This text presents the current knowledge of environmental colloids and includes reviews of the current understanding of structure, role and behaviour of environmental colloids and particles, whilst focussing directly on aquatic systems and soils. In addition, there is substantial critical assessment of the techniques employed for the sampling, size fractionation and characterisation of colloids and particles. Chemical, physical and biological processes and interactions involving colloids are described, and particular attention is paid to quantitative approaches that take account of particle heterogeneity and polydispersity. Presents critical reviews of the state-of-the-art knowledge of environmental colloids Critical assessment of techniques employed for the sampling, size fractionation and characterisation of colloids and particles are given Theoretical and experimental aspects of the methods as well as the required developments and possible recommendations are discussed Each chapter gives a brief introduction general enough for the non-specialist Written by a internationally recognized group of contributors