Dynamics of Radio Cesium Released by Fukushima Daiichi NPP Accident in Hydrological Cycle of Groundwater, Surface Water and Spring Water in the Headwater Catchments Maki TSUJIMURA Yuichi ONDA, Sho IWAGAMI, Yutaka ABE, Manami HADA, Pun ISHWAR, Masataka NISHINO, Ryohei KONUMA University of Tsukuba 1 This work was carried out as a commissioned study from the JAEA, as a part of FY2012 project entitled “The establishment of grasp method of long-term effects caused by radioactive materials from the Fukushima Dai-ichi Nuclear Power Plant accident”, financially supported by the Ministry of Education, Culture, Sports, Science and Technology, the Japanese Government.
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Dynamics of Radio Cesium Released by Fukushima Daiichi ... presentations...3 years Cs-137 variation in RW, TF, SW, GW, RW in Ko 11 (Bq /L) 10⁻² 1.0E-04 1.0E-03 1.0E-02 1.0E-01 1.0E+00
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Dynamics of Radio Cesium Released by Fukushima Daiichi NPP Accident in Hydrological Cycle of Groundwater,
Surface Water and Spring Water in the Headwater Catchments
This work was carried out as a commissioned study from the JAEA, as a part of
FY2012 project entitled “The establishment of grasp method of long-term
effects caused by radioactive materials from the Fukushima Dai-ichi Nuclear
Power Plant accident”, financially supported by the Ministry of Education,
Culture, Sports, Science and Technology, the Japanese Government.
137Cs deposition map obtained by aircraft monitoring
2
Fukushima
Daiichi NPP
Study area:
Yamakiya district
10 km
Targets
• To monitor dissolved radio cesium concentration in the rainfall, soil water, groundwater, and stream water in headwater catchments covered by grass, forest and crop located at 30 km west-north from Fukushima NPP.
• To understand hydrological processes during rainfall-runoff events regarding increase of Cs concentration in stream.
3
Behavior of nuclear isotopes with hydrological cycle
地下水観測 井戸 x2セット
土壌水3深度x6地点
三角堰による河川流量観測(左)とオートサンプラーによる河川水自動採水(右)
Sampling of GW using piezometers
Soil water sampling
Soil water Shallow GW Deep GW Runoff
Sampling of discharge water
Paddy field
Cultivated area
Forest
5
Grassland (Iboishi yama/ Recharge area)
Cultivated land (Ishidaira yama)
Farmland (Koutaishi yama/ Discharge area)
Kawamata Cop. (Mizusakai river)
FDNPP
Ib-watershed
Ko-watershed
Forest site
Ib
Ko
Ib watershed-
Grassland-Forest
Ko watershed- Forest
dominant
(10% farmland)
Sampling of soil water Young Forest
Ko watershed Old Forest
Ib watershed
7
Suction lysimeter Soil moisture sensors 0.1 m, 0.3 m, 0.5m
0.1 m, 0.2 m, 0.3 m
0.1 m, 0.3 m, 0.5m
Boreholes installation
8
30 m 15 m 5 m
0 m
10 m
20 m
30 m
20 m 6 m 3 m
Ib site Ko site
Len
gth
of
the
Bo
reh
ole
(m
)
Aaverage
Water level
Scr
een Boreholes at Ib watershed
Boreholes at Ko watershed
0
20
40
60
80
10010
100
1000
10000
降雨量
(mm
/h)
比流量
(l/s・km
²)
10
100
1000
10000
Rain
fall (mm
/h) Sp
ecif
ic d
isch
arge
(L
/s・
km²)
0
20
40
80
100
60
2011 2012
Ko watershed (Discharge area) Ib watershed (Recharge area)
0.1
1
10
100
1000
0 95 185 275
10
100
1000
0.1
1
95 185 275
Dis
char
ge
(mm
/day
) Ko watershed Ib watershed
(Days)
Rainfall
Runoff Characteristics
9
3 years Cs-137 variation in RW, TF, SW, GW, RW in Ib
Stream water Cs134 0~0.24 (Bq/L) Cs137 0~0.31 (Bq/L)
snowfall Cs134 0~0.89 (Bq/L) Cs137 0~2.42 (Bq/L)
Rainfall Aug~Dec.2011, Apr~Jun.2012 Snowfall Jan~Mar.2012 Stream water Jun.2011~Jun.2012 Ground water Sep.2011~Oct.2012
(near the point) Kawamori, 2012
25(years)
26(years)
28(years)
: Residence time by CFC-12
Summary of Ko watershed
Summary • Cs-137 conc. in stream water ranging from 0.12
to 1.18 Bq/L in 2011, decreased to below 0.1 Bq/L after 2012. Cs in groundwater and soil water ranged from 0.001 to 0.039 Bq/L, from 0.12 to 2.48 Bq/L, respectively in 2011, and recently no detected.
• Cs conc. in stream water during rainfall events ranging from 0.07 to 0.52 Bq/L.
• End-member mixing analysis (EMMA) suggesting GW contribution to storm runoff dominant ranging from 64.2 to 88.2%, but cannot represent Cs conc dynamcs.
• Source of Cs increase in runoff seems to be litter?