Current and promising technologies to reduce cadmium contamination in rice
Satoru Ishikawa, Tomoyuki Makino, and Masaharu Murakami,
Heavy metal pollution in monsoon Asia
Country Origin Element Place Reference
India Irrigation Pb, Ni, Cu, Cd Titagarh, West Bengal Sinha et al., 2006
China Mine, irrigation, Industry
Cd, As, Cr, Hg, Pb
Hunan, Yunnan, Guangdong , Guizhou province
Wong et al., 2002
Korea Mine, Industry As, Cd, Cu, Pb, Zn, Hg Dongjeong Chung et al.,
2005
Taiwan Mine, Industry Cd, Pb Taoyuan Chen 1991
Thailand Mine, Industry Cd, Zn Mae Sot District, Tak
Simmons et al. 2005, 2008
Malaysia Fertilizer Zn, Cu, Cr, Cd Cameron Highlands
Khairiah et al., 2006
Philippines Mine (irrigation) Hg Naboc area Appleton et al., 2006
Viet Nam Mine As, Cu Dai Tu district Ngoc et al., 2009
Designated sites for soil dressing in Japan (2008)
Mine wastes have flowed into rivers and then into paddy fields as irrigation water.
(Main cause of Cd pollution in paddy fields)
Cd - 1 mg kg-1 of brown rice (1970)
(Domestic criterion of Cd in Japan)
(Survey on grain Cd level in Japan )
0.3 % of total samples > 0.4 mg kg-1
(n=37,250 MAFF 2002)
Cd – 0.4 mg kg-1 of rice (polished and unpolished rice) (2011)
(Potentially low Cd-contaminated area ) 40,000 ha
Provisional Tolerable Weekly Intake (PTWI) : 7.0µg kg-1 body weight per week
Total diet : 3.0µg kg-1 body weight per week
Rice and rice products Wheat and tuber
Pulse and its products
Brightly colored vegetables Vegetables and sea weeds
Fishes and shellfishes
The others
Dietary intake of Cd for the Japanese people (2004)
µg k
g-1 b
ody
wei
ght p
er w
eek
Provisional Tolerable Monthly Intake (PTWI) : 25 µg kg-1 body weight per month
Countermeasures for reducing Cd concentration in rice
Soil dressing
Submerged conditions
Soil washing
Phytoextraction
Cd
Cd
Cd
Cd
Cd
Present techniques Promising techniques
Development of low-Cd rice
①Chemical washing ②Water washing ③Wastewater treatmentExtraction of soil Cd by FeCl3 Removing residual Cd and Cl
in the paddy waterRemoving Cd in the wastewater
by chelating material
FeCl3FeCl3
・Mixing・Soil sedimentation
Cd
Cd
CdCd
Cd
Cd
Cd
CdCd
Cd
CdCd
Cd
Cd
WaterWater
・Mixing・Soil sedimentation
Cd Cd
Cd
Water treatment
CdCd
Cd
Treated water
Cd removal
Discharge
compliance with environmental
standards
Paddy water
③
② CdCd
Cd
Cd ③
Cd
Chelating
Cd
Conceptual diagram of on-site soil washing
Soil washing is a mechanical process that uses extracting chemicals to remove hazardous metals from soils into aqueous solution.
Promising techniques for reducing Cd contamination in rice - Soil washing -
On-site process of soil washing
①Application of washing chemicals
②Mixing (Extraction of Cd)
④Treatment of wastewater
③Sedimentation and drainage
⑤Discharge of treated wastewater
⑥ Water washing Makino et al. (2006, 2007) Environmental Pollution Makino et al. (2008) Chemosphere
Changes of rice-Cd and -yield with the soil washing.
On site washing is effective to remove Cd from soils and rice.
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
So
il-
Cd c
on
ten
t (m
g/
kg)
Unwashed plot
Washed plot
Toyama Fukuoka
70% down
Changes of soil Cd content with the soil
washing.
0.0
2.0
4.0
6.0
8.0
Bro
wn
ric
e y
ield
(t
ha
-1) Unwashed plo t
Washed plo t
Nagano Toyama Fukuoka
Rice yield
0.0
0.5
1.0
1.5
Cd c
on
ce
ntr
ati
on
(m
g/
kg) Unwashed plo t
Washed plo t
Nagano Toyama Fukuoka
Rice Cd
Soil Cd
Promising techniques for reducing Cd contamination in rice - Phytoextraction -
Phytoextraction is a kind of phytoremediation that use plants to remove the heavy metals from soils.
0
10
20
30
40
50
60
70
WRC
01W
RC02
WRC
03W
RC04
WRC
05W
RC06
WRC
07W
RC09
WRC
10W
RC11
WRC
12W
RC13
WRC
14W
RC15
WRC
16W
RC17
WRC
18W
RC19
WRC
20W
RC21
WRC
22W
RC23
WRC
24W
RC25
WRC
26W
RC27
WRC
28W
RC29
WRC
30W
RC31
WRC
32W
RC33
WRC
34W
RC35
WRC
36W
RC37
WRC
38W
RC39
WRC
40W
RC41
WRC
42W
RC43
WRC
44W
RC45
WRC
46W
RC47
WRC
48W
RC49
WRC
50W
RC51
WRC
52W
RC53
WRC
55W
RC57
WRC
58W
RC59
WRC
60W
RC61
WRC
62W
RC63
WRC
64W
RC65
WRC
66W
RC67
WRC
68W
RC97
WRC
98W
RC99
WRC
100
Kosh
ihik
…Sa
sani
s…Ak
itako
…Hi
tom
e…Ch
oko-
…
Shoo
t Cd
conc
entr
atio
n (m
g k
g-1 )
Genotypic variation in Cd accumulation in rice
Jarjan
Anjana Dhan
Choko-koku
High Cd accumulating cultivars were selected for phyto-extracting Cd from the paddy fields in Japan.
Soil Cd concentration : 1.8 mg kg-1 (0.1 M HCl extractable)
Cd polluted soil Root Cd uptake
Xylem loading
Shoot Cd
grain Cd
Root Cd
0
100
200
300
400
500
600
A B C
Root
Cd
conc
entr
atio
n (m
g kg
-1)
varieties
Xylem Cd
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
A B C
Xyle
m C
d co
ncen
trat
ion
(mg
L-1)
0
10
20
30
40
50
60
A B C
Shoo
t Cd
con
cent
ratio
n (m
g kg
-1)
0
1
2
3
4
5
6
7
8
A B C
Grai
n C
d co
ncen
trat
ion
(mg
kg-1
) Shoot Cd
Grain Cd A:Nipponbare (Low -Cd cv.) B: Jarjan (High-Cd cv.) C:Anjana Dhan (High-Cd cv.)
Physiological process of rice Cd accumulation
A gene controlling shoot Cd accumulation (OsHMA3)
Vacuole
OsHMA3 Cd
Cd Cd Cd
Cd Cd
Cd
Cd
Cd
Cd
Vacuole
OsHMA3 Cd
Cd Cd Cd
Cd Cd
Cd
Cd
Cd
Cd
Root cell
xylem
Shoot
xylem
Shoot
Root cell Low Cd-accumulating cultivars
High Cd-accumulating cultivars
Miyadate et al. New Phytol. (2011), Ueno et al. PNAS (2010)
Murakami et al. (2009) Environ Sci Technol 43, 5878-5883
Systematic phytoextraction for Cd-contaminated paddy soils by high-Cd accumulating rice
1) Cultivation of high-Cd accumulating rice under drained conditions
2)Whole crop harvester
3) On-site drying
4) Incineration (or bioethanol)
5) Recovery of Cd
Murakami et al. (2009) Environ Sci Technol 43, 5878-5883 Arao et al. (2010) Paddy Water Environ, 8, 247-257
takeout
Ion-beam
M1 plants M2 seeds
Cultivation of 3,000 M2 Plants grown in Cd-polluted soil in pots
Grain harvest of each plant
Cd analysis by ICP-MS
Koshihikari(M1 seeds)
Promising techniques for reducing Cd contamination in rice - Development of low Cd rice -
Screening result
0
100
200
300
400
500
600
0.05 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4
Freq
uenc
y
Grain Cd concentration (mg kg-1)
Koshihikari (WT) Maximum level (0.4 mg kg-1)
lcd-kmt1 lcd-kmt2 lcd-kmt3
lcd-kmt: low cadmium koshihikari mutant
Field trials on Cd uptake in lcd-kmt1 rice
0.57
1.86
0.97
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
Field A Field B Field C
Gra
in C
d co
ncen
tratio
n (m
g kg
-1)
WT
lcd-kmt1
ML
ND 0.02 0.03 0
2
4
6
8
10
12
Field A Field B Field CS
traw
Cd
conc
entra
tion
(mg
kg-1
)
WT
lcd-kmt1
0.04 0.04 0.09
3.46
9.14
5.48
Soil Cd concentration (mg kg-1) Field A: 1.35 Field B: 1.21 Field C: 0.35
The lcd-kmt lines show nearly Cd-free in their grains.
Grain Cd Straw Cd
Agronomic traits of lcd-kmt1 line
WT lcd-kmt1
5mm
WT kmt1
20cm
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
WT lcd-kmt1
Gra
in y
ield
(t h
a-1 )
a a
0102030405060708090
100
WT lcd-kmt1
Eat
ing
qual
ity
(Sco
re v
alue
)
a a
lcd-kmt1 WT
Genetic mechanism of the decreased Cd uptake in lcd-kmt lines (Mutation of OsNramp5 gene)
Vacuole
OsHMA3
Cd
Cd Cd Cd
Cd Cd
Cd
Cd
Cd
Cd
xylem
Shoot Root cell Koshihikari (WT)
Vacuole
OsHMA3
Cd
Cd Cd Cd
Cd Cd
Cd
Cd
Cd
Cd xylem
Root cell lcd-kmt1, lcd-kmt2, lcd-kmt3
OsNramp5
OsNramp5
(Ishikawa S. et al. submitted)
Summary
• We developed three new technologies (soil washing, phyto-extraction, and low-Cd rice) for reducing rice Cd contamination.
• All techniques are very reliable and would be applicable to other countries in monsoon Asia.
If you have very interested in these techniques and obtain more detail, please contact us. Contact persons: Soil washing – Tomoyuki makino ([email protected]) Phytoextraction – Masaharu Murakami ([email protected]) Low-Cd rice – Satoru Ishikawa ([email protected])