Why is sea water salty?

Why is sea water salty?

Sea water is salty because it contains a high concentration of dissolved mineral salts deposited in the rivers that flow into the oceans and seas. To be more precise, it contains approximately 35 grams of salt per liter of water. These mineral salts are the result of the erosion of the rocks deposited in the sea over the years, causing it to reach a certain salinity index. This theory was introduced by English scientist Edmund Halley.

The process begins when the carbonic acid present in rainwater comes into contact with the rocks. This chemical compound, which results from the mixture of carbon dioxide in the air with water, has the ability to erode the rocks it falls on. The resulting ions are deposited into the rivers, and they later end up in the seas and oceans, producing their characteristic salinity. 

In addition to this deposit of eroded rocks, other secondary phenomena contribute to seawater’s salinity, such as water evaporation, volcanic eruptions, melting ice, and hydrothermal vents.  

What is the chemical composition of the salts in seawater?

Salt from seawater contains more than 80 of the 118 elements on the periodic table, which makes it an excellent mineral resource for the human body. In it, you can find:

• Elements like chlorine, sodium, magnesium, potassium, bromine, calcium, boron, strontium, and fluorine. 
• Trace elements such as iron, manganese, copper, iodine, silicon, and phosphorus. 
• Zooplankton and phytoplankton. 

Are all seas equally salty?

A sea’s degree of salinity will depend on its latitude. In colder areas like the Arctic Ocean, the salt concentration is lower compared to tropical areas like the Caribbean Sea, where the concentration of salt is higher. This is due to water being evaporated by solar energy. 

Similarly, in areas where it rains often, the salinity level is low,  as is the case for the Baltic Sea. There, we can find areas where the composition is only 0.6% salt. On the other hand, areas with a lower water flow may have higher salinity, as is the case with the Red Sea.

What is the salinity level of the Dead Sea?

Despite its name, the Dead Sea is not a sea but an inland lake, as it has no coastline. Its saline level is 35%. This is why it’s called a sea. It is located on the border between Jordan and Israel, and it is the fifth saltiest body of water in the world, with a depth of over 300 meters. 

Is it possible to desalinate seawater?

Desalination is  the process of obtaining drinking water from salt water. The main goal of seawater desalination is to meet needs for this resource in populations that don’t have easy access to fresh water. While two-thirds of the Earth’s surface is water, only 1% is suitable for human consumption. This is why the desalination process is necessary to provide this vital resource. 

The reverse osmosis method is most widely implemented worldwide to reduce salt levels in water. This is done by putting salt water under pressure to capture dissolved salt particles in a semi-permeable membrane. 

However, there are other methods, such as:

• Freezing, where water is frozen and pulverized to form ice crystals on the brine, which are then separated to obtain fresh water.
• Distillation, where water is heated to the point of evaporation and then condensed to extract fresh water. 
• Flash evaporation, where water enters a chamber as droplets, whose saturation pressure is low; they are converted into steam, which condenses to produce desalinated water.