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 (t_makino@affrc.go.jp) Phytoextraction – Masaharu Murakami (simple@affrc.go.jp) Low-Cd rice – Satoru Ishikawa (isatoru@affrc.go.jp)