学位专题

封面
声明
中文摘要
英文摘要
目录
Abbreviations
List of Figures
List of Tables
Chapter 1 Introduction
1.1Environmental significance of arsenicand cadmium in the environment
1.2Sources of As and Cd
1.2.1 Geogenic or natural sources of As and Cd
1.2.2 Anthropogenic sources of As and Cd
1.3 Arsenic and Cd speciation in nature
1.3.1 Organic and inorganic As species
1.3.2 Cdspecies
1.4 Biogeochemical cycles of arsenicand itsspeciation transformation by microorganisms in nature
1.4.1Microbial reduction of As (Ⅴ) to As (Ⅲ)
1.4.2Microbial oxidation of As (Ⅲ) to As (Ⅴ)
1.4.3 Arsenic methylation of As(Ⅲ)and the straight head disease
1.5 As and Cd toxicity and their dietary exposure to humans
1.6Aim of the study
1.7Research content and plan
Chapter 2A Critical Review of the Mechanisms and Strategy to Simultaneously Mitigate Arsenic and Cadmium Over-accumulation in Crop Food
2.1 Introduction
2.2The co-contamination of As and Cd in agricultural soils worldwide and their accumulation in the edible part
2.3 The biogeochemistry of As and Cd in soils and the influencing factors
2.3.1 Soil redox potential (Eh)
2.3.2 Soil pH
2.3.3Soil organic matter
2.3.4 Other factors
2.4The current approaches in mitigating As and Cdbio-availability and its associated mechanisms
2.4.1 Water management
2.4.2 Chemical passivation
2.4.3 Foliage dressing
2.4.4Cultivation with crops of low risk of As and Cd accumulation
2.4.5Phytoremediation with As and Cdhyper-accumulating plant
2.5 Conclusions and future perspectives of the study
Chapter 3Soil Ridge Cultivation Maintains Grain As and Cd at Low Levels and Inhibits As Methylation by Changing ArsM-harboring Bacterial Communities in Paddy Soils
3.1 Introduction
3.2Materials and Methods
3.2.1 Field experiments
3.2.2 Sample collection
3.2.3 Chemical analysis
3.2.4 Soil RNA extraction and RT-qPCR
3.2.5 High-throughput 16S rRNA and arsM sequencing
3.2.6Statistical analysis
3.3 Results
3.3.1Grain thousand-seed weight and As and Cd in rice tissues
3.3.2 As and Cd content in soil porewater
3.3.3.Grain and porewater As and Cd changed with soil Eh and pH
3.3.4 Porewater Fe, Mn, and S
3.3.5 RT-qPCR of functional genes regulating As transformation and Cd-resistance
3.3.6Amplicon sequencing of arsM and 16S rRNA
3.4 Discussion
3.4.1 Soil ridge cultivation achieved a low grain As and Cd trade-off by changing their mobility in paddy soil
3.4.2 Soil ridge cultivation decreased DMAs in rice grain and porewater
3.4.3 Soil ridge cultivation changed the microbial community associated with As methylation
3.5 Conclusion
Chapter 4 Simultaneous Alleviation of Arsenic and Cadmium in Contaminated Paddy Fieldby Water Management Plus Chemical Passivation
4.1 Introduction
4.2Materialand Methods
4.2.1 Field experiments
4.2.2Sample collection
4.2.3Chemical analysis
4.2.4Analysis of As and Cd in rice plants parts
2.6.Statistical analysis
4.3 Results
4.3.1 pHand Eh at field condition
4.3.2 As and Cd in gain and rice plant parts (husk, straw and root)
4.2.3 Fe, Mn and S contents in soil porewater in paddy field
4.4 Discussion
4.5 Conclusion
Chapter 5 General Conclusion
参考文献
致谢
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