210Po and 210Pb in the food chain lichen-reindeer-human

The arctic food chain lichen-reindeer-human, transmitting ²¹⁰Po and its precursor ²¹⁰Pb from natural fallout to human, was studied. Lichen, plant, mushroom, and reindeer samples were collected from Finnish Lapland. The ²¹⁰Po and ²¹⁰Pb activity concentrations and the ²¹⁰Po/²¹⁰Pb ratio in these samples were determined. Published in Russian in Radiokhimiya, 2006, Vol. 48, No. 6, pp. 567–568. The text was submitted by the authors in English. Reported at the 7th Russian-Finnish Symposium on Radiochemistry (St. Petersburg, November 2005).     

Metabolism of 210Po in rats: volatile 210Po from faeces

The metabolic formation of volatile (210)Po species in a rat that was intravenously administered with (210)Po-citrate was investigated in this study. A slurry of the faecal sample was prepared in water and was bubbled with nitrogen gas in a closed system. The discharged gas was passed through a trapping device filled with liquid scintillation cocktail in order to capture any volatile (210)Po species. The amount of (210)Po trapped in the scintillation cocktail was measured by a liquid scintillation analyser that provided evidence of the presence of volatile (210)Po species in the faeces. The presence of volatile (210)Po in the faeces indicates that the metabolic formation of volatile (210)Po is likely to occur in the gut due to bacterial activity. The amount of volatile (210)Po species was compared with the daily faecal excretion of (210)Po. After 2 h of bubbling, the volatile (210)Po collected from the faeces sample was found to be between 1.0 and 1.7 % of the daily faecal excretion for the 4 d following (210)Po-citrate administration.     

Time-efficient method for the determination of 210Pb, 210Bi, and 210Po activities in seawater using liquid scintillation spectrometry

A novel method has been developed for determining the natural decay series radionuclides (NDS), 210Pb, 210Bi, and 210Po, in seawater by way of state-of-the-art liquid scintillation spectrometry. For 210Pb analysis, the method makes use of a 212Pb yield tracer, prepared by ion exchange separation from aged Th(NO3)4. 210Bi recovery is determined using 207Bi as the yield tracer, and 210Po is determined using the conventional 208Po yield tracer. The limits of detection for this method are 0.32, 0.34, and 0.004 mBq 1-1 for 210Pb, 210Bi, and 210Po, respectively. The analysis can be completed within 10 days, as compared with up to one year for traditional methods. Results are presented for a preliminary study of 210Pb, 210Bi, and 210Po in the dissolved and particle-bound phases of Irish Sea water.     

Bioaccumulation of 210Po and 210Pb in cephalopods collected from Kudankulam (Southeastern coast of Gulf of Mannar, India) and assessment of dose in human beings

Activities of (210)Po and (210)Pb in various tissues of two common species of cephalopod molluscs (cuttlefishes) of Kudankulam coast were studied. Of all the tissues, (210)Po and (210)Pb were found accumulated more in the digestive gland, shell gland and intestine. Urotheuthis duvauceli accumulated more (210)Po and (210)Pb in certain organs when compared with Sepiella inermis. The activity ratio of (210)Po/(210)Pb fell within the range of 0.6-29.3 in the organs. The biological concentration factor for the organs ranged from 1.2×10(3) to 2×10(5) for (210)Po and 3.6×10(2) to 7.6×10(4) for (210)Pb. A significant variation in the accumulation of (210)Po and (210)Pb was noted between species, organs and seasons (p < 0.05). The whole-body internal dose rate due to (210)Po was 1.24 and 0.83 μGy h(-1) and it was 2×10(-3) and 3×10(-3) μGy h(-1) due to (210)Pb for both the species. The effective dose in humans due to (210)Po intake ranged from 96.3 to 376.6 μSv y(-1) and that of (210)Pb ranged from 35.2 to 105.7 μSv y(-1), respectively. The data generated will act as a reference database for these organisms of this coast in which a nuclear power station is under construction.     

210Pb, 210Po, 226Ra, U and Th in arable crops and ovine liver: variations in concentrations in the United Kingdom and resultant doses

Concentrations of a range of naturally occurring radionuclides have been determined in the same crops grown at two sites in the UK. Ovine liver has also been studied. One site was in an area where concentrations in soil are typical of the UK (the 'control' site) and the other in an area where levels were well above average (the 'test' site). For an average adult consumer of all of the foodstuffs studied, the doses from consumption for the test site were about 4 times higher than those for the control site. However, the differences were small compared with the variability in overall doses from natural background across the UK. 210Pb and 210Po were important contributors to doses for both sites, but at the test site the contribution from 226Ra was also significant. Of the foodstuffs studied, consumption of leafy vegetables and liver gave the highest doses. The doses from leafy vegetables were sensitive to the weather conditions prior to harvesting. Consequently, rigorous monitoring programmes should be based on several samples collected throughout the year; extrapolations based on a single annual sample are unlikely to be reliable.     

Preparation of a 210Pb target

After an ion-exchange separation of ²¹⁰Pb from its daughters ²¹⁰Bi and ²¹⁰Po, a ²¹⁰Pb target has been electrodeposited on a carbon film. We describe the different steps of the target preparation, keeping in mind that ²¹⁰Pb is a highly radioactive isotope and that consequently the techniques must be efficient. The sandwiched target finally obtained has the following configuration: C (10 μg/cm²)+ ²¹⁰Pb (about 500 μg/cm²) + C (15 μg/cm²) mechanically protected with a beam-evaporated collodion film.     

Radiogenic 234U and 210Po in humus acids of dyctionemic shale

Radiochemical analysis is made of different fractions of humic and fulvic acids separated from organic matter of graptolitic argillite (dyctionemic shale) of the Baltic basin. The relation between the decalcination of humates and fulvates and the isotopic composition of U is studied. The tightness of binding to humus substances, including humin, is different for ²³⁸U and ²³⁴U, which is probably due to preferential stabilization of the radiogenic uranium in the oxidation state +4. Based on the experiments on precipitation of humates at pH 0–2, it is suggested that the thiol groups of humic acids are involved in chemical binding of ²¹⁰Po. Experiments on partial decalcination of humates in 1 M HNO₃ revealed stronger binding of the radiogenic Po as compared to ^208,209Po. The results were interpreted in terms of the known models.     

Contribution of 210Pb bremsstrahlung to the background of lead shielded gamma spectrometers

Lead, which is often used as a shielding material, contains ²¹⁰Pb (T_1/2=22.3 y). The 46.54 keV γ-intensity of ²¹⁰Pb can be easily reduced by an inner lining, but the bremsstrahlung caused by the β-decay of its daughter, ²¹⁰Bi, with a maximal electron energy of 1.16 MeV, will contribute to the gamma detector background. The spectrum of this bremsstrahlung is calculated by numerically fitting the β-spectrum and integrating the Koch–Motz formula. The absorption of the bremsstrahlung in the lead and detection efficiencies for the HPGe detector are calculated by the effective solid angle algorithm, using corrections for the photopeak/Compton ratio of cross-sections in Ge. By comparison with the measured background spectrum, it is shown that, for the lead with 25 Bq/kg of ²¹⁰Pb up to 500 keV of gamma spectrum, the bremsstrahlung contribution to the background is about 20% for our surface-based detector system. Also, we compared our calculations with a Monte Carlo simulation of another detector system with a shield containing 1 Bq/kg of ²¹⁰Pb and found that our analytical method gives a value of roughly two times higher than the Monte Carlo one for the total bremsstrahlung contribution. The quality of the analytical semi-empirical method is proved by the reasonable agreement with the experimental results published.     

Speciation and behavior of <Superscript>210</Superscript>Po and <Superscript>210</Superscript>Pb in the riverine ecosystem of Cauvery,a major river of south India

The paper discusses the speciation and behavior of ²¹⁰Po and²¹⁰Pb in the soil and sediment samples in the Cauvery River environment. The samples were collected and the concentration of ²¹⁰Po and ²¹⁰Pb was measured using the standard radiochemical analytical method. The physicochemical parameters of the soil and sediment were studied to understand the dynamics of ²¹⁰Po and ²¹⁰Pb activity in the riverine environment. The dependence of the physicochemical parameters like clay and organic matter content on the speciation of ²¹⁰Po and ²¹⁰Pb in the riverine ecosystems were also studied. The mean activity of ²¹⁰Po and ²¹⁰Pb in soil was found to be 6.80 and 6.58 Bq kg^–1, respectively. The mean activity of ²¹⁰Po and ²¹⁰Pb in the sediment was found to be 3.30 and 6.34 Bq kg^–1, respectively. The activities of ²¹⁰Po and ²¹⁰Pb in both the soil and sediment are not in equilibrium. The activity concentrations of ²¹⁰Po and ²¹⁰Pb were correlated with the organic matter content in both the soil and sediment samples. Multivariate statistical analysis was used to confirm the interrelation between the physicochemical parameters and the activity of ²¹⁰Po and ²¹⁰Pb.     

Fraction of the positive 218Po and 214Pb clusters in indoor air

The fraction of the positively charged unattached radon decay products, 218Po and 214Pb in indoor air was determined by model calculations. The results of the calculations were confirmed by measurements in a test chamber (volume: 8 m3). The fraction of both radionuclides depends on the attachment parameter (S(1)) and the neutralisation rate (nu) in room air. The total removal parameter S1 = lambda1 + v + q(f) + X = lambda1 C1f/C0 considers the attachment rate to aerosol particles (X), plate-out rate to room surfaces (q(f)) and the ventilation rate (nu) (lambda1: decay constant of 218Po). The S1-value of room can be determined by measurement of the concentration of the unattached 218Po clusters (C1f) and radon (C0). The neutralisation rate (nu) in environmental air depends mainly on the ion production rate. The influence of the relative humidity in the range 30-95% (temperature: 20 degrees C) is negligible. In addition, equal neutralisation rates for 218Po and 214Pb could be derived. In room air with ion production rates between 5 and 500 nC kg(-1) h(-1) mainly generated by the alpha emitters of radon, thoron and their short-lived decay products, the fractions for positive 218Po clusters vary between 55 and 17% and for 214Pb clusters between 53 and 14%. For a typical average concentration of radon (50 Bq m(-3)) and thoron (10 Bq m(-3)) in homes, 48% of 218Po clusters and 45% of 214Pb clusters are positively charged.     

Transfer of Quantum Dots from Pregnant Mice to Pups Across the Placental Barrier

Fluorescent quantum dots (QDs) have great potential for in vivo biomedical imaging and diagnostic applications. However, these nanoparticles are composed of heavy metals and are very small in diameter, and their possible toxicity must therefore be considered. As yet, no studies have reported the transfer of QDs between mother and fetus. The transfer of CdTe/CdS QDs of different sizes and dosages, and with different outer capping materials, from pregnant mice to fetuses is investigated. It is shown that QDs may be transferred from female mice to their fetuses across the placental barrier. Smaller QDs are more easily transferred than larger QDs and the number of QDs transferred increases with increasing dosage. Capping with an inorganic silica shell or organic polyethylene glycol reduces QD transfer but does not eliminate it. These results suggest that the clinical utility of QDs could be limited in pregnant women.     

210Pb geochronology of flood events in large tropical river systems

Floodplain sedimentation removes particles from fluvial transport and constructs stratigraphic records of flooding, biogeochemical sequestration and other aspects of the environmental history of river basins-insight that is enhanced by accurate geochronology. The natural fallout radionuclide (210)Pb, often employed to date lacustrine and marine sediments, has previously been used to determine floodplain accumulation rates over decadal-to-century time scales using the assumption that both input concentration and sediment accumulation rates are constant. We test this model in approximately 110 cores of pristine floodplains along approximately 2000 km of the Rios Beni and Mamore in northern Bolivia; over 95 per cent of the (210)Pb profiles depict individual episodic deposition events, not steady-state accumulation, requiring a revised geochronological methodology. Discrete measurements of down-core, clay-normalized adsorbed excess (210)Pb activity are coupled with a new conceptual model of (210)Pb input during floods: constant initial reach clay activity, unknown sedimentation (CIRCAUS). This enhanced methodology yields (210)Pb dates that correspond well with (i) dates determined from meteoric caps, (ii) observed dates of river bar formation, (iii) known flood dates, and (iv) dates from nearby cores along the same transect. Similar results have been found for other large rivers. The CIRCAUS method for geochronology therefore offers a flexible and accurate method for dating both episodic (decadal recurrence frequency) and constant (annual recurrence) sediment accumulation on floodplains.     

Radioactivity of 210Pb in Japanese cigarettes and radiation dose from smoking inhalation

It is well known that cigarette tobaccos contain naturally occurring radioactive nuclides such as (210)Pb and (210)Po. In many countries, the radioactivity of tobaccos has been measured to estimate the effective dose from smoking inhalation. The present study covered 24 cigarette brands including the top 20 of sales in Japan between April 2008 and March 2009. The activity concentrations of (210)Pb were measured by gamma-ray spectrometry, and then those of its progeny ((210)Po) were evaluated assuming the radioactive equilibrium between the two nuclides. Their concentrations were in the range of 2-14 mBq cigarette(-1) with an arithmetic mean of 8±3 mBq cigarette(-1). The annual committed effective doses were also calculated, based on the scenario that a smoker consumes 20 cigarettes a day. The average doses from (210)Pb and (210)Po inhalations were 22±9 and 68±27 μSv y(-1), respectively.     

Trajectory Analysis of 210Pb and 7Be in Ground-Level Air in Southern Finland

The Finnish Meteorological Institute has been monitoring airborne natural radionuclides ²¹⁰Pb and ⁷Be at its geophysical observatory at Nurmijüarvi, southern Finland (60°30'N, 24°39'E, h = 105 m above see level). Daily aerosol samples (3500 m³/d) were collected onto glass-fiber filters with an aerosol sampler having an aerodynamic cutoff diameter of 10-15 m depending on the wind speed. The filters were analysed for ⁷Be with an electrically cooled HPGe -ray spectrometer and for 210Pb with -counting of the daughter ²¹⁰Po using an automatic /-analyzer. A trajectory analysis of the observed activity concentrations revealed that the highest ⁷Be and ²¹⁰Pb activity concentrations are associated with continental air masses coming from southeast. Meteorologically these situations often originate from high-pressure areas in central Russia. The associated air masses are often dry, which prevents the removal of radionuclides through precipitation scavenging. ²²²Rn, and thus ²¹⁰Pb too, originate practically entirely from land areas and not from oceans. The descending movement of air in high-pressure areas promotes the transfer of ⁷Be from upper air to the ground level. The production of ⁷Be increases toward the magnetic poles of the Earth. This is not reflected in the source areas of ⁷Be, because the concentration variations in the ground-level air are due to large-scale weather phenomena.     

238U, 226Ra, 210Po concentrations of bottled mineral waters in Hungary and their committed effective dose

Nowadays the consumption of bottled mineral waters has become very popular. The average consumption of these is 0.36 l d(-1) per person in Europe. A considerable segment of the population drinks almost only mineral water as drinking water, which is about 1 l d(-1). As is known, some kinds of mineral waters contain naturally occurring radionuclides in higher concentration than the usual drinking (tap) water. The WHO (1993) legislation concerning the drinking waters does not include the mineral waters. In our work, the concentrations of (226)Ra, (238)U and (210)Po were determined in mineral waters available in Hungary. To determine the (226)Ra concentration the emanation method was used. The (238)U and (210)Po concentrations were determined by alpha spectrometry using semiconductor detector. The dose contribution was calculated using the radionuclide concentrations and the dose conversion factors from the Basic Safety Standard IAEA (1995), for 1 l d(-1) mineral water consumption. In some cases the calculated doses were considerable higher than the limit for drinking waters. Especially for children the doses can be remarkably high.