Mean 210Po Research Articles

Baseline survey of sediment contamination with 210Polonium in three peri-urban creeks of Mombasa, Kenya

210Po in marine sediment from three peri-urban creeks in Mombasa was analyzed by alpha spectrometry in order to determine its baseline contamination levels. The mean 210Po activity in marine sediment from Mtwapa, Tudor and Makupa creeks were 18.67 ± 1.8, 21.17 ± 2.2 and 13.09 ± 1.6 Bq Kg−1 dw, for surface sediment and 37.56 ± 2.14, 28.64 ± 2.86 and 30.42 ± 2.1 Bq Kg−1 dw respectively, for sediment cores. Comparison of 210Po activity in surface sediment indicated that 210Po in the creeks could be originating from the same source. However, comparison of activities in the entire cores from the three creeks indicated that 210Po sources could have been different in the past. 210Po activities in this study were relatively elevated compared to marine environments under similar anthropogenic influence and there is need to understand its source and fate.

Natural and anthropogenic radionuclides in Norwegian farmed Atlantic salmon (Salmo salar)

Norway is one of the main producers of farmed fish and the world's second-largest exporter of seafood. Farmed Atlantic salmon (Salmo salar) represents the most exported species. This is the first comprehensive survey of anthropogenic (137Cs, 90Sr, 238Pu, 239,240Pu and 241Am) and natural (40K, 226Ra, 228Ra, 210Pb, 210Po) radionuclides in farmed salmon and manufactured fish feed from Norway. The only anthropogenic radionuclide detected in salmon and fish feed was 137Cs. The levels were low with arithmetic means in salmon and feed of 0.13 and 0.30 Bq/kg fresh weight (fw), respectively. The natural radionuclide 40K exhibited the highest levels with arithmetic means in salmon and feed of 115 and 239 Bq/kg fw, respectively. The arithmetic means of 210Po and 210Pb in salmon were 0.013 and 0.044 Bq/kg fw, respectively, with a mean 210Po:210Pb activity ratio of 0.32. For fish feed, the situation was reversed: the arithmetic means of 210Po and 210Pb were 3.8 and 0.67 Bq/kg fw, respectively, with a mean 210Po:210Pb activity ratio of 5.7. The radionuclide levels found in farmed salmon in the present study are comparable to or lower than the levels found in other fish species in the North Atlantic Ocean. A highly conservative dose estimate for consumption showed that doses were no higher than 1.2 μSv/year for toddlers and 4.0 μSv/year for adults. This suggests that the risk associated with radioactivity in farmed salmon is very low even when considering individuals with high consumption and the highest radionuclide levels found in this study.

Determination of 210Po and 210Pb depositions in lichen and soil samples collected from Köprübaşı-Manisa, Turkey

In this study, we aimed to determine the accumulations of 210Po and 210Pb in soil and lichen samples in Koprubasi. The Koprubasi district is home to the largest uranium deposits in Turkey. To date, there has been no study recorded in the literature related to 210Po and 210Pb depositions in lichens in Koprubasi. Six different lichen species (Cladonia convoluta, Parmelina tiliacea, Physcia stellaris, Pleurosticta acetabulum, Xanthoparmelia conspersa, and Xanthoria parietina) as well as soil samples were collected from seven sampling locations around Koprubasi. Lichens were used as biomonitors for 210Po and 210Pb deposition. The 210Po and 210Pb activity concentrations were measured in all the samples by alpha spectrometry. The activity concentrations in the lichen samples ranged from 64 to 577 Bq kg−1 with an average of 266 Bq kg−1 for 210Po and from 78 to 565 Bq kg−1 with an average of 333 Bq kg−1 for 210Pb. The activity ratios of 210Po/210Pb ranged from 0.80 to 1.99. In the lichen species, the mean 210Po activity values varied from 154 Bq kg−1 in Pleurosticta acetabulum to 390 Bq kg−1 in Xanthoparmelia conspersa. The range of the mean 210Pb activity was between 153 Bq kg−1 in Cladonia convoluta and 378 Bq kg−1 in Parmelina tiliacea. In the soil samples, 210Po and 210Pb activity concentrations were ranged from 14 to 1268 Bq kg−1 and from 19 to 1113 Bq kg−1, respectively. While the values of 210Po and 210Pb measured in the lichen samples are comparable with those of the literature, the results of 210Po and 210Pb in the soil taken from the uranium mine are higher than the results of the literature studies.

DISTRIBUTION AND BIOACCUMULATION OF 210Po AND 210Pb IN ABIOTIC AND BIOTIC COMPONENTS OF THE BAY OF BENGAL.

Marine environment is enriched source of heavy minerals associated with radionuclides which are largely responsible for human exposure to radiation. Bay of Bengal is one among the important marine ecosystems in the world because of its high biodiversity. The aim of this work was to generate a comprehensive data on distribution and bioaccumulation of 210Po and 210Pb in marine environment of the Bay of Bengal. For this water and sand samples (10 stations), shellfishes (21 species) and fishes (43 species) were collected and the concentrations of 210Po and 210Pb were measured by radiochemical separation followed by alpha counting method using ZnS(Ag) detector. 210Pb concentration in the marine water (mean: 7.6 ± 3.31 mBq l-1) is always higher than 210Po (mean: 4.1 ± 1.97 mBq l-1). The mean 210Po and 210Pb concentration in sand was 5.2 ± 1.87 and 3.1 ± 1.20 Bq kg-1, respectively; indicating that 210Po concentrations in the sand sample is always higher than that of 210Pb. The concentration of both 210Po and 210Pb depends on grain size of the sand. Surface samples of depth 0-10 cm recorded maximum 210Po (6.37 Bq kg-1) and 210Pb (4.07 Bq kg-1) concentration. The concentrations of 210Po and 210Pb in biota are following decreasing order: Oyster > Clam > Squid > Crab > Prawn > Fish. The committed effective dose rate calculated for shellfish species maintained a higher range of 81.0-281.2 μSv y-1. However, dose transfer rate from fish species fluctuated from 14.4 to 165.6 μSv y-1and this indicated that fish is radiologically safe as compared to shellfish.

An assessment of the 210Po ingestion dose due to the consumption of agricultural, marine, fresh water and forest foodstuffs in Gudalore (India)

The activity concentration of 210Po in cereals, pulses, food materials of animal origin, vegetables and spices collected from Gudalore (India) has been estimated by radiochemical method. The activity concentration of 210Po in cereals is found to vary from 124 to 604 mBq kg−1. Raw rice registered the highest mean activity 504 ± 61 mBq kg−1. In pulses 210Po activity concentration varies from 42 to 320 mBq kg−1 and the highest activity is found in black lentil with the average value of 172 ± 38 mBq kg−1. Leafy vegetables registered the highest 210Po activity concentration (662–7336 mBq kg−1) and are followed by tuber vegetables (390–1269 mBq kg−1) and then by other vegetables (75–595 mBq kg−1). The higher concentration of 210Po observed in leafy vegetables may be attributed to the dry deposition of 210Po and other daughter products of 222Rn on large leaf surfaces from the air. Among animal products fish of marine origin registered the highest 210Po activity concentration 36,850–48,964 mBq kg−1. The mean 210Po activity concentration in coffee has been estimated as 7500 mBq kg−1. The activity concentration of 210Po in leaf and bark of tree Cinnamom zeylanicum, a popular spice, is found to vary from 3500 to 11,100 mBq kg−1 and 1600–3400 mBq kg−1. The consumption of marine and fresh water fish contribute 60.7% (506.1 μSv y−1) to the total ingestion dose received. Cereals being consumed in a large scale, contribute 23.4% (194.9 μSv y−1) of the total ingestion dose received. The contribution from spices and leafy vegetables consumed is 5.8% (48.1 μSv y−1) and 6.5% (54.3 μSv y−1), respectively. The remaining 3.6% (30.0 μSv y−1) contribution to the total ingestion dose comes from other food materials and vegetables.

Natural radioactivity in various water samples and radiation dose estimations in Bolu province, Turkey

The level of natural radioactivity for Bolu province of north-western Turkey was assessed in this study. There is no information about radioactivity measurement reported in water samples in the Bolu province so far. For this reason, gross α and β activities of 55 different water samples collected from tap, spring, mineral, river and lake waters in Bolu were determined. The mean activity concentrations were 68.11mBqL−1, 169.44mBqL−1 for gross α and β in tap water. For all samples the gross β activity is always higher than the gross α activity. All value of the gross α were lower than the limit value of 500mBqL−1 while two spring and one mineral water samples were found to have gross β activity concentrations of greater than 1000mBqL−1. The associated age-dependent dose from all water ingestion in Bolu was estimated. The total dose for adults had an average value exceeds the WHO recommended limit value. The risk levels from the direct ingestion of the natural radionuclides in tap and mineral water in Bolu were determinated. The mean 210Po and 228Ra risk the value of tap and mineral waters slightly exceeds what some consider on acceptable risk of 10−4 or less.

Assessment of the effects of physical–chemical parameters on 210Po and 210Pb concentrations in cultivated and uncultivated soil from different areas

In this study, a total of 144 bulk soil samples were collected in cultivated and uncultivated sites in different areas for evaluation of the activity concentrations of 210Po and 210Pb. Moreover, 4 core samples were collected from four distinct reference points in the Gediz Basin in Turkey and investigated organic matter content, 210Po and 210Pb concentrations depending on the depth. The activity concentrations of 210Po and 210Pb were measured by means of alpha spectrometry. While the activity concentrations of 210Po and 210Pb in cultivated sites are in the ranges of 12±3–86±4Bqkg−1 dw and 17±3–36±3Bqkg−1 dw, for uncultivated sites the ranges for 210Po and 210Pb are 10±4–134±21Bqkg−1 dw and 23±3–78±5Bqkg−1 dw, respectively. In general, it is observed that the mean 210Po and 210Pb activity concentrations in cultivated sites are lower than the uncultivated sites. The relationships between soil properties and the activity concentrations of the radionuclides indicate that 210Po and 210Pb adsorption to soil is strongly related to organic matter content of the soil.

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.

137Cs and 210Po in Pacific walrus and bearded seal from St. Lawrence Island, Alaska

The activity concentration of Cesium-137 ( 137Cs) and naturally-occurring Polonium-210 ( 210Po) were measured in the muscle tissue, kidney and liver of Pacific walrus ( Odobenus rosmarus divergens) and bearded seal ( Erignathus barbatus) collected by native hunters from the Bering Sea during May 1996. The mean 137Cs concentrations in muscle, liver and kidney of Pacific walrus were 0.07, 0.09 and 0.07 Bq kg −1 ( n = 5, wet weight), respectively, and 0.17, 0.10, and 0.17 Bq kg −1 ( n = 2, wet weight), respectively, in bearded seal. In general, 137Cs tissue concentrations are significantly lower than those previously reported for mammals from other regions. By comparison, 210Po activity concentrations are more variable and appear to be higher level compared with mammal data from other regions. The mean 210Po concentration in the muscle tissue, liver and kidney of Pacific walrus ( n = 5, wet weight) were 28.7, 189, and 174 Bq kg −1, respectively. This compares with 210Po concentration values ( n = 2, wet weight) of 27, 207 and 68 Bq kg −1 measured in the muscle tissue, liver and kidney, of bearded seal, respectively. Estimated concentration factors—as defined by the radionuclide concentration ratio between the target tissue to that in sea water—were two to three orders of magnitude higher for 210Po that those of 137Cs. We conclude from radiological dose estimates that ingestion of 137Cs in foods derived from walrus and seal will pose no threat to human health. This work has important implications for assessment of risks of Alaskan coastal communities concerned about the dumping of nuclear waste in the Russia Arctic.

210Po concentration in Perna perna mussels: looking for radiation effects

Twenty ropes with 400 Perna perna mussels seeds (3 cm shell size) were set-up on floating structures at Cabo Frio Island, Arraial do Cabo, approximately 100 km northeast of Rio de Janeiro city. A rope was taken out on a monthly basis, and the shell sizes of 100 seeds were measured. The haemolymph of 10 male and 10 female individuals was taken, and the same individuals were separated for 210Po/ 210Pb determination. After one year of monthly sampling, no clear correlation was observed between the 210Po concentration, mussel's age and weight. A mean 210Po concentration of 155 Bq kg −1 wet weight basis, was obtained, which is comparable with data reported in the literature. The radiation dose did not have any observable effect on the micronuclei frequency and DNA breaks in the mussels. This was probably due to the low dose rate, 0.02 mGy d −1, in comparison with the suggested potential dose limit of 10 mGy d −1.

Large 210Po deficiency in the northern South China Sea

210Po and 210Pb were measured on the suspended particulate matter (SPM) and filtered water samples collected in profile from seven stations in the northern South China Sea (SCS), including the Luzon Strait, during three cruises aboard R/V Ocean Researcher I in 2000. The dissolved 210Pb profiles generally display a maximum around 15–23 dpm/100 kg in the surface layer due to atmospheric input. This maximum as an excess 210Pb may penetrate to a few hundred meters depth, and a minimum varying from 5 to 15 dpm/100 kg is observed around 500–1000 m. Below 1000 m, the dissolved 210Pb either remains unchanged or increases to a maximum of about 19 dpm/100 kg around 2500–3000 m depth. The particulate 210Pb is nearly constant around 3–5 dpm/100 kg for the entire water column. The dissolved 210Po profiles are somewhat parallel to the dissolved 210Pb profiles generally with much lower activity. The particulate 210Po is quite comparable to the particulate 210Pb at all the stations. Both the dissolved and the total (dissolved+particulate) 210Po to 210Pb activity ratios vary between 0.1 and 1 with a mean of 0.6, indicating a large and variable deficiency of 210Po relative to 210Pb in the northern SCS. The mean ratio corresponds to a 210Po scavenging mean residence time of about 10 months. Since the SPM values are generally 0.2 mg/kg or less, the high and comparable particulate 210Po and 210Pb activities obtained from the SPM samples yield very high and variable specific activities for these nuclides, ranging mostly from about 100 to 500 dpm/g. The time-averaged particulate flux in the deep water (∼3000 m) at a southern and a northern mooring station in the study area is about 250 and 550 mg/m 2/d, respectively. The 210Po flux in the deep water may vary at least from about 75 to 165 dpm/m 2/d if the mean 210Po specific activity of the SPM at comparable depth (about 300 dpm/g) is assumed to be the mean 210Po activity of the trapped particulates. However, even the upper value of 165 dpm/m 2/d can only account for about 20% of the total 210Po removal rate estimated from the total water column 210Po deficiency at about the same depth. Even greater imbalance has been observed in the Sargasso Sea where 210Po flux has been measured from sediment traps. Our observation supports a recent hypothesis that 210Po may be absorbed or utilized by plankton biomass through bacteria and cyanobacteria assimilation in an oligotrophic ocean. 210Po in the deep layer is deficient due to removal by preferential scavenging of organic particulates which may be transported laterally in addition to vertical sinking.

<SUP align=left>210</SUP>Po concentration in urine of residents in a high level background radiation area in Iran

As part of an epidemiological survey to determine public exposure to natural radiation and to estimate radionuclide levels in the diet of residents in a high level background radiation area at Ramsar in Iran, 210Po concentrations were determined in 24-hour urine samples by means of a liquid scintillation counting technique. The maximum and minimum mean concentrations of 210Po in 100 ml of urine were 2.61 (±0.09 SE) and 1.52 (±0.08 SE) mBq, respectively, with an overall mean of 2.00 (±0.86 SE) mBq in 45 samples; the mean 210Po concentration in 100 ml of 20 control samples from local residents in areas where background radiation has been determined as normal was 0.86 (±0.03 SE) mBq. We conclude that the urinary 210Po concentration in residents is elevated in proportion to the background levels, but so far there is no evidence of health problems.

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.

210Po in Mytilus edulis in the Irish marine environment

210Po is available to the Irish marine environment as a result of natural and anthropogenic processes. As it constitutes a significant portion of the radiation exposure of the population through the consumption of seafood, it is of interest to identify a suitable bio-indicator to monitor fluctuations of 210Po concentrations in the marine environment. Mytilus edulis was examined to assess the geographical variation in 210Po concentrations around the coast of Ireland. Temporal variations and the effect of mussel size on their 210Po contents at two sites, Sutton and Carlingford, were also examined. Chemical techniques for the separation of 210Po from mussels, seawater and suspended particulate are described. These methods use 209Po as a chemical yield monitor, microwave systems and Teflon bomb procedures for sample digestion. The concentration of 210Po in mussels around the coast was found to vary between 80±9 Bq kg -1 (dry wt.) at Seapark near Belfast and 468±32 Bq kg -1 (dry wt.) at Sutton in Dublin. The two sites at Sutton and Carlingford, which displayed similarities in terms of mussel morphology and 210Po concentration in water, exhibited significant temporal variations in mussel concentration. Furthermore, relationships derived from both sites indicate a strong linear dependency between mean 210Po content and mean mussel dry weight with higher concentrations of 210Po found in smaller mussels at a given site. Concentration ratios for mussels and water are also presented.

Particulate fluxes, 210Pb and 210Po measured from sediment trap samples in a canyon off northeastern Taiwan

Three time-series sediment-trap moorings were deployed and recovered within a canyon of the continental slope off northeastern Taiwan at different time periods during 1992 and 1993. The trapped particulate samples were determined for apparent mass flux, size distribution and activities of 210Pb and 210Po. The apparent mass fluxes determined from each trap deployed at about 300–600 m depth varied periodically with the mean flux from each trap ranging between 5 and 72 g m -2 d -1. These values were at least an order of magnitude greater than those observed else where. The mass flux increased with the depth deployed, and the synchronized periodic variation was related to the amplitude of the tidal velocity oscillation, i.e. high mass flux occurred when the amplitude was large. The trapped particulates were mainly silt and sand while the sediments in the canyon were mainly silt and clay. High mass flux was usually due to high sand and/or silt content in the trapped particulates which were most likely transported laterally from the shelf and upper slope areas. Except for a few samples, 210Po was lower than 210Pb with a mean 210Po/ 210Pb activity ratio of about 0.6. The low and variable activity ratio might suggest that 210Pb was preferentially scavenged by advecting and settling particulates of terrigenous origin. 210Po, known to be biophilic, might remain associated with the suspended organic particulates which could be dissolved or not collected by the traps. High mass flux was generally associated with high sand fraction and low concentrations of the two nuclides, and vice versa, indicating a dilution effect of the sand particles which contained little nuclides.

210Po content in sea water and its accumulation in southern Baltic plankton

This paper presents the results of an investigation from 1980 to 1985 on the content of 210Po in sea water and its accumulation in southern Baltic plankton. The mean value of the 210Po concentration in sea water has been determined to be about 0.5 mBq dm-3, with the proportion of the dissolved forms being ca 80%. It has been proved that 210Po is accumulated by plankton organisms. The mean 210Po concentration factors calculated on the basis of its content in plankton fall within the range from 5×103 to 4.2×104 and increase as follows: phytoplankton<macrozoo-plankton<mesozooplankton. Moreover, differences in 210Po concentration in mesozooplankton collected at the Slupsk Trough and the Gdansk Basin have been observed. The above differences have been related to intense blue-green alga blooming in the Gdansk Basin.

Polonium-210 in the environment around a radioactive waste disposal area and phosphate ore processing plant.

Polonium-210 concentrations were determined for soil, vegetation and small mammal tissues collected at a solid radioactive waste disposal area, near a phosphate ore processing plant and at two rural areas in southeastern Idaho. Polonium concentrations in media sampled near the radioactive waste disposal facility were equal to or less than values from rural area samples, indicating that disposal of solid radioactive waste at the Idaho National Engineering Laboratory Site has not resulted in increased environmental levels of polonium. Concentrations of 210Po in soils, deer mice hide and carcass samples collected near the phosphate processing plant were statistically (P less than or equal to 0.05) greater than the other sampling locations; however, the mean 210Po concentration in soils and small mammal tissues from sampling areas near the phosphate plant were only four and three times greater, respectively, than control values. No statistical (P greater than 0.05) difference was observed for 210Po concentrations in vegetation among any of the sampling locations.