How and where does salinization occur?

Answer 1

There is a lot of salt present in the crust of the earth. When it rains, the rains take the salt into solution, and that rain washes it downhill to the lowest place the water can go - the ocean. The water is taken up into the atmosphere through evaporation in what is called the water cycle. The water then condenses and it rains. Rain on land takes more salt into solution and washes it down to the sea. The water does not take the salt (or any other dissolved minerals) with it when it evaporates. The seas collect salt and become salty. Salinity has occurred.

Answer 2

'Silt' (crushed rocks and soil) is washed out to the ocean from all of the bodies of land, so it contains all sorts of chemicals. Different chemicals react with, or dissolve with the chlorine in the oceans and become 'salts'. Because the water stays relatively cool, the salts stay 'in solution' in the oceans.

But then again, I'm not a Science teacher and I could be all wrong about this.

Look it up for your self.

Answer 3

I recall that the Romans spread salt over the remains of Carthage to ensure it would remain infertile.

In the modern world, irrigation is a promoter of salinization! The salt will move freely from a region of high concentration to a region of low concentration, provided there is a water column between the two. This is osmosis. Thus deep salt ions will be drawn to the surface by the practice of irrigation.

This happened in historic times in the 'Fertile Crescent' of the Euphrates system, and the Romans record of the results of irrigation. The Romans used the fertile crescent as a great source of grain, but with irrigation, the soil eventually salinized, and crop yields fell. Their response to this was to switch to barley, which is more tolerant of salt, but eventually, the soils became so salt laden as to not be able to support barley. And the saline marshes of today exist in the region.

When the Brits moved into India, they introduced irrigation to the Indus Valley, but warned that the benefit would only last a hundred years or so before salinity would limit the improvement. Because they knew of the Roman experiments.

In fact it took nearly two hundred years, but history did repeat.

This experiment is being repeated in the Murray River system of Australia, and in parts of the South Island of New Zealand as well.

Sedimentary rocks, almost by definition, formed under oceanic water, and therefore naturally contain salt. With weathering, this eventually deposits on the plainlands, and with rainfall, is carried deep into the alluvium. Many constrained aquifers have enhanced salt levels, and are unsuitable for irrigation.