Sulphur Isotopes in Nature and the Environment: An Overview; Oxygen Isotope Fractionation for Understanding the Sulphur Cycle; The Isotopic Analysis of Sulphur and Oxygen; Lithospheric Sources of Sulphur; Sulphur Isotope Variations in the Atmosphere; Hydrosphere; Pedosphere and Biosphere; Sulphur Isotope Tracing of the Fate of Emissions from Sour Gas Processing in Alberta, Canada.