Chapter 1 Hydrological and Geochemical Processes Controlling the Fate and Transport of Contaminants in Fractured Bedrock ........................... 1 Philip M. Jardine, Tonia L. Mehlhorn, Y.Roh, and William E. Sanford Chapter 2 Mineral Controls in Colloid-Mediated Transport of Metals in Soil Environments ................................................................ 25 A.D.Karathanasis Chapter 3 A Web-Based Three-Dimensional Simulation System for Solute Transport in Soil ..................................................................... 51 Honghai Zeng, Vladimir J. Alarcon, William L. Kingery, H.Magdi Selim, and Jianping Zhu Chapter 4 Effect of Structural Charges on Proton Adsorption at Clay Surfaces .......... 79 Marcelo J. Avena and Carlos P. De Pauli Chapter 5 Molecular Modeling of Fulvic and Humic Acids: Charging Effects and Interactions with Al3+, Benzene, and Pyridine ........................... 113 James D. Kubicki and Chad C. Trout Chapter 6 Silicon-Organic Interactions in the Environment and in Organisms ........... 145 Nita Sahai Chapter 7 Formation of Biogenic Manganese Oxides and Their Influence on the Scavenging of Toxic Trace Elements .................................. 169 Yarrow M. Nelson and Leonard W. Lion Chapter 8 Zinc Speciation in Contaminated Soils Combining Direct and Indirect Characterization Methods ................................................... 187 Darryl Roberts, Andreas Scheinost, and Donald L. Sparks Chapter 9 Reduction/Cation Exchange Model of the Coincident Release of Manganese and Trace Metals following Soil Reduction .................................. 229 Dean M. Heil, Grant E. Cordon, and Colleen H. Green Chapter 10 Behavior of Heavy Metals in Soil: Effect of Dissolved Organic Matter ....... 245 Lixiang X. Zhou and J.W.C.Wong Chapter 11 Analytical Techniques for Characterizing Complex Mineral Assemblages: Mobile Soil and Groundwater Colloids ....................................... 271 John C. Seaman, M.Guerin, B.P.Jackson, P.M.Bertsch, and J.E.Ranville Chapter 12 Kinetic Modeling of Sulfate Transport in a Forest Soil ..................... 311 H.Magdi Selim, George R. Gobran, Ximing Guan, and Nicholas Clarke Chapter 13 Solubility of Fluoride in Semi-Arid Environments ........................... 331 K.J.Reddy, Michelle M. Patterson, J.Daniel Rodgers, Richard E. Jackson, and Barry L. Perryman Index ...................................................................... 351