Gamma-emitting radionuclides in the shallow marine sediments off the Sindh coast, Arabian Sea

Determination of gamma emitting radionuclides in shallow marine sediments off the Sindh coast has been carried out using a gamma spectrometry technique. The activity concentration measured in various sediment samples off the Sindh coast has been found to vary from 15.93 +/- 5.22 to 30.53 +/- 4.70 Bq kg(-1) for 226Ra, from 11.72 +/- 1.22 to 33.94 +/- 1.86 Bq kg(-1) for 228Ra and from 295.22 +/- 32.83 to 748.47 +/- 28.75 Bq kg(-1) for 40K. The calculated mean values of radium equivalent activity, absorbed dose rate and effective dose are 98 Bq kg(-1), 49 nGy h(-1) and 0.06 mSv y(-1), respectively. No artificial radionuclide was detected in the samples measured from the study area. As no data on radioactivity of the coastal environment of Pakistan are available, the data presented here will serve as baseline information on radionuclide concentration in shallow sea sediments off the Sindh coast. The data will also be useful for tracking pollution inventories from unusual radiological events (if any) in the territorial waters of the study area. Further, the information presented will contribute to modelling of a regional radioactivity database from the perspectives of the International Atomic Energy Agency's Asia-Pacific Marine Radioactivity Database and Global Marine Radioactivity Database.     

Activity concentrations of natural radionuclides in the sediments of Ogun River, Southwestern Nigeria

The concentrations of naturally occurring radionuclides in the sediments of the Ogun River in Southwestern Nigeria were measured using NaI(Tl) gamma-ray spectrometry. The measurements were made in an effort to better understand the spatial distribution of natural radioactivity and to form a database of radioactivity levels of the Ogun River. The total average activity concentrations of (40)K, (226)Ra and (232)Th in the sediment samples representing the whole Ogun River from the upper region through the middle to the lower region of the river were 499.476±59.167, 12.649±3.476 and 11.774±5.126, respectively. The range of the activity concentrations of (40)K, (226)Ra and (232)Th for the Ogun River were found to be from 370.969±19.261 (at Olopade) to 608.023±24.658 (at Owere), 5.567±2.359 (at Ekerin) to 20.395±4.516 (at Sokori) and 5.037±2.244 (at Mile 12-Maidan) to 23.096±4.806 (at Sokori). The values obtained were compared with internationally accepted values. No man-made radionuclides were detected at any of the locations.     

Speciation of Zr(IV) radionuclides in solutions

The speciation of Zr(IV) radionuclides at their concentration of ～10^?13 M in the solution was studied. The pH ranges where Zr(IV) exists as ions or as pseudocolloids were determined. The Zr⁴⁺ hydrolysis yields Zr(OH)³⁺ and Zr(OH) ₂ ²⁺ complexes. Their stability constants were calculated. At [Zr(IV)] > 1 × 10^?5 M, binuclear hydroxo complexes Zr₂(OH) _z+ ^x are formed.     

Speciation of Cr(III) radionuclides in solutions

The speciation of Cr(III) radionuclides in solutions within the concentration range 10^?6–10^?2 M at pH 1–12 was studied. Adsorption on the glass surface, ion exchange, migration in the electric field, centrifugation, dialysis, and ultrafiltration were used. It was found that, at a concentration of 10^?6 M at pH 1.0–4.4, Cr(III) exists in the solution as a monomeric species, and at pH > 4 it exhibits colloidal properties. At pH 1.0–3.4, Cr(III) exists in form of hydrated cations Cr(H₂O) ₃₊ ⁶ . At pH > 3.4, they are hydrolysed with formation of mononuclear hydroxo complexes Cr(OH)²⁺ [K _h (3.35 ⊥ 0.15) × 10^?5]. At the Cr(III) concentration exceeding 1 × 10^?4 M, binuclear hydroxo complexes Cr₂(OH)_q are formed.     

Modeling the long-term leaching behavior of (137)Cs, (60)Co, and (152,154)Eu radionuclides from cement-clay matrices

Leaching characteristics of some radionuclides that are commonly encountered in radioactive waste streams from immobilized waste matrices in different cement-clay grouts have been assessed to investigate the influence of the clay additives on the leaching behavior of the solid waste matrices. The International Atomic Energy's Agency (IAEA) standard leach method has been employed to study the leach pattern of (137)Cs, (60)Co, and (152,154)Eu radionuclides immobilized in ordinary Portland cement (OPC), OPC-bentonite, and OPC-red clay grouts. The examination of the leaching data revealed that adding clays to OPC reduces the leach pattern as OPC-bentonite相似文献   

Speciation of artificial radionuclides 60Co, 137Cs, 152Eu, and 241Am in bottom sediments of the Yenisei river

The speciation of artificial radionuclides ⁶⁰Co, ¹³⁷Cs, ¹⁵²Eu, and ²⁴¹Am in surface layers of bottom sediments of the Yenisei river, collected within the near zone of impact of the Mining and Chemical Combine (Rosatom), was studied. In these samples the radionuclides ⁶⁰Co, ¹⁵²Eu, and ²⁴¹Am are mainly associated with fractions of humic and fulvic acids. The fraction of ¹⁵²Eu associated with nonsilicate iron is approximately 92%. The migration capability of radionuclides collected near the Atamanovo settlement decreases in the order ¹⁵²Eu > ²⁴¹Am > ⁶⁰Co > ¹³⁷Cs. For samples collected near Bol’shoi Balchug settlement, this order is as follows: ¹⁵²Eu ≈ ²⁴¹Am > ⁶⁰Co > ¹³⁷Cs. The presence of radionuclide-bearing micro-particles in bottom sediments considerably complicates the distribution of radionuclides, in particular, of ²⁴¹Am and ¹³⁷Cs, among migration forms.     

Assessment of the radiological hazards due to naturally occurring radionuclides in soil samples collected from the north western areas of Pakistan

(226)Ra, (232)Th and (40)K were measured in soil samples, these were collected from different localities of the North West Frontier Province and Federally Administered Tribal Areas, Pakistan. In order to measure the specific activities in these samples P-type coaxial high purity germanium based gamma-ray spectrometer was used. Average values of the measured activities of (226)Ra, (232)Th and (40)K were 26 +/- 11, 39 +/- 17 and 485 +/- 177 Bq kg(-1), respectively. Average radium equivalent activity was found to be 122 +/- 42 Bq kg(-1). External and internal hazard indices were also calculated and found to be 0.33 +/- 0.12 and 0.40 +/- 0.14, respectively. Average effective dose received due to gamma rays was 0.34 +/- 0.12 mSv y(-1). Measured natural radioactivity, hazard indices and effective doses received by the population were found within the recommended limits. The aim of this work was to make a baseline data of natural radioactive elements for the soil of the area and to assess it radiological significance if used as a building material for the construction of houses.     

Medically used radionuclides (131I, 99mTc) in the urban sewage system: the case of the Daejeon metropolitan city, Korea

In order to assess the behaviour of radioactivity (specifically (131)I concentrations in wastewater and sludge at sewage treatment plant) discharged into municipal sewage by therapy patients receiving treatment, the use of radiopharmaceuticals in four hospitals was quantitatively evaluated and the patients were classified by their residence. (131)I concentrations were estimated using a simple assumption model for radioiodine treatments of 94 patients, and measured by HPGe in inflow points, respectively. A good agreement was found between (131)I concentrations estimated with the model and those measured in the inflow points at the sewage treatment plant.     

Choice of optimal conditions for the recovery of Fe(III) radionuclides from solutions

Speciation of Fe(III) radionuclides in aqueous solutions was examined as applied to the choice of optimal conditions for their recovery. To attain the required level of radionuclide concentration in discharged waters, it is necessary to combine several treatment methods: sorption and membrane filtration, or sorption and centrifugation. The suggested procedures correspond to the occurrence of Fe(III) in solutions in micro- and macroconcentrations.     

Speciation of <Superscript>226</Superscript>Ra in seabed sediments formed in hydrothermal cold fluid zones (Deryugin Deep,Sea of Okhotsk)

Specific features of the behavior of Ra in seabed sediments from hydrothermal cold fluid zones were considered. It was shown that increased content of ²²⁶Ra in sediments is associated with accumulation of fine-grained Mn hydroxides in the surface oxidized layer of the sediment. These hydroxides, formed in the zone of contact of reduced Mn with bottom water, act as the sorption matrix with which ²²⁶Ra is efficiently removed from bottom water to be further accumulated in the surface layer of the sediments. It was found that 75% of ²²⁶Ra in the sediment is that sorbed from seawater with Mn hydroxide. The proportion of ²²⁶Ra coprecipitated with Ba does not exceed 4%.     

Impregnated activated carbon for the adsorption of Gd(III) radionuclides from aqueous solutions

Activated carbons (ACs) impregnated by FeCl₃, SnCl₄ and ZnCl₂ are used as adsorbents for the removal of Gd(III) radionuclides from aqueous solutions. Adsorption of Gd(III) is investigated as a function of pH, concentration of adsorbate, contact time, ionic strength and temperature. Gadolinium is efficiently removed (R%?>?95%) at pH values ≥4.8 (for FeAC and SnAC) and 2.9 (for ZnAC). The pseudo-first-order, the pseudo-second-order and Elovich kinetic models are used to analyze the kinetic data of Gd(III), at the studied concentrations (30, 100 and 200?mg/L) onto the employed materials. Of these models, Elovich is the only one that well-fitted the experimental kinetics onto the applied materials at all of the studied Gd(III) concentrations. Equilibrium data of Gd(III) are analyzed by the Freundlich, Temkin, Dubnin–Radushkevich (D-R) and Redlich–Petrson isotherm models. The adsorption efficiency of Gd(III) onto FeAC and SnAC is deleteriously affected by increasing the ionic strength, while adsorption onto ZnAC is unaffected. The thermodynamic parameters are calculated and it is revealed that the adsorption of Gd(III) onto the employed materials is an endothermic process. Desorption studies of Gd(III)-loaded ACs are performed using different desorbing agents (HCl, ZnCl₂, FeCl₃ and SnCl₄) at various concentrations (0.0005, 0.0025, 0.01 and 0.025?M).     

Distribution of technogenic radionuclides in alluvial sediments and among fractions of the soil in the near zone of the krasnoyarsk mining and chemical combine

Distribution of technogenic radionuclides in the landscape of the Berezovyi Isl. (Yenisei River) is studied. The observed variations in the density of radioactive contamination are associated with nonuniform lithologic composition of soil-forming rocks and also with different duration of the flooding periods. Radionuclide distribution in alluvial sediments and among fractions of the soil in the region of the Balchug settlement is analyzed, making emphasis on the contribution of the clay fraction to accumulation of radionuclides.Translated from Radiokhimiya, Vol. 46, No. 5, 2004, pp. 471–476.Original Russian Text Copyright © 2004 by Linnik, Volosov, Korobova, Borisov, Potapov, Surkov, Borghuis, Brown, Alekseeva.     

Plutonium isotopes in marine sediments and some biota from the Sudanese coast of the Red Sea

Measurements of (239+240)Pu and (238)Pu were carried out on marine biota as well as on sediments from the fringing reefs area extending towards north and south (Flamingo Bay) of PortSudan harbour. The analyses were performed using radiochemical separation and alpha spectrometry. The range of the activity concentrations in marine sediments, in mBq kg(-1) dry weight, was found to be from 5.10 to 82.00 for (239+240)Pu and from 0.89 to 8.63 for (238)Pu. Corresponding activity concentrations of (239+240)Pu and (238)Pu in sediments from the harbours at PortSudan and Sawakin were 53-301 and 8.29-28.6 (PortSudan) and 163-343 and 4.7 (Sawakin), respectively. The higher values for plutonium in marine algae suggest their suitability as an indicator species for monitoring purposes. The results obtained are generally lower than those found by other studies and show that the Red Sea environment is mildly affected by plutonium contamination. Activity ratios of plutonium isotopes confirm that the existence of plutonium in the Red Sea is mainly due to atmospheric global fallout.     

The State of Disequilibrium between U and Th Series Isotopes in Marine Sediments from the Sudanese Red Sea Coast

The geochemical behavior of U, Th series nuclides in surface marine sediments collected fromthe Red Sea coastal environment of Sudan was examined using daughter/parent and nonisotopic activity ratios. Pronounced anomalous behavior of several series of nuclides has been observed, particularly at shallower depths. On the average, the ²³⁴U/²³⁸U ratio is fairly constant and close to 1.13, suggesting scavenging of ²³⁴U from the overlying water column. In shallow-water sediments collected from the biologically productive area of the fringing reef and from the tidal-flat of Sanganeb atoll, compared to harbor and deep-sea sediments, ²³⁸U was found in large excess relative to ²³²Th. The ²²⁸Th/²³²Th disequilibrium indicates rapid sedimentation at shallower sites, which agrees well with data reported in the literature for similar environments. Depletion was observed of precursor thorium isotopes (²³⁰Th, ²³²Th) with respect to their mobile daughter isotopes of radium (²²⁶Ra, ²²⁸Ra). On the other hand, there is surface enrichment of ²²⁸Th and ²¹⁰Po with respect to their progenitors ²²⁸Ra and ²²⁶Ra, as demonstrated by the ²²⁸Th : ²²⁸Ra and ²¹⁰Po : ²²⁶Ra activity ratio, which is greater than unity in all the sediments analyzed. The ²¹⁰Po/²²⁶Ra ratio is fairly constant (average 3.2).     

Measurement of radioactivity in the soil of Bahawalpur division, Pakistan

Bahawalpur is the largest division of the Punjab province in Pakistan. It is larger than many countries of the world. Gamma activity from the naturally occurring radionuclides namely 226Ra, 232Th, the primordial radionuclide 40K and the artificial radionuclide 137Cs was measured in the soil of the Bahawalpur division using gamma spectrometry technique. The mean activity of 226Ra, 232Th, 40K and 137Cs were found to be 32.9 +/- 0.9, 53.6 +/- 1.4, 647.4 +/- 14.1 and 1.5 +/- 0.2 Bq kg(-1), respectively. The mean radium equivalent activity Raeq, external hazard index, internal hazard index and terrestrial absorbed dose rate for the area under study are 158.5 +/- 4.1 Bq kg(-1), 0.4, 0.5 and 77.32 nGy h(-1), respectively. The annual effective dose equivalent to the public was found to be 0.5 mSv.     

Assessment of metal element concentrations in mussel (M. Galloprovincialis) in Eastern Black Sea, Turkey

The main goal of this work is to determine the effects of pollution of copper, lead and zinc mines on the Eastern Black Sea. Metal and heavy metal concentrations in the Eastern Black Sea mussels were measured using Energy Dispersive X-ray Fluorescence (EDXRF) and Flame Atomic Absorption Spectroscopy (FAAS). The analytical results showed that the tissue of mussel in Eastern Black Sea contains K, Ca, Fe, Cu, Zn, and Sr elements, and the shell of mussel contains Ca, Cu, Sr, and Ba elements. Due to the detection limit of EDXRF, the mussels were analyzed with FAAS for Cr, Mn, Ni, Cd and Pb elements. An ANOVA and Pearson correlation analyses were performed. The results showed although that the mean concentrations of Cu and Zn for the tissue of the mussels were markedly above the permissible levels of the Turkish regulations, Zn concentration is in the limits of the Food and Agriculture Organization (FAO).     

Analysis of induced radionuclides in low-activation concrete (limestone concrete) using the 12 GeV proton synchrotron accelerator facility at KEK

22Na is one of the long-lived radionuclides induced in shielding concrete of a beam-line tunnel of a high-energy particle accelerator facility and poses a problem of radiation wastes at the decommissioning of the facility. In order to estimate the 22Na concentration induced in shielding concrete, chemical reagents such as NaHCO3, MgO, Al203, SiO2 and CaCO3 were irradiated at several locations in the beam-line tunnel of the 12 GeV proton synchrotron accelerator at KEK, and the 22Na concentrations induced in those chemical reagents were measured. Low-activation concrete made up of limestone aggregates was also irradiated by secondary particles in the beam-line tunnel and the long-lived radionuclide, such as 22Na, concentrations induced in the concrete were measured. It was confirmed that 22Na concentrations induced in Mg, Al, Si and Ca were lower than that in Na, and that 22Na concentrations induced in the low-activation concrete was lower than those induced in ordinary concrete made up of sandstone aggregates.     

Natural and anthropogenic radionuclides in the granitic region of Kapidag peninsula, Western Anatolia, Turkey

Naturally occurring radionuclides of terrestrial origin (also called primordial radionuclides) are present in various degrees in all media in the environment. This study represents the reports on the natural and anthropogenic radionuclides in the Kapidag granitic region. For this purpose, activities of radionuclides in soil, beach sands and rocks of the region have been investigated to assess the radiological hazard of the natural radioactivity. The radium equivalent activities, the absorbed dose rates and the external hazard indexes have been calculated, and also in situ gamma dose rates have been measured in the region. The mean activities of (238)U, (232)Th and (40)K with the ranges were determined as 31.1±15.7 (12.1-71.9), 42.5±15.9 (19.7-94.9), 590.3±192.2 (184.7-892.5), in the soil, as 16.5±9.5 (4.9-40.8), 67.1±106.9 (18.5-433.0), 569.2±212.6 (162.0-821.1) in the sand and as 25.4±12.8 (4.8-50.7), 37.8±21.5 (4.5-96.7), and 592.4±285.5 (62.4-1121.6) Bq kg(-1) in the rocks, respectively. It was also observed that the average activities of (137)Cs were ranged 0-27.8 Bq kg(-1) in the soil and 0.6-3.8 Bq kg(-1) in the beach sands. The mean Ra(eq) activities of the rocks, sands and soil were found to be 125.1±59.5, 156.3±157.2 and 137.3±48.8 Bq kg(-1), respectively, lower than the recommended maximum value of 370 Bq kg(-1) with some exceptions. The maximum contributors to the total absorbed gamma dose rates in air were determined as (238)U (45%) for the beach sands, (238)U (40%) for the soil and (40)K (41%) for rocks. The average outdoor gamma dose rates for the soil due to terrestrial and cosmic radiations were found to be 64.6±22.7 and 47.1±9.6 nGy h(-1), respectively, with the total of 111.7±29.5 nGy h(-1) outdoor gamma exposure rate and the annual average effective outdoor gamma dose was calculated as 137±36.2 μSv for the region. The results of the study were discussed with similar studies in close regions and the worldwide averages.