This book provides a comprehensive overview of reaction processes in the Earth's crust and on its surface, both in the laboratory and in the field. A clear exposition of the underlying equations and calculation techniques is balanced by a large number of fully worked examples. The book uses The Geochemist's Workbench(r) modeling software, developed by the author and already installed at over 1000 universities and research facilities worldwide. Since publication of the first edition, the field of reaction modeling has continued to grow and find increasingly broad application. In particular, the description of microbial activity, surface chemistry, and redox chemistry within reaction models has become broader and more rigorous. These areas are covered in detail in this new edition, which was originally published in 2007. This text is written for graduate students and academic researchers in the fields of geochemistry, environmental engineering, contaminant hydrology, geomicrobiology, and numerical modeling.This book definitively demystifies geochemical modeling of water-rock reactions and makes it a breeze ... An outstanding book for students, teachers, researchers, and professionals ... interested in any low-temperature geochemical endeavor."Journal of Geology"The book is well organized, the concepts are rigorously and clearly explained, and the range of examples are relevant and interesting. The writing style is lucid and concise, and I found the book a pleasure to read. The author also takes a refreshingly balanced view of the role and limitations of modeling."Meteoritics & Planetary Science"... this is a unique book with many valuable insights. Mathematical derivations are balanced by clear, qualitative descriptions of what is going on ... Essential reading for anyone starting off in the study of water-rock interactions, as well as being an extremely valuable reference for people already wrestling with such problems.Bruce Yardley, "Journal of Petrology"... students who have taken appropriate mathematics courses at university level will find their use of geochemical modelling enriched, becoming competent in the use of software by virtue of understanding its mathematical limitations as well as limitations imposed by analytical chemistry. Assuming that the reader is able to grapple with the theory, this book is an extremely valuable resource. ... It is easily accessible to a mathematically literate reader and demonstrates the breadth of application of modelling to a range of geological and engineering problems. Those lacking a strong maths background will find this book challenging but rewarding given its diversity of application and clarity of explanation."Minerological Magazine"