Distribution pattern of artificial radionuclides in the Baltic Sea in the special event of the Chernobyl fallout

Extensive investigations on radioactive contamination and on its spatial and temporal changes in the Baltic Sea have been carried out by the National Board for Atomic Safety and Radiation Protection since 1986. The results were compared with data obtained in the years prior to the Chernobyl accident. Due to the composition of the accidental releases and the physical half-life of the released radionuclides, special emphasis was laid on Cs-134 and Cs-137. Other radionuclides, such as H-3, Sr-90, Ru-103 and Ru-106 turned out to be insignificant compared with the caesium isotopes. The radionuclides Cs-134 and Cs-137 accounting for the highest percentage of the released long-lived radionuclides were deposited on the sea surface with an initial ratio of 0.5. Their distribution pattern on the sea surface was affected by the meteorological conditions prevailing during the release period. The horizontal dislocation of higher contaminated water masses and the vertical penetration of radioactive caesium resulted in a prolonged uniformity of the contamination level of the Baltic Sea.     

Radioactive caesium (134Cs and 137Cs) in mushrooms of the genus Boletus from the Reggio Emilia in Italy and Pomerania in Poland

Activity concentrations of ¹³⁴Cs and ¹³⁷Cs were determined in mushrooms of the Boletus species B. aereus, B. reticulatus, B. appendiculatus, B. calopus, B. edulis, B. erythropus, B. fechtneri, B. pinophilus, B. pseudoregius, B. rhodopurpureus, B. rhodoxanthus collected in the Reggio Emilia, Italy, in 1993 and 1994 and in B. edulis collected in Pomerania in northern Poland in the period from 1995–2015. Boletus edulis from the Reggio Emilia showed presence of ¹³⁷Cs at 330?±?220?Bq?kg^?1 dry biomass in 1993 and at 370?±?180?Bq?kg^?1 dry biomass in 1994. In B. edulis sampled in the Reggio Emilia in 1993 and 1994, the pre-Chernobyl ¹³⁷Cs from global fallout amounted to 39–46?% of the total activity concentrations of isotope ¹³⁷Cs. B. edulis from Pomerania contained ¹³⁷Cs in caps at 270?±?15?Bq?kg^?1 dry biomass in 1995, and in whole fruiting bodies it was found to be 470?±?9?Bq?kg^?1 dry biomass in 2015. The activity concentrations of ¹³⁷Cs determined in fruiting bodies of B. edulis from Pomerania fluctuated but persisted over the period from 1995 to 2015, while the maximum activity concentrations were well below the tolerance limit of 600?Bq?kg^?1 fresh product.     

Plutonium fractionation in southern Baltic Sea sediments

In this study, different chemical plutonium fractions (dissolved in water, connected to carbonates, connected to oxides, complexed with organic matter, mineral acids soluble and the rest) in sediments from the Vistula River estuary, the Gdańsk Basin and the Bornholm Deep were determined. The distribution of ^239+240Pu in analysed sediments samples was not uniform but dependent on its chemical form, depth and the sediment geomorphology. The highest amount of plutonium exists in middle parts of sediments and comes from the global atmospheric fallout from nuclear tests in 1958–1961. According to all analysed fractions, the biggest amount of ^239+240Pu was in the mobile form, connected to carbonate fractions from the Vistula River estuary, the Gulf of Gdańsk and the Bornholm Deep sediments.     

Fission products from the damaged Fukushima reactor observed in Hungary

Fission products, especially ¹³¹I, ¹³⁴Cs and ¹³⁷Cs, from the damaged Fukushima Dai-ichi nuclear power plant (NPP) were detected in many places worldwide shortly after the accident caused by natural disaster. To observe the spatial and temporal variation of these isotopes in Hungary, aerosol samples were collected at five locations from late March to early May 2011: Institute of Nuclear Research, Hungarian Academy of Sciences (ATOMKI, Debrecen, East Hungary), Paks NPP (Paks, South-Central Hungary) as well as at the vicinity of Aggtelek (Northeast Hungary), Tapolca (West Hungary) and Bátaapáti (Southwest Hungary) settlements. In addition to the aerosol samples, dry/wet fallout samples were collected at ATOMKI, and airborne elemental iodine and organic iodide samples were collected at Paks NPP. The peak in the activity concentration of airborne ¹³¹I was observed around 30 March (1–3 mBq m^?3 both in aerosol samples and gaseous iodine traps) with a slow decline afterwards. Aerosol samples of several hundred cubic metres of air showed ¹³⁴Cs and ¹³⁷Cs in detectable amounts along with ¹³¹I. The decay-corrected inventory of ¹³¹I fallout at ATOMKI was 2.1±0.1 Bq m^?2 at maximum in the observation period. Dose-rate contribution calculations show that the radiological impact of this event at Hungarian locations was of no considerable concern.     

Nitrogen retention in the Szczecin Lagoon,Baltic Sea

Nitrogen (N) retention and transformation in the Szczecin Lagoon, southern Baltic Sea, were studied by means of budget calculations and stable isotope data of dissolved and particulate matter. Two stations, one located at the main outlet of the lagoon (?wina Strait) and the other 100 km to the south, on the Oder River (Widuchowa), were sampled biweekly over the years 2000–2002. The Oder River is one of the five largest rivers draining into the Baltic Sea and the largest one discharging its waters into the western Baltic. According to our data, the Oder River carried approximately 60 kt y^?1 total N, of which 7 kt y^?1 (<12 %) are particulate organic nitrogen and 46 kt y^?1 (77 %) dissolved inorganic nitrogen. Seasonal patterns of particulate nitrogen and nitrate concentrations were similar at Widuchowa and ?wina Strait station, but nitrate concentrations in the ?wina Strait were much lower, pointing not only to the dilution effect but also to considerable nutrient removal capacity (especially of nitrate) in the lagoon. The loss of nitrate suggests that denitrification is the major N-removal process, whereas primary production was only a minor contributor, due to the very low particle load. Combining budget calculations with stable isotope measurements reveal unique information about nitrogen turnover processes in the lagoon.     

Environmental and radio-ecological studies on shallow marine sediments from harbour areas along the Red Sea coast of Egypt for identification of anthropogenic impacts

Analysis of marine sediments of the studied localities provides investigators with data to characterise the composition of these sediments allowing for the identification of particular pollution sources. A study of texture, geochemistry, X-ray diffraction and natural radionuclide content of shallow marine sediments from Quseir harbour, Safaga harbour and El-Esh area in the Red Sea coast of Egypt was conducted for the purpose of assessing the possible influence of human activities on the composition of the sediments. The activity concentrations of the naturally occurring radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K were measured by using γ-ray spectrometry. The mean activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in all areas studied were found to be 71±6, 66±5 and 92±7 Bq kg^?1 for ²²⁶Ra, 83±5, 71±7 and 162±23 Bq kg^?1 for ²³²Th and 513±10, 493±20 and 681±28 Bq kg^?1 for ⁴⁰K, respectively. The results of the study presented were compared with corresponding results obtained in other coastal and aquatic environments in the Red Sea.     

Effect of salinity on the concentrations of radioisotopes in the aquatic environment of a hypersaline coastal lagoon

Research of the effect of salinity on the fate of radionuclides has been focused on seas or estuarine systems while there is almost no information on marine environments with a salinity higher than that of sea water. The hypersaline Bardawil lagoon is a concentration basin, with evaporation exceeding precipitation. This study presents the characteristics of some environmental factors including salinity and their influence on the distribution of natural and artificial radionuclides in different compartments of the lagoon. The concentrations of ²³⁸U, ²³⁴Th, ²²⁸Ra and ¹³⁷Cs in sediments show some degree of dependency on the water's salinity. Migration of these radionuclides in the lagoon's sediments must take place from high salinity to low-salinity regions. Cluster analysis revealed the data structure for sediment by separating ¹³⁷Cs and ⁴⁰K from ²³²Th, ²²⁶Ra, and ²³⁴Th and for sand by separating ⁴⁰K from the other radioisotopes.     

Anomalous ratios of radioisotopes in PM10 as tracer of global fallout impact in the centre of Mexico

The monitoring and evaluation of radioactive content in samples of PM₁₀ aerosols have been investigated. The specific radioactivity concentrations (SRC) of ²³⁴U, ²³⁵U, ²³⁸U and ²³²Th were determined using inductively coupled plasma-sector field mass spectrometry in 13 samples collected in Mexico City and 8 samples collected in Cuernavaca in the centre of Mexico. The SRC of the radioisotopes analysed in PM₁₀ were larger than those reported in PM_2.5. The enrichment factor was greater than 5, indicating anthropogenic influences in both sites. The activity ratios of these isotopes in the samples were determined. The ²³⁵U/²³⁸U ratio showed variations with respect to the natural value, while the ²³⁴U/²³⁸U and ²³²Th/²³⁸U ratios did not show any secular equilibrium in all sites, corroborating that the increase of uranium is not influenced by natural sources. The annual dose results obtained have no impact on health.     

Bladder wrack (Fucus vesiculosus) as a multi-isotope bio-monitor in an urbanized fjord of the western Baltic Sea

The spatial variations in the elemental and stable carbon, nitrogen, and sulphur isotope composition of bladder wrack (Fucus vesiculosus) growing along the shore line of the semi-enclosed urbanized Kiel Fjord (western Baltic Sea) was investigated at more than 60 sites. The analyses of the carbon-nitrogen-sulphur (CNS) stoichiometry and C and N stable isotope signature of F. vesiculosus displayed substantial differences between the north-western and the south-eastern parts of the Kiel Fjord. Different size classes displayed in part differences in C:N and C:S ratios, and the carbon isotope composition, reflecting the impact of the boundary conditions during growth. Whereas the sulphur isotope composition was controlled by the assimilation of seawater sulphate, the carbon isotope composition reflected the difference in the composition of surface waters. The δ¹⁵N values of the organic tissue tend to be an integrated monitor of anthropogenic impacts on the fjord. Results are compared to the composition of surface waters.     

Geological influence on the activity concentration of terrestrial radionuclides 226Ra, 232Th and 40K in the Jos Plateau,Nigeria

The Jos Plateau has been reported to have elevated levels of natural background radiation. A few earlier studies have measured the levels of natural radioactivity for specific locations in the area. Our interest is to investigate how geology of the study area influences the activity concentrations of natural radionuclides. Thus, the activity concentrations of terrestrial radionuclides in soil samples collected across the geological formations of the Jos Plateau were determined by gamma spectrometry technique. The mean activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K were found to exceed their corresponding world reference values of 35, 40 and 400?Bq?kg^?1, respectively. Data were compared using statistical methods, analysis of variance (ANOVA) and post hoc tests. The results revealed in some instances significant influences of geological types on the activity concentrations in the area. The spatial distribution maps of activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K were geostatistically interpolated by ordinary Kriging method using ArcGIS software.     

Determination of concentrations of fissionable elements in the Black Sea sediment samples before and after Chernobyl using neutron radiography method

The fissionable elements content, particularly uranium, of the Blask Sea sediment samples obtained in 1978 and 1989 as surfacial sediments were determined by neutron radiography using solid state nuclear track detectors (SSNTDs).     

春季南黄海表层海水中二氧化碳的分布特征及其影响因素

根据2007年4月南黄海区块(SYS)表层海水中二氧化碳分压(pCO₂)的连续走航数据,结合水温(T)、盐度(S)、叶绿素 (Chla)以及pH的同步观测资料,对该海域pCO₂分布特征及其主要影响因素进行了初步探讨。分析结果表明：春季南黄海pCO₂的范围在365.2~734.9 μatm之间,平均值为548.0 μatm;最高值出现在121.5°E,33.4°N海域,最低值出现在123°E,32.3°N海域。受海水中物理、化学和生物因素的综合影响,pCO₂的分布存在较大的不均匀性,总体上表现为西部高于东部,中间高于南北两边;在苏北浅滩和鲁南海区,pCO₂与水温的变化呈正相关关系,与盐度的大小呈明显的负相关关系,而在长江入海口变化趋势则相反;此外,在整个调查海区pCO₂与叶绿素、pH基本上呈负相关关系。研究将两台检测器串联进行互校,同时利用二氧化碳标准气体对其中一台仪器进行全程校准,可连续不间断观测海水和大气中的pCO₂。该方法操作简单,获得的数据准确可靠,可为节能减排能力建设提供技术支持。