Natural radioactivity levels in topsoil from the Pearl River Delta Zone, Guangdong, China

Concentrations of the natural radionuclides ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K have been measured by γ-ray spectrometry in 796 topsoil samples from the Pearl River Delta Zone (PRDZ) of Guangdong, China. The mean concentrations for ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K were found to be 140 ± 37 Bq kg⁻¹, 134 ± 41 Bq kg⁻¹, 187 ± 80 Bq kg⁻¹ and 680 ± 203 Bq kg⁻¹ dry mass, respectively. These values were all higher than the mean values in soil for China and the world. Outdoor air-absorbed dose rates, calculated from activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K, ranged from 86 to 237 nGy h⁻¹, with a mean value of 165 ± 46 nGy h⁻¹. The corresponding annual outdoor effective dose rate per person was estimated to be between 0.11 and 0.29 mSv y⁻¹, with a mean value of 0.20 ± 0.06 mSv y⁻¹, which was also higher than the world mean value of 0.07 mSv y⁻¹. The radium equivalent activity (Ra_eq) and the external hazard index (I_r) resulted from the natural radionuclides in soil, were also calculated and found to vary from 230 to 676 Bq kg⁻¹ and from 0.6 to 1.8, respectively. The Ra_eq and the I_r in all the investigated regions were up to 75% higher than the set limits of 370 Bq kg⁻¹ and 1.0, respectively.     

Comparative study of natural radioactivity levels in soil samples from the Upper Siwaliks and Punjab,India using gamma-ray spectrometry

Natural radioactive materials under certain conditions can reach hazardous radiological levels. So, it becomes necessary to study the natural radioactivity levels in soil to assess the dose for the population in order to know the health risks and to have a baseline for future changes in the environmental radioactivity due to human activities. The natural radionuclide (²²⁶Ra, ²³²Th, and ⁴⁰K) contents in soil were determined for 26 locations around the Upper Siwaliks of Kala Amb, Nahan and Morni Hills, Northern India, using high-resolution gamma-ray spectrometric analysis. It was observed that the concentration of natural radionuclides viz., ²²⁶Ra, ²³²Th and ⁴⁰K, in the soil varies from 28.3 ± 0.5 to 81.0 ± 1.7 Bq kg⁻¹, 61.2 ± 1.3 to 140.3 ± 2.6 Bq kg⁻¹ and 363.4 ± 4.9 to 1002.2 ± 11.2 Bq kg⁻¹ respectively. The total absorbed dose rate calculated from activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K ranged from 71.1 to 162.0 nGy h⁻¹. The radium equivalent (R_eq) and the external hazard index (H_ex), which resulted from the natural radionuclides in soil, were also calculated and found to vary from 149.4 to 351.8 Bq kg⁻¹and from 0.40 to 0.95 respectively. These values in Upper Siwaliks area were compared with that from the adjoining areas of Punjab. The radium equivalent activities in all the soil samples were lower than the limit (370 Bq kg⁻¹) set in the Organization for Economic Cooperation and Development (OECD) report and the dose equivalent was within the safe limit of 1 mSv y⁻¹.     

Radionuclides in marine mammals off the Portuguese coast

Radionuclide analyses were performed in tissue samples including muscle, gonad, liver, mammary gland, and bone of marine mammals stranded on the Portuguese west coast during January-July 2006. Tissues were collected from seven dolphins (Delphinus delphis and Stenella coeruleoalba) and one pilot whale (Globicephala sp.). Samples were analyzed for ²¹⁰Po and ²¹⁰Pb by alpha spectrometry and for ¹³⁷Cs and ⁴⁰K by gamma spectrometry. Po-210 concentrations in common dolphin’s muscle (D. delphis) averaged 56 ± 32 Bq kg⁻¹ wet weight (w.w.), while ²¹⁰Pb averaged 0.17 ± 0.07 Bq kg⁻¹ w.w., ¹³⁷Cs averaged 0.29 ± 0.28 Bq kg⁻¹ w.w., and ⁴⁰K 129 ± 48 Bq kg⁻¹ w.w. Absorbed radiation doses due to these radionuclides for the internal organs of common dolphins were computed and attained a 1.50 μGy h⁻¹ on a whole body basis. ²¹⁰Po was the main contributor to the weighted absorbed dose, accounting for 97% of the dose from internally accumulated radionuclides. These computed radiation doses in dolphins are compared to radiation doses from ²¹⁰Po and other radionuclides reported for human tissues. Due to the high ²¹⁰Po activity concentration in dolphins, the internal radiation dose in these marine mammals is about three orders of magnitude higher than in man.     

Natural radionuclide concentrations in two phosphate ores of east Algeria

Ore is considered as an important source of many elements such as the iron, phosphorus, and uranium. Concerning the natural radionuclides, their concentrations vary from an ore to other depending on the chemical composition of each site.In this work, two phosphate ores found in East of Algeria have been chosen to assess the activity concentration of natural radionuclides represented mainly by three natural radioactive series ²³⁸U, ²³⁵U and ²³²Th, and the primordial radionuclide ⁴⁰K where they were determined using ultra-low background, high-resolution gamma-ray spectroscopy.The measured activity concentrations of radioactive series ranged from 6.2 ± 0.4 to 733 ± 33 Bq.kg⁻¹ for the ²³²Th series, from 249 ± 16 to 547 ± 39 Bq.kg⁻¹ for the ²³⁸U series, around 24.2 ± 2.5 Bq.kg⁻¹ for the ²³⁵U series, and from 1.4 ± 0.2 to 6.7 ± 0.7 Bq.kg⁻¹ for ⁴⁰K.To assess exposure to gamma radiation in the two ores, from specific activities of ²³²Th, ⁴⁰K and ²²⁶Ra, three indexes were determined: Radium equivalent (Ra_eq), external and internal hazard indexes (H_ex and H_in), their values ranged from 831 ± 8 to 1298 ± 14 Bq.kg⁻¹ for Ra_eq, from 2.2 ± 0.4 to 3.5 ± 0.7 Bq.kg⁻¹ for H_ex, and from 4.2 ± 0.7 to 4.5 ± 0.7 Bq.kg⁻¹ for H_in.     

Natural and artificial radioactivity determination of some medicinal plants

Several medicinal plants used in Italy were analysed to determine natural and artificial radioactivity in those parts (leaves, fruits, seeds, roots, peduncles, flowers, barks, berries, thallus) used generally as remedies. The radionuclides were determined by alpha (²³⁸U, ²¹⁰Po) and gamma (²¹⁴Pb-Bi, ²¹⁰Pb, ⁴⁰K and ¹³⁷Cs) spectrometry. ²³⁸U ranged between <0.1 and 7.32 Bq kg_dry⁻¹; ²¹⁰Po between <0.1 and 30.3 Bq kg_dry⁻¹; ²¹⁴Pb-²¹⁴Bi between <0.3 and 16.6 Bq kg_dry⁻¹; ²¹⁰Pb between <3 and 58.3 Bq kg_dry⁻¹; ⁴⁰K between 66.2 and 3582.0 Bq kg_dry⁻¹; ¹³⁷Cs between <0.3 and 10.7 Bq kg_dry⁻¹. The percentage of ²¹⁰Po extraction in infusion and decoction was also determined; the arithmetical mean value of percentage of ²¹⁰Po extraction resulted 20.7 ± 7.5.     

Rare earth elements in fly ashes created during the coal burning process in certain coal-fired power plants operating in Poland - Upper Silesian Industrial Region

The subject of the study covered volatile ashes created during hard coal burning process in ash furnaces, in power plants operating in the Upper Silesian Industrial Region, Southern Poland. Coal-fired power plants are furnished with dust extracting devices, electro precipitators, with 99-99.6% combustion gas extracting efficiency. Activity concentrations ofTh-232, Ra-226, K-40, Ac-228, U-235 and U-238 were measured with gamma-ray spectrometer. Concentrations of selected rare soil elements (La, Ce, Nd, Sm, Y, Gd, Th, U) were analysed by means of instrumental neutron activation analysis (INAA). Mineral phases of individual ash particles were identified with the use of scanning electron microscope equipped with EDS attachment. Laser granulometric analyses were executed with the use of Analyssette analyser. The activity of the investigated fly-ash samples is several times higher than that of the bituminous coal samples; in the coal, the activities are: 226Ra - 85.4 Bq kg⁻¹, 40 K-689 Bq kg⁻¹, 232Th - 100.8 Bq kg⁻¹, 235U-13.5 Bq kg⁻¹, 238U-50 Bq kg⁻¹ and 228Ac - 82.4 Bq kg⁻¹.     

External gamma-ray dose rate and radon concentration in indoor environments covered with Brazilian granites

Health hazard from natural radioactivity in Brazilian granites, covering the walls and floor in a typical dwelling room, was assessed by indirect methods to predict external gamma-ray dose rates and radon concentrations. The gamma-ray dose rate was estimated by a Monte Carlo simulation method and validated by in-situ measurements with a NaI spectrometer. Activity concentrations of ²³²Th, ²²⁶Ra, and ⁴⁰K in an extensive selection of Brazilian commercial granite samples measured by using gamma-ray spectrometry were found to be 4.5-450 Bq kg⁻¹, 4.9-160 Bq kg⁻¹ and 190-2029 Bq kg⁻¹, respectively. The maximum external gamma-ray dose rate from floor and walls covered with the Brazilian granites in the typical dwelling room (5.0 m × 4.0 m area, 2.8 m height) was found to be 120 nGy h⁻¹, which is comparable with the average worldwide exposure to external terrestrial radiation of 80 nGy h⁻¹ due to natural sources, proposed by United Nations Scientific Committee on the Effects of Atomic Radiation. Radon concentrations in the room were also estimated by a simple mass balance equation and exhalation rates calculated from the measured values of ²²⁶Ra concentrations and the material properties. The results showed that the radon concentration in the room ventilated adequately (0.5 h⁻¹) will be lower than 100 Bq m⁻³, value recommended as a reference level by the World Health Organization.     

Pre-concentration of naturally occurring radionuclides and the determination of (212)Pb from fresh waters

A novel technique has been developed for determining the ²¹²Pb activity of fresh waters. This is of interest to environmental monitoring programmes that utilise gross α-activity methods to screen for anthropogenic radionuclides. The contribution from ²¹²Pb varies, and is difficult to experimentally measure due to its relatively short half-life (t_½ = 10.6 h) and low environmental activity (<0.1 Bq l⁻¹). The use of a three-stage technique that encompasses a unique form of pre-concentration, separation and analysis by liquid scintillation counting allows a lower detection limit of 0.006 Bq l⁻¹ with a chemical yield of 92.5 ± 5.6%. The measurement can be obtained within 7 h of sample collection, and is calculated using the radioactive decay of ²¹²Bi. Other naturally occurring radionuclides may also be extracted using the pre-concentration stage of the technique, with efficiencies above 90% at a range of pH values.     

Biomonitoring of ²¹⁰Po and ²¹⁰Pb using lichens and mosses around coal-fired power plants in Western Turkey

Mosses and lichens are useful biological indicators of environmental contamination for a variety of metals and radionuclides of both natural and artificial origin. These plants lack a well-developed root system and rely largely on atmospheric deposition for nourishment. Therefore in the study, different lichens (Cladonia convoluta, Cladonia foliacea) and mosses (Homalothecium sericeum, Hypnum lacunosum, Hypnum cupressiforme, Tortella tortuosa, Didymodon acutus, Syntrichia ruralis, Syntrichia intermedia, Pterogonium graciale, Isothecium alopecuroides, Pleurochatae squarrosa) were collected around the Yata?an (Mu?la), Soma (Manisa), Seyitömer - Tunçbilek (Kütahya) coal-fired power plants and investigated for potential use as biomonitors for ²¹⁰Po and ²¹⁰Pb deposition. While the activity concentrations of ²¹⁰Po and ²¹⁰Pb in lichens are in the ranges of 151 ± 7-593 ± 21 and 97 ± 5-364 ± 13 Bq kg⁻¹, for mosses the ranges for ²¹⁰Po and ²¹⁰Pb are 124 ± 5-1125 ± 38 and 113 ± 4-490 ± 17 Bq kg⁻¹, respectively. In the study, the moss samples were observed to accumulate more ²¹⁰Po and ²¹⁰Pb compared to lichens. While the most suitable biomonitor was a moss species (H. lacunosum) for Yata?an (Mu?la), it was another moss species (S. intermedia) for Soma (Manisa) and Seyitömer - Tunçbilek (Kütahya) sites. ²¹⁰Po concentrations were found higher than ²¹⁰Pb concentrations at the all sampling stations.     

Factors affecting 210Po and 210Pb activity concentrations in mussels and implications for environmental bio-monitoring programmes

The activity of ²¹⁰Po and ²¹⁰Pb was determined in mussels of the same size (3.5-4.0 cm shell length) sampled monthly over a 17-month period at the Atlantic coast of Portugal. Average radionuclide concentration values in mussels were 759 ± 277 Bq kg⁻¹ for ²¹⁰Po (range 460-1470 Bq kg⁻¹ dry weight), and 45 ± 19 Bq kg⁻¹ for ²¹⁰Pb (range 23-96 Bq kg⁻¹ dry weight). Environmental parameters and mussel biometric parameters were monitored during the same period. Although there was no seasonal variation of radionuclide concentrations in sea water during the study period, the concentration of radionuclide activity in mussels varied seasonally displaying peaks of high concentrations in winter and low concentrations in summer. Analysis of radionuclide data in relation to the physiological Condition Index of mussels revealed that ²¹⁰Po and ²¹⁰Pb activities in the mussel (average activity per individual) remained nearly constant during the investigation period, while mussel body weight fluctuated due to fat storage/expenditure in the soft tissues. Similar variation of radionuclide concentrations was observed in mussels transplanted from the sea coast into the Tejo Estuary. However, under estuarine environmental conditions and with higher food availability throughout the year, transplanted mussel Condition Index was higher than in coastal mussels and average radionuclide concentrations were 210 ± 75 Bq kg⁻¹ (dry weight) for ²¹⁰Po and 10 ± 4 Bq kg⁻¹ (dry weight) for ²¹⁰Pb, therefore lower than in coastal mussels with similar shell length. It is concluded that the apparent seasonal fluctuation and inter-site difference of radionuclide concentrations were mostly caused by mussel body weight fluctuation and not by radionuclide body burden fluctuation. This interpretation can be extended to the apparent seasonal fluctuation in concentrations of lipophilic and lipophobic contaminants in mussels, and provides an explanation for occasional high concentrations of ²¹⁰Po and man-made contaminants measured in mussels far from pollution sources.     

Radiological monitoring: terrestrial natural radionuclides in Kinta District,Perak, Malaysia

Natural background gamma radiation and radioactivity concentrations were investigated from 2003 to 2005 in Kinta District, Perak, Malaysia. Sample locations were distant from any ‘amang’ processing plants. The external gamma dose rates ranged from 39 to 1039 nGy h⁻¹. The mean external gamma dose rate was 222 ± 191 nGy h⁻¹. Small areas of relatively enhanced activity were located having external gamma dose rates of up to 1039 ± 104 nGy h⁻¹. The activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K were analyzed by using a high-resolution co-axial HPGe detector system. The activity concentration ranges were 12–426 Bq kg⁻¹ for ²³⁸U, 19–1377 Bq kg⁻¹ for ²³²Th and <19–2204 Bq kg⁻¹ for ⁴⁰ K. Based on the radioactivity levels determined, the gamma-absorbed dose rates in air at 1 m above the ground were calculated. The calculated dose rates and measured dose rates had a good correlation coefficient, R of 0.94. To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the gamma-absorbed dose rate and the mean population weighted dose rate were calculated. An isodose map for the Kinta District was also produced.     

Seasonal and inter-annual variation of Beryllium-7 deposition in birch-tree leaves and grass in the northeast upland area of the Czech Republic

The activity concentrations of Beryllium-7 (⁷Be), a naturally occurring radioisotope produced in the atmosphere, were measured in leaves of birch-trees, above-ground parts of grass, soil and rainwater in the mountain massive Kralicky Sneznik (the northeast of the Czech Republic, altitude about 750 m) in the years of 2005, 2006 and 2007. Dried and ground samples of the plants and soils, and water samples from wet deposition were used to determine the ⁷Be content using a semiconductor gamma spectrometer. The ⁷Be values ranged from 147.0 to 279.6 Bq kg⁻¹, from 48.7 to 740.8 Bq kg⁻¹, from 2.1 to 8.7 Bq kg⁻¹, and from 0.6 to 1.9 Bq kg⁻¹ in birch-tree leaves, grass samples, soils, and rainwater, respectively. Insignificant inter-annual variations but significant increase in the ⁷Be activity concentrations during the spring and summer months were observed in birch-tree leaves and grass samples. The seasonal variation of the ⁷Be concentrations in grass samples correlated (R² = 0.4663 and 0.6489) with precipitation. No similar correlation was found for ⁷Be in birch-tree leaves. Beryllium-7 content in birch-tree leaves and in aerial parts of grass was mainly caused by direct transport of ⁷Be from wet deposition into aerial parts of the observed plants.     

Escaping radioactivity from coal-fired power plants (CPPs) due to coal burning and the associated hazards: a review

Coal, like most materials found in nature, contains trace quantities of the naturally occurring primordial radionuclides, i.e. of ⁴⁰K and of ²³⁸U, ²³²Th and their decay products. Therefore, the combustion of coal results in the released into the environment of some natural radioactivity (1.48 TBq y⁻¹), the major part of which (99 %) escapes as very fine particles, while the rest in fly ash. The activity concentrations of natural radionuclides measured in coals originated from coal mines in Greece varied from 117 to 435 Bq kg⁻¹ for ²³⁸U, from 44 to 255 Bq kg⁻¹ for ²²⁶Ra, from 59 to 205 Bq kg⁻¹ for ²¹⁰Pb, from 9 to 41 Bq kg⁻¹ for ²²⁸Ra (²³²Th) and from 59 to 227 Bq kg⁻¹ for ⁴⁰K. Fly ash escapes from the stacks of coal-fired power plants in a percentage of 3-1% of the total fly ash, in the better case. The natural radionuclide concentrations measured in fly ash produced and retained or escaped from coal-fired power plants in Greece varied from 263 to 950 Bq kg⁻¹ for ²³⁸U, from 142 to 605 Bq kg⁻¹ for ²²⁶Ra, from 133 to 428 Bq kg⁻¹ for ²¹⁰Pb, from 27 to 68 Bq kg⁻¹ for ²²⁸Ra (²³²Th) and from 204 to 382 Bq kg⁻¹ for ⁴⁰K. About 5% of the total ash produced in the coal-fired power plants is used as substitute of cement in concrete for the construction of dwellings, and may affect indoor radiation doses from external irradiation and the inhalation of radon decay products (internal irradiation) is the most significant. The resulting normalized collective effective doses were 6 and 0.5 man-Sv (GW a)⁻¹ for typical old and modern coal-fired power plants, respectively.     

Distribution of radionuclides in the guano sediments of Xisha Islands, South China Sea and its implication

Several natural and anthropogenic radionuclides (²¹⁰Pb, ²²⁶Ra and ¹³⁷Cs) in guano-phosphatic coral sediments and pure guano particles collected from Ganquan, Guangjin, Jinqing and Jinyin Islands of the Xisha archipelago, South China Sea, were analyzed. The Constant Initial Concentration (CIC) model and the Constant Rate of Supply (CRS) model were applied for age calculation. The average supply rate of ²¹⁰Pb was 126 Bq m⁻² a⁻¹, very close to the flux of northern hemisphere average (125 Bq m⁻² a⁻¹). The activities of anthropogenic radionuclides in the sediments were very low, indicating that human nuclear tests did not notably impact this region. The main source of radionuclides in the sediments was from atmospheric precipitation, and the organic matter derived from plant and produced by nutrient-rich guano could further enhance them.     

Determination activity of radionuclides in marine sediment by gamma spectrometer with anti cosmic shielding

In this work, the activities of radionuclides in a marine sediment sample have been determined. The gamma spectrometer comprises an N type coaxial HPGe detector with active shielding to reduce cosmic background. The mass activities of radionuclides have been derived and found to be around a few Bq kg⁻¹ to several hundreds Bq kg⁻¹ with relative uncertainties in this paper quoted corresponding to the combined standard uncertainties (k = 1).     

Evaluation and assessment of 25 years of environmental radioactivity monitoring data at Tarapur (India) nuclear site

The evaluation and assessment of monitoring data generated over a period of 1983-2007 (25 years) of a nuclear facility is presented. Time trends of particulate radioactivity, correlation between ¹³⁷Cs in discharge canal seawater and station discharged activity and correlation of ¹³⁷Cs, ⁶⁰Co, and ¹³¹I in marine species such as sponge and Nerita (gastropod) and corresponding discharged activity are discussed. The concentration of ¹³⁷Cs and ¹³¹I in seawater versus biota are discussed. A good correlation between ¹³⁷Cs in seawater and ¹³⁷Cs in liquid waste discharged was observed (R² = 0.8, p < 0.001). Similarly, correlation was good for Nerita and discharged concentration of ¹³⁷Cs, ¹³¹I and ⁶⁰Co (R² = 0.55-0.73 and p < 0.001). The measurements over the years indicated that there is no accumulation of radionuclides in either the terrestrial or aquatic environments. The mean ¹³⁷Cs decreased from the pre-operational levels: 7.0-3.6 Bq kg⁻¹ in soil, 0.91-0.016 Bq L⁻¹ in milk and 0.28-0.036 Bq kg⁻¹ in vegetation. Similarly, the mean ⁹⁰Sr in these matrixes decreased from 3.9 to 0.26 Bq kg⁻¹; 0.37-0.011 Bq L⁻¹ and 0.34-0.022 Bq kg⁻¹ respectively. Cesium-137 of about 700 μBq m⁻³ was measured in the air filter disks during 1986 and there was a decrease of three orders of magnitude in concentration over the 25 years. The evaluation of environmental data indicated that the radionuclide concentrations and potential impacts, in terms of effective dose to the members of public, have significantly reduced since 1969.     

Variation of radiation level and radionuclide enrichment in high background area

Significantly high radiation level and radionuclide concentration along Quilon beach area of coastal Kerala have been reported by several investigators. Detailed gamma radiation level survey was carried out using a portable scintillometer. Detailed studies on radionuclides concentration in different environmental matrices of high background areas were undertaken in the coastal areas of Karunagapalli, Kayankulam, Chavara, Neendakara and Kollam to study the distribution and enrichment of the radionuclides in the region. The absorbed gamma dose rates in air in high background area are in the range 43-17,400 nGyh⁻¹. Gamma radiation level is found to be maximum at a distance of 20 m from the sea waterline in all beaches. The soil samples collected from different locations were analysed for primordial radionuclides by gamma spectrometry. The activity of primordial radionuclides was determined for the different size fractions of soil to study the enrichment pattern. The highest activity of ²³²Th and ²²⁶Ra was found to be enriched in 125-63 μ size fraction. The preferential accumulation of ⁴⁰K was found in <63 μ fraction. The minimum ²³²Th activity was 30.2 Bq kg⁻¹, found in 1000-500 μ particle size fraction at Kollam and maximum activity of 3250.4 Bq kg⁻¹ was observed in grains of size 125-63 μ at Neendakara. The lowest ²²⁶Ra activity observed was 33.9 Bq kg⁻¹ at Neendakara in grains of size 1000-500 μ and the highest activity observed was 482.6 Bq kg⁻¹ in grains of size 125-63 μ in Neendakara. The highest ⁴⁰K activity found was 1923 Bq kg⁻¹ in grains of size <63 μ for a sample collected from Neendakara. A good correlation was observed between computed dose and measured dose in air. The correlation between ²³²Th and ²²⁶Ra was also moderately high. The results of these investigations are presented and discussed in this paper.     

Polonium (210Po) and lead (210Pb) in marine organisms and their transfer in marine food chains

The determination of ²¹⁰Po and ²¹⁰Pb was performed in marine organisms from the seashore to abyssal depths, encompassing a plethora of species from the microscopic plankton to the sperm whale. Concentrations of those radionuclides ranged from low values of about 5 × 10⁻¹ Bq kg⁻¹ (wet wt.) in jellyfish, to very high values of about of 3 × 10⁴ Bq kg⁻¹ (wet wt.) in the gut walls of sardines, with a common pattern of ²¹⁰Po > ²¹⁰Pb.These radionuclides are primarily absorbed from water and concentrated by phyto- and microzooplankton, and then are transferred to the next trophic level along marine food chains. Investigation in epipelagic, mesopelagic, bathypelagic and abyssobenthic organisms revealed that ²¹⁰Po is transferred in the marine food webs with transfer factors ranging from 0.1 to 0.7, and numerically similar to those of the energy transfer in the marine food chains. As ²¹⁰Po preferentially binds to amino acids and proteins, its transfer in food chains likely traces protein transfer and, thus, ²¹⁰Po transfer factors are similar to ecotrophic coefficients. ²¹⁰Pb is transferred less efficiently in marine food chains and this contributes to increased ²¹⁰Po:²¹⁰Pb activity ratios in some trophic levels.     

Transport and distribution of artificial gamma-emitting radionuclides in the River Yenisei and its sediment

Discharges from the Krasnoyarsk Mining and Chemical Industrial Complex (KMCIC) near Krasnoyarsk resulted in radioactive contamination of sediments of the River Yenisei. Between 1999 and 2006, 16 sediment cores were collected at different positions 15-1500 km downstream from the discharge point. The concentration of artificial gamma-emitting radionuclides (¹³⁷Cs, ⁶⁰Co, ¹⁵²Eu, and ²⁴¹Am) was determined with the objective to analyze the migration processes leading to the transport of these radionuclides along the river and to their vertical distribution within the sediment. In cores taken in the vicinity of the reactors, the average activity concentration of ¹³⁷Cs, ¹⁵²Eu, and ⁶⁰Co was about 1000 Bq kg⁻¹, and the activity concentration of ²⁴¹Am was about 20 Bq kg⁻¹. Contamination levels of artificial radionuclides were decreasing with increasing distance downstream the KMCIC: The fastest decrease of average activity by a factor of 10 over a distance of 300 km was observed for ²⁴¹Am, whereas for ¹³⁷Cs this decrease occurred over a distance of 1100 km. Sequential extraction experiments revealed that in all depths and at all distances the studied radionuclides were tightly bound to the sediment.To investigate the mechanisms of transport of the ¹³⁷Cs and ⁶⁰Co contamination, mathematical models have been used to describe the contamination in the river water and within the sediments.     

Polonium-210 and lead-210 in the terrestrial environment: a historical review

The radionuclides ²¹⁰Po and ²¹⁰Pb widely present in the terrestrial environment are the final long-lived radionuclides in the decay of ²³⁸U in the earth’s crust. Their presence in the atmosphere is due to the decay of ²²²Rn diffusing from the ground. The range of activity concentrations in ground level air for ²¹⁰Po is 0.03-0.3 Bq m⁻³ and for ²¹⁰Pb 0.2-1.5 Bq m⁻³.In drinking water from private wells the activity concentration of ²¹⁰Po is in the order of 7-48 mBq l⁻¹ and for ²¹⁰Pb around 11-40 mBq l⁻¹. From water works, however, the activity concentration for both ²¹⁰Po and ²¹⁰Pb is only in the order of 3 mBq l⁻¹.Mosses, lichens and peat have a high efficiency in capturing ²¹⁰Po and ²¹⁰Pb from atmospheric fallout and exhibit an inventory of both ²¹⁰Po and ²¹⁰Pb in the order of 0.5-5 kBq m⁻² in mosses and in lichens around 0.6 kBq m⁻². The activity concentrations in lichens lies around 250 Bq kg⁻¹, dry mass.Reindeer and caribou graze lichen which results in an activity concentration of ²¹⁰Po and ²¹⁰Pb of about 1-15 Bq kg⁻¹ in meat from these animals. The food chain lichen-reindeer or caribou, and Man constitutes a unique model for studying the uptake and retention of ²¹⁰Po and ²¹⁰Pb in humans. The effective annual dose due to ²¹⁰Po and ²¹⁰Pb in people with high consumption of reindeer/caribou meat is estimated to be around 260 and 132 μSv a⁻¹ respectively.In soils, ²¹⁰Po is adsorbed to clay and organic colloids and the activity concentration varies with soil type and also correlates with the amount of atmospheric precipitation. The average activity concentration levels of ²¹⁰Po in various soils are in the range of 20-240 Bq kg⁻¹.Plants become contaminated with radioactive nuclides both by absorption from the soil (supported Po) and by deposition of radioactive fallout on the plants directly (unsupported Po). In fresh leafy plants the level of ²¹⁰Po is particularly high as the result of the direct deposition of ²²²Rn daughters from atmospheric deposition. Tobacco is a terrestrial product with high activity concentrations of ²¹⁰Po and ²¹⁰Pb. The overall average activity concentration of ²¹⁰Po is 13 ± 2 Bq kg⁻¹. It is rather constant over time and by geographical origin.The average median daily dietary intakes of ²¹⁰Po and ²¹⁰Pb for the adult world population was estimated to 160 mBq day⁻¹ and 110 mBq day⁻¹, corresponding to annual effective doses of 70 μSv a⁻¹ and 28 μSv a⁻¹, respectively. The dietary intakes of ²¹⁰Po and ²¹⁰Pb from vegetarian food was estimated to only 70 mBq day⁻¹ and 40 mBq day⁻¹ corresponding to annual effective doses of 30.6 μSv a⁻¹ and 10 μSv a⁻¹, respectively. Since the activity concentration of ²¹⁰Po and ²¹⁰Pb in seafood is significantly higher than in vegetarian food the effective dose to populations consuming a lot of seafood might be 5-15 fold higher.