Effects of negative ion generators on radon- and thoron-progeny concentrations in an occupied residence

Operation of negative ion generators in three rooms of an occupied residence caused decreases in indoor concentrations of the radon decay products²¹⁸Po,²¹⁴Pb and²¹⁴Bi, and of the thoron progeny²¹²Pb. Activity levels of²¹²Pb were lowered more than those of²¹⁴Pb, resulting in a decrease in the potential alpha energy concentration ratio, PAEC(Tn:Rn). The change in PAEC(Tn:Rn) is a function of the halflives of²¹⁴Pb and²¹²Pb and their respective precursors and is similar to the effect brought about by increased room ventilation. Decay products are also removed from indoor air by plateout of charged particles on room walls. Plateout rates calculated for²¹⁴Pb suggest that even in well-ventilated houses, the potential alpha energy concentration of radon is affected as much by wall plateout as by infiltration of outside air.     

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.     

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.     

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.     

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.     

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.     

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.     

Field alpha-spectroscopy of radon (<Superscript>222</Superscript>Rn) and actinon (<Superscript>219</Superscript>Rn) progeny in soil gas: Locating a radon source

Summary The activities of²¹⁸Po,²¹⁴Po and²¹¹Bi were determined in samples obtained of soil/gas. Sampling work was taken in Jáchymov (Czech Republic) at the outcrop of the Geister-vein,by electrostatic precipitation from filtered soil gas on stainless steel disks.The samples were measured in a field laboratory using a semi-conductor alpha-spectrometer.The activities of²¹⁸Po,²¹⁴Po and²¹¹Bi were calculated.Samples taken from active dump material (near-by radon source) exhibited a high²¹¹Bi/²¹⁴Po ratio, while those of the vein outcrop (a relatively deeper source) had a low ratio.A mathematical model was employed to determine the radon age calculated from the actinon/radon input ratio.This varied in a range of 5.6 to -7.7 seconds.Negative age values are probably caused by the preference for actinon, which rapidly comes into equilibrium with the source of this gas.     

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.     

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.     

Determination of210Pb and210Po in human tissues of Japanese

To determine the levels of²¹⁰Pb and²¹⁰Po in human tissues of people in Japan, various tissue samples were obtained at autopsy from the cadavers of 22 oncologic cases, mainly in Niigata Prefecture in northern Japan, from 1986 to 1988.Wet ashing, followed by electrochemical deposition and alpha spectrometry were used to separate and determine the²¹⁰Pb and²¹⁰Po present. Among the tissues analyzed, the highest concentrations of²¹⁰Pb and²¹⁰Po were observed in bone (sternum), liver, and kidneys. The total body burden of²¹⁰Pb and²¹⁰Po was found to be approximately 427 pCi and 514 pCi, respectively. This estimated²¹⁰Po value did not differ significantly from values found in populations in the U.S.A. and European countries.     

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.     

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.     

Evaluating the potential alpha energy of radon progeny

Potential alpha energy concentration of radon progeny can be measured using the alpha-spectroscopy with the silicon semiconductors detectors and the gross-counting attached with the ZnS detectors. The decay method was applied where the alpha particles emitted from the ²¹⁸Po to ²¹⁴Po were detected. In the case of the decay products, the amount and aerodynamic behavior of radioactivity are important, and also need to be measured. During the experiment, the radon gas was supplied and evaluated from the experimental room with constant concentration. Then the air sample was used as the known volume and the grab sampling technique was developed for estimating the concentration of radon decay products. However the proper calculation was applied for estimating the potential alpha energy of radon progeny through of ²¹⁸Po, ²¹⁴Pb and ²¹⁴Bi.     

Distribution of137Cs in soil in Central Slovakia and fast prediction of contamination

This paper describes the measurement of²¹⁰Bi by Cerenkov counting in a commercial liquid scintillation counter. The counting efficiency in water is 0.17 counts per second per Becquerel (17%). When the enhancers Triton X-100 (15% v/v) and sodium salicylate (1% m/v) are added to the solution the counting efficiency for²¹⁰Bi increases from 17% to 75%. The²¹⁰Po daughter of²¹⁰Bi causes interference of 0.85 counts per second per Becquerel in the presence of the enhancers but not in water. When²¹⁰Bi and²¹⁰Po are present in secular equilibrium the total counting efficiency is 160%. When²¹⁰Bi and²¹⁰Po are not in secular equilibrium the²¹⁰Po can be removed immediately before counting by plating onto silver foil. The use of the enhancers gives a substantial increase in counting efficiency compared to counting in water. Compared with solutions used in liquid scintillation counting the enhancer solution is inexpensive and can be disposed of without environmental hazard.     

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.     

Leachability of naturally occurring radioactive materials

Summary Naturally occuring radioactive materials (NORM) are present in the environment and can be concentrated by technical activities, particularly those involving natural resources. These NORM deposits are highly stable and very insoluble under environmental conditions at the earth's surface. However, reducing or oxidant conditions or pH changes may enable a fraction of naturally occurring radionuclides to eventually be released to the environment. In this paper the leachability of²¹⁰Pb and²¹⁰Po was determined in three samples coming from a refractories production plant (dust, sludge, finished product), in one dust sample from a steelwork and in one ash sample coming from an electric power station. A sequential extraction method consisting of five operationally-defined fractions was used. The average leaching potential observed in the samples from the refractory industry is very low (mean values: 5.8% for²¹⁰Pb and 1.7% for²¹⁰Po). The²¹⁰Pb and²¹⁰Po leachability increases for the ash sample coming from an electric power plant using carbon (17.8% for²¹⁰Pb and 10.0% for²¹⁰Po); for the dust sample coming from a steelwork, the percent soluble fraction is 41.1% for²¹⁰Pb and 8.5% for²¹⁰Po. For all samples the results obtained show that²¹⁰Pb is slightly more soluble than²¹⁰Po.     

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%.     

Transfer of210Pb and210Po to the environment during mining and processing of uranium ores

Transfer of²¹⁰Pb and²¹⁰Po from an uranium mine and mill to the environment was studied by measuring their concentrations in different stages of uranium extraction technology, in waste products from the mill and in environmental waters. A slightly modified radiochemical method was used for²¹⁰Po and²¹⁰Pb determination.     

Determination of atmospheric lead-210 by alpha-scintillation counting of air filters

Alpha-counting of filters used to sample large volumes of air provides a convenient way of determining atmospheric concentrations of²¹⁰Pb. Following decay of short-lived²²²Rn and²²⁰Rn progeny, alpha activity of the filters increases as²¹⁰Pb decays to²¹⁰Po. After transient equilibrium is reached at about 3 y, alpha activity diminishes with the 22.3 y halflife of²¹⁰Pb. The degree of equilibrium between²¹⁰Pb and²¹⁰Po can be calculated subsequent to sampling, and the average concentration of²¹⁰Pb in the air during the sampling period can be computed. Contributions to the total²¹⁰Pb from ambient short-lived radon progeny are small, typically 2–4%. Using high volume air samplers with collection rates of 1.1–1.7 m³/min for 24 h periods, and using counting times of 2 h for 20 cm² filter sections, we measured alpha counts ranging from 0.0100±0.0050 to 0.200±0.0200 dps. Periodic measurements on 100 of these filters over a 4 y period yielded mean²¹⁰Pb levels with standard deviations less than ±15%. The method requires minimal sample preparation and can be used to determine past atmospheric²¹⁰Pb concentrations on filters stored for up to 20 y and more.