Simultaneous measurements of cosmogenic radionuclides 32P, 33P and 7Be in dissolved and particulate forms in the upper ocean

Radionuclides' Recovery from Seawater Using FIC and FIC A Sorbents

To solve radioecological and oceanological problems (estimate the vertical transport, flows of particulate organic carbon, phosphorus biodynamics, submarine groundwater discharge, etc.), it is necessary to determine the natural values of the radionuclides' activity in seawater and particulate matter. For the first time, the radionuclides' sorption from seawater was studied using sorbents based on activated carbon modified with iron(III) ferrocyanide (FIC) and based on activated carbon modified with iron(III) hydroxide (FIC A-activated FIC) obtained by FIC sorbent treatment with sodium hydroxide solution. The possibility of trace amounts of phosphorus, beryllium, and cesium recovery in laboratory conditions has been investigated. Distribution coefficients, dynamic, and total dynamic exchange capacities were determined. The physicochemical regularities (isotherm and kinetics) of sorption have been studied. The results obtained are characterized via Langmuir, Freindlich, and Dubinin-Radushkevich isotherm equations, as well as pseudo-first and pseudo-second-order kinetic models, intraparticle diffusion, and the Elovich model. Under expeditionary conditions, the sorption efficiency of ¹³⁷Cs using FIC sorbent, ⁷Be, ³²P, and ³³P-using FIC A sorbent with a single-column method by adding a stable tracer, as well as the sorption efficiency of radionuclides ²¹⁰Pb and ²³⁴Th with their natural content by FIC A sorbent in a two-column mode from large volumes of seawater was assessed. High values of efficiency of their recovery by the studied sorbents were achieved.

7Be Recovery from Seawater by Sorbents of Various Types

For the first time, a comprehensive study of sorbents based on manganese dioxide was carried out for beryllium sorption from seawater in laboratory and expeditionary conditions. The possibility of using several commercially available sorbents based on manganese dioxide (Modix, MDM, DMM, PAN-MnO₂) and phosphorus(V) oxide (PD) for ⁷Be recovery from seawater for solving oceanological problems was evaluated. Beryllium sorption under static and dynamic conditions was studied. The distribution coefficients and dynamic and total dynamic exchange capacities were determined. Sorbents Modix (K_d = (2.2 ± 0.1) × 10³ mL/g) and MDM (K_d = (2.4 ± 0.2) × 10³ mL/g) showed high efficiency. The dependences of the degree of recovery on time (kinetics) and the capacity of the sorbent on the beryllium equilibrium concentration in solution (isotherm) were established. The data obtained were processed using kinetic models (intraparticle diffusion, pseudo-first and pseudo-second orders, Elovich model) and sorption isotherm equations (Langmuir, Freindlich, Dubinin-Radushkevich). The paper contains results of expeditionary studies to evaluate the sorption efficiency of ⁷Be from large volumes of the Black Sea water by various sorbents. We also compared the sorption efficiency of ⁷Be for the considered sorbents with aluminum oxide and previously obtained sorbents based on iron(III) hydroxide.

Assessment of Seasonal Variability in Phosphorus Biodynamics by Cosmogenic Isotopes 32P, 33P around Balaklava Coast

The sorption efficiency of phosphorus from seawater by aluminum oxide and sorbents based on Fe(OH)₃ obtained by various methods (using prepared sodium ferrate or precipitation of Fe(OH)₃ with ammonia) was assessed. It was shown that phosphorus was recovered most efficiently at a seawater flow rate of one-to-four column volumes per minute with a sorbent based on hydrolyzed polyacrylonitrile fiber with a precipitation of Fe(OH)₃ with ammonia. Based on the results obtained, a method for phosphorus isotopes recovery with this sorbent was suggested. Using this method, the seasonal variability of phosphorus biodynamics in the Balaklava coastal area was estimated. For this purpose, the short-lived isotopes of cosmogenic origin ³²P and ³³P were used. Volumetric activity profiles of ³²P and ³³P in particulate and dissolved forms were obtained. Based on ³²P and ³³P volumetric activity, indicators of phosphorus biodynamics were calculated: the time, rate, and degree of phosphorus circulation to inorganic and particulate organic forms. In spring and summer, elevated values of phosphorus biodynamic parameters were determined. This is explained by the peculiarity of the economic and resort activities of Balaklava, which negatively affect the state of the marine ecosystem. The results obtained can be used to assess the dynamics of changes in the content of forms of dissolved and suspended phosphorus, and the biodynamic parameters when performing a comprehensive environmental assessment of the state of coastal waters.

Physical and Chemical Regularities of Phosphorus and Beryllium Recovery by the Sorbents Based on Acrylic Fiber Impregnated by Iron Hydroxide (III)

The paper investigates the physicochemical regularities (kinetics and isotherm) of phosphorus and beryllium recovery by sorbents based on polyacrylonitrile (PAN) fiber and Fe(OH)3 obtained by various methods: PAN or pre-hydrolyzed PAN with precipitation of FeCl3 with ammonia, using ready-made or electrochemically generated Na2FeO4, pre-hydrolyzed PAN treated with an alkaline solution of Na2FeO4, as well as their comparison with granular aluminum oxide. The Langmuir, Freudlich and Dubinin–Radushkevich models show high performance of materials for sorption of stable P and Be used as tracers for the release of 7Be, 32P, and 33P from seawater. The obtained kinetic data are processed using kinetic models of intraparticle diffusion and the pseudo-first-order, pseudo-second-order, and Elovich models. Optimal conditions for obtaining sorbents are established, namely, the effect of NaOH concentration at the stages of preparation on the properties of sorbents based on the PAN fiber and Fe(OH)3 obtained by various methods.

The Sorbents Based on Acrylic Fiber Impregnated by Iron Hydroxide (III): Production Methods, Properties, Application in Oceanographic Research

Sorbents based on Fe(OH)3 and aluminum oxide are widely used in oceanology for the recovery of cosmogenic radionuclides 7Be, 32Si, 32P, and 33P from the seawater. It is also possible to use them for the recovery of the natural radionuclides 210Pb, 234Th. A comparative study of the sorbents based on Fe(OH)3 and acrylic fiber obtained through various impregnation methods was carried out, and their comparison with granulated aluminum oxide. The possibility of extracting trace amounts of phosphorus and beryllium under laboratory and field conditions with these sorbents was studied. The sorption of 7Be, 210Pb, and 234Th on the natural content by the two-column method was investigated. It is shown that fiber samples obtained by oxidation with sodium ferrate and the “classical” method have the highest sorption characteristics.

DECLAB: a software for liquid scintillation spectra deconvolution

The deconvolution of liquid scintillation (LS) spectra is meaningful in several scenarios like supporting incomplete radiochemical separations, for screening purposes and determining different isotopes of the same element, which is explored in this paper for the case of 89Sr/90Sr. In this paper DECLAB, an online application for liquid scintillation spectra analysis is presented. The software considers the classical calibration modes like constant efficiency and quenching curve and furthermore, the deconvolution of multicomponent spectra by means of Partial Least Square Regression. DECLAB is designed to analyse Perkin Elmer Wallac Quantulus 1220 spectra. However, in further upgrades, the applicability of this tool will be extended to other LS spectrometers.

Sorption methods in marine radiochemistry

The review presents the general methodology of using sorption methods to solve problems of marine radiochemistry, including sampling, preconcentration and radiochemical preparation and methods for measuring the activity of radionuclides. The possible methodological errors at various stages of sampling and sample concentration are discussed. The most widely used artificial (90Sr, 134Cs, 137Cs, 239Pu, 240Pu), natural (210Pb, 210Po; radium quartet: 223Ra, 224Ra, 226Ra, 228Ra; thorium isotopes, mainly 234Th) and cosmogenic (7Be, 32P, 33P) radiotracers are considered. The sorption of uranium from seawater is not addressed, since its concentration in seawater is usually calculated from the known dependence of uranium concentration on seawater salinity.

The bibliography includes 200 references.

Distribution of beryllium-7 (7Be) in the Black Sea in the summer of 2016

The spatial distribution of ⁷Be activity in the surface layer of the Black Sea was studied using the data of field observations made during the 87th cruise of R/V Professor Vodyanitskii. Activity of ⁷Be varied spatially from 4.6 to 9.5 Bq m^-3 (mean 7.5 ± 1.3 Bq m^-3) where about 9% was found on suspended matter. The minimum values of activity were typical for samples taken in the shelf waters and the maximum-offshore. The influence of different factors on ⁷Be activity was analyzed. It was revealed that variation of both ⁷Be wet deposition on the sea surface and concentration of suspended matter were the most significant for spatiotemporal variability of ⁷Be activity in seawater during the study period. The estimates of ⁷Be distribution coefficient between dissolved and particulate forms were obtained. This coefficient varied from 1.5·10⁵ to 2.4·10⁵ L kg^-1, averaged (1.9 ± 0.3)·10⁵ L kg^-1.

Numerical simulation of the intra-annual evolution of beryllium-7 (7Ве) in the surface layer of the Black Sea

A numerical model simulating the distribution of ⁷Ве in the Black Sea was developed and applied to study the spatial and temporal variations in the content of ⁷Be in the surface waters. Variations in the distribution of ⁷Ве were analyzed for the period from January to December of 2012. The average seasonal content of ⁷Ве in the surface layer ranges from 2.2 to 6.2 Bq m^-3. The maximum concentration is typical for the eastern part of the sea in winter to spring, and the minimum concentration is typical for the central and western parts of the sea in summer. The seasonally averaged activity of ⁷Ве on suspended matter ranges from 440 to 1560 Bq kg^-1. The highest values are observed in the sea in winter to spring, and the lowest values are typically observed in the central and western parts of the sea in summer. It was revealed that the adsorption of ⁷Ве on suspended matter is most significant for the evolution of the content of this radionuclide in shelf waters.

Simultaneous determination of specific alpha and beta emitters by LSC-PLS in water samples

Liquid scintillation counting (LSC) is a commonly used technique for the determination of alpha and beta emitters. However, LSC has poor resolution and the continuous spectra for beta emitters hinder the simultaneous determination of several alpha and beta emitters from the same spectrum. In this paper, the feasibility of multivariate calibration by partial least squares (PLS) models for the determination of several alpha (^natU, ²⁴¹Am and ²²⁶Ra) and beta emitters (⁴⁰K, ⁶⁰Co, ⁹⁰Sr/⁹⁰Y, ¹³⁴Cs and ¹³⁷Cs) in water samples is reported. A set of alpha and beta spectra from radionuclide calibration standards were used to construct three PLS models. Experimentally mixed radionuclides and intercomparision materials were used to validate the models. The results had a maximum relative bias of 25% when all the radionuclides in the sample were included in the calibration set; otherwise the relative bias was over 100% for some radionuclides. The results obtained show that LSC-PLS is a useful approach for the simultaneous determination of alpha and beta emitters in multi-radionuclide samples. However, to obtain useful results, it is important to include all the radionuclides expected in the studied scenario in the calibration set.

Vertical distributions of (99)Tc and the (99)Tc/(137)Cs activity ratio in the coastal water off Aomori, Japan

Using a sector-field ICP-MS the vertical distributions of the (99)Tc concentration and (99)Tc/(137)Cs activity ratio were measured in the coastal waters off Aomori Prefecture, Japan, where a spent-nuclear-fuel reprocessing plant has begun test operation. The (99)Tc concentrations in surface water ranged from 1.8 to 2.4 mBq/m(3), no greater than the estimated background level. Relatively high (99)Tc/(137)Cs activity ratios (10-12 × 10(-4)) would be caused by the inflow of the high-(99)Tc/(137)Cs water mass from the Japan Sea. There is no observable contamination from the reprocessing plant in the investigated area. The (99)Tc concentration and the (99)Tc/(137)Cs activity ratio in water column showed gradual decreases with depth. Our results implied that (99)Tc behaves in a more conservative manner than (137)Cs in marine environments.