Effect of Fertilizer and Soil Amendments on Extraction Yields and Soil-to-Plant Transfer
Factor of I and Cs Added to Soil
Hirofumi TSUKADA, Akira TAKEDA, Yuichi TAKAKU, Shun’ichi HISAMATSU
Department of Radioecology
Abstract
Aging of radionuclides in soil after deposition is an important factor for their speciation andsoil-to-plant transfer, which changes with the application of fertilizer and soil amendments. Radioiodine andradiocesium released from nuclear fuel reprocessing plants are important radionuclides for the assessment ofradiation exposure for the public. We have already reported the aging effect of Cs and I in a soil sample,Andosol, collected from grassland in Rokkasho where a large-scale spent nuclear fuel reprocessing plant islocated. In FY 2009, the effect of fertilizer and soil amendments on the aging was examined using a soilsample. The soil sample was mixed with a composite chemical fertilizer, which had the N-P-K composition
recommended by the Department of Agriculture, Forestry, and Fisheries of Aomori Prefectural Government,
and then stable Cs or I was added. The sample was stored in an artificial climate chamber, and its watercontent was adjusted to its maximum water holding capacity every 2 weeks. The extraction yield of I withwater, and that of Cs with water or 1 M ammonium acetate solution from the soil was determined at
predetermined period after the addition. The soil-to-plant transfer factor of both elements, which was definedas the concentration in plant divided by that in soil, was also determined by cultivating orchardgrass. To
investigate the effect of each of the chemical fertilizers, compost and clay minerals like montmorillonite, 125I
and 137Cs were used in a similar experiment to that with stable element addition, except a smaller amount of
the soil sample was uesd. Results were not largely different between the experiments using stable elements
and radionuclides.
The water extraction yield of 125I added as I- or IO3- in the soil mixed with compost was higher than thecontrol values without adding any fertilizer and amendments, and depended on the content of dissolved
organic carbon in the water extract. On the other hand, the soil-to-plant transfer factor of the 125I in the soil
mixed with compost was lower than that in the control sample.
The extraction of 137Cs with water was enhanced by the application of nitrogen fertilizer and compost,
whereas it was depressed by the application of clay minerals. The extraction of 137Cs with ammonium acetate
was also depressed by the application of the clay minerals. However, the soil-to-plant transfer factor of 137Cs
in the soil with added fertilizers and soil amendments did not differ clearly from the control value.

0.10

*30 d

*

0.05
0.00

Mt-3101
Mt-3102
MtSc
VtZl
It
KnCNPK
NPK

0.00

10 d*

Mt-3101
Mt-3102
MtSc
VtZl
ItKn0.05*IO3-125C

0.100.1530 dNPKNPK10 dNAI

Water extraction yield*125 -NA

Water extraction yield

0.15

Fertilizer or soil amendment

Fertilizer or soil amendment

Fig. 1 Water extraction yield of 125I- and 125IO3- at 10 and 30 d after the addition of the radionuclides into the soil.
Error bars indicate a standard deviation (number of samples=3). Asterisks indicate statistically significant
differences between NA and fertilizer or soil amendment (p<0.01). NA, Non-application; N, Nitrogenfertilizer; P, Phosphate fertilizer; K, Potassium fertilizer; NPK, Mixed fertilizer with N, P, and K; C,Compost; Mt-3101, Mt-3102 and Mt, Montmorillonite; Sc, Sericite; Vt, Vermiculite; Zl, Zeolite; It, Illite;
Kn, Kaolinite.
0.3

Cultivation 1（2-24 d）

0.4

Transfer factor

0.3
0.2
0.1

0.2
0.1

137

**

**

Cs

10 d30 d**

0.01** ** ****

00.8
Ammonium acetate
extraction yield

0.03

*
*0.6

**Mt

C137

10 d30 d*** * * * ** ** *Cs0.40.2Fertilizer and soil amendment

NP
K
NPKNA

Mt-3101
Mt-3102
MtScVtZlItKnCNPK
NPK0NA

Water extraction yieldFig. 2 Soil-to-plant transfer factor of 125I (I- or IO3-) for
orchardgrass (number of samples =3). Error bars
indicate a standard deviation. NA, Non-application;
C, Compost; Mt, Montmorillonite.

Soil-to-plant transfer factor of 137Cs fororchardgrass. Error bars indicate a standard
deviation (number of samples=3). NA,Non-application; N, Nitrogen fertilizer;
NPK, Mixed fertilizer with N, P, and K; C,
Compost; Mt, Montmorillonite.

Mt-3101
Mt-3102
Mt
Sc
VtZlItKn

Fig. 4IO3-NPKNA

MtCNAMt

CNAI-N

000.02

Cultivation 1（2-24 d）

C

Transfer factor

0.5

Fertilizer and soil amendment

Fig. 3 Water and ammonium acetate extraction yield of 137Cs at 10 and 30 d after the addition of the radionuclide
to the soil. Error bars indicate a standard deviation (number of samples=3). Asterisks indicate statisticallysignificant differences between NA and fertilizer or soil amendment (p<0.01). NA, Non-application; N,Nitrogen fertilizer; P, Phosphate fertilizer; K, Potassium fertilizer; NPK, Mixed fertilizer with N, P, and K;
C, Compost; Mt-3101, Mt-3102 and Mt, Montmorillonite; Sc, Sericite; Vt, Vermiculite; Zl, Zeolite; It, Illite;
Kn, Kaolinite.