Salt evaporation pond in Île de Ré, France

A salt evaporation pond is a shallow artificial salt pan designed to extract salts from sea water or other brines. The salt pans are shallow and expansive, allowing sunlight to penetrate and reach the seawater. Natural salt pans are formed through geological processes, where water evaporating, leaving behind salts deposits. Some salt evaporation ponds are only slightly modified from their natural version, such as the ponds on Great Inagua in the Bahamas, or the ponds in Jasiira, a few kilometres south of Mogadishu, where seawater is trapped and left to evaporate in the sun.

The seawater or brine is fed into large ponds and water is drawn out through natural evaporation which allows the salt to be subsequently harvested.

The ponds also provide a productive resting and feeding ground for many species of waterbirds, which may include endangered species.[1] The ponds are commonly separated by levees. Salt evaporation ponds may also be called salterns, salt works or salt pans.

Algae and color

San Francisco Bay salt ponds

Due to variable algal concentrations, vivid colors (from pale green to bright red) are created in the evaporation ponds. The color indicates the salinity of the ponds. Microorganisms change their hues as the salinity of the pond increases. In low- to mid-salinity ponds, green algae such as Dunaliella salina are predominant, although these algae can also take on an orange hue. Halobacteria, a type of halophilic Archaea (also known as Haloarchaea), are responsible for changing the color of middle to high-salinity ponds to shades of pink, red, and orange. Other bacteria such as Stichococcus also contribute tints.

Examples

Notable salt ponds include:

Until World War II, salt was extracted from sea water in a unique way in Egypt near Alexandria.[8] Posts were set out on the salt pans and covered with several feet of sea water. In time the sea water evaporated, leaving the salt behind on the post, where it was easier to harvest.

Production

Salt pans are shallow open, often metal, pans used to evaporate brine. They are usually found close to the source of the salt. For example, pans used in the solar evaporation of salt from sea water are usually found on the coast, while those used to extract salt from solution-mined brine will be found near to the brine shaft. In this case, extra heat is often provided by lighting fires underneath.

See also

References

  1. ↑ Athearn, Nicole D.; Takekawa, John Y.; and Shinn, Joel M. (2009) Avian response to early tidal salt marsh restoration at former commercial salt evaporation ponds in San Francisco Bay, California, USA, Natural Resources and Environmental Issues: Vol. 15, Article 14.
  2. ↑ Napa Salt Pond Complex Archived 2011-08-19 at the Wayback Machine, The Bay Institute
  3. ↑ Salt ponds, South San Francisco Bay, NASA Earth Observatory
  4. ↑ "NASA Helps Reclaim 15,100 Acres Of San Francisco Bay Salt Ponds". Space Daily. Moffett Field. July 14, 2003.
  5. ↑ "Cargill Salt - San Francisco Bay". Archived from the original on 2011-08-07. Retrieved 2011-08-09.
  6. ↑ "The Salt Works". 19 July 2011.
  7. ↑ "Baleni Cultural Camp". African Ivory Route. Transfrontier Parks Destinations. Retrieved 11 September 2019.
  8. ↑ Salt, Grown On Sticks Harvested From Sea, Popular Science, March 1933
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