Geochemistry Revisited: Selected Aspects -- Characterization of the Subsurface Environment -- Selected Geochemical Processes -- Properties of Potential Contaminants: Environmental and Health Hazards -- Inorganic and Organometallic Compounds -- Organic Compounds -- Contaminant Partitioning in the Subsurface -- Sorption, Retention, and Release of Contaminants -- Contaminant Partitioning in the Aqueous Phase -- Partitioning of Volatile Compounds -- Selected Research Findings: Contaminant Partitioning -- Contaminant Transport from Land Surface to Groundwater -- Water Flow in the Subsurface Environment -- Transport of Passive Contaminants -- Transport of Reactive Contaminants -- Selected Research Findings: Contaminant Transport -- Transformations and Reactions of Contaminants in the Subsurface -- Abiotic Contaminant Transformations in Subsurface Water -- Abiotic Transformation at the Solid-Liquid Interface -- Biologically Mediated Transformations -- Selected Research Findings: Transformations and Reactions.