Aqueous Geochemistry

  1. Oxidation-Reduction (Redox) Reactions
    1. Fundamental Concepts
      1. Oxidation States
        1. Assigning Oxidation Numbers
          1. Rules and Conventions
          2. Half-Reactions
            1. Writing Half-Reactions
              1. Balancing Redox Reactions
              2. Electron Donors and Acceptors
                1. Common Donors in Natural Waters
                  1. Common Acceptors in Natural Waters
                    1. Redox Couples
                  2. The Electron Activity and Redox Potential
                    1. Defining pE and Eh
                      1. Relationship between pE and Eh
                        1. Standard Electrode Potentials
                        2. The Nernst Equation
                          1. Derivation and Application
                            1. Application to Natural Waters
                              1. Activity Corrections
                              2. The pE-pH Relationship
                                1. Coupled Reactions
                                  1. Interpretation and Use
                                2. Redox Disequilibrium in Natural Waters
                                  1. Causes of Disequilibrium
                                    1. Kinetic Limitations
                                      1. Multiple Redox Couples
                                      2. Consequences of Disequilibrium
                                        1. Examples in Environmental Systems
                                        2. pE-pH (Pourbaix) Diagrams
                                          1. Construction and Interpretation
                                            1. Thermodynamic Basis
                                              1. Axes and Fields
                                                1. Reading Stability Regions
                                                  1. Activity Assumptions
                                                  2. Stability Fields of Water
                                                    1. Upper and Lower Stability Limits
                                                      1. Oxygen and Hydrogen Evolution
                                                      2. Diagrams for Key Elements
                                                        1. Iron System
                                                          1. Manganese System
                                                            1. Sulfur System
                                                              1. Nitrogen System
                                                                1. Carbon System
                                                                2. Applications and Limitations
                                                                3. Redox Zonation in Natural Systems
                                                                  1. The Redox Ladder
                                                                    1. Thermodynamic Sequence
                                                                      1. Sequence of Electron Acceptors
                                                                        1. Energy Yields
                                                                        2. Redox Sequences in Groundwater
                                                                          1. Oxic Zone
                                                                            1. Nitrate Reduction Zone
                                                                              1. Manganese Reduction Zone
                                                                                1. Iron Reduction Zone
                                                                                  1. Sulfate Reduction Zone
                                                                                    1. Methanogenic Zone
                                                                                    2. Redox Sequences in Sediments
                                                                                      1. Vertical Zonation
                                                                                        1. Seasonal Variations
                                                                                        2. Redox Sequences in Lakes
                                                                                          1. Stratification Effects
                                                                                            1. Hypolimnetic Anoxia
                                                                                          2. Microbial Mediation of Redox Reactions
                                                                                            1. Role of Microorganisms
                                                                                              1. Enzymatic Catalysis
                                                                                                1. Biogeochemical Cycles

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                                                                                              4. Mineral-Water Interactions

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                                                                                              6. Complexation and Speciation