Distribution and environmental impact of radionuclides in marine sediments along the Venezuelan coast

The activity concentrations of ¹³⁷Cs, ⁴⁰K, ²²⁶Ra and ²³²Th in Bq/kg from 42 marine sediment samples collected at nine sampling sites were determined in order to establish a radiological baseline along the Venezuelan coast. The radioactivity levels were determined by means of a gamma-ray spectroscopy system using a hyper-pure germanium detector in a low-background configuration. Particle size distribution and total organic matter content were also determined. Activity concentrations of ¹³⁷Cs were lower than the detection limit of the analytical technique (0.9 Bq/kg) in all studied sites. The results suggest that the variation of grain-size distribution is one of the most important factors influencing the spatial variations of ⁴⁰K, ²²⁶Ra and ²³²Th in sediments along the Venezuelan coasts. In all sampling sites, average concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th were lower than the world average values. Activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in coastal marine sediments along the Venezuelan coast could be considered to be low when compared with global average values, indicating that they are not apparently above of the range that might be considered normal or background. These results suggest that the studied sites do not pose any significant radiological threat to the population. The results attained in this study should be of considerable value as baseline data and background reference levels for Venezuelan coastlines.     

Lognormal distribution of natural radionuclides in freshwater sediments and coal-ash repositories

The distribution of natural radionuclides,⁴⁰K,²²⁶Ra, and²³²Th, in freshwater sediments and in coal-fired power-plant ash repositories has been tested for lognormality. Thereafter, lognormality for natural radionuclide concentration frequency distribution was accepted with a high probability. The lognormal natural radionuclide distribution in sediments and coal-ash indicated single population groups. The anthropogenic modifications of the natural radionuclide concentrations in the environment are indicated. The adsorbed dose rates, in mGy y^–1, in air from gamma field of the natural radionuclides were calculated.     

Geochemical aspects and distribution of long-lived radionuclides in marine sediments from Palomares

The main objective of this paper is to point out problems associated with interpretation of bioassay monitoring in view of the existing biokinetic models. The exposure to thorium in Brazil is given in this paper as an example of the seriousness of the problem.     

Temporal evolution of lead isotope ratios and metal concentrations in sediments of the north Aegean Sea,in Turkish coast

In present research, fifteen surficial and two profile sediment samples were studied in terms of sediment chronology and pollution degree on the ground of pollution indexes such as enrichment factor (EF), contamination factor (CF), Pollution Load Index (PLI) and lead isotope ratios (²⁰⁶Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁶Pb). Lead-210 (polonium-210) activity concentrations were measured by utilizing alpha spectrometry. Sediment chronology was determined via modified CRS mathematical model. Average mass accumulation rates are 0.301 and 0.227 g cm^?2 year^?1 in Bak?rçay River mouth and Ayval?k offshore stations respectively. Mass accumulation rates do not display the systematic increases along the cores from bottom layers to top layers. In Bak?rçay River mouth station ²¹⁰Pb flux is higher than the range of global atmospheric ²¹⁰Pb flux value. Due to the high CF and EF values of Sr both of stations have hydrothermal features. Ayval?k offshore station has displayed Na, Cd pollution since 1945, but Na, Cd, As, Mo, Ag pollutions have existed in Bak?rçay River mouth station since 1983 in terms of CF and EF values. According to PLI index, Bak?rçay River mouth station has “starting level pollution” degree and it displayed an “acute corruption” in 1981. ²⁰⁶Pb/²⁰⁷Pb ratios range from 1.17 to 1.25, ²⁰⁸Pb/²⁰⁶Pb ratios range from 1.99 to 2.16 in study area. When ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb ratios are evaluated with together, it is seen that both of the stations have had the natural (geologic) sediments since 2011.     

Vertical distribution of the natural and artificial radionuclides in various soil profiles to investigate soil erosion

Vertical distributions of ¹³⁷Cs and ²¹⁰Pb in soil profiles were examined to study their availability in soil erosion at Gökova region where there exists intensive agricultural activities on sloppy fields. Since the mobility of these radionuclides depend on soil characteristics, soil samples were analyzed also for their physical and chemical properties. From ¹³⁷Cs inventories measured, erosion rates for cultivated and disturbed (no cultivation) soils were calculated to range from 79.1 to 6.5 t^.ha^-1.y^-1 and from 79.9 to 3.5 t^.ha^-1.y^-1, respectively. The ²¹⁰Pb technique is found to be not suitable for erosion determination for this area, presumably due to the coal-fired power plants operating in the region.     

Depth-wise distribution of 238U, 232Th and 40K in sand samples of high background radiation areas (Tamilnadu coast), India

Journal of Radioanalytical and Nuclear Chemistry - To understand the depth wise distribution of the primordial radionuclides, especially in high background radiation areas, their radioactivity...     

Activity concentration of some anthropogenic radionuclides in the surface marine sediments near the Saudi coast of the Arabian (Persian) Gulf

Activity concentrations of some anthropogenic radionuclides (⁹⁰Sr, ¹³⁷Cs, ²³⁸Pu, ^239+240Pu and ²⁴¹Am) have been measured in the surface of marine sediments along the Saudi coast of the Arabian (Persian) Gulf. The samples were collected at different locations and water depths. The spatial distribution of the concentrations of the measured radionuclides showed a heterogeneous pattern and is independent of location or water depth. The obtained results are discussed and some conclusions are drawn.     

Intake of 210Po, 234U and 238U radionuclides with beer in Poland

²³⁸U, ²³⁴U and ²¹⁰Po activity concentrations were determined in beer in Poland by alpha-spectrometry with low-level activity silicon detectors. The results revealed that the mean concentrations of ²³⁸U, ²³⁴U and ²¹⁰Po in the analyzed beer samples were 4.63, 4.11 and 4.94 mBq·dm⁻³, respectively, the highest in Tyskie (5.71 for ²¹⁰Po, 5.06 for ²³⁴U and 6.11 for ²³⁸U) and the lowest in Lech (2.49 for ²¹⁰Po). The effective radiation dose due to uranium and polonium ingestions by beer was calculated and were compared to the effective radiation dose from drinking water. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study of apatite behaviour in the presence of the radionuclides U and Rn and local modification of their crystalline and electronic structure

The ability of apatites to retain radionuclides and improvement in this ability through annealing, has led us to carry out a study of apatite structure and microstructure. Band structure calculations for a number of reference apatites (fluorapatite; chloroapatite and bromoapatite) have been carried out. The results of these calculations show that the substitution on the A-site causes a slight change in the shape of the density of states without any Fermi level shift or bandgap change. However it has been noticed that a change occurred in the charge and potential distributions in the Ca II environment. The Mulliken population and the projected state density analysis are consistent with a highly ionic model for these apatites.     

Natural and artificial radionuclides in soils from Paraná State,Brazil

Soil samples from Paraná State, Brazil, were collected in 1991 and compared with others collected at the same location in March 1977 and at the end of 1983. Pedological analyses were practiced on these samples and¹³⁷Cs and²³²Th,²²⁶Ra and⁴⁰K activities were determined by gammaray spectrometry. A latitude dependence of¹³⁷Cs was found as well. It was impossible to determine the¹³⁷Cs contribution from Chernobyl nuclear accident because of low fallout and intense leaching, erosion and re-suspension in soils of regions with high annual precipitation. Natural radionuclides did not show such effects.     

Methodology for the U.S. Food and Drug Administration's radionuclides in foods program

The U.S. Food and Drug Administration (FDA) is responsible for the wholesomeness of the nation's food supply. The FDA modified its food monitoring program in January, 1973, to include radioactive isotopes. The methodology used to perform, analyses on these food products are taken from the standerd setting societies such as the AOAC International, American Society for Testing Materials and American Public Health Association Standard Methods. In addition, methods not tested by these societies are taken from the literature or from Department of Energy manuals such as the Health and Safety Laboratory and also from Environmental Protection Agency, Public Health Service, and Food and Agricultural Organization manuals. These include the methods for long-lived radionuclides such as tritium, strontium-90, cesium-137 and plutonium. Also, the short-lived radionuclides such as iodine-131, radiocesium, radiocerium and radioruthenium. In addition, they include the natural occurring radionuclides such as radium and uranium isotopes. The activity concentrations of gamma-emitters such as radiocesium, iodine-131 and radioruthenium are determined by gamma-ray spectrometry. This is done using intrinsic germanium detectors with the appropriate hardware and software. The alpha and “pure” beta-emitters are determined by various radiochemical methods and techniques. The radiochemical methodology and equipment used in analyzing these radionuclides are described and discussed. Also, the methodology and equipment for the gamma-emitters are described in more detail in this paper. In addition, the limits of detection for the methods used will be discussed.     

Bentonite stability,speciation and migration behaviour of some critical radionuclides

The contribution is focused on chemical, geochemical and mineralogical research of bentonite stability with the aim to determine the effect of saturation medium composition and loading by heat on bentonite stability. The main part of the research is directed to the experimental results of bentonite and bentonite leachate samples obtained for the bentonite interaction under laboratory experiments. Computer-modeling methods were used to calculate equilibrium thermodynamic principles, the distributions of predominant aqueous species, and potential solubility controls for the environmentally important oxidation states of each investigated radioactive contaminants. The Eh–pH diagrams of individual chemical species of the tested radionuclides were calculated by the geochemical software tool Geochemist’s Workbench that included the actual chemical compositions of the solid–liquid systems under the given experimental conditions. It was confirmed that smectites are transformed to more stable silicate phases, such as illite/smectite mixed layers, illite. The data obtained from the model calculations conform with experimental results. The effect of the variable aqueous phase composition on bentonite stability using Ca–Mg and Na–Ca bentonites for the experiments was studied. The synthetic granitic waters with the higher concentration of the K⁺ and Mg²⁺ cations were applied for the study of bentonite stability.     

Peculiarities of the distribution of man-made radionuclides in several European seas.

Results of a study on the distribution of the man-made radionuclides 137Cs and 90Sr in the surface waters of several European seas are presented. Based on an analysis of the ratio of these two radionuclides, an attempt was made to isolate the 'Chernobyl water' and to estimate the contribution of 'Chernobyl radioactivity' to the total radioactivity in the waters of the seas investigated.     

Layout of the artificial coast in Lianyungang and its implementation

The “artificial coast” refers to a coast section, with considerable spatial dimension, reformed by human activities. The purposes of coastal reform may be diversified. It should be consistent with the economic principles and must lay emphasis on the improvement of coastal ecosystems, and the affinity of man to marine environment. One of the basic studies in the artificial coast planning is to construct the dynamic model of coastal erosion and accretion. From such understandings, the West Great Seawall in Lianyungang can be considered as a successful project in artificial coast engineering.

     

Layout of the artificial coast in Lianyungang and its implementation

The "artificial coast" refers to a coast section, with considerable spatial dimension, reformed by human activities. The purposes of coastal reform may be diversified. It should be consistent with the economic principles and must lay emphasis on the improvement of coastal ecosystems, and the affinity of man to marine environment. One of the basic studies in the artificial coast planning is to construct the dynamic model of coastal erosion and accretion. From such understandings, the West Great Seawall in Lianyungang can be considered as a successful project in artificial coast engineering.     

Distribution of radionuclides and elements in Cubatão River sediments

Summary Cubat?o River is located in Santos Basin, S?o Paulo State, Brazil. This region is characterized by the occurrence of estuaries and mangrove. Due to its location, near the coastal line, it is also an important industrial area, where phosphate fertilizer plants, petrol refineries, and chemical and steel industries are present. Such human activities contribute to the enhancement of elemental composition in sediments and, in some cases, also increase the radionuclide concentrations, the so called Technologically Enhanced Natural Occurring Radioactive Materials (TENORM). The contamination of land and sediments by TENORM is of major concern. The activity concentration of U and Th series radionuclides was determined in five sediment samples from Cubat?o River. The activity concentration ratio was also determined. Equilibrium was observed for the ratio ²³⁴U/²³⁸U. The activity ratios of Th/²³⁸U, ²²⁸Ra/²²⁶Ra and ²¹⁰Pb/²²⁶Ra were higher than the unity. In the first two cases, the observed values are due to the higher activity of Th in the sediment and in the last case are probably due to the atmospheric deposition of ²¹⁰Pb.     

Distribution of some natural and anthropogenic radionuclides in Sudanese harbour sediments

The distribution of some natural and anthropogenic radionuclides (²²⁶Ra,²²⁸Ra,²¹⁰Po,⁴⁰K,¹³⁷Cs) in surface marine sediments from the harbours at Port Sudan and Sawakin on the Sudanese coast of the Red Sea has been investigated using α-spectrometry and direct high-resolution γ-spectrometry. The prime ams were to assess the levels of radioactivity and the influence of factors such as dredging and the organic matter content of the sediments on the distribution pattern of the radionuclides. The results have been evaluated and the leves indicate the absence of any possible enhancement by anthropogenic influx from the hinterland. The spatial distribution pattern is more heterogeneous in Sawakin harbour where some parts have recently been dredged and the sludge is removed to maintain the required depth. The data also show an insignificant relationship between the activity concentrations of all the radionuclides and the content of organic matter in the sediments.