This newly published book is an organized collection of papers dealing with changes in the quality of water as it moves through the world's hydrologic cycle-from the sea, lakes, and rivers-to its hydrosphere and then back to earth as precipitation, where the water again percolates through the soil or falls on the ocean, rivers, or lakes. (Changes that occur are physical, chemical, and biological.) Though chapters discuss results of specific lab or field experiments which in themselves have value for the scientist, focus is on processes involved. Many general concepts of water quality are provided in this cohesively organized book.