This main goal of this book is to educate environmental engineers in the applications of aqueous chemical principles in concert with engineering principles in the analysis of both engineered and natural environmental systems. Contexts include water/wastewater treatment, surface mining, agricultural systems, landfills, subsurface saturated and unsaturated porous media, aqueous and marine sediments, surface waters, and atmospheric moisture. Selected concepts and principles have been assembled and then applications of the principles have been examined in various contexts, inclusive of example problems and numerous posed problems that cut across the various contexts of interest.  Many past students, finding the notes immensely helpful, have queried as to when the notes will be updated into a text. Also included is the use of a MathCAD worksheet for mathematically modeling the various systems arising from consideration of the equilibrium behavior of chemical species. Additional topics (environmental reactions and ideal reactors) are included that addresses the application of basic math, engineering and science in multimedia fate and transport.