Sedimentological study of a lagoon through natural radioactivity and <Superscript>137</Superscript>Cs determinations

Profiles of artificial fallout (such as ¹³⁷Cs) and natural radioactivity radionuclides in sediment cores are useful tools to study sedimentological properties of different aquatic environments as well as to evaluate average sedimentation rates. In the Portil lagoon, a small natural reservoir located in Huelva province (southwest of Spain), and through the analysis of ²¹⁰Pb, ²²⁶Ra, ¹³⁷Cs, ²³⁸U and ²¹⁰Po vertical profiles in sediment cores, it is shown how the accumulative or transport character of the collection zones may be inferred. In the accumulation zone of the lagoon the influence of focusing effects has been analysed and an average sedimentation rate has been determined through ²¹⁰Pb in one sediment core. This ²¹⁰Pb-sedimentation rate is consistent with sediment dating based on the ¹³⁷Cs data.     

Soil depth profile of 137Cs, 210Pb and 40K in Algeria

ABSTRACT

Three soil depth profiles of ²¹⁰Pb, ¹³⁷Cs and ⁴⁰K at different areas of Algeria were studied. The soil sampling areas are near the location where the French nuclear tests took place at 1960–1966. The two depth soil profiles were collected at Ghardaia region and the third one at Reggane region. The vertical distributions of radionuclides at the two soil depth profiles from Ghardaia region are different, probably due to the different soil composition. The soil depth profile from sandy soil show uniformity in the distribution of radionuclides without a clear maximum (peak). The soil depth profile that characterised by silty sand show a clear peak at 20–50?cm depth for all studied radioactive nuclides, while the observed activities are two times higher than the corresponding values in sandy soil samples. More specifically in Ghardaia region the ²¹⁰Pb, ¹³⁷Cs, ⁴⁰K activity concentrations ranged between 27 and 50?Bq?kg^?1, 0.2 and 3?Bq?kg^?1 and 75 and 90?Bq?kg^?1 respectively in sandy soil type and between 37 and 75?Bq?kg^?1, 4 and 6?Bq?kg^?1 and 140 and 180?Bq?kg^?1 respectively in silty sand soil type. Finally, the third depth soil profile collected from Reggane site presents a completely different distribution of the studied radionuclides. The activity concentrations of ²¹⁰Pb, ¹³⁷Cs, ⁴⁰K ranged between 37 and 51?Bq?kg^?1, 0.16 and 0.39?Bq?kg^?1 and 120 and 309?Bq?kg^?1 respectively. Three peaks in the ¹³⁷Cs distribution revealed, were most probably, Chernobyl related ¹³⁷Cs accounts for the surface peak, while the deeper peaks are connected to the weapons fallout.     

Radiometric and tephroanalysis dating of recent Ionian Sea cores

Summary An accurate dating of recent Ionian Sea sediment cores has been performed by the²¹⁰Pb radiometric method and by a detailed tephroanalysis. The markers of the historical volcanic eruptions which occurred in the Campanian area (Vesuvius, Phlegrean Fields, Ischia) during the last two millenia have been identified along the cores. Among the others, the famous Plinian Vesuvius eruption of 79 AD, which buried the Roman town of Pompei, has been recognized. Direct²¹⁰Pb dating is limited to the last two centuries. The tephroanalysis demonstrates that the sedimentation rate estimated by the²¹⁰Pb method is correct and it is constant, at least for the last 2 ky. The presence of the¹³⁷Cs peak due to the intense activity of nuclear-weapon testing in the atmosphere in 1963–64 AD assures that the top of the core is present and not disturbed. The high precision of the core dating allows to transform the depth scale into a time scale with an accuracy of ∼1%. The analysis of several cores taken in the same area demonstrates that the results presented here are of general validity, at least in this region. The carbonatic mud deposited in the last millennia in the Gallipoli Terrace can be successfully utilized for investigating the environmental conditions in the recent past.     

<Superscript>210</Superscript>Pb and <Superscript>210</Superscript>Po determination in environmental samples using liquid scintillation counting and alpha spectrometry

A simple radiochemical procedure has been developed to determine ²¹⁰Pb and ²¹⁰Po in environmental samples from the same matrix. Sediment samples are decomposed by leaching with mineral acids or by microwave digestion, while water samples are pre-concentrated. One part of the resulting solution, spiked with ²⁰⁹Po, is used for ²¹⁰Po determination by spontaneous deposition onto nickel disks (α-spectrometry). The other part is assayed for ²¹⁰Pb, separating the Pb either by anion-exchange (sediment samples), or by solvent extraction (water samples). The ²¹⁰Pb source is finally prepared by precipitation as oxalate and the chemical recovery determined by gravimetry. The ²¹⁰Pb activity concentration is determined by liquid scintillation. A standard sediment sample supplied by IAEA and spiked water samples were analysed to check the procedure. The ²¹⁰Pb and ²¹⁰Po measurements agreed well with the certifications, deviations being less than 10%. The mean recoveries for Pb and Po were (70±12)% and (77±8%) for sediments, and (70±10)% and (81±7)% for waters, respectively.     

Measurement of 137Cs in cultivated soils from two loess areas in Poland

In this paper, a vertical distribution of ¹³⁷Cs in agricultural soil was investigated. ¹³⁷Cs is an anthropogenic radioisotope which is strongly adsorbed in soil and can be used to study soil erosion. This paper presents some preliminary results of measurements of activity of ¹³⁷Cs in soil in Bia?a and Odonów areas. In both areas, the upper part of the soil profile was cultivated. The experimental results show that the vertical distribution of ¹³⁷Cs in agricultural soil is different from the vertical distribution of ¹³⁷Cs in undisturbed soil. The ¹³⁷Cs is more uniformly distributed in the cultivated soil layer than in an undisturbed site. Migration of ¹³⁷Cs below plough depth is limited. These data show that the depth distribution of ¹³⁷Cs in soil profiles for cultivated fields should be considered for precise determination of soil erosion.     

Spatial and seasonal variations in the stable C isotope composition of dissolved inorganic carbon and in physico-chemical water parameters in the Plitvice Lakes system

Plitvice Lakes waters were collected at 14 sampling points, including springs, tributaries and lakes, for the period 2002–2007. The results of the physical and chemical conditions of calcite precipitation as well as the δ¹³C values of dissolved inorganic carbon (DIC) were used to study the processes influencing calcite precipitation. Significant differences between spring, lake and stream waters as well as changes in the downstream direction were observed. The correlation between δ¹³C_DIC values and physico-chemical conditions for calcite precipitation showed that calcite precipitates in lake waters which are oversaturated with respect to CaCO₃ (I _sat values 4–10) and with δ¹³C_DIC values between?11.5 and?8.5 ‰. In spring waters, the δ¹³C_DIC values were more negative, from?14 to?12 ‰, and I _sat values of 1–2 indicated that equilibrium conditions for calcite precipitation were not attained. The downstream increase in δ¹³C_DIC correlated with the increase in the δ¹³C values of calcite in the lake sediments, suggesting that the freshwater calcite was mainly of autochthonous origin and precipitated within the water column in isotopic equilibrium with DIC.     

Radiological and hyperfine characterization of soils from the Northeastern region of the Province of Buenos Aires, Argentina

The activity concentrations of both natural (²³⁸U and ²³²Th chains and ⁴⁰K) and anthropogenic (¹³⁷Cs) radionuclides down along the soil profile have been determined in soil samples collected from inland and coastal areas of the La Plata River, located in the Northeastern region of the Province of Buenos Aires, Argentina. These studies were complemented with ⁵⁷Fe Mössbauer spectroscopy characterization, pH, texture and organic carbon content measurements. From Mössbauer results, the sample compositions differ from one area to the other. Spectra from both soil samples are dominated by the Fe^3+? paramagnetic signal. For soil samples from the coastal area, the ??-Fe₂O₃ contribution is lower, Fe₃O₄ was not detected, and the relative areas of each spectral contribution are nearly constant with depth. For samples from the inland area, the Fe^3+? paramagnetic fraction increases up to 82%, mainly at the expense of the magnetically ordered phase. The main observed activity originates from the decay of ⁴⁰K (540?C750 Bq/kg), followed by ²³⁸U (60?C92 Bq/kg) and ²³²Th (37?C46 Bq/kg) chains. The activity of ²³⁵U was in all the cases lower than the detection limit (L_D?=?0.02 Bq/kg). The only determined anthropogenic nuclide was ¹³⁷Cs, arising from the fallout of the Southern Hemisphere nuclear weapon tests. Three of the observed differences in the depth distributions can be described by the dispersion-convection model. A correlation between the natural nuclide activities and the Mössbauer relative fractions was found, whereas no correlation was found between the ¹³⁷Cs profile and the relative fraction of Fe₃O₄ or with other iron species.     

Isotope Geochemical Studies on Carbonates of Quaternary Glacio-Lacustrine Lake Sediments as indicators of Paleoenvironment

Selected silty “summer” and argillaceous “winter” layers of profiles of the rhythmically bedded glacio-lacustrine ice-marginal lake sediment of the Dehlitz-Leipzig varved clay (Leipziger Tieflandsbucht, Central Germany) have been examined for isotope composition (¹⁸O/¹⁶O, ¹³C/¹²C) of carbonate and organic fraction. In addition, mineralogical and grain size compositions were determined. The results show 1) a change in source of carbonate sediment (provenance) through time; 2) the oxygen isotope ratios differed between the “summer” and “winter” layers of varves couplets due to different rates of sedimentation; 3) anoxic events occurred in the lake; 4) carbon isotope ratios suggest organics in lake sediments which were derived from land and the primary productivity was low in the lake itself. In the study of cold-climatic lake sediments, isotope investigations can efficiently be used as additional paleosedimentological and facies indicators.     

The GaP(001) surface and the adsorption of Cs

GaP(001) cleaned by argon-ion bombardment and annealed at 500°C showed the Ga-stabilized GaP(001)(4 × 2) structure. Only treatment in 10^?5 Torr PH₃ at 500°C gave the P-stabilized GaP(001)(1 × 2) structure. The AES peak ratio $\text{P}\text{Ga}$ is 2 for the (4 × 2) and 3.5 for the (1 × 2) structure. Cs adsorbs with a sticking probability of unity up to 5 × 10¹⁴ Cs atoms cm^?2 and a lower one at higher coverages. The photoemission measured with uv light of 3660 Å showed a maximum at the coverage of 5 × 10¹⁴ atoms cm^?2. Cs adsorbs amorphously at room temperature, but heat treatment gives ordered structures, which are thought to be reconstructed GaP(001) structures induced by Cs. The LEED patterns showed the GaP(001)(1 × 2) Cs structure formed at 180°C for 10 h with a Cs coverage of 5 × 10¹⁴ atoms cm^?2, the GaP(001)(1 × 4) Cs formed at 210°C for 10 hours with a Cs coverage of 2.7 × 10¹⁴ atoms cm^?2, the GaP(001)(7 × 1) and the high temperature GaP(001)(1 × 4), the latter two with very low Cs content. Desorption measurements show three stability regions: (a) between 25–150°C for coverages greater than 5 × 10¹⁴ atoms cm^?2, and an activation energy of 1.2 eV; (b) between 180–200°C with a coverage of 5 × 10¹⁴ atoms cm^?2, and an activation energy of 1.8 eV; (c) between 210–400°C with a coverage of 2.7 × 10¹⁴ atoms cm^?2, and an activation energy of 2.5 eV.     

Radionuclides in deposition in the Ignalina NPP region in 2005

Results of radionuclide activity concentration measurements in deposition and ground-level air conducted at the station of the Institute of Physics situated 3.5 km from the Ignalina Nuclear Power Plant (Ignalina NPP) in 2005 are analyzed. Atmospheric depositional fluxes of ⁷Be, ⁶⁰Co and ¹³⁷Cs are estimated. Radionuclide particle deposition rates are calculated. The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model of the global dispersion and deposition is used to explain variations in the ¹³⁷Cs activity concentration in the ground-level air in the Ignalina NPP region in 2005. An increase in the ¹³⁷Cs activity concentration of up to 17.4 μBq m⁻³ on 30 October-5 November is studied. Modelling results show that the Chernobyl NPP Unit 4 Sarcophagus and the radiocaesium resuspension from the Chernobyl NPP accident polluted regions are sources of ¹³⁷Cs to the environment of the Ignalina NPP. Results on solubility in water of aerosols — carriers of ¹³⁷Cs — are discussed.     

Growth rates in modern speleothems from Santana Cave,Brazil, by the 210Pb-method

The Santana Cave is located at the Upper Ribeira Touristic State Park (PETAR-Parque Estadual Turístico do Alto Ribeira) in southern São Paulo State, Brazil. This paper describes ²¹⁰Pb activity concentration data in soda straw stalactites samples collected at Salão das Flores in Santana Cave that is a fossil tributary of the cave river. Non-expensive alpha counting following some analytical steps for extracting and depositing ²¹⁰Po were used for providing the ²¹⁰Pb data. In the analyzed samples, ²¹⁰Pb values of increasingly older samples fitted an exponential curve, thus suggesting that the production of ²¹⁰Pb has been constant with time. Also, the near-ideal fit indicated that the growth was uniform and there was no break in the continuous growth. The soda straw growth rates were determined from the best fit to the exponential curve through the ²¹⁰Pb activity concentration. The results of the measurements allowed estimate a longitudinal rate corresponding to 1.3 mm/yr and a lateral rate of 0.01 mm/yr, which permitted calculate times of 70 years and 317–498 years for their formation, respectively. The lateral growth rate is compatible with values from studies of chemical weathering rates held under laboratory and natural conditions.     

Speciation of radionuclides of the Chernobyl origin in aerosol and soil samples

Speciation of^134,137Cs,⁹⁰Sr,²³⁴U,²³⁸U,²³⁸Pu,^239,240Pu and²⁴¹Am was investigated in aerosol samples collected after the Chernobyl accident and in the Chernobyl soil. Sequential extraction experiments have shown a wide range of association of radionuclides, depending on sources, transformation perculiarities and radionuclide nature. Changes in speciation of¹³⁷Cs and⁹⁰Sr at various temperatures in the Chernobyl soil were analyzed. It was found that at 200°C–700°C a transformation of speciation of¹³⁷Cs took place and more available physico-chemical forms of Cs were formed. After heating at 900°C, up to 94% of¹³⁷Cs was found in the residual form and was not extractable even with 7 M HNO₃. Heating of the soil to 450°C and 900° C resulted in the formation of less available forms of⁹⁰Sr.     

137Cs and 40K in some traditional herbal teas collected in the mountain regions of Serbia

Herbal teas are an important part of traditional medicine in Serbia. The objective of the present study was to determine the activity concentrations of ⁴⁰K and ¹³⁷Cs in herbal tea, using the gamma spectroscopy method. The samples were collected during the period 2011–2012 in three mountain regions in Western and Central Serbia. The activity concentrations of ⁴⁰K and ¹³⁷Cs were found to be in the range of 130–1160 and 0.7–124 Bq kg^?1, respectively. The average annual effective dose equivalents from ingestion of ⁴⁰K and ¹³⁷Cs for an adult person consuming one cup of herbal tea daily were found to be 588.4–5250.2 nSv for ⁴⁰K and 4.0–706.1 nSv for ¹³⁷Cs. Our investigation showed that the herbal teas originating from Maljen, Zlatibor and Tara mountains are radiologically safe for human consumption.     

Cross-calibration between beta and gamma sources using quartz OSL: Consequences of the use of the SAR protocol in optical dating

The radiation dose delivered by the ⁹⁰Sr beta source of a TL-OSL reader and the one delivered by a ¹³⁷Cs gamma source were compared using OSL dating techniques and tools. Three sets of quartz of different origins (rock, sediment and loess) were studied and measured by the SAR protocol (Single aliquot regenerative dose protocol) after irradiations carried out either by the ⁹⁰Sr source or by a ¹³⁷Cs source. Measurements show that the values obtained by the SAR protocol must be corrected in order to provide an acceptable cross-calibration of the beta and gamma source. Once applied, measurement sets become self-consistent and compatible with expected values. The consequences of the above mentioned observations on the methodology of OSL dating are discussed and suggest that a mixed protocol be used including both the SAR protocol and an added dose techniques close to the SARA protocol (Single aliquot regenerative and added dose protocol).     

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.     

Isotopic fingerprints of the Lake Żabińskie (NE Poland) hydrological system on contemporary carbonates precipitated in the lake

An isotopic monitoring was undertaken in 2012–2014 at Lake ?abińskie (Mazurian Lakeland, NE Poland). The aim was to identify the factors and processes controlling an isotopic composition of the lake water and to explore the mechanism responsible for recording the climatic signal in stable isotope composition of deposited carbonates. δ¹⁸O and δ²H in the precipitation, lake water column, inflows and outflow, δ¹⁸O and δ¹³C in the carbonate fraction of sediments trapped in the water column were recorded with monthly resolution. A relationship between δ¹⁸O and δ²H in local precipitation was used to estimate the local meteoric water line. The dataset obtained for the water enabled to identify the modification of the water’s isotopic composition due to evaporation, connected with seasonal lake water stratification and mixing patterns. Statistically significant correlation coefficients suggest that the δ¹⁸O of the carbonate fraction in the sediment traps depends on the δ¹⁸O of rainfall water and on air temperature. The fractionation coefficient α shows that in summer months the carbonate precipitation process is closest to equilibrium. As expected for an exorheic lake, no significant correlation was observed between δ¹⁸O and δ¹³C in precipitated carbonate.     

Study of spin-orbit interaction of13C and15N nuclei in14C induced transfer reactions on138Ba

Angular distributions of single nucleon transfer reactions populating single particle states in the reactions¹³⁸Ba(¹⁵C,¹⁴N)¹³⁷Cs and¹³⁸Ba(¹⁴C,¹³C)¹³⁹Ba have been studied. The shapes of the angular distributions show differences for different final configurations. Using the reaction asymmetry it is possible to describe these differences consistently for all transitions by a spin-orbit potential. The polarisation of the outgoing fragments is discussed and its dependence on final configurations is explained. The spin-orbit potentials deduced from the reaction asymmetry are large, as compared to predictions of folding potentials. They are, however, consistent with measurements of spin-flip probabilities. The origin of theL-S interaction is to be found in coupling effects of second order in the heavy ion reaction.     

Fe2+/Fe3+ ratios in bottom sediments of some lakes in British Columbia,Canada

Fe²⁺/Fe³⁺ ratio versus sediment depth values have been determined for ten lakes in British Columbia. The values often reflect the local topography of the lakes, the weathering history of the deposited minerals, and the diagenesis of the minerals after deposition in the lake.     

Monte Carlo modelling of human body for dose conversion coefficients of 137Cs in soil of the Eastern Black Sea region of Turkey

Absorbed dose conversion coefficients for a human body standing on the soil surface were calculated for ¹³⁷Cs in the soil of Eastern Black Sea region of Turkey using the Monte Carlo simulation method. The results were given in nGy h^?1 per Bq cm^?2 as a function of depth. Simple numerical integration of this function multiplied with the known specific activity as a function of depth gives the absorbed dose conversion coefficients for any distribution of ¹³⁷Cs in soil. Gaussian distribution of ¹³⁷Cs in the soil was considered for calculations.     

The beta branching ratio and conversion coefficients in the137Cs decay

The decay of¹³⁷Cs has been reinvestigated using several precision counting methods. The emission rate ofβ-particles plus internal conversion electrons was measured by the 4π-proportional counter method using vacuum evaporated sources free of self-absorption and checked by the liquid scintillation method. TheK-conversion coefficient was determined by the electron X-ray coincidence method using a magnetic spectrometer and a high resolution Si(Li) detector. TheK/(L+M+...) conversion ratio and a second less accurate value for the β-branching ratio were obtained from the recorded electron spectra. Theγ-ray emission rate of all sources was determined to within ±0.14%, on the average, with a calibrated NaI(Tl) crystal detector. As results the intensity of theβ-decay to the ground state of¹³⁷Ba could be determined to (5.4±0.3)% of the¹³⁷Cs decays, theK-conversion coefficient to 0.0916±0.0004, and theK/(L+M+...) conversion ratio to 4.41±0.04. From these values the γ-ray emission intensity is (85.1±0.4)% of the¹³⁷Cs decays and theK X-ray emission intensity is (8.13±0.10)% of the emittedγ-rays. All errors are discussed in detail.