Radiocesium transfer from Andosols to brown rice in the northern and northwest areas of Tochigi Prefecture, in the first 3 years following the 2011 Fukushima Daiichi nuclear power plant accident

Figures & data

Table 1. Statistical values of radiocesium concentrarions in brown rice and TF values among the soil groups.

		R-Cs
	Statistical values	Bq kg^−1							TF
Year	Soil groups	A		G			R	W	A		G			R	W
2011	number	10		8				18	10		8				18
	arithmetic mean	32.0	a	14.0	b	*		24.0	0.061		0.031		-		0.048
	min.	3.2		<0.8				<0.8	0.001		0.001				0.001
	max.	64.9		38.1				64.9	0.231		0.170				0.231
	RSD	0.63		0.95				0.81	1.10		1.81				1.32
	median	35.6		8.2				22.5	0.042		0.010		ns		0.024
	geometric mean								0.031		0.010				0.019
	95％CI (lower)								0.010		0.003				0.009
	95％CI (upper)								0.090		0.038				0.042
2012	number	66		17			1	84	66		17			1	84
	arithmetic mean	19.0		11.5		-	76.5	18.2	0.019		0.013		-	0.257	0.020
	min.	<0.8		<0.8				<0.8	0.001		0.001				0.001
	max.	65.9		62.0				76.5	0.115		0.117				0.257
	RSD	1.01		1.53				1.10	1.12		2.11				1.68
	median	11.0		5.1		ns		9.5	0.012a		0.004b		*		0.010
	geometric mean								0.010		0.005				0.009
	95％CI (lower)								0.007		0.002				0.007
	95％CI (upper)								0.014		0.009				0.012
2013	number	10		5			1	16	10		5			1	16
	arithmetic mean	7.1		1.2		-	37.1	7.1	0.016		0.003		-	0.212	0.024
	min.	0.5		0.2				0.2	0.0008		0.001				0.0008
	max.	33.4		4.1				37.1	0.054		0.007				0.212
	RSD	1.52		1.30				1.67	1.09		0.889				2.18
	median	1.5		0.6		ns		1.1	0.009		0.002		ns		0.004
	geometric mean								0.0080		0.003				0.007
	95％CI (lower)								0.0030		9E-04				0.003
	95％CI (upper)								0.021		0.005				0.015

R-Cs: Total (¹³⁴Cs+¹³⁷Cs) radiocesium concentrations in brown rice. The detection limit in 2011 and 2012 was about 0.8 Bq kg^−1. The value was used for statistical calculation of the nondetected samples.

TF:Transfer factor.

Soil groups were based on the classification of cultivated soils in Japan (third approximation), by the Cultivated Soil Classification Committee (1995). A: Andosols, G:ｇray lowland soils, R: regosolic lowland soils, W: Whole the samples.

RSD: Relative standard deviation, The ratio of the standard deviation to arithmetic mean.

95％CI:95％ confidential intervals.

The arithmetic mean values between Andosols and gray lowland soils were not compared using Student’s t-test or Welch’s t-test because the values of at least one group were not normally distributed. In this case, differences in medians between the groups were compared using Mann–Whitney’s U test.

Values within a column followed by different letters are significantly different at the 5％ level. *: significant at the 5％ level. ns: Not significant at the 5％ level.

Table 2. Statistical values of radiocesium soil concentrations, and soil properties along with plow depth among the soil groups in 2012.

	Soil groups	T-Cs	Ex-Cs				Ｔ－Ｃ		Ｔ－Ｎ		ＣＥＣ		Ex-ＣaＯ		Ex-ＭgＯ		Ex-Ｋ2Ｏ		Av-N	Clay		Silt
	Statistical values	Bq kg^−1	Bq kg^−1	ｐH (Ｈ２O)	Phosphate adsorption coefficient		g kg^−1		g kg^−1		cmolc kg^−1		mg kg^−1		mg kg^−1		mg kg^−1		mg kg^−1	％		％	Fine sand ％		Coarse sand ％		Plow depth cm
Andosols (n = 66)
	arithmetic mean	1098	44.3	6.1	1944a		81.9		5.96		36.1a		3963		491	a	275		154	12.2a		36.7	32.6		18.5b		17
	min.	112	10.0	5.6	1540		25.0		2.50		14.9		1245		100		133		19	4.4		22.2	25.1		5.5		13
	max.	2931	213.2	7.0	2360		135.8		9.30		52.7		10,628		1422		593		266	21.5		49.8	47.9		31.5		21
	RSD	0.55	0.66	0.05	0.11		0.30		0.23		0.22		0.38		0.46		0.41		0.32	0.27		0.16	0.14		0.31		0.12
	median	977	37.1	6.0	1960		80.3a		5.89a		34.9		3645a		481		234b		148	12.0		37.1	32.0b		18.9		17a
gray lowland soils (n = 17)
	arithmetic mean	1095	53.7	6.0	1145b		45.1		3.51		24.6b		2758		367b		328		129	10.6b		27.8	37.1		24.5a		16
	min.	111	14.5	5.7	740		14.3		1.43		12.7		590		28		158		55	5.5		5.6	25.9		7.5		10
	max.	2195	122.0	7.0	1490		101.0		7.01		46.2		4232		631		542		215	22.4		44.0	57.5		46.1		21
	RSD	0.57	0.59	0.06	0.23		0.61		0.51		0.40		0.41		0.47		0.34		0.33	0.34		0.42	0.21		0.40		0.18
	median	980	45.1	5.9	1140		36.7b		2.95b		21.3		2835b		350		321a		127	10.7		28.1	37.0a		24.1		15b
	arithmetic mean	-	-	-	*		-		-		*		-		*		-		-	*		-	-		*		-
	median	ns	ns	ns			*		*				*				*		ns			ns	*				*
regosolic lowland soils (n = 1)
		298	38.2	6.2	900		32.8		2.49		16.6		2108		156		172		76	3.2		14.9	33.6		48.3		15
Whole the samples (n = 84)
	arithmetic mean	1087	46.1	6.1	1770		73.9		5.42		33.5		3697		462		285		148	11.8		34.6	33.5		20.1		16
	min.	111	10.0	5.6	740		14.3		1.43		12.7		590		28		133		19	3.2		5.6	25.1		5.5		10
	max.	2931	213.2	7.0	2360		135.8		9.30		52.7		10,628		1422		593		266	22.4		49.8	57.5		48.3		21
	RSD	0.56	0.64	0.05	0.23		0.40		0.33		0.29		0.41		0.48		0.40		0.33	0.30		0.24	0.17		0.38		0.13
	median	959	37.9	6.0	1880		74.4		4.58		33.4		3563		457		241		143	11.6		36.5	32.5		19.8		16

Arithmetic mean values between Andosols and gray lowland soils were not compared using Student’s t-test or Welch’s t-test because the values of at least one group were not normally distributed. In this case, differences in medians between the groups were compared using Mann–Whitney’s U test.

Values within a column followed by different letters are significantly different at the 5％ level. * significant at the 5 ％ level.ns: Not significant at the 5％ level.

Table 3. Pearson’s correlation coefficients (r) among radiocesium concentrations in brown rice, TF, and main soil properties for Andosls in 2012.

R-Cs,TF Soil properties	R-Cs		TF		Ex-Cs		Ｔ－Ｃ		Ex-Ｋ2Ｏ		Clay
TF	―		―
Ex-Cs	0.091		−0.157		―
Ｔ－Ｃ	−0.004		0.027		−0.445**		―
Ex-Ｋ2Ｏ	−0.353**		−0.426**		0.317**		−0.278*		―
Clay	−0.334**		−0.334**		0.084		−0.054		0.330**		―
Coarse sand	0.412**		0.264*		−0.013		−0.019		−0.197		−0.579**

** and * Significant at the 1％ and 5％ levels, respectively.

n＝66.

Table 4. Pearson’s correlation coefficients (r) among radiocesium concentrations in brown rice, TF, and main soil properties for gray lowland soils in 2012.

R-Cs,TF Soil properties	R-Cs	TF	Ex-Cs	Ｔ－Ｃ	Ex-Ｋ2Ｏ	Clay
TF	―	―
Ex-Cs	−0.246	−0.260	―
Ｔ－Ｃ	0.406	0.044	−0.190	―
Ex-Ｋ2Ｏ	−0.301	−0.400	0.121	−0.033	―
Clay	−0.345	−0.396	−0.092	0.019	0.085	―
Coarse sand	0.265	0.522*	−0.199	−0.318	−0.126	−0.632*

* Significant at the 5％ level.

n＝17.

Figure 1. Relationship between the Clay/T-C value and Ex-K₂O content in the soil after the harvest in 2012.

Figure 2. Relationship between Ex-K₂O content in the soil after the harvest and TF in 2012.

Figure 3. Relationship between Ex-Cs concentration in the soil after the harvest and TF in 2012.

Figure 4. Relationship between T-Cs concentration in the soil after the harvest and TF in 2012.

Table 5. Comparison of TF values between Andosols and gray lowland soils with the same Ex-Ｋ₂Ｏ content.

	Soil groups	Ｋ2Ｏ < 200 mg kg^−1							Ｋ2Ｏ ～400 mg kg^−1							Ｋ2Ｏ > 400 mg kg^−1
		Ex-Ｋ2Ｏ				T-C	Clay		Ex-Ｋ2Ｏ				T-C	Clay		Ex-Ｋ2Ｏ				T-C	Clay
Year	Statistical values	mg kg^−1		TF	Clay/T-C	g kg^−1	％		mg kg^−1	TF		Clay/T-C	g kg^−1	％		mg kg^−1	TF		Clay/T-C	g kg^−1	％
2011	Andosols	n = 4							n = 3							n = 3
		132 ± 27		0.102 ± 0.089	1.34 ± 0.33	101.6 ± 22.3	13.7 ± 4.6		295 ± 39	0.046 ± 0.034		1.68 ± 0.45	103.7 ± 15.2	17.2 ± 3.8		449 ± 33	0.020 ± 0.029		1.85 ± 0.23	97.3 ± 34.1	17.6 ± 4.5
	gray lowland soils	n = 2							n = 4
		178 ± 31		0.057 ± 0.076	2.89 ± 1.10	45.2 ± 14.7	11.9 ± 0.9		310 ± 83	0.0059 ± 0.0064		3.76 ± 0.82	34.3 ± 9.5	12.5 ± 2.8
				-						-							-
2012	Andosols	n = 15							n = 41							n = 10
		168 ± 18		0.034 ± 0.033	1.27 ± 0.40	87.6 ± 18.5	10.8 ± 3.1		250 ± 51	0.017 ± 0.015		1.61 ± 0.83	83.6 ± 24.1	12.2 ± 3.1		498 ± 66	0.0049 ± 0.0063		2.86 ± 2.20	66.4 ± 30.6	14.2 ± 3.9
										0.012	a						0.0022
	gray lowland soils	n = 2							n = 11							n = 4
		159 ± 1		0.067 ± 0.071	1.91 ± 0.56	33.2 ± 5.0	6.2 ± 0.9		303 ± 55	0.0053 ± 0.0056		3.83 ± 2.83	44.7 ± 27.2	11.8 ± 3.7		482 ± 64	0.0076 ± 0.0080		2.48 ± 1.25	52.2 ± 37.5	9.7 ± 2.7
										0.0036	b						0.0060
									(n = 3	0.011 ± 0.080)						(n = 2	0.0092 ± 0.012)
				-						*							ns
2013	Andosols	n = 4							n = 3							n = 3
		97 ± 53		0.032 ± 0.015	1.30 ± 0.32	97.4 ± 19.3	12.8 ± 4.5		253 ± 32	0.0071 ± 0.0058		3.06 ± 1.32	65.6 ± 18.0	18.5 ± 3.3		604 ± 232	0.0022 ± 0.0012		4.21 ± 3.43	65.8 ± 43.0	18.5 ± 2.3
	gray lowland soils								n = 2							n = 3
									383 ± 14	0.0015 ± 0.0005		2.98 ± 0.45	36.8 ± 6.1	10.8 ± 0.2		684 ± 242	0.0034 ± 0.0030		4.83 ± 0.92	29.1 ± 9.9	14.4 ± 7.1
				-						-							-

Because TF values were not normal distributed, the differences in medians between Andosols and gray lowland soils were compared by using Mann–Whitney’s U test. -: the test was not carried out because of the small sample numbers.

Values denote arithmetic mean ± standard deviation, and medians were additionally shown below the values when Mann–Whitney’s U test was carried out.

Values within a column followed by different letters are significantly different at the 5％ level. *significant at the 5％ level. ns: Not significant at the 5％ level.

TF values of gray lowlands soils samples with T-C contents greater than 60 g kg⁻¹ were shown in parentheses.

Figure 5. Relationship between Ex-K₂O content in soil after the harvest and TF for the 3 years of the study.

Table 6. Changes in TF values and Ex-Ｋ₂Ｏ in samples collected in each of the three years, and the samples with TF exceeding 0.1.

Year					2011			2012			2013
TF, Soil properties			T-C	Clay	Ex-Ｋ2Ｏ			Ex-Ｋ2Ｏ			Ex-Ｋ2Ｏ
Soil groups	Samples	Clay/T-C	g kg^−1	％	mg kg^−1	TF		mg kg^−1	TF		mg kg^−1	TF
Andosols	A	0.94	81.0	7.6	95	0.231		147	0.115		51	0.035
	B	1.76	99.4	17.4	145	0.081		150	0.027		164	0.021
	C	1.34	115.9	15.5	340	0.085		310	0.021		115	0.021
	D	1.82	82.0	14.9	285	<0.02*		295	0.008		239	0.005
	E	3.29	58.5	19.2	407	<0.007*		241	0.002		552	0.003
	F	4.77	45.5	21.5	405	<0.03*		342	0.010		290	0.003
	G	7.87	25.9	20.4	460	<0.006*		416	0.003		402	0.003
gray lowland soils	H	4.03	22.1	8.9	376	0.015		310	0.006		963	0.007
	I	2.75	39.8	10.9	486	<0.03*		321	0.006		373	0.002
	J	7.20	17.6	12.1	529	<0.005*		234	0.002		560	0.001
	K	6.74	35.9	22.4	662	<0.04*		358	0.004		528	0.002
	L	3.46	35.6	12.3	194	0.170		-	-		-	-
	M	1.50	36.7	5.5	-	-		158	0.117		-	-
regosolic lowland soils	N	0.98	32.8	3.2	-	-		172	0.257		63	0.212

The values of clay/T-C, T-C and clay were used average values for three (two) years.

* the seven samples of which radiocesium in brown rice was not detected because of short counting time for measurement with a germanium semiconductor detector. These data were not used for the statistical analysis.

-:Not collected.

Figure 6. Relationship between Ex-Cs/Ex-K₂O in the soil after the harvest and TF in 2012.

Cultivated Soil Classification Committee. 1995. “Classification of Cultivated Soils in Japan, Third Approximation.” Miscellaneous Publication of National Institute for Agro-Environmental Sciences 17: in Japanese. 18–37.

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