Paul Alexandre is an experienced isotope scientist. He trained in France before perfecting his skills as a leading member of the Queen’s Facility for Isotope Research in Canada. He has applied isotopes to areas ranging from rainwater and human health to mineral exploration, and he is particularly interested in applications of isotopes in economic geology and mineralogy. Paul is a dedicated professor, who teaches and supervises at Brandon University, Canada.

• Preface.- 1. Introduction.- 2. Theory of isotopes.- 3. Analytical methodology.- 4. Applications in the natural environment.