Artificial radionuclides in sediments of the Don River Estuary and Azov Sea

The Don River Estuary-Azov Sea system is an extension of the shallow continental shelf area of the Black Sea. A large data set of artificial radionuclides in bottom sediments of the Azov Sea has been compiled in order to examine the storage and migration of radionuclides within this highly restricted inland sea and to estimate the annual dose received by individuals in the local population who regularly consume fish. In recent years (1997-1999), the radionuclide content of surface sediments has been: 137Cs < or = 0.5-100 Bq/kg d.w. (mean = 33.8 +/- 25.9 Bq/kg d.w., n = 57), 90Sr = 0.2-5.7 Bq/kg d.w. (mean = 2.1 +/- 1.4 Bq/kg d.w., n = 34) and 239,240Pu = 0.31-0.51 Bq/kg d.w. (n = 2). In general, 137Cs activities increase with distance from the mouth of the Don River and correlate negatively with sediment grain size (r2 = 0.77, n = 21). The annual 137Cs-derived dose received by an individual through the trophic chain water-fish-humans (approximately 10(-6) Sv/yr) is well below regulatory recommended limits, indicating that current levels of radioactivity in the environment pose no threat to commercial fisheries operations for the bordering nations of Russia and Ukraine.     

90Sr, 137Cs and (239,240)Pu concentration surface water time series in the Pacific and Indian Oceans--WOMARS results

Under an IAEA's Co-ordinated Research Project "Worldwide Marine Radioactivity Studies (WOMARS)" 90Sr, 137Cs and (239,240)Pu concentration surface water time series in the Pacific and Indian Oceans have been investigated. The Pacific and Indian Oceans were divided into 17 latitudinal boxes according to ocean circulation, global fallout patterns and the location of nuclear weapons test sites. The present levels and time trends in radionuclide concentrations in surface water for each box were studied and the corresponding effective half-lives were estimated. For the year 2000, the estimated average 90Sr, 137Cs and (239,240)Pu concentrations in surface waters of the Pacific and Indian Oceans varied from 0.1 to 1.5 mBq/L, 0.1 to 2.8 mBq/L, and 0.1 to 5.2 microBq/L, respectively. The mean effective half-lives for 90Sr and 137Cs in surface water were 12+/-1 years for the North, 20+/-1 years for the South and 21+/-2 years for the Equatorial Pacific. For (239,240)Pu the corresponding mean effective half-lives were 7+/-1 years for the North, 12+/-4 years for the South and 10+/-2 years for the Equatorial Pacific. For the Indian Ocean the mean effective half-lives of 137Cs and (239,240)Pu were 21+/-2 years and 9+/-1 years, respectively. There is evidence that fallout removal rates before 1970 were faster than those observed during recent decades. The estimated surface water concentrations of 90Sr, 137Cs and (239,240)Pu in latitudinal belts of the Pacific and Indian Oceans for the year 2000 may be used as the average levels so that any new contribution from nuclear facilities, nuclear weapons test sites, radioactive waste dumping sites and from possible nuclear accidents can be identified.     

Studies of Np and Pu in the marine environment of Swedish-Danish waters and the North Atlantic Ocean

The long-lived anthropogenic radionuclides (237)Np, (239)Pu and (240)Pu were determined in marine environmental samples (seaweed and seawater) collected from Swedish-Danish waters and the North Atlantic Ocean at various locations on different occasions during the period 1991-2001. The measurements were performed with sector field Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and conventional alpha spectrometry. The (237)Np activity concentrations in Fucus vesiculosus and surface seawater from the Swedish west coast and Danish waters ranged from 0.16+/-0.02 to 1.02+/-0.09 mBq kg(-1) (dry weight) and 0.65+/-0.02 to 1.69+/-0.02 mBq m(-3), respectively, depending on the location and sampling year. Most of the (237)Np in these waters is believed to originate from the Sellafield nuclear reprocessing plant, with some contribution from global fallout. The (240)Pu/(239)Pu atomic ratios in F. vesiculosus samples are reported in this study with an overall average of 0.17+/-0.03. The (237)Np and (239)Pu activity concentrations observed in surface seawater collected in North Atlantic waters ranged from 0.16+/-0.01 to 0.62+/-0.08 mBq m(-3) and from 0.64+/-0.05 to 4.27+/-0.08 mBq m(-3), respectively, and the (237)Np/(239)Pu atomic ratios were a good indicator of conservative behaviour of Np in marine waters.     

90Sr, 238U, 234U, 137Cs, 40K and 239/240Pu in Emmental type cheese produced in different regions of Western Europe

A method is presented for the determination of (90)Sr and uranium in Emmental type cheese collected in dairy plants from different European countries. Results display a significant correlation (r = 0.708 Student t-test = 6.02) between the (90)Sr content of the cheese and the altitude of grazing. The highest (90)Sr activity is 1.13 Bq kg(-1) of cheese and the lowest is 0.29 Bq kg(-1). Uranium activity is very low with a highest (238)U value of 27 mBq kg(-1). In addition, (234)U/(238)U ratio shows a large enrichment in (234)U for every location. Without any significant indication of the geographic origin of the cheese, this enrichment is believed to be due to the geological features of the pasture, soil and underground water. These results tend to prove that the contamination of milk by uranium originates principally from the water that the cows drink instead of the forage. This finding may have a great importance in models dealing with dairy food contamination by radionuclides following a nuclear accident. Also, the (90)Sr content and to a lesser extent the (234)U/(238)U ratio could be used to trace the authenticity of the origin of the cheese. (137)Cs activity is lower than the detection limit of 0.1 Bq kg(-1) in all the samples collected (n = 20). Based on natural (40)K activity in cheese (15-21 Bq kg(-1)), the decontamination factor for the alkaline cations from milk to cheese is about 20. Plutonium activity stays below the detection limit of 0.3 mBq kg(-1).     

Radioactive contamination in the marine environment adjacent to the outfall of the radioactive waste treatment plant at ATOMFLOT,northern Russia

RTP "ATOMFLOT" is a civilian nuclear icebreaker base located on the Kola Bay of northwest Russia. The objectives of this study were to determine the distributions of man-made radionuclides in the marine environment adjacent to the base, to explain the form of the distributions in sediments and to derive information concerning the fate of radionuclides discharged from ATOMFLOT. Mean activity concentrations (d.w.) for surface sediment, of 63 Bq kg(-1 137Cs, 5.8 Bq kg(-1) 90Sr and 0.45 Bq kg(-1 239,240)Pu were measured. Filtered seawater activity levels were in the range of 3--6.9 Bq m(-3) 137Cs, 2.0-11.2 Bq m(-3) 90Sr, and 16-40 m Bq m(-3), 239,240Pu. Short-lived radionuclides were present at sediment depths in excess of 10cm indicating a high degree of sediment mixing. Correlations of radionuclide activity concentrations with grain-size appear to be absent; instead, the presence of relatively contaminated sediment appears to be related to the existence of radioactive particles.     

Intake of uranium and radium-226 due to food crops consumption in the phosphate region of Pernambuco--Brazil

The phosphate region located in the Northeast of Brazil covers an area of approximately 150 km long with an average width of 4 km, along the coast of the states of Pernambuco and Paraíba. The inhabitants of this area are exposed to natural radioactivity levels higher than the background values recorded in the literature, mainly due to the presence of uranium and its decay products in the phosphatic sediments. The main aim of this study was to determine the activity concentration of uranium and (226)Ra in foodstuffs cultivated in this area, where the phosphate mineral has been extracted. The activity concentrations found for uranium and (226)Ra in the foodstuffs analyzed varied from 13 to 186 mBq kg(-1) (wet weight), with a mean value of 46 mBq kg(-1) and from 43 to 2209 mBq kg(-1) (wet weight), with a mean value of 358 mBq kg(-1), respectively. The annual intake of these radionuclides, for rural residents, was 7.45 Bq for uranium and 69.3 Bq for (226)Ra.     

Impact of trace metals and nutrients levels on phytoplankton from the Kuwait coast

The impact of marine pollution was estimated from seven stations of Kuwait coastal waters. The mean concentrations of all trace metals in seawater (0.07-7.04 microg/l) and in phytoplankton (14.90-52.01 microg/g) revealed less phytoplankton abundance in Stations IV VI during the four seasons. However, a relative surge in the phytoplankton abundance, with an increase in the mean concentrations of all trace metals in seawater (0.15-8.94 microg/l) and phytoplankton (22.82-61.25 microg/g), was observed in Station II. A low phytoplankton abundance was noted in Stations I, III, and VII despite low mean concentrations of all the trace metals in seawater (0.11-5.77 microg/l) and phytoplankton (1.40-20 microg/g) during the four seasons. Statistical tests revealed significant difference in Fe, Ni, and Pb between the four seasons in seawater and Fe and Co in phytoplankton. No significant difference in trace metals between locations was observed in seawater and in phytoplankton. The major nutrients in all the four seasons were found in the magnitude of SiO3 > NO3 > PO4 in all the stations, and thus, support the presence of rich diatoms and dinoflagellates than other phytoplankton groups. The seven stations also represented indicator species of oil and industrial waste pollution.     

137Cs in marine samples from the Brazilian southeastern coastal region

The present work presents the results of ¹³⁷Cs concentration in seawater, fish and sediments samples collect in 11 sampling points, crossing the Brazilian Southeastern coastal region, from Vitória (ES) to Santos (SP), on a routine basis from 1997 to 2002. This monitoring program was carried out by the Instituto de Radioproteção e Dosimetria (IRD/CNEN/MCT), in cooperation with the Instituto de Estudos do Mar Almirante Paulo Moreira (IEAPM/Brazilian Navy), aiming at determining artificial radionuclides in marine samples. Additionally to the ¹³⁷Cs results, ⁹⁰Sr concentrations in fish samples from 1998 to 2002 are also reported.The ¹³⁷Cs in seawater follows a lognormal distribution, with a geometric mean of 1.8 Bq m^-3 and a geometric standard deviation of 1.4 (n=54), decay corrected to June/2002. For ¹³⁷Cs levels in fish samples a geometric mean of 0.19 Bq kg⁻¹ and a geometric standard deviation of 2.9 (n=39), decay corrected to June/2002, with a range of 0.03 to 1.7 Bq kg⁻¹, were obtained. Based on the ¹³⁷Cs mean concentration in fish as well as in seawater, a transfer factor of 1 × 10² was calculated, which is quite in agreement with the recommended value found in the Safety Report Serie 19.     

Natural radioactivity measurements in building materials in Southern Lebanon

Using gamma-spectroscopy and CR-39 detector, concentration C of naturally occurring radioactive nuclides (226)Ra, (222)Rn, (214)Bi, (228)Ac, (212)Pb, (212)Bi and (40)K, has been measured in sand, cement, gravel, gypsum, and paint, which are used as building materials in Lebanon. Sand samples were collected from 10 different sandbank locations in the southern part of the country. Gravel samples of different types and forms were collected from several quarries. White and gray cement fabricated by Shaka Co. were obtained. gamma-spectroscopy measurements in sand gave Ra concentration ranging from 4.2+/-0.4 to 60.8+/-2.2 Bq kg(-1) and Ra concentration equivalents from 8.8+/-1.0 to 74.3+/-9.2 Bq kg(-1). The highest Ra concentration was in gray and white cement having the values 73.2+/-3.0 and 76.3+/-3.0 Bq kg(-1), respectively. Gravel results showed Ra concentration between 20.2+/-1.0 and 31.7+/-1.4 Bq kg(-1) with an average of 27.5+/-1.3 Bq kg(-1). Radon concentration in paint was determined by CR-39 detector. In sand, the average (222)Rn concentration ranged between 291+/-69 and 1774+/-339 Bq m(-3) among the sandbanks with a total average value of 704+/-139 Bq m(-3). For gravel, the range was found to be from 52+/-9 to 3077+/-370 Bq m(-3) with an average value of 608+/-85 Bq m(-3). Aerial and mass exhalation rates of (222)Rn were also calculated and found to be between 44+/-7 and 2226+/-267 mBq m(-2)h(-1), and between 0.40+/-0.07 and 20.0+/-0.3 mBq kg(-1)h(-1), respectively.     

Spatial variability of fallout-90Sr in soil and vegetation of an alpine pasture

According to the soil-to-plant transfer concept generally used in dose assessment modeling, the plant uptake of a radionuclide should depend linearly on its concentration in the soil. In order to validate this concept for (90)Sr in a semi-natural ecosystem, plant and soil samples were taken at 100 plots of a 100 x 100 m(2) area within an alpine pasture near Berchtesgaden, Germany. At three plots, the vertical distribution of (90)Sr in the soil was determined in addition. A statistically significant correlation between the soil and plant concentration of (90)Sr was not detectable (Spearman correlation coefficient R=-0.116, p>0.05) within the range of the Sr-concentration covered (15-548 Bq kg(-1) dry soil and 17-253 Bq kg(-1) dry plant material). Thus, the prerequisite of the soil-to-plant transfer concept was not fulfilled for (90)Sr at this site. Organic carbon and total nitrogen were also determined in the soil samples. Both elements were highly correlated (R=0.912, p<0.001), their ratio being C/N=10.9+/-0.7. While C was positively correlated with the (90)Sr concentrations in the soil (R=0.342, p<0.001), negative correlations were observed for the plant concentrations (R=-0.286, p<0.01) and the concentration ratios (R=-0.444, p<0.001) of (90)Sr. These results are compared with those recently obtained for (137)Cs by Bunzl et al. (J Environ Radioactiv 48 (2000) 145).     

Rapid screening of 90Sr activity in water and milk samples using Cherenkov radiation

A method for screening 90Sr in milk samples is proposed. This method is based on a liquid scintillation technique taking advantage of Cherenkov radiation, which is produced in a liquid medium and then detected by the photomultipliers of a Liquid Scintillation Counter (LSC). Twenty millilitres of water and milk samples spiked with various concentrations of 90Sr/90Y in equilibrium were added in plastic vials and then were measured with an LSC (TriCarb 3170 TR/SL). The derived efficiencies were 49% for water samples and 14% for milk samples. The detection limit was 470 mBq L(-1)(90)Sr for water, without any pretreatment. Milk contains potassium, which also produces Cherenkov radiation due to the presence of 40K. For this reason, the interference of 40K in the measurements of 90Sr in milk samples was also investigated. The detection limit for milk was 1.7 Bq L(-1)90Sr.     

Plutonium concentration and 240Pu/239Pu atomic ratio in liver of squid collected in the coastal sea areas of Japan

Plutonium isotopes, 239Pu and 240Pu, were measured in liver samples from Surume squid using a sector-field high resolution ICP-MS after radiochemical purification. Surume squid samples were obtained from nine landing ports in Japanese inshore during fishery season from September to December 2002. Concentrations of 239Pu and 240Pu ranged from 1.5 to 28 mBq kg(-1) and 1.1 to 24 mBq kg(-1), respectively. Plutonium (239,240Pu) concentrations in liver were several thousand times higher than levels found in seawater. The concentration factor (CF) compared to seawater for 239,240Pu and 13 other elements ranged from 10(0) to 10(7). The CF values for 239,240Pu, V and Th were 10(2)-10(4). Pu had an intermediate CF between conservative and scavenged elements. 240Pu/239Pu atomic ratios in the squid liver ranged from 0.177 to 0.237 which were slightly higher than 0.178+/-0.014 for global fallout. The variations of 240Pu/239Pu atomic ratios in ocean currents with different source functions are important for interpreting high 240Pu/239Pu atomic ratios in Surume squid liver. It seems likely that Pu with high 240Pu/239Pu atomic ratio is continuously transported through the solubilization and seawater transport from the North Equatorial Current to Kuroshio and its branch, Tsushima Current. By assuming that Pu found in Surume squid liver is a mixture of global fallout Pu (0.178) and close-in fallout Pu with high 240Pu/239Pu atomic ratio (0.30-0.36) around Bikini Atoll, Pu contribution from Bikini close-in fallout Pu accounts for close to 35% of the whole plutonium in Surume squid liver. These results highlight that Surume squid is a useful organism for evaluating environmental Pu levels of larger sea area and facilitate the development of models to understand oceanic transport of close-in fallout Pu from Bikini Atoll.     

The impact of phosphate loading activities on near marine environment: the Syrian coast.

The impact of loading cargoes of phosphate ore into ships on the near marine environment at the Syrian coast has been evaluated. Results have shown a significant enhancement of 210Po, 210Pb and other natural radionuclides in sediment and surface water inside the port area. The highest 210Po and 210Pb concentrations observed in sediment were found to be 170 and 64 Bq kg(-1) respectively, while 210Pb and 210Po concentrations in surface water ranged from 5 to 20 mBq l(-1) and 0.93 to 3.23 mBq l(-1). In addition, comparable values of 210Po and 210Pb for all marine organisms (algae, crab and fish) suggest that their use as indicators for phosphate pollution is not recommended. However, the effect of loading cargoes on the port marine environment of Tartous was found to be mainly related to wind direction where radioactive air particulate are either being dispersed to land or sea.     

Variation of the activity concentrations and fluxes of natural (210Po, 210Pb) and anthropogenic (239,240Pu, 137Cs) radionuclides in the Strait of Gibraltar (Spain)

The activity concentrations and fluxes of natural (210Pb, 210Po) and anthropogenic (239,240Pu, 137Cs) radionuclides have been determined in the different water masses crossing the Strait of Gibraltar. New data have been gathered during four multidisciplinary and multinational sampling campaigns, performed between 1997 and 1999 within the framework of the CANIGO-FLUGIST Project. Mean activity concentrations of 210Po (1.53+/-0.34 Bq m(-3), n = 30) and 210Pb (1.16+/-0.50 Bq m(-3), n = 31) in the Atlantic water entering the Mediterranean basin are about double those measured in the Mediterranean outflow, namely 0.84+/-0.34 Bq m(-3) (n = 22) for 210Po and 0.66+/-0.34 Bq m(-3) (n = 22) for 210Pb. The opposite trend is observed for 231,240Pu, with average concentrations of 9.9+/-3.0 mBq m(-3) (n = 29) in the incoming Atlantic flow and 22.0+/-3.0 mBq m(-3) (n = 22) in the outpouring Mediterranean water. In the case of 137Cs, the same concentrations were quantified in the waters moving inwards (2.52+/-0.28 Bq m(-3), n = 27) and outwards (2.14+/-0.52 Bq m(-3), n = 21) from the Mediterranean Sea. On this basis, the Mediterranean basin experiences a net annual input flux of 14 TBq of 210Pb and 19 TBq of 210Po, and a net annual loss of 0.34 TBq of 239,240Pu, while--at present--137Cs input and output fluxes appear to be balanced.     

Bioaccumulation and distribution of plutonium in fish from Gdansk Bay

In this paper, the results of 238Pu and 239 + 240Pu determinations in four representative species of Baltic fish collected in Gdansk Bay; flounder, herring, cod and sprat, are presented and discussed. The plutonium isotopes are amongst the more radiotoxic nuclides. In the marine environment, the highest concentrations of plutonium are found in the sediments, but the complex biogeochemical cycle of the element means that it is also found in all other compartments. The activities of the fish samples were measured using alpha spectrometry and the concentrations of plutonium 238Pu and 239 + 240Pu were estimated for particular organs and tissues and the whole body. The 239 + 240Pu concentrations for fish species were: flounder 0.94 mBq kg-1 w.w., herring 2.22 mBq kg-1 w.w., cod 2.35 mBq kg-1 w.w. and sprat 0.33 mBq kg-1 w.w. On the basis of the 238Pu/239 + 240Pu activity ratio in the organs and tissues, the proportion of Chernobyl-derived plutonium in the Baltic Sea was calculated. The lowest values of Chernobyl plutonium were accumulated in flounder stomach, herring skin, cod intestine, the highest in cod gills and skin.     

Investigation of dissolved uranium content in the watershed of Seine River (France)

A systematic survey of dissolved uranium activity was carried out in the Seine and the Marne over one year. A small watershed, the Grand Morin, included in the Seine one, was also investigated from stream to medium-sized rivers. The Melarchez stream exhibits low but variable dissolved 238U levels (3.3 +/- 2.0 mBq l(-1)). Thereafter, uranium activities show a rapid increase to reach, from the Grand Morin River, a rather constant range (8-11 mBq l(-1)). On the Marne before the confluence with the Seine, dissolved 238U is nearly invariable (9.1 +/- 0.8 mBq l(-1)), for flow rates comprised between 60 and 423 m3 s(-1). Dissolved 238U in the Seine corresponds to almost triple the global mean riverine uranium concentration. In the estuary of the Seine, uranium shows a gradual increase, resulting from conservative mixing of river with sea waters.     

Bioaccumulation of 137Cs in pelagic food webs in the Norwegian and Barents Seas

Knowledge and documentation of the levels of radioactive contamination in fish stocks important to Norwegian fisheries is of major importance to Norwegian consumers and fish export industry. In the present study, the bioaccumulation of caesium-137 ((137)Cs) has been investigated in marine food webs in the Barents and Norwegian Seas. The contents of (137)Cs in the different organisms were generally low (<1 Bq kg(-1) wet weight), but a marked bioaccumulation was apparent: The concentration of (137)Cs was about 10-fold higher in the harbour porpoise Phocoena phocoena, representing the upper level of the food web, than in the amphipod Themisto sp., representing the lower level of the food web. The Concentration Factors (CF=Bq kg(-1) wet weight/Bq l(-1) seawater) increased from 10+/-3 for a mixed sample of krill and amphipods to 165+/-5 for harbour porpoises.     

The investigation of 137Cs and 90Sr background radiation levels in soil and plant around Tianwan NPP, China

(137)Cs and (90)Sr background levels in soil and plant around Tianwan Nuclear Power Plant (NPP) are reported. Eighty-four soil samples and 44 plant samples were collected from March 2000 to April 2002. The samples were analyzed by gamma spectrometry and radiochemical separation procedure to quantify (137)Cs and (90)Sr radioactivities. The concentrations (Bqkg(-1) dry weight) have been observed in the range of 0.6-1.6 for (90)Sr and 1.4-6.9 for (137)Cs in soils, their average values are 1.0+/-0.3 and 4.6+/-1.6, respectively, which are relatively lower than the reported values in neighboring countries. The mean concentrations (in Bqkg(-1) fresh weight except for tea and grass which is expressed in Bqkg(-1) dry weight) of (137)Cs and (90)Sr are 0.1+/-0.03 and 7.7+/-4.1 in pine needle, 0.27+/-0.05 and 3.0+/-1.1 in tea, 0.65+/-0.19 and 2.1+/-0.3 in grass, 0.033+/-0.021 and 0.084+/-0.045 in wheat, 0.019+/-0.01 and 0.23+/-0.06 in China cabbage, and 0.009+/-0.007 and 0.024+/-0.084 in rice, respectively. The pine needle and tea can be regarded as indicator species for (90)Sr and (137)Cs. The soil-to-plant transfer factor (TF) values of (90)Sr and (137)Cs are, respectively, 0.022 and 0.031 for rice, 0.066 and 3.83 for China cabbage, 0.0088 and 0.089 for wheat, and 0.037 and 0.56 for grass.     

Bioavailability of radiostrontium in soil: experimental study and modeling

Parameters related to 90Sr mobility in the soil-plant system are reported: exchangeable content, selectivity coefficient, and transfer factor. Large mobility of 90Sr in different soil types was shown. The fraction of exchangeable 90Sr varied between 70 and 90%. The selectivity coefficient K(C)(90Sr/Ca) values were in the range 1.3-2.5. The radionuclide transfer factors (TF) varied by a factor of 9.6 for barley seedlings and by a factor of 6.6 for lupine seedlings. The exchangeable Ca content was the determinant soil parameter responsible for differences in 90Sr biological availability. A static model was devised that describes 90Sr sorption from soil solution by soil and on the root surface. The parameter of 90Sr bioavailability (A) has been suggested. Parameter A was calculated from data on soil exchangeable Ca content and 90Sr mobility indicators--exchangeable fraction of the radionuclide and the selectivity coefficient K(C)(90Sr/Ca). A correlation was found between TF and parameter A.