Alkalinity (Environmental & Earth Science)
Alkalinity
In oceanography, alkalinity is a property of sea water (Seas of the world) operationally defined as the excess positive charge to be balanced by carbonate (CO3) and bicarbonate (HCO3) ions. The carbonate ion content of any unit of sea water is equal to its alkalinity (i.e. excess positive charge) minus its total dissolved carbon content.
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More broadly in the water chemistry field, alkalinity is the quantitative measure of a given sample to neutralize acid; in other words, alkalinity is the measure of the quantity of acid that can be added to a liquid without causing a significant change in pH. Alkalinity is not an equivalent concept to pH, because a water sample may have high alkalinity without being highly basic (high pH). In the commercial water treatment field, alkalinity is typically expressed in milligrams per liter of equivalent calcium carbonate.
Common constituents of alkalinity
Within the natural environment, carbonate ions comprise the majority of alkalinity in natural waters, due to the widespread occurrence and dissolution of carbonate rocks and also the presence of carbon dioxide in the atmosphere (Earth's atmosphere). Other common naturally occurring chemical species that contribute to alkalinity include hydroxide, borate, phosphate, silicate, nitrate, dissolved ammonia, the conjugate bases of certain organic acids and sulfide ions.
Further Reading
- Physical Oceanography Index, an EoE article.
- Wallace S. Broecker, Tsung-hung Peng and Zhonghong Beng (1982), Tracers in the Sea, Eldigo Press, ISBN 0-9617511-0-X.
- Stanley E. Manahan (2005), Environmental Chemistry, 8th Edition, CRC Press, ISBN 1-56670-633-5.
