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Name: Cheyenne
Status: student
Grade: 9-12
Location: AL



Question:
Do the salt we use really come from the ocean and if so about what percentage of salt do we take and about what percentage is left?


Replies:
If you mean table salt, I think the vast majority of it is mined, not evaporated from the ocean. At least in the US anyway. Sea salt is from the ocean, and you can get that if you want.

The amount of sea salt taken from the ocean for human use is so extraordinarily small, I hesitate to calculate. The oceans overall volume is 1.3 billion cubic kilometers, roughly. So making the math easy, let us call it 1 billion cubic kilometers, which in liters is 1 followed by 21 zeroes. 1 liter of water weighs roughly 1 kilogram (actually more for seawater). Roughly 3-4% of seawater is salt. That means there are 3-4 followed by 19 zeroes kilograms of salt in the ocean. Let us exaggerate and say the world's population is 10 billion, and each person consumers 10 kilograms of salt a year (30g per day) -- . That is 1 following by 11 zeroes. With these over-estimated numbers we still would only use 0.000001% of the ocean's salt in one year. In reality, we put salt back into the ocean as well.

Hope this helps,
Burr Zimmerman


Hi Cheyanne,

Table salt mainly comes from salt mines, only a relatively small amount of it comes from evaporation ocean water. But even if all our salt came from the ocean, there is no danger of "using it up". Compared to the amount of salt in the ocean, the amount we use is immeasurably small. Note, however, that the salt in underground salt mines was deposited millions of years ago as primordial oceans dried up. So salt does indirectly come from the oceans of long ago.

Regards,
Bob Wilson


Cheyenne,

There are actually two important sources of salt, the sea and mined minerals. Sea salt is obtained by channeling sea water into shallow basins and allowing the water to evaporate. If the salt thus collected is scheduled to end up as table salt, this is further refined to remove unwanted minerals that affect taste, if it is used for clearing snow and other industrial usage, this may be used as is. Mineral salts are mined in deposits that are high in salt. Such deposits are usually the result of evaporated ancient lakes.

Sea water contains about 3.5% salt. The world production of salt is about 210 million metric tons per year (but I do not know how much of that is from the sea and how much is from minerals). Assuming that all comes from the sea, you can calculate how much sea water has to be used. You can then calculate how much of the ocean (knowing the total volume of the ocean) would have to be dried out to produce that much salt. However, you would also have to factor in the replenishment of this salt from rivers that carry minerals into the ocean (I do not know what that statistic is).

Hope this helped a bit.

Greg (Roberto Gregorius)



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