Salt evaporation pond

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Salt evaporation pond in Île de Ré, France
Natural salt evaporation ponds at Pedra de Lume, Sal island, Cape Verde
A salt pan worker in a salt evaporation pond in Tamil Nadu, India.

Salt evaporation ponds, also called salterns or salt pans, are shallow artificial ponds designed to extract salts from sea water or other brines. 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.

Algae and colour of evaporation ponds[edit]

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. In middle- to high-salinity ponds, Halobacteria, which is actually a group of halophilic Archaea (sometimes called Haloarchaea), shift the colour to pink, red and orange. Other bacteria such as Stichococcus also contribute tints.[citation needed]

Notable salt ponds[edit]

Notable salt ponds include:

Until World War II, salt was extracted from sea water in a unique way in Egypt near Alexandria.[6] 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.

Salt pans[edit]

Salt pans are shallow open, often metal, pans used to evaporate brine for the production of salts. 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[edit]

References[edit]

  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, 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. ^ [1]
  6. ^ Salt, Grown On Sticks Harvested From Sea, Popular Science, March 1933

External links[edit]