Supplementary Material

Fractionation of radiocesium in soil, sediments, and

aquatic organisms in Lake Onuma of Mt. Akagi, Gunma

Prefecture using sequential extraction

Masanobu Moria,*, Kin-ichi Tsunodaa, Shoichi Aizawaa, Yoichi Saitoa, b, Yuko

Koikea, Takahiro Gondaa, Shunji Abea, Kyuma Suzukic, Yumi Yuasac, Toshihiro

Kugec, Hideki Tanakac, Hajime Araic, Shun Watanabec, Seiichi Noharad,

Yoshitaka Minaie, Yukiko Okadaf, Seiya Nagaog

aGraduate School of Science and Technology, Gunma University

bKiryu Bureau of Waterworks in Kiryu City

cGunma Prefectural Fisheries Experiment Station

dNational Institute for Environmental Studies

eFaculty of Humanities, Musashi University

fAtomic Energy Research Laboratory, Tokyo City University

gLow Level Radioactivity Laboratory, Kanazawa University

1

Comparison of radiocesium (radio-Cs) concentrations in wakasagi in

several mountain lakes

Fig. S1. Changes in the radio-Cs concentrations in wakasagi (hypomesus

nipponensis) collected at several mountain lakes in surrounding area of FNDPP.

2

Cation-exchange capacity (CEC) of surrounding soil and lake sediment samples

The CEC values of the samples were determined based on the Standard for

Soil Quality Testing (ISO 11260) recommended by the Japanese Geotechnical

Society. 2.5 g of the sample was pulverized with a mortar and pestle and placed

in a 50-mL centrifuge tube to which 30 mL of barium chloride solution (0.10 M)

was added followed by shaking for 1 h. After discarding the supernatant, 30 mL

of a more dilute solution of barium chloride (2.5 × 10−3 M) was added to the

residue, and the tube was shaken for 14 h. After discarding the supernatant, 30

g of magnesium sulfate solution (0.020 M) was added to the residue, and the

tube was shaken again for 14 h. When 0.2 mL of supernatant was obtained, 0.3

mL of barium aqueous solution was transferred to a 100-mL volumetric flask

and diluted with water to volume. To prepare the diluted blank solutions, 0.2 mL

of 0.20 M magnesium sulfate, 0.3 mL of 0.10 M barium chloride, and 10 mL of

lanthanum solution (10 mg/L) were transferred to a 100-mL volumetric flask and

diluted with water to volume. The concentration of magnesium in the solution

was determined by inductively coupled plasma atomic emission spectroscopy.

These measured values were subsequently used in equations (S1) and (S2), to

calculate the CEC:

C2 = C1·(a + m2 – m1) / a (S1)

CEC = (Cb – C2)·100a / m (S2)

where C1 is the concentration of magnesium in the sample solution (M); C2 is

the concentration of magnesium calculated by Eq. (1) (M); m1 is the weight of

the centrifuge tube with the dry solid sample (g); m2 is the weight of the

centrifuge tube with the wet solid sample (g); a is the weight of magnesium

sulfate with the cation-exchanger (30 g); CEC is the cation-exchange capacity

(cmol/kg); Cb is the concentration of magnesium in the blank solution (mol/L);

and m is the weight of the air-dried solid (g).

3

4

Difference of radio-Cs concentrations among the meshed soil samples

Fig. S2. The 137Cs concentrations in nine different meshes at soil St. 5. These

samples were collected in November 21, 2012 and June 12, 2013. Photo and

picture in left trace are a grouping into nine meshes and the numbering.

5

Relationship between 134Cs and 137Cs concentrations

The relationships between 134Cs and 137Cs concentrations in all collected

samples were investigated. The calibration curve for each sampling date

provided the high linearity, and the correlation coefficient (r) ranged from 0.993

– 0.999 (Fig. S3). The slopes of the approximations became larger depending

on the elapsed days from FDNPP accident, that is, changes in the slopes would

be related to half-life of 134Cs and 137Cs. For example, the slope of the

approximation in Jun. 4, 2012, was 1.48 and that in Oct. 28, 2015, was 3.92.

The slope also indicates the abundance ratio of 137Cs to 134Cs as a function of

the elapsed day from FDNPP accident. The theoretical ratios (137Cs/134Cs) were

estimated from equation (S3), and those in Jun. 4, 2012 and in Oct. 28, 2015

were 1.42 and 3.90, respectively. The theoretical values agreed with those

obtained from the slope as mentioned above.

C=C0×2−tτ (S3)

where C is each theoretical concentration of 134Cs and 137Cs, C0 is each initial

concentration of 134Cs and 137Cs predicted in the day of FDNPP accident, t is the

elapsed day from the accident, and τ is the half-life.

6

Fig. S3. Relationship between concentrations of 134Cs and 137Cs in soil,

sediment, plankton, and wakasagi samples.

7

Fractionations of 137Cs in sediment and soil samples

Fig. S4. The distributions of radio-Cs (137Cs) concentrations for each fraction in lake sediment and surrounding soil samples by using sequential extraction method. Sampling dates were same as in Fig. 2.

8

XRD pattern of soil samples

In this study, we discussed that cray such as illite related to insolubility of radio-

Cs in soil and sediment samples, referring to previous reports (Tsukada et al., J.

Environ. Radioactiv. 99 (2008) 875. Nakao et al., Eur. J. Soil Sci. 60 (2009)

127.). From the X-ray diffraction (XRD) patterns of lake sediment, and soil

samples (Sts. 1, 2 and 5), the peak originated from illite (2θ = 8.8o) was found in

the soil samples.

Fig. S5. XRD patterns of sediment and soil samples. XRD system: RINT2200VF

(Rigaku, Tokyo, Japan). The XRD patterns were obtained from the claysoriented

on glass slides. Goniometer: RINT2000. Scanning range: 2o – 35o. The particle

sizes of analyte samples ranged of 2 – 200 μm.

9

Changes in radio-Cs concentration to cation-exchange capacity (CEC) in sediment and soil

Fig. S6. Concentrations of radio-Cs (137Cs) as functions of CEC in sediment and

soil samples.

10

Aluminum and titanium in aquatic organisms and suspended solid samples collected in Lake Onuma at Mt. Akagi

Fig. S7. Concentrations of Al (left) and Ti (right) in aquatic organisms collected

in 2014. PP: phytoplankton; ZP: zooplankton; WK: wakasagi; and SS:

suspended solid. Al and Ti in sample completely dissolved by strong acid were

measured by ICP-MS.

11

Fractionation of dissolved and particle forms of radio-Cs in lake water collected in Lake Onuma

Fig. S8. Fractionations of dissolved and particle forms of radio cesium (137Cs) in

lake water to the water depth. The values in right side of bar graphs are whole

concentration of 137Cs in dissolved and particle forms.

12