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Reducing Cd and As uptake by rice in contaminated paddy soils: From biogeochemical processes to improved paddy management

English title Reducing Cd and As uptake by rice in contaminated paddy soils: From biogeochemical processes to improved paddy management
Applicant Kretzschmar Ruben
Number 170120
Funding scheme Bilateral programmes
Research institution Institut für Biogeochemie und Schadstoffdynamik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Other disciplines of Environmental Sciences
Start/End 01.08.2017 - 31.07.2021
Approved amount 344'954.00
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All Disciplines (2)

Other disciplines of Environmental Sciences
Agricultural Engineering

Keywords (7)

arsenic; cadmium; contamination; soil; bioavailability; irrigation; rice

Lay Summary (German)

In China sind nach neueren Schätzungen knapp 20% der Ackerflächen mit Schwermetallen belastet, wobei Cadmium (Cd) und Arsen (As) zu den wichtigsten Schadstoffen zählen. Eine chronische Aufnahme von Cd und As mit der Nahrung stellt ein erhebliches Gesundheitsrisiko für die Bevölkerung in China und anderen Teilen Asiens dar. Reis spielt dabei eine zentrale Rolle, weil Reispflanzen einerseits das Cd und As leicht aufnehmen und in den Spross verlagern, und andererseits Reis ein wichtiges Grundnahrungsmittel ist. Die Aufnahme von Cd und As durch Reispflanzen aus dem Boden hängt in sehr komplexer Weise von verschiedenen Boden- und Pflanzenfaktoren sowie deren Interaktionen ab, die bislang noch unzureichend gut bekannt sind.
Lay summary

Die Ziele dieses interdisziplinären Projektes sind: (i) Die Entwicklung eines empirischen Modells zur Vorhersage der Cd und As Aufnahme durch Reis in Abhängigkeit von Bodenparametern, (ii) Ein besseres Prozessverständnis der chemischen Bindungsformen, Mobilität und Pflanzenaufnahme von Cd und As in Reisböden, insbesondere des Einflusses von Mn-Oxiden und Schwefel während Redoxprozessen im Boden, und (iii) Die Entwicklung neuer Strategien zur Minimierung der Cd und As Aufnahme durch Reis, welche in Gewächshaus- und Feldversuchen getestet werden. Die Ergebnisse dieses Projektes sollen einen Beitrag zur Produktion sicherer Nahrungsmittel in Asien und weltweit leisten.         

Direct link to Lay Summary Last update: 31.07.2017

Responsible applicant and co-applicants


Name Institute

Project partner


Microbial sulfate reduction decreases arsenic mobilization in flooded paddy soils with high potential for microbial Fe reduction
Xu Xiaowei, Wang Peng, Zhang Jun, Chen Chuan, Wang Ziping, Kopittke Peter M., Kretzschmar Ruben, Zhao Fang-Jie (2019), Microbial sulfate reduction decreases arsenic mobilization in flooded paddy soils with high potential for microbial Fe reduction, in Environmental Pollution, 251, 952-960.


Group / person Country
Types of collaboration
Nanjing Agricultural University China (Asia)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Goldschmidt Conference Poster Comparing sampling strategies for solute arsenic speciation in paddy soils 18.08.2019 Barcelona, Spain Fang Xu; Zhao Fangjie; Kretzschmar Ruben;
15th International Conference on the Biogeochemistry of Trace Elements (ICOBTE) Talk given at a conference Predicting As and Cd concentration in rice grain from soil parameters in southern China: A field survey study 05.05.2019 Nanjing, China Zhao Fangjie; Fang Xu; Kretzschmar Ruben;
WFSC Research Symposium 2018 Poster Facing rice challenge by As and Cd in southern China: From origin to soil-based prediction 08.11.2018 Zurich, Switzerland Zhao Fangjie; Fang Xu; Kretzschmar Ruben;
WFSC Research Symposium 2018 Poster Trace metal(loid) bioavailability and mapping of chemical gradients in the rhizosphere of rice (Oryza sativa) 08.11.2018 Zurich, Switzerland Kretzschmar Ruben; Fang Xu; Zhao Fangjie;

Associated projects

Number Title Start Funding scheme
156392 Mobility of trace metals in periodically flooded soils: Influence of reduced iron, manganese, and sulfur 01.05.2015 Project funding (Div. I-III)


Rapid industrialization and urbanization in China over the last three decades, coupled with a lack of stringent environmental protection, has resulted in widespread soil contamination in China’s farmland. A recent nationwide survey shows that 19.4% of the agricultural soils in China are contaminated, mostly with heavy metals and metalloids. Cadmium (Cd) and arsenic (As) rank the first and the third, respectively, in the percentage of soil samples in the survey exceeding the China’s soil quality standard. Chronic intake of elevated levels of Cd and As poses considerable health risks to humans. The uptake of Cd and As by rice depends on a number of soil and plant factors, some of which can be influenced by paddy management. For example, paddy water management has a large impact on the uptake of both As and Cd by rice. However, the effects are opposite, with flooded (anaerobic) conditions enhancing As accumulation by rice while drained (oxic) conditions favouring Cd accumulation. Maintaining flooded conditions in paddy field is one of the most effective measures to control Cd accumulation by rice, but it leads to high As accumulation. Decreased Cd uptake under flooded paddy conditions can be attributed to increased soil pH, formation of CdS or CdCO3 precipitates, and increased Mn2+ inhibiting Cd2+ uptake by rice roots. The difficulties in using soil properties to predict Cd and As accumulation by rice under field conditions are to a large extent due to a lack of knowledge on the interactions and relevance of biotic and abiotic factors controlling contaminant bioavailability and uptake by rice, in particular during the grain filling period preceding harvest. Innovative paddy management strategies are needed to minimise Cd and As availabilities in paddy soil simultaneously.The goals of this interdisciplinary project are to (i) develop an empirical model for predicting Cd and As uptake by rice based on soil parameters, (ii)-(iv) study the effects of soil pH, Mn oxides, reducible S, and flooding regime on the speciation and solubility of Cd and As in paddy soils, uptake of Cd and As by rice, and soil microbial communities with emphasis on bacteria driving reduction and/or oxidation of Mn, As, and S, and (v) based on the results of (i)-(iv), develop improved paddy management strategies for reducing both Cd and As uptake simultaneously. These strategies will be tested as far as possible in pot experiments and field trials.In the first project year, we will conduct a field survey collecting soils and rice plants at 30 sites in southern China to explore which soil parameters can be used to empirically predict Cd and As uptake by rice. The collected soils will also be used in soil incubation (microcosms) and pot experiments to study Cd and As mobilization and uptake under controlled environmental conditions. In the second and third project years, field trials will be conducted at two selected field sites, in which various paddy management strategies will be studied. Soil and plant parameters will be measured to explore the effects of liming, S fertilization, irrigation scheme, and Mn additions on soil biogeochemistry (e.g., pore water composition) and plant uptake of nutrients and the toxic trace elements Cd and As. The field trials will be complemented by soil mesocosm and column experiments in which soil redox dynamics and speciation of Cd and As can be followed in much greater detail. These experiments will provide new information on the kinetics of CdS and Mn oxidation in paddy soils and its influence on Cd and As speciation and solubility. Overall, this project will enhance our understanding of Cd and As biogeochemistry in paddy soils and, thereby, to the development of improved paddy management strategies for minimizing Cd and As uptake by rice grown in contaminated soils of China and other rice-growing regions. Thus, the project will make an important contribution to securing safe food for a growing population in Asia and worldwide.