Sect. I. Isotope Fundamentals -- Fundamentals of Environmental Isotopes and Their Use in Biodegradation / Patrick Hohener and C. Marjorie Aelion -- Analysis of Stable Isotopes / Daniel Hunkeler and Stefano Bernasconi -- Principles and Mechanisms of Isotope Fractionation / Daniel Hunkeler and Martin Elsner -- Isotope Fractionation During Transformation Processes / Daniel Hunkeler and Barbara Morasch -- Sect. II. Isotopes and Microbial Processes -- Isotopes and Aerobic Degradation / C. Marjorie Aelion and Silvia A. Mancini -- Isotopes and Methane Cycling / Edward R.C. Hornibrook and Ramon Aravena -- Isotopes and Processes in the Nitrogen and Sulfur Cycles / Ramon Aravena and Bernhard Mayer -- Sect. III. Isotopes in Field Applications -- Investigating the Origin and Fate of Organic Contaminants in Groundwater using Stable Isotope Analysis / Daniel Hunkeler and Ramon Aravena -- Stable Isotope Fractionation of Gases and Contaminant Vapors in the Unsaturated Zone / Patrick Hohener, Daniel Bouchard and Daniel Hunkeler -- Sect. IV. Isotope Emerging Areas -- Isotopic Labeling in Environmental and Biodegradation Studies / C. Margorie Aelion and R. Sean Norman -- Combined Use of Radiocarbon and Stable Carbon Isotopes in Environmental and Degradation Studies / C. Marjorie Aelion -- Nontraditional Stable Isotopes in Environmental Sciences / Christopher S. Romanek [and others].