Mineralogical and geomicrobial examination of soil contamination by radioactive Cs due to 2011 Fukushima Daiichi Nuclear Power Plant accident

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<ul><li><p>tioaii</p><p>aki</p><p>aDepartment of Geology, Faculty of Science, Niigata University, Ikarashi-2, 8050, Niigata 950-2181, JapanbGraduate School of Science and Technology, Niigata UncDepartment of Chemistry, Faculty of Science, Niigata UdDepartment of Biology, Faculty of Education, Niigata UeDepartment of Environmental Sciences, Faculty of Scienf Fukushima-Higashi High School, Fukushima, Japan</p><p>due to strong sorption of Cs by soil. Soil is fundamentally com-posed of minerals containing clay minerals and organic matters,and various organisms living in it.</p><p>Cesium has a similar nature to other alkali metals such as K andbinds weakly to organic and inorganic ligands. Organic materials insoil are derived from plants and microorganisms. Organisms in thesoil are plants, lamentous and single-celled bacteria, algae, fungi,and small invertebrates such as protozoa, worms, insects and ani-</p><p>stick et al., 2002;</p><p>suggested that Csreleased inlkaline sol. 15% and</p><p>ca. 70% of Cs remains after treatment (Hou et al., 2003). Ttype clay minerals show stronger sorption ability than 1:clay minerals and frayed edge sites in clay minerals mainlyCs (Sawhney, 1972; Ebel, 1980; Kitamura et al., 2008). The Cs sorp-tion characteristics by zeolite, e.g., clinoptilolite, is well known(e.g., Bailey et al., 1999). Clinoptilolite, which is highly selectivefor Cs, is used for removal of Cs from contaminated waters (Cheli-shchev, 1995). Therefore, current method for treatment of Cs is byion exchange of clinoptilolite offering ion exchange sites, moderateresistance to radiometric degradation and low solubility.</p><p> Corresponding author. Tel.: +81 25 2626186.</p><p>Physics and Chemistry of the Earth 5860 (2013) 5767</p><p>Contents lists available at</p><p>i</p><p>w.eE-mail address: akai@geo.sc.niigata-u.ac.jp (J. Akai).The Fukushima Daiichi Nuclear Power Plant accident hascaused wide soil contamination by radioactive Cs as Chernobylaccident did (e.g., Ebihara et al., 2012; Watanabe et al., 2012;UNSCEAR, 2008). It is well known that sorption of radioactiveCs in soil does not go so deep: Most of the Cs is less than10 cm deep (e.g., Arapis et al., 1997; Ohno et al., 2012). This is</p><p>1992; Maes and Cremers, 1986; Cornell, 1993; BoNakano et al., 2003).</p><p>Dissolution and extraction experiments havestrongly combined to clay minerals is not easilykinds of solutions; for example water, acid and aHowever, ammonium acetate releases Cs of ca1474-7065/$ - see front matter 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.pce.2013.04.010manyutions.nallyhe 2:11 typeabsorbTEMleaves in Iitate village, Fukushima Pref. and bacterial strains of Bacillus subtillis, Rhodococus erythropolis,Streptomyces aomiensis and Actinomycetospora chlora were carried out. Non-radioactive 1% Cs solution(CsCl) was added to the culture media. Two types of strong or considerable bacterial uptakes of Cs werefound in bacterial cells. One is that Cs was contained mainly as globules inside bacteria and the other isthat Cs was absorbed in the whole bacterial cells. The globules consisted mainly of Cs and P. Based on allthese results, future diffusion and re-circulation behavior of Cs in the surface environment was discussed.</p><p> 2013 Elsevier Ltd. All rights reserved.</p><p>1. Introduction mals. Clay minerals, especially 2:1 type clay minerals strongly ab-sorb Cs (Sawhney, 1972; Comans et al., 1991; Comans and Hockley,a r t i c l e i n f o</p><p>Article history:Available online 25 April 2013</p><p>Keywords:CesiumFukushimaLeavesRecirculationBacterial sorptioniversity, Ikarashi-2, 8050, Niigata 950-2181, Japanniversity, Ikarashi-2, 8050, Niigata 950-2181, Japanniversity, Ikarashi-2, 8050, Niigata 950-2181, Japance, Niigata University, Ikarashi-2, 8050, Niigata 950-2181, Japan</p><p>a b s t r a c t</p><p>Soil contamination by radioactive Cs from Fukushima Daiichi Nuclear Power Plant accident was investi-gated. Absorption and desorption experiments of Cs were conducted for several phyllosillicates (kaolin-ite, sericite, montmorillonite, vermiculite, chrysotile and biotite), zeolite and solid organic matter (deadand green leaves). The results conrmed the characteristic sorption and desorption of Cs by these mate-rials. The 2:1 type phyllosilicate, especially, vermiculite and montmorillonite absorbed Cs well. Heatedvermiculite for agricultural use and weathered montmorillonite also adsorbed Cs. Leaves also absorbedCs considerably but easily desorbed it. In summary, the relative capacity and strength of different mate-rials for sorption of Cs followed the order: zeolite (clinoptilolite) &gt; 2:1 type clay mineral &gt; 1:1 type claymineral &gt; dead and green leaves. Culture experiments using bacteria of both naturally living on deadJinko Matsumoto fMineralogical and geomicrobial examinaradioactive Cs due to 2011 Fukushima Daccident</p><p>Junji Akai a,, Nao Nomura b, Shin Matsushita b, Hisa</p><p>Physics and Chem</p><p>journal homepage: wwn of soil contamination bychi Nuclear Power Plant</p><p>Kudo c, Haruo Fukuhara d, Shiro Matsuoka e,</p><p>SciVerse ScienceDirect</p><p>stry of the Earth</p><p>l sevier .com/locate /pce</p></li><li><p>lated to enzyme necessity and afnity of K (Bossemeyer et al.,</p><p>1991). Later, Kato et al. (2000) suggested Cs uptake by Streptomyces</p><p>ry olividans TK-24 and Streptomyces sp. TOHO-2. Uptake of Cs by ac-tively metabolizing microorganisms may be proved more effec-tively, but microbial biosorption has suggested low Cs uptakeover zeolite use (Macaskie, 1991).</p><p>Soil contamination by radioactive Cs from a reactor at the Fuku-shima Daiichi Nuclear Power Plant which resulted from meltdownof fuel rods, has spread over the wide area especially in FukushimaPrefecture. Regarding radioactive Cs behavior, many research stud-ies have been reported in relation to the Chernobyl accident andalso to nuclear weapons test effects in the 1960s (e.g., Lloyde andEncesah, 1999; Elles and Lee, 2002).</p><p>First, this study described the basic data of Cs contamination inFukushima. Second, fundamental experiments of Cs sorption anddesorption by various clay minerals and leaves were conducted.Some previous studies on sorption of Cs by typical clay mineralspecies have been carried out (e.g., Hou et al., 2003). Therefore, thisstudy examined the Cs sorption properties by more varieties ofphyllosilicate types. Sorption of Cs by leaves was also compara-tively conducted. Desorption characteristics of Cs by clay mineralshave been reported and are well known. Then, we carried out thedesorption experiments from leaves in details. Thirdly, in orderto clarify the bacterial role in the environment, culture experi-ments were carried out using both a natural bacterial mixture liv-ing on the dead leaves in Iitate village, Fukushima Pref. and on fourpure strains. These strains were randomly selected among verycommonly found types of bacteria in the surface environments.All of these results lead to a clarication of the detailed formationprocess of the so-called hot spot where Cs is highly concentratedin local scales. Future diffusion and recirculation behaviour ofradioactive Cs in the surface environments, and the fate of Cs inthe future environments are nally discussed.</p><p>2. Materials and methods</p><p>This study is composed of sampling in the eld and laboratoryexperiments. So-called hot spot, where Cs is highly concentratedlocally, were found in the eld survey for sampling in Fukushimaprefecture. Using these samples, laboratory experiments wereconducted.</p><p>2.1. Materials</p><p>2.1.1. Soil and sandy dust specimens from highly Cs-concentratedareas</p><p>Soils beneath the rain drainspout from house roof in Date city(sampled by S. Sato): Radiation intensity of b and c rays measured1989). Appanna et al. (1996) suggested that Cs was immobilizedby Pseudomonas uorescence as an insoluble precipitate when usingculture media containing ferric iron. However, the details for thesemicrobial processes are not fully claried, and more varieties ofexamples in different conditions are needed to be collected forwide interpretation of natural processes and also for remediationpossibilities. Another algal and fungal model system of Cs sorptionis also suggested (Harvey and Patrick, 1967; DeRome and Gadd,In general, the role of bacteria in surface environments isimportant due to the interaction between microbe and minerals.Regarding Cs contamination, bacterial behaviour has been re-viewed by Avery (1995, 2006). Because of the similarity of K andCs, both may be absorbed by the same metabolic pass. Escherichiacoli have characteristic K+ uptake transport systems which is re-</p><p>+</p><p>58 J. Akai et al. / Physics and Chemistby the dosimeter (TGS-121/Aloka) was 60 lSv/h at the site and5 lSv/h at the position of 1 cm apart from the sample of ca.100 cc in the laboratory. Sandy dust sample on the housetop ofTachibana High School in Fukushima City was collected by Mat-sumoto. They were collected 20th March 2011 and the c-ray mea-surements were carried out 25th March 2011. Radiation intensityof b and c rays measured by dosimeter (Gamma Scout) was3.8 lSv/h at the position of 1 cm apart from the sample of ca.100 cc in the Laboratory. The sample used for c ray spectroscopywas 0.695 g. A soil sample with some black dead leaves was col-lected from the street gutter at Iitate village where there is a so-called hot spot. The radiation intensity of b and c rays measuredby dosimeter at this point was 132 lSv/h (b and c rays)</p><p>2.1.2. Mineral and leaf samplesClay mineral species with their localities are shown below. 1.</p><p>Kaolinite in Kanpaku; 2. Kaolinite in Hakurou, Hokkaidou; 3. Ser-pentine (chrysotile) in Oheyama, Kyoto; 4. Montmorillonite inOdo, Niigata; 5. Weathered montmorillonite (kaolinmontmoril-lonite) in Hanetsu, Niigata; 6. Vermiculite (Materials importedfrom China), 7. Heated vermiculite of (6), 8. Biotite in Ishikawa,Fukushima Pref.; 9. Sericite in Nabeyama (with impurity of kaolinmineral), 10. Chlorite in Kamioka, Gifu Pref. (with impurity ofantigorite). Natural zeolite samples (mineral species, locality in Ja-pan) were also prepared as follows.</p><p>1. Clinoptilolite in Itaya, Yamagata; 2. Mordenite in Kamihoro,Iwamizawa, Hokkaido.</p><p>Leaf samples were used for sorption experiments. Varieties ofdead and green leaf samples were collected around Niigata Univer-sity, as follows; 1. Camellia (Camellia japonica), 2. Cherry treeSomei-yoshino (Cerasus yedoensis), 3.orange osmanthus (Osman-thus fragrans var. aurantiacus), 4. Reed (Phragmites australis), 5.Timothy, timothy grass (Phleum pretense), 6. Pine (Pinus thunbergii).</p><p>2.1.3. BacteriaThe natural bacterial mixtures living on dead leaves obtained</p><p>from the so-called hot spot of a street gutter at Iitate village, Fuku-shima Prefecture were collected.</p><p>Pure bacterial strains of Rhodococus erythropolis (RIKEN BRC JCMNo. 9804), Streptomyces aomiensis (RIKEN BRC JCM No. 17986) andBacillus subtillis (RIKEN BRC JCM No. 18293) and Actinomycetosporachlora (RIKEN BRC JCM No. 17979) were obtained from JAPAN COL-LECTION OF MICROORGANISMS in RIKEN Bioresource Center.</p><p>2.2. Experimental methods</p><p>2.2.1. Radiation measurements and XRD analysisRadiation dosimeter of GM counter (Gamma Scourt) which</p><p>measure a, b and c rays was used for eld and laboratory experi-ments. Radiation dosimeter of GM counter (TGS-121/Aloka) whichmeasure b and c rays were partly used for eld use. c-ray spec-trometry was carried out for identication and determinations ofradioisotopes. This is composed of a high purity Ge coupled witha multi-channel pulse-height analyzer. The resolution is 2.0 keVat 1332 keV c-ray of 60Co. Autoradiography was carried out usingBlack and White lm with sensitivity of ISO 400. Sandy dust parti-cles (Sample A) and Date soil sample (Sample B) were placed onthe lm and kept for 5 days in a dark room to develop. XRD (X-ray Diffraction) analysis was carried out using Ultima IV (Rigaku)for powdered samples.</p><p>2.2.2. Sorption and desorption experiments by clay minerals, zeoliteand leaves</p><p>For phyllosilicates, 10 ppm and 1% Cs solution were prepared asnon-radioactive CsCl solution. 1% solution is too high in a concen-tration for accidental contamination by Cs but this experiment was</p><p>f the Earth 5860 (2013) 5767designed in order to check the fundamental capacity of sorption incomparison with other materials. Powdered phyllosilicate was putinto Cs solution. They were then stirred for 24 h and centrifuged for</p></li><li><p>analysis. 1 g of phyllosilicate was put in 40 cc of 10 ppm or 1% Cssolution and stirred for 24 h. They were centrifuged and the Cs con-centration was measured by Atomic Absorption Spectrometer (AA-6200: Shimadzu).</p><p>Sorption experiments by zeolite samples were carried out forcomparison to clay minerals and leaf samples. Using 10 ppm and1% Cs solution (non-radioactive CsCl) and 1 g of zeolite, sampleswere put in 40 cc of 10 ppm or 1% Cs solution and stirred for24 h. The other conditions are the same as those described for clayminerals.</p><p>Dead and green leaves were collected, washed with distilled</p><p>types of solutions of 50 cc: Distilled water, NaOH (0.1 mol), HCl</p><p>by CsCl. 10 cc of Sakurai medium and 40 cc of 1% Cs solution weremixed and used for natural bacteria in Iitate village. A small pieceof muddy dead leaf (square of ca. 5 mm) was added to culture solu-tion as a natural bacterial source. They were cultured at room tem-perature (25 C) for two weeks. Culture experiments of strains ofRIKEN BRC were carried out using 20 cc of corresponding mediumand 20 cc of 1% Cs solution. They were cultured at room tempera-ture (25 C) for 2 weeks.</p><p>TEMEDS (Energy Dispersive Spectrometer) analysis was car-ried out as follows. TEM of JEM 2010 was operated at 200 kV.The EDS system used was Voyager IV (Noran Inst). Dead leaves</p><p>The spectrum indicates the presence of 137Cs, 134Cs, 131I, 132Te,</p><p>J. Akai et al. / Physics and Chemistry of the Earth 5860 (2013) 5767 59(0.1 mol), (NH4)2C2O4H2O (0.1 mol), KCl (0.1 mol), H2SO4(0.1 mol), HNO3 (0.1 mol).</p><p>They were stirred for 1 h and centrifuged, and the Cs concentra-tion was measured. Desorption ratio was calculated, using the fol-lowing equation:</p><p>Desorption ratio % Absorbed Cs content Remaining Cs content=Absorbed Cs content 100</p><p>2.2.3. Bacterial culture experiments and TEM (Transmission ElectronMicroscopy) observations</p><p>The following culture media were prepared. Sakurai Mediumwas prepared as follows. 0.075 g of glucose, 0.3 g of polypeptonand 0.15 g of yeast extract were dissolved in 150 ml distilled water.Other Media for each corresponding bacterial strain was preparedas follows. For R. erythropolis, Bacto peptone (10 g), Yeast extract(5 g), Malt extract (5 g), Casamino acid (5 g), Glycerol (2 g), andMgSO4/7H2O were dissolved in 1 L of distilled water. For Strepto-mycesm aomiensis, Yeast extract (4 g), Malt extract (10 g) and Glu-cose (4 g) were dissolved in 1 L distilled water. For B. subtillis,Peptone (5 g), and Beef extract (3 g) were dissolved in 1 L distilledwater. For A. chlora, Yeast extract (1 g) and Oatmeal agar (20 g)were dissolved in 1 L distilled water. 1% Cs solution was preparedwater, and then air dried. The procedure was the same as inthe mineral sorption experiments. 1...</p></li></ul>

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