Iodine isotopes in precipitation: Four-year time series variations before and after 2011 Fukushima nuclear accident

Mass-spectrometric determination of iodine-129 using O2-CO2 mixed-gas reaction in inductively coupled plasma tandem quadrupole mass spectrometry

This paper presents a mass-spectrometric method for determining the radionuclide iodine-129 (¹²⁹I) from the significant amount of interference in inductively coupled plasma tandem quadrupole mass spectrometry (ICP-MS/MS) using a dynamic reaction cell passing a mixture gas of O₂ and CO₂. Thus far, mass spectrometry analysis of trace amounts of ¹²⁹I has been hampered by the presence of xenon-129 (¹²⁹Xe) and the formation of polyatomic ions from excess amounts of stable isotope ¹²⁷I. In this study, flowing a mixture gas of O₂ and CO₂ into the dynamic reaction cell (Q2) successfully removed both ¹²⁹Xe interference and polyatomic interference (¹²⁷IH₂) in the analysis of ¹²⁹I in ICP-MS/MS. The resulting ratio of (background noise of m/z 129)/¹²⁷I was 4.6 × 10^-10 ± 3.3 × 10^-10, which enables the analysis of 10 mBq/L of ¹²⁹I in the presence of 100 mg/L of stable ¹²⁷I without chemical separation. The detection limit of this method was 0.73 mBq/L (= 0.11 ng/L) with an APEX-Q sample inlet desolvation device. For demonstration purposes, spike and recovery analysis of rainwater was performed, and good agreement between the spiked and recovered amounts was achieved.

Enhanced removal of radioactive iodine anions from wastewater using modified bentonite: Experimental and theoretical study

Efficient and cost-effective removal of radioactive iodine anions from contaminated water has become a crucial task and a great challenge for waste treatment and environmental remediation. Herein, we present hexadecylpyridinium chloride monohydrate modified bentonite (HDPy-bent) for the efficient and selective removal of iodine anions (I^- and IO₃^-) from contaminated water. Batch experiments showed that HDPy-bent could remove more than 95% of I^- and IO₃^- within 10 min, and had maximum I^- and IO₃^- adsorption capacities of 80.0 and 50.2 mg/g, respectively. Competitive experiments indicated that HDPy-bent exhibited excellent I^- and IO₃^- selectivity in the excessive presence of common concomitant anions including PO₄^3-, SO₄^2-, HCO₃^-, NO₃^-, Cl^- (maximum mole ratio of anions vs iodine anions was ∼50,000). An anion exchange mechanism was proposed for the selective adsorption of iodine anions. Optimal adsorption structure of HDPy⁺/I^- (IO₃^-) at atomic level and driving forces of the I^- (IO₃^-) adsorption were calculated by density functional theory (DFT) simulations. Moreover, the good durability and reusability of the HDPy-bent has been demonstrated with 5 adsorption-desorption cycles. Dynamic column experiment also demonstrated that HDPy-bent exhibited excellent removal and fractional recovery capabilities towards I^- and IO₃^- from simulated groundwater and environmental water samples. In conclusion, this work presents a promising adsorbent material for the decontamination of radioactive iodine anions from wastewater on a large scale.

Radiochemical analysis of the drain water sampled at the exhaust stack shared by Units 1 and 2 of the Fukushima Daiichi Nuclear Power Station

Radioactive gas of Unit 1 of the Fukushima Daiichi Nuclear Power Station was released from the exhaust stack shared by Units 1 and 2 through the venting line on March 12th, 2011. In the present study, radiochemical analysis of drain water sampled at the drain pit of the exhaust stack was conducted to study radionuclides released during venting of the Unit 1. Not only volatile ¹²⁹I, ¹³⁴Cs and ¹³⁷Cs but also ⁶⁰Co, ⁹⁰Sr, ¹²⁵Sb and Unit 1-originated stable Mo isotopes were detected. Although Unit 1-originated stable Mo isotopes were clearly detected, their amounts were quite low compared to Cs, suggesting that the formation of Cs₂MoO₄ was suppressed under the accident condition. Approximately 90% of iodine existed as I⁻ and 10% as IO₃⁻ in November 2020. Furthermore, larger amount of ¹²⁹I than ¹³⁷Cs was observed, suggesting major chemical form of ¹³¹I was molecular iodine rather than CsI at the accident time. The ¹³⁴Cs/¹³⁷Cs radioactivity ratio decay-corrected to March 11th, 2011 was 0.86, supported the results that Unit 1 originated radiocesium in environment has smaller ¹³⁴Cs/¹³⁷Cs radioactivity ratio than Unit 2 and 3 originated radiocesium.

Atmospheric iodine, selenium and caesium depositions in France: I. Spatial and seasonal variations

The spatial distribution and seasonal variations of atmospheric iodine (I), selenium (Se) and caesium (Cs) depositions remain unclear and this precludes adequate inputs for biogeochemical models. We quantified total concentrations and fluxes of these elements in rainfalls from 27 monitoring sites in France with contrasted climatic conditions; monthly measurements were taken over one year (starting in 2016/09). Since speciation of I and Se can impact their behaviour in the environment, analysis of their inorganic compounds was also conducted. Our results showed that annual I concentrations in rainfall were much higher than those of Se and Cs (annual means = 1.56, 0.044 and 0.005 μg L^-1, respectively). The annual iodine concentrations were highly positively correlated with those of marine elements (i.e. Na, Cl and Mg), involving higher I concentrations under oceanic climate than for transition, continental and mountainous ones. Furthermore, common patterns were found between Se concentrations and both marine and terrestrial components consistent with the various sources of Se in atmosphere. The association of Cs with two anthropogenic components (i.e. NH₄⁺ and NO₃^-) used in agriculture supports the hypothesis of its terrestrial origin (i.e. from atmospheric dusts) in rainfall. We found higher rainfall concentrations of I during the warmest months for all climates. However, no specific seasonal trend occurred for Se and Cs. On annual average, rainfall contained mostly unidentified selenium compounds (inorganic Se proportions = 25-54%) and equal proportions of inorganic and unidentified I compounds. Concentrations of iodate were higher under oceanic climate consistent with an iodine marine-origin.

Application of synchrotron radiation and other techniques in analysis of radioactive microparticles emitted from the Fukushima Daiichi Nuclear Power Plant accident-A review

During the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, large amounts of radioactive materials were released into the environment. Among them, a large proportion of the radionuclides, such as Cs, entered into the environment as radioactive microparticles (RMs). In recent years, the characterization of RMs based on synchrotron radiation (SR) techniques has been reported, since their physical and chemical properties played an important role in evaluating the chemical reactions and physical changes that occurred when the nuclear material meltdowns took place. In this review, we summarize separation and measurement technologies used in studies of RMs, and we emphasize the application of SR-based techniques in the characterization of RMs. We report research progress, including information for elemental composition, isotopic distribution, radioactivity, and formation processes. Also, we compare the RMs from the FDNPP and the Chernobyl Nuclear Power Plant accidents. The SR-based technologies offer great improvement in the resolution and precision compared to conventional technologies, such as X-ray fluorescence and X-ray diffraction.