Fast concentration of dissolved forms of cesium radioisotopes from large seawater samples
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Fast concentration of dissolved forms of cesium radioisotopes from large seawater samples Jan Kamenı´k • Henrieta Dulaiova • Ferdinand Sˇebesta • Kamila Sˇt’astna´
Received: 11 July 2012 / Published online: 21 August 2012 Ó Akade´miai Kiado´, Budapest, Hungary 2012
Abstract The method developed for cesium concentration from large freshwater samples was tested and adapted for analysis of cesium radionuclides in seawater. Concentration of dissolved forms of cesium in large seawater samples (about 100 L) was performed using composite absorbers AMP-PAN and KNiFC-PAN with ammonium molybdophosphate and potassium–nickel hexacyanoferrate(II) as active components, respectively, and polyacrylonitrile as a binding polymer. A specially designed chromatography column with bed volume (BV) 25 mL allowed fast flow rates of seawater (up to 1,200 BV h-1). The recovery yields were determined by ICP-MS analysis of stable cesium added to seawater sample. Both absorbers proved usability for cesium concentration from large seawater samples. KNiFC-PAN material was slightly more effective in cesium concentration from acidified seawater (recovery yield around 93 % for 700 BV h-1). This material showed similar efficiency in cesium concentration also from natural seawater. The activity concentrations of 137 Cs determined in seawater from the central Pacific Ocean were 1.5 ± 0.1 and 1.4 ± 0.1 Bq m-3 for an offshore (January 2012) and a coastal (February 2012) locality, respectively, 134Cs activities were below detection limit (\0.2 Bq m-3).
J. Kamenı´k (&) H. Dulaiova K. Sˇt’astna´ Department of Geology and Geophysics, School of Ocean and Earth Science and Technology, University of Hawai‘i at Ma¯noa, 1680 East–West Road, Honolulu, HI 96822, USA e-mail: [email protected] F. Sˇebesta K. Sˇt’astna´ Department of Nuclear Chemistry, Czech Technical University in Prague, Brˇehova´ 7, 115 19 Prague 1, Czech Republic
Keywords Cesium 134Cs Composite ion-exchangers
137
Cs Seawater
Introduction Cesium concentration from larger sample volumes is usually required for radioanalytical determination of 134Cs (T1/2 = 2.07 years) and 137Cs (T1/2 = 30.08 years) in seawater. Some of the well-established methods include cesium adsorption on ammonium molybdophosphate (AMP) (e.g., [1–3]) and co-precipitation with various insoluble hexacyanoferrates(II) (e.g., [4–6]). Applications of these materials in chromatography columns for seawater analysis were reviewed by Gaur [7]. Insoluble hexacyanoferrates(II) were also used in impregnated cartridges (e.g., [1, 8, 9]) that as well as the chromatography columns usually reduced chemicals consumption and analysis time. Acidification of seawater is required in the methods where AMP is used due to its chemical stability. Insoluble hexacyanoferrates(II) can be used for concentration of cesium directly from non-acidified seawater, but lower pH may help reducing the uptake of other radionuclides [10] potentially interfering with gamma counting by scintillator detectors with lower energy resolution. The historic
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