Distribution Of 210Po Research Articles

Studies on the distribution of 210Po and 210Pb in the ecosystem of Point Calimere Coast (Palk Strait), India

A systematic study on the natural radionuclides such as 210Po and 210Pb in the environmental matrices of Point Calimere ecosystem has been undertaken to establish a baseline data on the radiation profile of Point Calimere environment. The environmental samples such as water, sediment and biota (seaweeds, crustaceans, molluscs and fish) have been subjected to analyses. It has been observed that the concentration of 210Po and 210Pb in the water samples of Point Calimere to be 0.5 mBq/l and 1.3 mBq/l, respectively. The soft tissues of the organisms accumulated higher 210Po content while shells and bones contained more 210Pb. The bivalve molluscs Meretrix casta have been identified to accumulate higher concentration of 210Po suggesting that they could serve as bio-indicator of radionuclides like 210Po in the Point Calimere ecosystem. The concentration factor of 210Po for the biotic components ranged from ∼10 3 to 10 6 while for 210Pb it ranged from ∼10 3 to 10 5.

Exploring the connection between 210Po and organic matter in the northwestern Mediterranean

The disequilibrium between 210Po and its grandparent 210Pb has been proposed as a tracer of the vertical flux of sinking particulate organic matter in the ocean. The mechanism of association between 210Po and organic matter is, however, still unclear. To investigate this association we measured trace metals, minerals, organic carbon, nitrogen, and the natural radioisotopes 234Th, 228Th, 210Po, and 210Pb in sinking particles collected in sediment traps at 200 m in the northwestern Mediterranean. Pigments, fatty acids, and amino acids were used to identify the types and sources of particulate organic matter. Multivariate analyses were used to determine which components of sinking particulate matter are traced by 210Po and/or by the 210Po/ 210Pb ratio. Statistical analysis of the results indicates that the distribution of polonium in sinking marine particles is influenced by fresh phytoplankton-derived, nitrogen-rich organic matter as well as sulfur-containing amino acids. These findings are consistent with previous laboratory observations that the distribution of 210Po in biota parallels the distributions of both sulfur and protein, and indicate that these associations persist as material sinks through the water column. While this research generally supports the use of 210Po as a specific tracer of the flux of organic matter, the signals traced by 210Po/ 210Pb and 234Th/ 238U are not as distinct in the field as in laboratory experiments. Further work is needed to determine more precisely what 210Po/ 210Pb traces in order to increase the correspondence of 210Po/ 210Pb measurements to biogeochemically important rates and quantities.

The effect of water treatment on the presence of particle-bound210Po and210Pb in groundwater

SummaryThe distribution of210Po and210Pb in various particle-size fractions in Finnish groundwater was studied at five private homes. Each site had water treatment equipment comprising either an ion exchange unit or a granular activated carbon filter. Samples of both raw and treated water were filtered using pore sizes ranging from 450 nm to 100 kDa and the activity concentration of210Po and210Pb in the filtrate was determined. In untreated groundwater 86% of210Pb, on average, was found in the large particle fraction (>450 nm). However, in Fe- and Mn-rich water with a high Fe/Mn ratio and in organic-rich water, the majority of210Pb was found in either the intermediate particle (100 kDa–450 nm) or small particle (<100 kDa) fractions. Compared to210Pb,210Po was bound more to the intermediate and small particle fraction. After water treatment,210Pb was found most frequently in the large particle fraction. The size distribution of particle-bound210Po was not as clear as that for210Pb, and in treated water,210Po was more evenly distributed among fractions. The ion exchange unit removed210Pb and210Po bound to the intermediate or small particle fraction, whereas the efficiency of the activated carbon filters in removing210Pb and210Po was independent of the particle size.

Trace metals and 210Po ( 210Pb) concentrations in mussels ( Mytilus galloprovincialis) consumed at western Anatolia

The mussels ( Mytilus galloprovincialis) have been evaluated for their bioavailability as biomonitors of trace and toxic elements in coastal water of western Anatolia. The levels of Fe, Cu, Zn, Pb, Br and Sr in the edible part of mussels were determined using X-ray fluorescence method during the period of September 1999–July 2000. Distribution of 210Po and 210Pb activities were measured by radiometric methods and their ratios were calculated. The activity concentrations of 210Po and 210Pb were found to vary between 52±6–1344±108 and 6±2–167±10 Bq kg −1 dry wt, respectively. The highest values for 210Po and 210Pb were measured in Foça mussels and also observed the highest Fe, Zn and Br concentrations in the same species. 210Po/ 210Pb activity ratio were derived as between 3.1 and 25.0.

Concentration and distribution of 210Po in the tissues of the scallop Chlamys varia and the mussel Mytilus edulis from the coasts of Charente-Maritime (France)

Polonium-210 ( 210Po) has been analysed in the soft parts of two bivalves species, the scallop Chlamys varia and the common mussel Mytilus edulis, from the Bay of La Rochelle and Ré Island, on the French Atlantic coast. Between those sites, the highest 210Po concentrations have been found in whole scallop soft parts from La Rochelle, reaching 1181±29 Bq kg −1 dry weight (dwt), a size effect being related to the highest 210Po concentration in the smallest scallops. The results show a significant difference in concentrations for similar size individuals between species in each site ( C. varia>M. edulis ) and between sites for each species ( R e ́ Island> Bay of La Rochelle ). Very high 210Po concentrations have been found in the digestive gland of C. varia, ranging 3150–4637 Bq kg −1 dwt. Thus, the digestive gland contains up to 60% of the radionuclide. Subcellular investigations have shown that approximately 40% of the 210Po contained in the digestive gland is in the cytosolic fraction, suggesting a high bioavailability of the 210Po from this fraction to the trophic upper level. Calculations will show that approximately 4 kg of scallops flesh intake would be necessary to reach the annual incorporation limit of 1 mSv.

Determination and Distribution of 210Po in Tobacco Plants from Poland

The aim of this study was the determination one of the most radiotoxic elements, 210Po in different parts of tobacco plant from Poland. Investigation revealed that polonium is non-uniformly distributed within tobacco plant. Tobacco leaves constituting about 50% of the wet mass, contain 87.1% of the total burden of 210Po. Among the analyzed leaves about 66% of polonium is located in the oldest, over-ground part. The data obtained here indicate that 210Po is generally taken up by tobacco from the dry or wet deposition of the radioactive fall-out onto the plant. Moreover, 210Po concentration in tobacco leaves from Poland are higher than that in the other countries.

Effect of Cd on accumulation and loss of 210 Po in the mussel Mytilus edulis

As a result of 210Po's previously identified association with sulphur-rich proteins, metallothioneins could have a significant effect on the behaviour and fate of 210Po in molluscs. Starved control and cadmium-exposed mussels, Mytilus edulis, were fed 210Po-labelled algae (Isochrysis galbana) for 5 d and then allowed to depurate in clean sea water. Cadmium-exposed M. edulis accumulated less 210Po in the digestive gland and the remainder of the tissue than control mussels, although this was due to a decrease in tissue weight. More than 40% of 210Po was identified as being associated with high molecular weight and heat-treated cytosol proteins in M. edulis. Mussels in a starved state are known to recycle as much as 90% of their amino acids. It is proposed that 210Po associated with these and other proteins is recycled, explaining why no significant loss of 210Po was observed from the remainder of the tissue in either control or Cd-exposed mussels. Cadmium-induced metallothioneins had no effect on the distribution of 210Po in M. edulis; <5% associated with the cytosolic fraction was considered to principally contain metallothioneins. It is suggested that 210Po's apparent relationship with metallothioneins is coincidental rather than connected with its role in the regulation of metals.

The size distribution of210Po in the atmosphere around Mt. Sakurajima in Kagoshima prefecture, Japan

The concentration and size distribution of210Po in particulate matters in the atmosphere were measured around the active volcano, Mt. Sakurajima in Kagoshima prefecture, Japan. The samples were collected eight times at four sampling points for the period from June 1994 to January 1996. The highest concentration of210Po was 2940 μBq/m3 at Akamizu located 2 km away from the crater of Mt. Sakurajima. The210Po concentrations decreased with the increase of distance from Mt. Sakurajima. The size distribution curves of210Po in the particulate matters showed that210Po is usually condensed to fine particles smaller than 2 μm in diameter. In addition, it was suggested that the210Po concentration in particulate matters collected at Akamizu was affected by the wind direction over Mt. Sakurajima.

A study on distribution of natural radionuclide polonium-210 in a pond ecosystem

This paper presents the results of an investigation on the distribution of210Po in Mutharasanallur pond ecosystem. It has been demonstrated that210Po is non-uniformly distributed within the ecosystem. The results of the study show a dissolved210Po concentration in pond water of 1 4mBq 1−1. The sediment samplso recorded a210Po activity of 59 9 Bq kg−1. The aquatic organisms showed differential accumulation of the radionuclide with enhanced bioaccumulation in soft tissues and muscle. The210Po activity in the biota fell within the range of 1·2–53 3 Bq kg−1 (wet wt). The bivalve mussel,Lamellidens marginalis was identified to accumulate higher concentration of210Poin soft tissues, suggesting that these organisms could serve as a bio-monitor of210Po radionuclide in a freshwater system. The concentration factors of210Po for the biotic components ranged from ∼102–∼104. Analyses of the results indicate that prawn and fish represent an important source of supply of210Po to humans via dietary intake. Results of210Po activity in the abiotic and biotic components of the pond ecosystem were higher when compared with those of Cauvery river system, the primary water source of the pond.

Transfer of polonium to the embryo and foetus of rat and guinea pig.

Transfer of 210Po to the foetus measured 3 days after administration in rat and 7 days later in guinea pig increased with increasing gestational age to about 0.1% injected activity per rat foetus at birth and 0.6% per guinea pig foetus on day 57, corresponding to whole-body foetus:mother concentration ratios of about 0.1:1 in both species. The greatest concentrations of 210Po were measured in the rat yolk sac during its haemopoietic stage, an order of magnitude greater than concentrations in the placenta and two orders of magnitude greater than foetal concentrations. The results obtained have been used to estimate in utero doses to haemopoietic tissues, taking account of transfer to the blastocyst/egg cylinder, yolk sac, liver and bone marrow. The concentration ratios relative to maternal liver for these tissues were taken to be 1, 3, 0.1 and 0.05 respectively and were applied to periods of human gestation of 0-2.5, 2.5-6, 6-12 and 12-38 weeks respectively. For chronic maternal intake by ingestion of 210Po during the year of pregnancy giving a committed effective dose (CED) to the mother of 1 mSv, the total in utero dose to haemopoietic tissue was about 340 microSv compared with a maternal red bone marrow dose of 2.2 mSv. The yolk sac and bone marrow accounted for 66 and 27% of the in utero dose respectively. In addition, the total CED to the offspring was calculated assuming a whole-body foetus:mother concentration ratio of 0.1:1 and that the distribution of 210Po between tissues was the same in the foetus as in adults and children. For chronic intake of 210Po during the year of pregnancy as assumed above, the CED to the offspring was estimated to be 8% of that to the mother.

210Pb and 210Po distributions and disequilibrium in the coastal and shelf waters of the southern North Sea

Concentration profiles of 210Pb and 210Po were measured at 10 stations in the coastal and shelf areas of the southern North Sea. Scavenging processes in this study area are revealed by 210Po/ 210Pb disequilibrium and their distributions in the water column. Results for 210Po show strong excess, relative to 210Pb, in both dissolved and particulate forms, indicating an additional flux of 210Po from the coastal and shelf sediment. A significant maximum of the dissolved 210Po and 210Pb over the fine grained depositional area (Oyster Ground) was observed to correspond with resuspension of the underlying muddy sediments. The relative greater uptake rate of dissolved 210Po, derived from a ☐ model calculation of mass balance, suggest that the 210Po is more preferentially scavenged from the water column than 210Pb, probably due to its higher activity and its high recycling efficiency. The low concentration of 210Pb in the study area is related to the low atmospheric input of 210Pb, the high concentration of suspended matter and the high sediment resuspension rates. A comparison of the data between the water and sediment columns shows that the excess of 210Po found in the water body could be balanced by only a small amount of deficit of 210Po in the sediment, due to the characteristics of this continental shelf area.

The distribution of 210Po in human bone

Recent measurements of natural radioactivity in human bone using alpha particle autoradiography have indicated that the alpha activity concentration in the bone marrow is similar to that found in the calcified bone. This paper describes radiochemical measurements made on the calcified bone and the associated bone marrow from three human femurs. A technique was developed to separate and analyse these tissues for the principal naturally-occurring alpha emitter, 210Po. In all cases the activity concentration of the calcified bone was greater than that of the associated bone marrow. As predicted by the metabolic models used by International Commission on Radiological Protection, the majority of the 210Po in whole bone was found to be in the calcified region.

Distribution of 210Po in Mytilus Edulis and Fucus Vesiculosus Along the Channel Coast of France: Influence of Industrial Releases in the Seine River and Estuary

Distribution of 210Po in Mytilus Edulis and Fucus Vesiculosus Along the Channel Coast of France: Influence of Industrial Releases in the Seine River and Estuary

Distribution of 210Po in Mytilus Edulis and Fucus Vesiculosus Along the Channel Coast of France: Influence of Industrial Releases in the Seine River and Estuary

Distribution of 210Po in Mytilus Edulis and Fucus Vesiculosus Along the Channel Coast of France: Influence of Industrial Releases in the Seine River and Estuary

Study of 210Pb and 210Po distributions in environmental samples by CR-39 track detector

Activity concentration distributions of long-lived alpha-emitters in aerosol samples are analysed by high-resolution autoradiography in CR-39. A study of the alpha-activity attached to aerosols of different particulate sizes separated by a cascade impactor is also performed. It is found that, in the majority of samples, the alpha-activity can be dominantly related to the presence of 210Po produced by its beta-active precursor 210Pb. In our studies we have applied the following methods: 1) analysis of alpha-decay properties by means of autoradiographs taken at different post-sampling times, 2) spectroscopical study of individual alpha-tracks and track clusters by a method developed by us for high- -resolution alpha-energy determination. In the second method the parameters to be measured are the major axis of surface track opening, the diameter of etched out track end, the total length measurable on the surface along the projected track, and the thickness of layer etched away from the detector surface.

210Pb/ 226Ra and 210Po/ 210Pb disequilibria in seawater and suspended particulate matter

The distribution of 210Po and 210Po in dissolved (<0.4 μm) and particulate (>0.4 μm) phases has been measured at ten stations in the tropical and eastern North Atlantic and at two stations in the Pacific. Both radionuclides occur principally in the dissolved phase. Unsupported 210Pb activities, maintained by flux from the atmosphere, are present in the surface mixed layer and penetrate into the thermocline to depths of about 500 m. Dissolved 210Po is ordinarily present in the mixed layer at less than equilibrium concentrations, suggesting rapid biological removal of this nuclide. Particulate matter is enriched in 210Po, with 210Po/ 210Pb activity ratios greater than 1.0, similar to those reported for phytoplankton. Box-model calculations yield a 2.5-year residence time for 210Pb and a 0.6-year residence time for 210Po in the mixed layer. These residence times are considerably longer than the time calculated for turnover of particles in the mixed layer (about 0.1 year). At depths of 100–300 m, 210Po maxima occur and unsupported 210Po is frequently present. Calculations indicate that at least 50% of the 210Po removed from the mixed layer is recycled within the thermocline. Similar calculations for 210Pb suggest much lower recycling efficiencies. Comparison of the 210Pb distribution with the reported distribution of 226Ra at nearby GEOSECS stations has confirmed the widespread existence of a 210Pb/ 226Ra disequilibrium in the deep sea. Vertical profiles of particulate 210Pb were used to test the hypothesis that 210Pb is removed from deep water by in-situ scavenging. With the exception of one profile taken near the Mid-Atlantic Ridge, significant vertical gradients in particulate 210Pb concentration were not observed, and it is necessary to invoke exceptionally high particle sinking velocities to account for the inferred 210Pb flux. It is proposed instead that an additional sink for 210Pb in the deep sea must be sought. Estimates of the dissolved 210Pb/ 226Ra activity ratio at depths greater than 1000 m range from 0.2 to 0.8 and reveal a systematic increase, in both vertical and horizontal directions, with increasing distance from the sea floor. This observation implies rapid scavenging of 210Pb at the sediment-water interface and is consistent with a horizontal eddy diffusivity of 3−6 × 10 7 cm 2/sec. The more reactive element Po, on the other hand, shows evidence of rapid in-situ scavenging. In filtered seawater, 210Po is deficient, on the average, by ca. 10% relative to 210Pb; a corresponding enrichment is found in the particulate phase. Total inventories of 210Pb and 210Po over the entire water column, however, show no significant departure from secular equilibrium.

Polonium-210 in euphausiids: A detailed study

A detailed study of 210Po, the predominant alpha-emitting nuclide found in most marine organisms, has been undertaken in a particular zooplanktonic species, the euphausiid Meganyctiphanes norvegica. The purpose was to obtain information concerning the origin, the localization and the flux of the nuclide in and through this organism. Measurements of 210Po were made in euphausiids of different sizes, in dissected organs and tissues, and in excretion products. The results show higher concentrations in the smaller specimens; this fact cannot be explained on the basis of surface adsorption, but is probably related to the ingestion of food. Dissection results show that the distribution of 210Po in euphausiids is not homogeneous, but that the majority is concentrated in the internal organs, the alimentary tract and the hepatopancreas in particular. The natural radiation dose received by these organs is in consequence much higher than that received by the whole animal. Use of a dynamic model allowed the flux of 210Po through M. norvegica to be calculated. The calculations confirm that food is the principal source of 210Po for this species, and clearly show that fecal pellets constitute the major elimination route. Extrapolation of the data to zooplankton in general leads to the conclusion that zooplankton metabolic activity plays an important role in transporting 210Po from the surface layers of the ocean to depth.

The effect of chelating agents on the distribution of 210 Po in rats.

Es wurde der Einfluss verschiedener intraperitoneal oder peroral verabreichter Chelatbildner auf die Verteilung von210Po im Organismus der Ratte untersucht. Die Wirksamkeit nimmt in der Reihenfolge: 2,3-Dimercaptopropan-1-sulfonat>Diäthyldithiocarbaminat >2-Mercaptopropionyl-glycin>d-Penicillamin ab, während Diäthylentriaminpentaacetat sich als unwirksam erwies.