Fast concentration of dissolved forms of cesium radioisotopes from large seawater samples

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 Cs-137 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, 134 Cs activities were below detection limit (<0.2 Bq m(-3)).