Acid-Base Phenomena in the Hydrosphere

Acid-base phenomena in water involve the exchange of ions. An important water quality parameter is the presence of species capable of accepting ions, which is called alkalinity it is a characteristic that is important in the biology, chemistry, and chemical treatment of water. Normally due to the presence of bicarbonate ion, HCOJ, alkalinity serves as a pH buffer and reservoir for inorganic carbon required for algal photosynthesis. Most natural waters are somewhat alkaline. The following three reactions show water alkalinity in the form of bicarbonate, carbonate, and hydroxide ions accepting H ions  

A characteristic that is analogous to alkalinity is acidity, the capability of species in water to produce H ion or to neutralize OH ion. The most common acidic component of water is dissolved CO2, which produces weakly acidic water. Relatively more acidic water with a low pH generally indicates pollution. Acidity may be due to dissolved hydrated metal ions, such as Fe(H20)g, which readily release H ion. Strong acids including H2SO4 and HCl in water are called free mineral acids. Water containing a substantial concentration of free mineral acid may be quite toxic to most forms of aquatic life. The pollutant acid mine water contains an appreciable concentration of free mineral acid, and free mineral acid may enter bodies of water from the atmosphere as acid rain. 

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