Speciation Analysis of ¹²⁹I in Seawater by Carrier-Free AgI–AgCl Coprecipitation and Accelerator Mass Spectrometric Measurement

A rapid and simple method was developed for speciation analysis of ¹²⁹I in seawater by selective coprecipitation of carrier-free iodide and accelerator mass spectrometry (AMS) measurement of ¹²⁹I. Iodide was separated from seawater and other species of iodine by coprecipitation of AgI with Ag₂SO₃, AgCl, and AgBr by addition of only 100 mg/L Ag⁺ and 0.3 mmol/L NaHSO₃ at pH 4.2–5.5. The separation efficiency of iodide was more than 95%, and crossover between ¹²⁹IO₃^– and ¹²⁹I^– fractions is less than 3%. Iodate and total inorganic iodine were converted to iodide by use of NaHSO₃ at pH 1–2 and then separated by the same method as for iodide. Ag₂SO₃ in the coprecipitate was removed by washing with 3 mol/L HNO₃ and the excess AgCl and AgBr was removed by use of diluted NH₃, and finally a 1–3 mg precipitate was obtained for AMS measurement of ¹²⁹I. The recovery of iodine species in the entire procedure is higher than 70%. Six seawater samples collected from the Norwegian Sea were analyzed by this method as well as a conventional anion-exchange chromatographic method; the results from the two methods show no significant difference (<i>p</i> = 0.05). Because only one separation step and fewer chemicals are involved in the procedure, this method is suitable for operation on board sampling vessels, as it avoids the transport of samples to the laboratory and storage for a longer time before analysis, therefore significantly improving the analytical capacity and reliability of speciation analysis of ¹²⁹I. This improvement can stimulate oceanographic tracer studies of ¹²⁹I

Method of Polonium Source Preparation Using Tellurium Microprecipitation for Alpha Spectrometry

A thin-layer source for the counting of polonium isotopes by alpha spectrometry can be rapidly prepared using microprecipitation with tellurium. Polonium was first coprecipitated with the reduction of tellurium by stannous chloride, followed by microfiltration onto a membrane filter for counting. This microprecipitation method is faster, cheaper, and more convenient than the traditional spontaneous deposition method, with an excellent Po recovery (>90%) under optimal conditions. The influences of several experimental parameters, including Te­(IV) quantity, reaction time, and HCl molarity, were examined to determine the optimal conditions for Te microprecipitation. The decontamination factors of potential interferences from various radionuclides (Ra, Th, U, Pu, Am) for the counting of long-lived polonium isotopes (²⁰⁸Po, ²⁰⁹Po, and ²¹⁰Po) were also evaluated, and the results confirmed a good selectivity on polonium by this microprecipitation method. Due to its strong resistance to high acidity up to 12 M HCl, the method would be particularly suitable for rapid determination of ²¹⁰Po in acid leaching solution of solid samples

Iodine-129 in Seawater Offshore Fukushima: Distribution, Inorganic Speciation, Sources, and Budget

The Fukushima nuclear accident in March 2011 has released a large amount of radioactive pollutants to the environment. Of the pollutants, iodine-129 is a long-lived radionuclide and will remain in the environment for millions of years. This work first report levels and inorganic speciation of ¹²⁹I in seawater depth profiles collected offshore Fukushima in June 2011. Significantly elevated ¹²⁹I concentrations in surface water were observed with the highest ¹²⁹I/¹²⁷I atomic ratio of 2.2 × 10^–9 in the surface seawater 40 km offshore Fukushima. Iodide was found as the dominant species of ¹²⁹I, while stable ¹²⁷I was mainly in iodate form, reflecting the fact that the major source of ¹²⁹I is the direct liquid discharges from the Fukushima NPP. The amount of ¹²⁹I directly discharged from the Fukushima Dai-ichi nuclear power plant to the sea was estimated to be 2.35 GBq, and about 1.09 GBq of ¹²⁹I released to the atmosphere from the accident was deposited in the sea offshore Fukushima. A total release of 8.06 GBq (or 1.2 kg) of ¹²⁹I from the Fukushima accident was estimated. These Fukushima-derived ¹²⁹I data provide necessary information for the investigation of water circulation and geochemical cycle of iodine in the northwestern Pacific Ocean in the future