Our oceans cover about 71% of the total Earth and most water in the atmosphere and crust comes from these saline (salty) oceans. Freshwater accounts for only 2.5% of the total area!
What is ‘Salinity’ and how do we measure?
Salinity is related to the concentration of dissolved salts in seawater. In the past, this was measured by evaporating the water and weighing the amount of salt remaining. Since that method is time consuming, electrical conductivity is now used to measure and gives fast and accurate seawater salinity data.
Conductivity increases as salt content of the water increases and salinity is greatest in warm, tropical surface waters. It is lowest in areas with large inputs of water from rivers.
Salinity is more or less equal to the weight of salt dissolved in 1000 g of seawater. This is the salt concentration in parts per thousand (‰). Average ocean water has a salinity of 35.0 In other words; 1000 gram of average seawater contains 965 g of water and 35 g of salts.
Where sea salts came from?
Sea salts mostly came from the weathering of rocks on land (the cations) and from the interior of the earth (anions). The weathering of rock on land is a slow process of breakdown by water. Rivers carry the dissolved ions to the oceans.
The ocean salt composition and concentration is in "steady state". This means that it does not change significantly over time. Evidence indicates that sea salt concentration and composition has been about the same for 1.5 billion years at least. The tolerances of bacteria that probably lived 3.8 billion years before present, indicate that sea salt concentration and composition were not too different, even that long ago.
What is SALT and what about the chemistry of it?
The salt we put on our food is actually Sodium-Chloride and is made up of a metal, Na1 (Sodium), and a non-metal Cl1 (Chlorine). Usually, you see this written as NaCl.
How do Sodium and Chlorine get together and ‘transform’ to SALT?
- A Sodium atom has one electron in the outer shell, and it really wants to get rid of it because every atom wants eight electrons and it don’t like to have seven more….
- A Chlorine atom has seven electrons in the outer shell and need only one more to become to eight, which is an easy ‘deal’….
When the two atoms come together, the sodium electron ‘jumps’ to the chlorine. Sodium is loosing one to zero and the chlorine is ‘getting’ one to eight! Now both atoms are happy….!
But what is really happening? When the neutral Sodium atom loses an electron, it becomes a positively charged ion, and when the neutral Chlorine atom gains one, it becomes a negatively charged ion. An ion is a positive (cation) or negative (anion) charged atom.
Almost similar as humans, opposites attract so, ions become bonded and SALT is formed!
When salt dissolves in water, the compound breaks apart into the cations and anions! Therefore, salt is called an Ionic bond, which is a moderate strong chemical bond were ions are held together by electrostatic forces. Water, H2O, e.g., is a strong chemical or ‘covalent’ bond with 1 Oxygen and 2 Hydrogen atoms who are ‘sharing’ their electrons and who are not opposite charged!
What about salt and (sea) water?
Six major ions make up more than 99% of the total dissolved ions in seawater and they are conservative. This means that they have constant ratios, to one another and to salinity, in almost all ocean water. Another way of saying this; sea salts have constant compositions; 55% sodium (Na+), 31% chloride (Cl-), 8% sulfate (SO42-), 4% magnesium (Mg2+), 1% calcium (Ca2+), and 1% potassium(K+).
What about Substances, Nutrients and Elements in sea water?
Most of the substances (other than sea salts) in seawater are non-conservative. Their concentrations vary geographically and with depth, most often due to uptake and release by organisms. Several important gases are non-conservative. These include oxygen and carbon dioxide. Carbon dioxide can react with water to form bicarbonate and carbonate ions. Organisms use carbonate ion and calcium ion to make calcium carbonate shells, which sink after the organisms die to form calcareous sediments.
Another important group of non-conservative substances dissolved in seawater are the nutrients. Nutrients are fertilizers essential for the growth of plants, including algae. Major nutrients include nitrate, phosphate, and silicate. Nutrients are depleted in surface waters, where plants grow, and are found in higher concentrations in deep waters, where the plant and animal remains that sink from surface waters decay.
What about the ‘Elements’?
Every naturally occurring element has been found in seawater! Some, however, have minuscule dissolved concentrations, like: Iron, 0.06 parts per billion (ppb) - Lead, 0.002 ppb - Gold, 0.005 ppb -Protactinium, 0.00000005 ppb.
The conclusion is: "Water is not the source of life, it is life"
We are grateful for using a part of this information of the Ocean Health Team. For more information, please visit: http://oceanplasma.org