This book discusses the impacts of uranium pollution and its geochemistry and behaviour in abandoned uranium mining sites. The author starts by presenting an overview of uranium occurrence in nature, its radioactivity, uses and market trends as well as the major uranium deposits of the world, followed by the main characteristics of abandoned uranium sites. Particular attention is given to the common reasons for mine abandonment, conventional and non-conventional uranium extraction techniques, and to ore processing and ore extraction chemistry. The author then explores the topic of uranium mining waste and dives into the uranium dynamics in different abandoned mining sites, including abandoned underground mines, abandoned open pit mine lakes, and abandoned in-situ leaching mines. In this book, readers will also find more about uranium dispersion, ecotoxicological hazards, radioecology and biogeochemistry in abandoned mines. The book ends with a chapter devoted to uranium attenuationin abandoned mining sites, in which the author offers valuable insights into natural attenuation mechanisms and discusses the challenges of natural attenuation in abandoned mines. Readers will find in each chapter a brief introduction to the topic and a chapter conclusion that gathers the main scientific outputs and the author's perspective from the discussion. This book is a valuable resource to understand the environmental issues of uranium in abandoned mine sites and given its breadth, it will appeal to scholars, researchers, professionals and policymakers alike.