Chapter 1 Characterization and Disposal of Bauxite Residue 1.1 Introduction 1.2 Generation of Bauxite Residue 1.2.1 Bauxite Production and Global Reserves 1.2.2 Production Process of Alumina 1.2.3 Annual Production and Inventory of Bauxite Residue 1.3 Properties of Bauxite Residue 1.3.1 Physical Properties 1.3.2 Chemical Properties 1.3.3 Biological Properties 1.4 Management of Bauxite Residue 1.4.1 Conventional Disposal of Bauxite Residue 1.4.2 Utilization of Bauxite Residue 1.5 Alkalinity Transformation of Bauxite Residue 1.5.1 Alkaline Solid Transformation 1.5.2 Waste Acid Synergy 1.5.3 Acid Gas Sequestration 1.5.4 Chloride Salt Neutralization 1.6 Soil Formation and Revegetation of Bauxite Residue 1.6.1 Amelioration of Bauxite Residue 1.6.2 Screening of Tolerant Plant Species and Microorganisms 1.6.3 Soil Formation in Bauxite Residue References Chapter 2 Novel Predictors of Soil Genesis in Bauxite Residue under Natural Weathering Processes 2.1 Natural Evolution of Alkaline Characteristics in Bauxite Residue 2.1.1 Transformation of Basic Alkalinity 2.1.2 Transformation of Electrical Conductivity 2.1.3 Transformation of Exchangeable Cations 2.1.4 Transformation of Acid Neutralizing Capacity 2.1.5 Environmental Management for Long-Term Disposal 2.2 Natural Plant Colonization Improves Physical Conditions of Bauxite Residue 2.2.1 Particle Size Distribution 2.2.2 Bulk Density and Total Porosity 2.2.3 Mean Weight Diameter (MWD) and Water-Stable Aggregates (WSA) 2.2.4 Structural Stability Index (SI) 2.3 Development of Alkaline Electrochemical Characteristics 2.3 . l Mineralogy 2.3.2 Zeta Potential Curves and |soelectric Point 2.3.3 Surface Protonation and Alkaline Group 2.4 Dynamic Development of Bacterial Community Diversity and Structure 2.4.1 Residue Properties 2.4.2 Diversity of Bacterial Community 2.4.3 Composition of Bacterial Community 2.4.4 Correlation between Bacterial Community and Residue Property 2.5 Novel Predictors of Soil Genesis in Bauxite Residue 2.5.1 Variation of Chemical Properties 2.5.2 Variation of Physical Properties 2.5.3 Effects on Aggregate Stability 2.5.4 Novel Predictors of Soil Genesis
References Chapter 3 Aggregate Formation and Stability in Bauxite Residue Following Soil Genesis 3.1 Erosion Resistance of Water-Stable Aggregates in Bauxite Residue 3.1.1 Distribution of Aggregate Fractions and MWD by the Modified Yoder's Method 3.1.2 Distribution of Aggregate Fractions and MWD by the Modified Le Bissonnais' Method 3.1.3 The Erodibility Factor (K) of Bauxite Residues 3.1.4 Variable Effectiveness of Mechanisms to Erosion of Bauxite Residue 3.2 Effects of Iron-Aluminum Oxides and Organic Carbon on Aggregate Stability 3.2.1 Iron-Aluminum Oxide Contents and Their Relationship with Aggregate Stability 3.2.2 Aggregate-Associated Carbon and the Relationship with Aggregate Stability 3.2.3 Variation of Aggregate-Associated Organic Carbon Functional Groups 3.3 Fractal Features of Residue Microaggregates in Bauxite Residue Disposal Areas 3.3.1 Particle Size Distribution of Residue Microaggregates 3.3.2 Microaggregate Stability of the Residues 3.3.3 Single-Fractal Features of Residue Microaggregates 3.3.4 Multi-Fractal Dimension of Residue Microaggregates 3.3.5 Relationship between Microaggregate Stability and Fractal Parameters 3.4 Effects of Binding Materials on Micro-Aggregate Size Distribution in Bauxite Residues 3.4.1 Effect of Organic Matter 3.4.2 Effect of Carbonate on Residue Microaggregate Size Distribution 3.4.3 Effect of Electrolyte on Residue Microaggregate Size Distribution 3.4.4 Effect of Clay Mineralogy on Residue Microaggregate Size Distribution 3.4.5 Effect of Iron-Aluminum Oxides on Residue Microaggregate Size Distribution 3.5 Evaluation on Aggregate Microstructures Following Natural Regeneration 3.5.1 Residue Micromorphology 3.5.2 Visualization of Soil Aggregates 3.5.3 Porosity and Pore-Size Distribution 3.5.4 Shape Parameters in Residue Aggregates 3.5.5 Effects on Residue Aggregate Microstructure 3.6 Vermicompost and Gypsum Improve Aggregate Formation in Bauxite Residue 3.6.1 Residue Properties 3.6.2 Residue Macroaggregate Formation 3.6.3 Residue Microaggregate Formation 3.6.4 Residue Micromorphology References Chapter 4 Regulation on Saltinity and Alkalinity of Bauxite Residue Following Soil Genesis 4.1 Migration and Distribution of Saline Ions in Bauxite Residue during Water Leaching 4.1.1 Change of Saline Cation Concentration in Leachate 4.1.2 Change of Saline Anion Concentration in Leachate 4.1.3 Vertical Distribution of Saline Cations in Residue 4.1.4 Vertical Distribution of Saline Anion in Residue 4.1.5 Potential Implication for Revegetation 4.2 Leaching Optimization and Dissolution Behavior of Alkalin 4.2.6 Leaching Kinetics of Critical Anions 4.3 Effect of Ammonium Chloride on leaching Behavior of Ions in Bauxite Residue 4.3.1 Effect of Ammonium Chloride Addition 4.3.2 Effect of L/S Ratio 4.3.3 Effect of Leaching Temperature 4.3.4 Effect of Leaching Time 4.3.5 Orthogonal Experimental Analysis for Optimized Regulating Conditions 4.3.6 Mineral and Morphology Characteristics 4.4 Acid Transformation of Bauxite Residue: Conversion of Its Alkaline Characteristics 4.4.1 Mineral Chemistry 4.4.2 Solution Chemistry 4.4.3 Morphology Characteristics 4.4.4 Implications for Bauxite Residue Disposal 4.5 Alkalinity Stabilization Behavior of Bauxite Residue Following Gypsum Regulation 4.5.1 Effect of Gypsum Addition 4.5.2 Effect of Stabilized Time 4.5.3 Effect of Stirring Strength 4.5.4 Behavior of Chemical Regulation 4.5.5 Behavior of Physical Immobilization 4.6 Phosphogypsum Stabilization of Bauxite Residue: Conversion of Its Alkaline Characteristics 4.6.1 The Influence of Phosphogypsum Quantity upon Bauxite Residue 4.6.2 Effect of Contact Time upon Interaction of Phosphogypsum and Bauxite Residue 4.6.3 Evaluation of Dissolution of Bauxite Residue 4.6.4 Mineral Phase and Morphology Characteristics 4.7 Organic Acid and Gypsum Improve Alkalinity Transformation of Bauxite Residue 4.7.1 Mineralogy 4.7.2 Isoelectric Point 4.7.3 Alkaline Group 4.7.4 Particle Micromorphology 4.7.5 Mineral Acids Addition 4.7.6 Organic Acid Addition 4.7.7 Gypsum Addition 4.7.8 Implications for Bauxite Residue Management References Chapter 5 Environmental Risk Assessment on Bauxite Residue Disposal Areas Following Soil Genesis 5.1 Regional-Scale Investigation of Salt Ion Distribution Characteristics in Bauxite Residue 5.1.1 Salt Composition in Bauxite Residue 5.1.2 Mineralogical Composition in Bauxite Residue 5.1.3 Correlation Analysis of Salt Ions in Bauxite Residue 5.1.4 Degree of Salinization and Alkalization in Bauxite Residue 5.2 Spatial Distribution of Soil Chemical Properties Around Bauxite Residue Disposal Area 5.2.1 Descriptive Statistics of Soil Surrounding BRDA 5.2.2 Chemical Compositions of the Bauxite Residue 5.2.3 Spatial Distribution of Heavy Metals, Salinity, and Alkalinity in Soils 5.2.4 Correlation Analysis 5.2.5 Potential Source Analysis of Chemicals in Soils 5.2.6 Assessment of Environmental Impact
5.3 Effect on the Leaching of Metals from Bauxite Residue 5.3.1 Properties of the Materials 5.3.2 Evaluation of NA and FS Neutralization 5.3.3 Effect of Ferrous Sulfate and Nitrohumic Acid on the Composition of Bauxite Residue 5.3.4 Changes of Metal Fractionation in Bauxite Residue 5.3.5 Leaching Property of Metals from Bauxite Residue References Chapter 6 Ecological Rehabilitation on Bauxite Residue Disposal Areas: Field Studies 6.1 Indicators of Soil Formation in Restored Bauxite Residues 6.1.1 Restoration Strategies on the Disposal Area 6.1.2 Changes on Properties of Bauxite Residue 6.1.3 Screening on Indicators of Soil Formation 6.2 An Evaluation of Revegetation Success on Bauxite Residue 6.2.1 Plant Diversity on the Resoted Bauxite Residue 6.2.2 Evaluation of Revegetation Success 6.3 Nematode Assemblages in Bauxite Residue with Different Restoration Histories 6.3.1 Soil Properties under Different Bauxite Treatments 6.3.2 Nematode Assemblages 6.3.3 Relationships between Soil and Nematode Assemblage Properties 6.4 Macro-Arthropod Succession in Grassland Growing on Bauxite Residue 6.4.1 Arthropods and Soil Properties in Bauxite Residue Treatments 6.4.2 Macro-Arthropod Succession on Bauxite Residue 6.5 Bacterial Communities Established in Bauxite Residues 6.5.1 DNA Extraction and Amplification 6.5.2 Quantitative Amplification 6.5.3 Gel Electrophoresis 6.5.4 DNA Fingerprinting 6.5.5 Alpha and Beta Diversity 6.5.6 Surface Properties of Bauxite Residues 6.5.7 Taxonomic Analysis 6.5.8 Effects of Bacterial Communities on Bauxite Residue 6.6 Sustained Bauxite Residue Rehabilitation 16 Years after Initial Treatment 6.6.1 Sampling Observations 6.6.2 Substrate Characteristics 6.6.3 Geochemistry of20-Year Old Untreated Bauxite Residue 6.6.4 Treated Bauxite Residue 6.6.5 Long-Term Maintenance of Beneficial Conditions References
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