Table Of ContentArsenic & Rice
Andrew A. Meharg (cid:129) Fang-Jie Zhao
Arsenic & Rice
Andrew A. Meharg Fang-Jie Zhao
University of Aberdeen Rothamsted Research
Aberdeen Harpenden
United Kingdom United Kingdom and
Nanjing Agricultural University
Nanjing
China
ISBN 978-94-007-2946-9 e-ISBN 978-94-007-2947-6
DOI 10.1007/978-94-007-2947-6
Springer Dordrecht Heidelberg London New York
Library of Congress Control Number: 2012930919
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Acknowledgements
The work synthesised in this book is indebted to many people who have actively
been involved in the research presented. Key amongst these are colleagues at
Aberdeen (Joneil Abedin, Eureka Adomako, Anne-Marie Carey, Claire Deacon,
Joerg Feldmann, Helle Hansen, Daniel Lou-Hing, Adrien Mestrot, Meher Niger,
Gareth Norton, Adam Price, Andrea Raab, Mahmud Sumon and Paul Williams) and
Rothamsted (Sarah Dunham, Asaduzzaman Khan, Renying Li, Wenju Liu, Charlotte
Lomax, Steve McGrath, Jackie Stroud, Yuhong Su, Zhongchang Wu, Xiaoyan Xu
and Wenling Ye) with whom we have worked with over the years, as well as inter-
national colleagues based in Bangladesh (Shahid Hossain, Rafi ql Islam, Mazibur
Rahman, ARM Solaiman), Australia (Enzo Lombi), China (Ying Lu, Ping Wu,
Yongguan Zhu), USA (Tracy Punshon, Kirk Schekel), Spain (Angel Carbonell-
Barrachina, Toni Signes-Pastor, Antia Villada), Japan (Jian Feng Ma), India (Tapash
Dasgupta) and UK (Hugh Brammer, Claudia Cassini, Bill Davison, Parvez Haris,
Katie Moore, Dave Polya and Hao Zhang) who have also been central to this work.
We are grateful to the following people who have kindly provided images, graphs
or data that are used in the book: Katja Bogdan, Ann-Marie Carey, John Duxbury,
Scott Fendorf, Wenju Liu, Enzo Lombi, Jian Feng Ma, Adrien Mestrot, Katie
Moore, Lenny Winkel and Maozhong Zheng. We thank Steve McGrath for com-
menting on the last four chapters of the book.
Thanks are due to our families Caroline, Annie, Christine and Kenny (AAM) and
Xiaoyun and Tina (FJZ) for their support over the years of writing this book.
v
Contents
1 Introduction ............................................................................................... 1
1.1 Arsenic Exposure from Rice .............................................................. 1
1.2 Historical Context .............................................................................. 3
1.3 Biogeochemistry of Paddy Soils ........................................................ 3
1.4 Plant Physiology ................................................................................ 5
1.5 Summary ............................................................................................ 6
References ................................................................................................... 6
2 Arsenic in Rice Grain ............................................................................... 11
2.1 Introduction ........................................................................................ 11
2.2 Quantifi cation of Arsenic in Rice Grain ............................................ 11
2.2.1 Total Arsenic Analysis ........................................................... 12
2.2.2 Arsenic Speciation by Chromatographic Separation ............. 13
2.2.3 Certifi ed Reference Materials (CRMs) .................................. 16
2.3 Arsenic Speciation in Rice Grain ....................................................... 16
2.4 Total Grain Arsenic ............................................................................ 21
2.5 Rice Products ..................................................................................... 25
References ................................................................................................... 27
3 Risk from Arsenic in Rice Grain ............................................................. 31
3.1 Rice Consumption .............................................................................. 31
3.2 Studies on the Total Intake of Inorganic Arsenic ............................... 35
3.3 Considering Rice as an Arsenic Source in Epidemiological
Studies ................................................................................................ 38
3.4 The Effects of Cooking Rice on Its Arsenic Content ......................... 39
3.5 Human Bioavailability of Arsenic in Rice ......................................... 40
3.6 Risk Assessment from Arsenic in Rice .............................................. 41
3.7 Food Arsenic Standards ..................................................................... 43
3.8 Limiting Arsenic Exposure to Rice .................................................... 46
References ................................................................................................... 48
vii
viii Contents
4 Sources and Losses of Arsenic to Paddy Fields ...................................... 51
4.1 Introduction ........................................................................................ 51
4.2 Sources of Arsenic to Paddy Ecosystems .......................................... 51
4.2.1 Natural Sources ...................................................................... 52
4.2.2 Non-point Source Industrial/Urban Pollution ........................ 55
4.2.3 Fertilizers and Manures Contaminated with Arsenic ............. 55
4.2.4 Point Source Industrial Pollution ........................................... 57
4.2.5 Arsenical Pesticides ............................................................... 58
4.2.6 Contamination of Irrigation Water ......................................... 59
4.3 Paddy Field Arsenic Cycling
in a Wider Hydrological Context ....................................................... 65
References ................................................................................................... 66
5 Biogeochemistry of Arsenic in Paddy Environments ............................ 71
5.1 Overview of the Biogeochemistry of Paddy Soil ............................... 71
5.2 Arsenic Transformations in Paddy Soil ............................................. 75
5.2.1 Arsenic Reduction and Oxidation .......................................... 75
5.2.2 Arsenic Adsorption and Desorption ....................................... 82
5.2.3 Arsenic Biomethylation,
Volatilisation and Demethylation ........................................... 87
5.2.4 Predicting Available Arsenic in Paddy Soil ........................... 92
5.3 Impact of Groundwater Irrigation
on Arsenic Dynamics in Paddy Fields ............................................... 94
References ................................................................................................... 96
6 The Physiology of Arsenic in Rice ........................................................... 103
6.1 Introduction ........................................................................................ 103
6.2 Mechanisms of Arsenic Uptake by Roots .......................................... 103
6.2.1 Uptake of Arsenate ................................................................. 104
6.2.2 Uptake of Arsenite ................................................................. 107
6.2.3 Uptake of Methylated Arsenic Species .................................. 110
6.3 Transformation of Arsenic Species in Plant ...................................... 113
6.3.1 Arsenate Reduction ................................................................ 113
6.3.2 Arsenite Complexation ........................................................... 114
6.3.3 Arsenic Methylation ............................................................... 115
6.4 Arsenic Sequestration in Plant ........................................................... 116
6.4.1 Iron Plaque ............................................................................. 116
6.4.2 Sequestration of Arsenic in the Vacuoles ............................... 119
6.5 Long-Distance Transport and Unloading
of Arsenic in Rice Grain .................................................................... 121
6.5.1 Xylem Transport .................................................................... 121
6.5.2 Phloem Transport ................................................................... 122
6.5.3 Transport of Arsenic into Rice Grain ..................................... 122
6.6 Arsenic Toxicity and “Straighthead Disease” .................................... 125
6.6.1 Toxicity of Inorganic Arsenic ................................................ 125
6.6.2 “Straighthead Disease”........................................................... 126
References ................................................................................................... 132
Contents ix
7 Strategies for Producing Low Arsenic Rice ............................................ 139
7.1 Introduction ........................................................................................ 139
7.2 Paddy Field Water Management ........................................................ 139
7.2.1 Aerobic Rice........................................................................... 141
7.2.2 Alternate Wetting and Drying (AWD) ................................... 141
7.2.3 Raised Bed Cultivation ........................................................... 142
7.2.4 Effects of Water Management
on the Accumulation of Other Elements ................................ 143
7.3 Cultivar Selection and Breeding Low Arsenic Rice .......................... 144
7.3.1 Cultivar Difference in Arsenic Accumulation ........................ 144
7.3.2 Quantitative Trait Loci for Arsenic Accumulation ................ 147
7.4 Fertilization and Soil Amendments ................................................... 147
References ................................................................................................... 149
8 Arsenic in Other Crops............................................................................. 153
8.1 Introduction ........................................................................................ 153
8.2 Wheat ................................................................................................. 153
8.3 Maize .................................................................................................. 160
8.4 Potato ................................................................................................. 161
8.5 Pulses ................................................................................................. 162
8.6 Vegetables .......................................................................................... 162
8.7 Fruits .................................................................................................. 164
References ................................................................................................... 164
Index ................................................................................................................. 167
