Exchangeability of ¹³⁷Cs and K in soils of agricultural fields after decontamination in the eastern coastal area of Fukushima

Figures & data

Figure 1. Locations of the sampling sites in Tomioka town, Fukushima prefecture, Japan. The pin indicates the location of the Fukushima Daiichi Nuclear Power Plant (FDNPP) in Okuma town. This map is based on the blank map and aerial photograph published by Geospatial Information Authority of Japan (https://maps.gsi.go.jp/development/ichiran.html)

Table 1. Selected physicochemical properties of the soils

		Total-^137Cs	Ex-^137Cs	^137Cs desorption ratio	AlO+1/2FeO	Total C	Sand	Silt	Clay
Sample No.	Soil group^a	Bq kg^−1	Bq kg^−1	%	g kg^−1	g kg^−1	%	%	%
1	Andosols	3200	350	11	5.87	15.8	-	-	-
14	Andosols	2300	60	2.5	8.51	23.5	53.0	28.0	19.0
15	Andosols	2500	210	8.4	7.13	13.2	56.8	27.2	16.0
23	Andosols	4400	120	2.7	7.40	17.0	53.8	30.7	15.5
29	Muck soils	3500	110	3.3	3.96	14.8	57.5	30.0	12.5
32	Muck soils	3700	240	6.5	5.76	26.8	40.7	36.3	23.0
33	Muck soils	2800	170	6.0	3.99	12.9	62.7	23.6	13.7
57	Lowland soils	3900	200	5.1	2.35	13.3	69.0	21.8	9.19
72	Andosols	2600	340	13	4.23	10.6	71.5	18.1	10.3
78	Andosols	2800	510	18	6.88	12.2	48.5	29.5	22.0
81	Lowland soils	2200	100	4.5	3.10	8.59	75.4	18.1	6.48
86	Lowland soils	2200	110	4.9	5.64	14.6	53.5	33.4	13.2
92	Lowland soils	3900	230	6.0	2.48	10.1	66.7	23.2	10.1
93	Lowland soils	2200	40	1.9	2.09	7.89	57.2	33.7	9.09
94	Lowland soils	2200	230	11	3.06	11.5	65.4	24.1	10.5
96	Lowland soils	3200	380	12	2.35	11.6	70.3	20.0	9.75
97	Andosols	3900	200	5.1	2.55	8.72	64.1	23.1	12.8
101	Andosols	2700	150	5.5	9.10	32.7	58.9	25.1	16.0
103	Andosols	2500	170	6.8	9.49	24.2	70.3	15.2	14.4
105	Andosols	3600	40	1.0	4.91	17.4	63.7	25.3	11.0
110	Lowland soils	2400	140	5.9	1.98	5.46	83.7	10.6	5.76
120	Lowland soils	4000	350	8.8	2.66	9.59	69.4	21.9	8.68
122	Lowland soils	3200	120	3.9	1.62	13.4	76.3	15.1	8.65
127	Lowland soils	4200	180	4.4	4.57	15.1	49.4	34.5	16.1
152	Not classified	2400	520	22	14.4	30.5	20.1	37.3	42.6
156	Lowland soils	2100	410	20	2.86	5.97	77.1	14.4	8.51
161	Lowland soils	2100	90	4.3	3.22	13.8	69.2	20.9	9.83
165	Muck soils	2800	270	10	2.74	14.0	65.0	24.5	10.5
169	Lowland soils	2100	270	13	1.57	7.38	70.5	21.7	7.80
172	Lowland soils	3200	120	3.7	5.19	13.1	49.9	34.7	15.4
173	Andosols	2500	410	17	5.38	13.1	62.5	34.2	3.33
174	Andosols	3900	500	13	7.77	26.2	-	-	-

^aClassification of cultivated soils in Japan (3rd approximation) (Cultivated soil classification committee 1995).

Figure 2. Boxplots of the distribution of the total ¹³⁷Cs content in soils before and after decontamination. The quartiles and median value are shown as the boxes and the maximum and minimum values are shown as the whiskers. The total ¹³⁷Cs content (collected in May 2014 and February 2016) before and after decontamination are from Tomioka town (2016) and corrected for decay from the sampling date

Figure 3. Comparison of the hourly air dose rate at a height of 1 m before and after decontamination (bars indicate standard deviation). The dose rate (measured from 30 July 2013 to 9 May 2016) before and after decontamination are from Tomioka town (2016)

Figure 4. Relationship between the total ¹³⁷Cs content in soils and the hourly air dose rate at a height of 1 m (n = 170) (** indicates P ≤ 0.01). The darker plots indicate fields located close to the border of forests or difficult-to-return zone

Figure 5. Relationship between the exchangeable K content in soils and the total ¹³⁷Cs content in soils (n = 172) (** indicates P ≤ 0.01)

Figure 6. Relationship between the exchangeable K content in soils and the nonexchangeable K content in soils (n = 173)

Table 2. Correlation coefficients between the ¹³⁷Cs desorption ratio and selected physicochemical properties of the soils

	Total-^137Cs	Ex-^137Cs	Ex-K	Nex-K	AlO+1/2FeO	Total-C	Sand	Silt	Clay
^137Cs desorption ratio	−0.20	0.94	0.19	−0.42	0.10	−0.16	−0.09	−0.18	−0.09
Statistical significance	ns	**	ns	*	ns	ns	ns	ns	ns

**, *, and ns indicate statistical significance at the level of p < 0.01, p < 0.05, and “not significant’, respectively.

Cultivated soil classification committee 1995: Classification of Cultivated Soils in Japan (3rd Approximation). Misc. Publ. Natl. Inst. Agro-Environ. Sci., 17, 1–75.

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