This book covers the fundamentals of aquatic chemistry, the chemistry of aqueous solutions, and their application to natural waters and other aquatic systems. The various chemical reactions are discussed in detail based on thermodynamic equilibria and kinetic principles, and quantitatively addressed with numerous examples and exercises. This foundational knowledge allows for an understanding of the chemical processes in natural waters and in technical systems for wastewater treatment and drinking water purification. In the new edition, all chapters have been revised in light of current developments. An additional chapter addresses applications to lake, river, and groundwater systems. The book is aimed at students of natural and environmental sciences and related fields such as hydrology, limnology, and hydrogeology.