and Yamamoto. The media used in the pH range of 7 to 9 are natural waters like fresh water, sea water and a mixture of them at different compositions, at 25°C temperature and 1 atm pressure. In fresh water, both nickel and cobalt dominate as free cations at lower pH, and as carbonato complexes at higher pH. In sea water, chloro complexes are significant. In mixtures of the two kinds of water, as might be found in a totally mixed estuary, chloro complexes are important, varying slowly with pH. Sea water plays an important role in complexation. The present results are in excellent agreement with experimental data obtained by the resin exchange method.     

An efficient quantitative technique for the simultaneous analyses of radon daughters (210)Pb, (210)Bi and (210)Po

An improved and time efficient technique has been developed for quantitative determination of the long-lived (222)Rn daughters ((210)Pb, (210)Po and (210)Bi) in atmospheric and oceanic samples. The sample is first spiked with yield tracers for polonium (208 or 209), bismuth (207), and lead (stable lead carrier). These nuclides may then be scavenged through iron hydroxide precipitation and redissolved in a dilute (pH approximately 2) nitric acid plating medium with citrate and hydroxylamine hydrochloride at 90 degrees centrigrade with constant stirring. First a silver planchet is suspended in the solution which plates polonium to high efficiency. Second, a nickel planchet is suspended in the same solution which is maintained hermetic (e.g. bubbling with helium) and bismuth is plated next with high efficiency. Third, lead is purified from the same solution using anion exchange techniques and isolated for beta counting as the sulfate. Polonium is analyzed by isotope dilution alpha spectrometry. Bismuth and lead are analyzed by anti-coincident beta counting in a low level shield. In the case of bismuth, the 207 tracer is added in quantities at least comparable to the background of the beta system such that counting before and after the decay of (210)Bi gives the bismuth yield. The unique characteristics of this technique are its speed and efficiency; all three radon daughters can be isolated for counting within 4 hr of pre-treating the sample. The remaining solution can be treated subsequently for other analyses as appropriate.     

Separation of the radioelements210Pb−210Bi−210Po by spontaneous deposition onto noble metals and verification by Cherenkov and liquid scintillation counting

A method for the separation of²¹⁰Pb,²¹⁰Bi and²¹⁰Po using spontaneous deposition has been developed. The²¹⁰Bi and²¹⁰Po are simultaneously removed by deposition onto nickel foil (copper and tin could also be used but less effectively) while the²¹⁰Po is separated from²¹⁰Bi, after dissolution of the nickel foil, by deposition onto silver foil. The effectiveness of each separation was evaluated by adding aliquot portions of each solution to a cocktail and counting with a liquid scintillation counter. Water was used as the medium to observe the Cherenkov count of the sample solution.     

Isolation and electroplating of210Po

Extraction coefficients for all lanthanides have been determined in two systems: 0.2M TBP-3M NaNCS, and 3.6M TBP-0.2M NaNCS. The data have been used for the calculation of relative changes in thermodynamic functions accompanying the investigated extraction process. The compensation of enthalpy and entropy changes is found as a result of dehydration of the lanthanide aquaions.     

Determination of210Po in lead

A quantitative separation procedure for²¹⁰Po in lead has been developed by cupferron and dithizone extraction. The²¹⁰Po activity is plated on a silver foil for counting with a ZnS(Ag) scintillator, or by α-spectrometry with a surface barrier semiconductor. Different lead samples were analyzed ranging from very old lead with a negligible²¹⁰Po content to recently manufactured lead samples showing up to 9100 disintegrations per hour and per gram of lead. The reproducibility and the accuracy of the analyses are satisfactory.     

Measurements of210Pb and210Po in Japanese human hair

²¹⁰Pb and²¹⁰Po in human hair have been measured to serve as an aid in order to estimate the dietary intake and body burden of these radionuclides of Japanese. The²¹⁰Po concentrations found in 83 hair samples were ranging from 4.0 to 59.3 mBq/g with a mean (median) value of 18.2±12.2 (14.9) mBq/g as compared to the²¹⁰Pb concentrations from 0.7 to 6.5 mBq/g with a mean (median) value of 2.3±1.1 (2.0) mBq/g. The²¹⁰Po/²¹⁰Pb activity ratios (mean: 8.7±5.1, median: 7.1) were surprisingly higher compared with the available literature value of about 2. The high concentration of²¹⁰Po in human hair of Japanese may be due to the ingestion of animal protein mainly in the form of seafood.