1. Introduction. - 1. 1 Persistence of Organic Contaminants in the Subsurface Environment. - 1. 2 Nonequilibrium Transport Remediation of Contaminated Sites. - 1. 3 Diffusion in Sediments and Rocks. - 2. Basics of Sorption and Diffusion in Soils and Sediments. - 2. 1 Sorption of Organic Compounds in Soils and Sediments. - 2. 2 Mass Transfer by Diffusion. - 3. Modeling of Diffusion Processes. - 3. 1 Intraparticle Diffusion. - 3. 2 Diffusion into Layers of Low Permeability. - 4. Measured Diffusion Coefficients. - 4. 1 Time-Lag Experiments. - 4. 2 Diffusion Coefficients from Sorption/Desorption Kinetics. - 4. 3 Prediction of Diffusion Coefficients. - 5. Dissolution Kinetics of Non Aqueous Phase Liquids. - 5. 1 Aqueous Solubility of Organic Compounds. - 5. 2 Dissolution Kinetics. - 6. Risk Assessment Remediation. - 6. 1 Risk Assessment: Release Rates. - 6. 2 Time Scales of Soil and Groundwater Remediation. - 6. 3 Transport by Diffusion Compared to Advection. - References. - Appendices. - I. Analytical Methods: TCE and Phenanthrene. - II. Methods of Solids Characterization. - III. TCE-Diffusion Data: Time-Lag Method. - IV. Tracer Diffusion Data. - V. Examples for Long-Term Sorption Kinetics of Phenanthrene. Language: English