Geochemical Equilibrium Modeling in Soils and Sediments

I. Introduction a. The dynamic nature of sediments and soils b. A brief history of applying equilibrium concepts to soils c. Overview of geochemical modeling d. The structure of this textbook e. Average elemental composition of soils and sediments f. Problems g. References II. Theoretical development of chemical equilibrium concepts a. Thermodynamic development b. The equilibrium constant c. Ionic strength and activity coefficients d. Oxidation/reduction reactions e. Measurement of pH and Eh f. Problems g. References III. Geochemical models and modeling a. Overview of types of models available b. Model components needed for application to soils and sediments c. Structure of the model d. Input requirements e. Output structure f. Limitations of equilibrium modeling i. Primary vs secondary minerals ii. The importance of dissolution/precipitation kinetics iii. Non-equilibrium 1. Oxy-anions 2. Some redox transitions g. Visual MINTEQ: brief tutorial h. Problems i. References IV. Aluminum a. Table of equilibrium constants: solids, solution species b. Solubility of aluminum oxides, hydroxides, sulfates i. Primary minerals: theoretical but unattainable equilibrium c. Solution complexes of Al3+: hydrolysis, fluorides, sulfates, chlorides, others d. Estimating Al3+ activity from solubility data i. Hand calculations ii. MINTEQ modeling e. Published examples f. Redox reactions of Al in soil and sediments g. Problems h. References V. Silica a. Table of equilibrium constants: solids, solution species b. Forms of silica in soils and sediments: crystalline, amorphous, nanocrystalline c. Solubility of silicon oxides d. Stability diagrams for silicates e. Solution species of Si f. Published examples g. Problems h. References VI. Aluminosilicate minerals a. Table of equilibrium constants: solids, solution species b. Primary vs secondary minerals; dissolution/precipitation kinetics c. Brief summary of types of aluminosilicate minerals i. Conventions in writing unit cell formulae d. Stability diagrams for aluminosilicates e. Unique issues and challenges for chemical equilibria of aluminosilicates f. Published examples g. Problems h. References VII. Carbon dioxide and carbonate equilibria a. CO2 and carbonate equilibria in pure aqueous systems b. Carbonates in soils and sediments c. Published examples d. Problems e. References VIII. Calcium a. Table of equilibrium constants: solids, solution species b. Calcium silicates and aluminosilicates c. Carbonates, sulfates, others d. Stability diagrams for calcium minerals e. Solution complexes f. The phase rule i. CO2-H2O pure system equilibria ii. CaO-CO2-H2O pure system equilibria iii. H2SO4-CaO-CO2-H2O pure system equilibria g. Published examples; apparent calcite nonequilibrium h. Problems i. References IX. Magnesium a. Table of equilibrium constants: solids, solution species b. Magnesium silicates and aluminosilicates c. Carbonates, sulfates, others d. Stability diagrams for magnesium minerals e. Solution complexes f. Published examples g. Problems h. References X. Sodium and Potassium a. Table of equilibrium constants: solids, solution species b. Sodium and potassium solid phases c. Stability diagrams for Na and K minerals d. Solution complexes e. Published examples f. Problems g. References XI. Iron a. Table of equilibrium constants: solids, solution species, redox species b. The critical role of oxidation reduction potentials in Fe chemistry in soils, sediments, and water c. Ferric, ferrous, and mixed solid phases d. Stability diagrams for Fe(III), Fe(II), and mixed oxide minerals e. Solution complexes f. Published examples; the complex world of Fe in the environment g. Problems h. References XII. Manganese a. Table of equilibrium constants: solids, solution species, redox species b. The critical role of oxidation reduction potentials in Mn chemistry in soils, sediments, and water c. Manganic, manganous, and mixed solid phases d. Stability diagrams for manganese minerals e. Solution complexes f. Published examples; the unique chemistry of Mn in natural systems g. Problems h. References XIII. Phosphate a. Table of equilibrium constants: solids, solution species b. Solution chemistry of orthophosphate c. Solubility of Fe phosphates d. Solubility of Al phosphates e. Effect of redox on the solubility of Fe phosphates f. Solubility of Ca phosphates g. Solubility of Mn phosphates h. Stability diagrams for phosphates i. Published examples i. Evidence for amorphous Al phosphate ii. Evidence for the presence of Mn(II)phosphate and its amorphous analog iii. Ca phosphate solubility j. Problems k. References XIV. Zinc a. Table of equilibrium constants: solids, solution species b. Zinc solid phases c. Stability diagrams for zinc minerals d. Solution complexes e. Published examples; “soil-Zn” f. Problems g. References XV. Copper a. Table of equilibrium constants: solids, solution species b. Copper solid phases c. Stability diagrams for copper minerals d. Solution complexes e. Published examples; criteria for possible formation of solid phases f. Problems g. References XVI. Nitrogen a. Table of equilibrium constants: solids, solution species b. Oxidation states of nitrogen c. Challenges in applying equilibrium to gaseous nitrogen compounds i. Theoretical equilibrium between atmospheric N2 and O2 d. Redox equilibria for gaseous nitrogen species e. Redox equilibria for soluble nitrogen species f. Stability diagrams for nitrogen species g. Published examples; nitrogen transformations in soil, water, atmosphere h. Problems i. References XVII. Sulfur a. Table of equilibrium constants: solids, solution species b. Overview of the complexity of sulfur in solid phase and solution c. Effect of redox on sulfur solution species d. Sulfate solids e. Sulfide solid phases f. Effect of redox on solubilities i. Sulfide solids ii. Metal solubilities g. Stability diagrams for sulfur-based minerals h. Solution species, complexes i. Published examples; sulfur transformations in soil, water, atmosphere j. Problems k. References XVIII. Lead a. Table of equilibrium constants: solids, solution species b. Lead solid phases c. Stability diagrams for Pb minerals d. Solution complexes e. Published examples; the immobility of Pb f. Problems g. References XIX. Cadmium a. Table of equilibrium constants: solids, solution species b. Cadmium solid phases c. Stability diagrams for Cd minerals d. Solution complexes e. Published examples; the challenges of traces metals f. Problems g. References XX. Arsenic a. Table of equilibrium constants: solids, solution species b. Arsenic solid phases c. Role of redox in As transitions d. Stability diagrams for As minerals e. Solution complexes f. Published examples; interactions between As and phosphate g. Problems h. References XXI. Strontium a. Table of equilibrium constants: solids, solution species b. Strontium solid phases c. Stability diagrams for Sr minerals d. Solution complexes e. Published examples; environmental significance of Sr f. Problems g. References XXII. Plutonium a. Table of equilibrium constants: solids, solution species b. Plutonium solid phases c. Pu redox reactions d. Stability diagrams for Pu minerals e. Solution complexes f. Published examples; Pu and other radionuclides g. Problems h. References XXIII. Natural Organic ligands a. Background b. Occurrence c. Table of equilibrium constants: acidity, complexation d. Acid/base chemistry e. Redox relationships f. Ligand complexation g. Problems h. References XXIV. Chelate equilibria a. Occurrence of chelates in soils i. Natural ii. Synthetic b. Potential importance of chelates in the chemistry of soils and sediments c. Table of selected equilibrium constants for selected metals d. Applications of geochemical modeling of chelate equilibria e. Published examples f. Problems g. References