[en] Analysis data of global fallout ⁹⁹Tc in environmental samples should give useful information for predicting the nuclide's behavior. However, due to its low concentration and analytical difficulties with environmental samples, there are not many data. The authors improved a simple separation method, which had been previously reported for Tc in soil samples and used a combustion apparatus. In this study, two fundamental experiments were performed; one clarified the possibility of using deionized water for a trap solution instead of an alkaline solution, and the other checked for differences in Tc volatilities between 1-y-aged ⁹⁹Tc and freshly added ^95mTc in a soil sample. The results showed that deionized water can trap volatilized Tc as well as alkaline solution, and the volatilities of aged ⁹⁹Tc and freshly added ^95mTc from the soil sample do not differ. The procedure proposed is as follows: Tc in a soil sample is volatilized in a combustion apparatus for 3 h at 1000 degreeC and trapped in deionized water. Then the trap solution is passed through an extraction chromatographic resin (TEVA · Spectrademark resin). After the eluate (ca. 8 M HNO₃) is evaporated to dryness and dissolved in a 2% HNO₃ solution, the ⁹⁹Tc concentration in the solution is measured by inductively coupled plasma mass spectrometry (ICP-MS). This method was employed to measure three environmental soil samples collected in Japan. The recoveries and ⁹⁹Tc concentrations were 62--73% and 5--30 mB1/kg dry basis, respectively

[en] Technetium-99 is an artificial radionuclide with a long half-life of 2.1 x 10⁵ y. The main sources of environmental ⁹⁹Tc are nuclear weapons tests and nuclear industries such as nuclear fuel processing plants and waste disposal facilities. Due to its high mobility in the terrestrial environment, it is one of the most important radionuclides for does assessment. In this study, the authors propose a separation procedure for Tc in environmental waters using a resin, after which samples can be measured by ICP-MS. Tracer experiments were carried out to determine a suitable concentration of HNO₃ for separation of Tc from Ru in environmental waters on TECA·Spec^trademark resin. This was necessary, because, with a common procedure, a small amount of Ru was found in the eluate of 12 M HNO₃ solution. Ruthenium has an isotopic abundance of 12.7% at mass 99 which interferes with Tc counting by ICP-MS. Most of the Ru sorbed on the resin was desorbed by 40 mL of 2 M HNO₃. Sorbed Tc was readily recovered using 4 mL of 8 M HNO₃. No Ru was found in the eluate of 9 M HNO₃ solution. The authors also checked the concentrations of major elements, such as Mg, Na and Ca, in the eluates passing through the resin column by ICP=AES. It was clear that most of the major elements in the environmental waters, adjusted to 0.1 M HNO₃, passed through the resin column and, subsequently, concentration of each coexisting element in the strip solution by 8 M HNO₃ was lower than 20 ppm. The procedure was applied to 2 L each for both river water and seawater. The recoveries of Tc for both waters in 4 mL of the strip solution by 8 M HNO₃ were more than 98% and the detection limit of ⁹⁹Tc by this procedure with ICP-MS measurement was 0.3 mB1 L^-1

[en] Analysis of the artificial radionuclide ⁹⁹Tc in environmental samples requires a chemical separation due to its low concentration, and therefore the use of a chemical yield tracer is peremptory. From a practical viewpoint, Re can be used for this purpose, due to its chemical similarities with Tc. Thus, the use of a radioactive tracer for Tc recovery calculation can be avoided. However, results from a recent intercomparison exercise showed that using of Re as a chemical yield tracer appears to underestimate the Tc concentration relative to the result obtained with isotopes of Tc. In the present work, the methodology used to design a simple separation method for the measurement of ⁹⁹Tc in environmental samples is described. Tc recovery is estimated throughout the Re recovery calculation by the isotope dilution technique coupled with ICP-MS (ID-ICP-MS) technique. For chemical separation, a chromatographic resin is used. Interfering elements are removed using a resin washing step carefully designed to avoid any element fractionation between Re and Tc; the care taken in this step is of major importance to assure the equivalence of the chemical recoveries for both elements. Agreement is tested using five replicates of five seaweed samples. The average recoveries for ^95mTc and Re were 93±6 and 95±7%, respectively, those are within the uncertainty intervals for each other. The results explained here demonstrate the possibility of applying Re chemical recoveries to calculate the Tc concentrations with the advantage of not introducing systematic errors

[en] Tracer experiments were carried out to compare the plant uptake behavior of Tc and Re from nutrient solutions. Radish plants, transplanted to nutrient solution including various tracers, showed the same uptake and distribution of ^95mTc and ¹⁸³Re. The trend was the same when the ⁹⁹Tc and stable-Re concentrations were increased in nutrient solution. The behavior of other elements was different from that of Tc and Re. These findings suggest the possible use of Re as the chemical analogue of Tc in soil solution to plant uptake experiments

[en] To estimate the radiocesium decreasing rates from persimmon trees during a period of about 3 y following the accident at Tokyo Electric Power Company's Fukushima Dai-ichi Nuclear Power Plant (FDNPP), we conducted measurements of tree tissue parts collected in 2011–2013. The sampling was carried out in Chiba, 220 km south of FDNPP; radioactive fallouts discharged from FDNPP had mainly been observed in March–April 2011 on the sampling site. We measured "1"3"7Cs concentrations in the tree tissue parts, i.e., fruits (flesh, skin and seeds), leaves and newly emerged branches, and then the effective half-lives (T_e_f_f) of "1"3"7Cs were calculated. Leaf samples were classified into two types by sampling months according to the growing stages, that is, immature (April–May) and mature (June–November) leaves. All these parts showed exponential declines in "1"3"7Cs concentration with good adjusted contribution ratios of higher than ca. 0.7. The calculated T_e_f_f values from all tissue parts were similar with the average of 229 d (range: 216–243 d). From these results, we concluded that each tree tissue was representative for the calculation of T_e_f_f. For comparison to these observation results, open source food monitoring data from 2011 to 2013 including "1"3"7Cs data for persimmon fruits collected in Fukushima Prefecture were used to calculate T_e_f_f for persimmon trees. Values of T_e_f_f were obtained for persimmon fruits grown in each local government area in Fukushima Prefecture and they ranged from 303 to 475 d. - Highlights: • "1"3"7Cs decreased exponentially from persimmon trees in Chiba after the Fukushima accident. • The effective half-lives (T_e_f_f) of "1"3"7Cs from fruit, leaf and new branch tissues were similar. • The Food monitoring data were used to calculate effective half-lives for persimmon trees in Fukushima. • The average of T_e_f_f in Chiba was ca. 230 d while that in Fukushima was ca. 400 d

[en] Concentrations of "1"3"7Cs and "4"0K in different tissues of edible wild herbaceous plants, that is, leaf blade and petiole for giant butterbur (Petasites japonicas (Siebold et Zucc.) Maxim.), and leaf, stem and strobilus for fertile shoot of field horsetail (Equisetum arvense L.) were measured in 2012–2014 to clarify the effect in Japan from the Fukushima Daiichi Nuclear Power Plant accident. The concentrations of "1"3"7Cs decreased with time with effective half-lives of ca. 450 d and 360 d for giant butterbur and field horsetail, respectively. The ANOVA test revealed that "4"0K and "1"3"7Cs distributions in leaf blade and petiole for giant butterbur and leaf and stem for field horsetail were different. Therefore, other plants, leaf and stem for Japanese knotweed (Fallopia japonica (Houtt.) Ronse Decr.) and Canada goldenrod (Solidago canadensis L.), and leaf blade and petiole for gingko (Ginkgo biloba L.) and Someiyoshino cherry (Cerasus × yedoensis (Matsum.) A.V.Vassil. ‘Somei-yoshino’) were collected from the same sampling field and their "1"3"7Cs and "4"0K concentrations were compared to those in the giant butterbur and field horsetail parts. For "1"3"7Cs, concentrations in leaf blade and leaf parts were 1.1–6.0 times higher than those in petiole and stem parts for all six plants. On the other hand, "4"0K concentrations in leaf blade and leaf parts were 0.40–0.97 of those observed in petiole and stem parts. Discrimination ratios of "4"0K/"1"3"7Cs of leaf blade to petiole or leaf to stem were then calculated and they ranged from 0.09 to 0.57. These results suggested that Cs and K did not behave similarly in these plants. Thus, to understand the radiocesium fate in plants, K measurement results should not be used as an analog for Cs behavior although Cs is known to have a similar chemical reactivity to that of K. - Highlights: • "1"3"7Cs amounts in leaf blade and leaf were higher than those in petiole and stem in plants. • "4"0K amounts in leaf blade and leaf were lower than those in petiole and stem in the same plants. • K and Cs behave differently until proven otherwise; K cannot be used as a Cs analog

[en] After the large releases of radionuclides due to the nuclear power plant accident in March 2011, trees in wide areas were directly contaminated. The contaminated leaves (mostly ever green trees) fell in the late spring to early summer, newly emerged leaves contained some radiocesium which were translocated from tree branches and trunks, and from soil through roots. The concentrations of radiocesium in tree leaves are decreasing due to dilution effect. However, for the case of bamboo shoots, decrease in radiocesium concentration was not observed in some areas when 2011 and 2012 samples were compared. In order to understand the fate of radiocesium in bamboos, "1"3"7Cs concentration changes in leaves and branches from bamboos and litter layer and soil samples in a bamboo forest were measured. It was found that the concentration was higher in the following order: litter > leaves > branches > soil on 9 May 2011, however, the order changed to litter > soil >> leaves, branches on 20 October 2011. Removal of contaminated leaves from the bamboo trees and decomposition of the litter layer to soil organic matter was suggested from the results. Since the root zone of bamboo shoots was in the soil organic layer, radiocesium was taken up through roots to the shoots, and thus the concentration would be high. (author)

[en] Following the Fukushima Daiichi Nuclear Power Plant accident, iodine-131 concentrations in tap water higher than 100 Bq L"-"1 were reported by several local governments in the Kanto Plain in March 2011. To remove iodine-131 from tap water, five methods were tested in this study, that is, (1) boiling, (2) adding charcoals from oak or bamboo, (3) activated charcoals, (4) water purifiers, and (5) reverse osmosis (RO) treatments. Boiling was shown to be not effective in removing iodine-131 from tap water; indeed even higher concentrations may result from the liquid-volume reduction accompanying this process. Adding charcoals and activated charcoal treatment could not remove iodine-131, because no reduction of iodine-131 was observed in tap water samples after these treatments. Only limited effect was found with water purifiers with first several portions; no effect was expected with further water treatment. On the other hand, the RO showed high iodine-131 removal percentage of more than 95%, although the method needs about 5-10 L water to obtain 1 L of RO treated water. (author)

[en] After the Fukushima Daiichi Nuclear Power Plant accident, it was found that deciduous trees took up fallout radiocesium (¹³⁴Cs + ¹³⁷Cs) through their barks and stored them in the tree bodies in 2011. After that, radiocesium concentrations in trees have been decreasing, and in 2013, most fruits harvested in Fukushima prefecture became lower than detection limits. Although fresh fruits were low in radiocesium concentrations, dried fruits can have higher radiocesium concentration during drying process of fresh fruit without any loss. Thus dried fruits would exceed the standard limit of 100 Bq kg^-1 in some case. Dried persimmon is one of the special food products in Fukushima prefecture; it is therefore important to know the effective half-life (T_eff) of radiocesium in persimmon trees. In this study, we measured radiocesium concentrations in persimmon leaves and fruits from the end of April 2011 until November 2013 to calculate T_eff. The observed T_eff values for ¹³⁷Cs were 210 d for leaves and 270 d for fruits showing small differences among them. Thus the use of ¹³⁷Cs concentration data for fruits in Fukushima Prefecture to estimate T_eff in persimmon trees would be applicable. Food monitoring data compiled by Ministry of Health, Labour and Welfare, Japan were used for this purpose. Using detected persimmon fruits data collected in six local communities in 2011-2013, T_eff value was calculated in each community; the average value was 405±63 d (301 - 469 d), which was about 130 d slower than that was observed in Chiba. However, it was clear that the effective half-life of radiocesium in persimmon trees was about 1 year for the last three years. Since the T_eff is expected to become longer in the long-term period compared to the early stage after the accident, it is necessary to carry out continuous ¹³⁷Cs measurements to predict ¹³⁷Cs in persimmon more precisely. (author)

[en] Obtaining data on ⁹⁹Tc in the rice paddy field environment is important because Tc is a redox sensitive element. The behavior of Tc is expected to be different under upland field and rice paddy field conditions since the redox conditions in the soil environment differ. However, most of the data on the nuclide behavior in soil were obtained under upland field conditions. To understand the global fallout ⁹⁹Tc distributions in soil samples collected in Japan, a simple and rapid separation method was developed in order to determine low-levels of ⁹⁹Tc in soil samples by an inductively coupled plasma mass spectrometry. Also, radiotracer experiments using soils under aerobic and anaerobic conditions were carried out to clarify the Tc behavior under paddy field conditions. The results of determination of global fallout ⁹⁹Tc in Japanese soils indicated that the radionuclide had been accumulating in rice paddy fields. The mechanisms can be explained by the immobilization of Tc in soil under anaerobic conditions. From the radiotracer experiments, it was clear that under waterlogged conditions, the highly mobile TcO₄^- in soil was readily changed to other immobilized forms, such as TcO₂, TcS₂ and organically bound forms. To this immobilization, the microbial activity seemed to have an important role in Tc sorption reactions. When the soil, which was once kept in anaerobic conditions, was air-dried again and kept in aerobic conditions, the chemical forms of immobilized Tc did not change remarkably. Interestingly, the similar Tc behavior was observed in a real wet forest near the Chernobyl Reactor. (author)