TABLE OF CONTENTS Water supplies are not pure in the sense that they are devoid of all dissolved chemical compounds like distilled deionized water but are contaminated by a wide range of trace elements and compounds. In the early days of chemistry, water was known as the universal solvent, due to its ability to slowly dissolve into solution anything it comes into contact with, from gases to rocks. So as rain falls through the atmosphere, flows over and through the Earth s surface, it is constantly dissolving material, forming a chemical record of its passage from the clouds. Therefore, water supplies have a natural variety in quality, which depends largely on its source.
The total volume of water in the world remains constant. What changes is its quality and availability. Water is constantly being recycled, a system known as the water or hydrological cycle. Hydrologists study the chemical and physical nature of water, and its movement both on and below the ground. In terms of total volume, 97.5% of the world s water is saline with 99.99% of this found in the oceans, and the remainder making up the salt lakes. This means that only 2.5% of the volume of water in the world is actually non-saline. However, not all of this freshwater is...
