Why is the ocean salty? (2022)
usgs.gov
usgs.gov
The two ions that are present most often in seawater are chloride and sodium. These two make up over 90% of all dissolved ions in seawater.
The other ten percent are micronutrients that are also essential to life.
Most land animals have a skeleton not just to provide physical scaffolding to hang tissue on but because we need a store of calcium to mediate blood pH, something sea life doesn't require thanks to those minerals in the water. That's why you can have sharks which are mostly supported by cartilage with one set of bones: Their jaws.
https://en.wikipedia.org/wiki/Orbit_(anatomy)#/media/File:Ey...
Looking at yourself in a mirror, if you hold your finger over the top of your nose your eyes will see under your finger. Move your finger just low enough so you’re seeing over it and you should be touching the bottom of your nasal bone. At that point your nose should be more than a finger width froward from the bottom of your orbital socket which is where the hole in skulls starts in those skulls.
Why is there a hole? Because your nasal canal extends inside your skull to connect with the back of your throat. I guess I don't fully understand the question there.
From memory it’s more like the stiff parts of your nose running near/along the bone and unlike your ears in any way.
Blood pH is regulated mainly by dissolved carbon dioxide and bicarbonate [1]. There's an order of magnitude less calcium in the blood, usually in the form of calcium phosphate, than either of those, and the amount is extremely tightly regulated within a very narrow concentration range -- far too narrow to have a notable effect on pH.
https://en.m.wikipedia.org/wiki/Calcium_buffering
I raised and homeschooled two kids and watched a lot of when dinosaurs ruled the earth type stuff. That's my source for the idea that a store of calcium was critical for allowing life to leave the ocean and I've tried repeatedly to search for additional info on this and can never find it.
I have no problem imagining that calcium is essential for buffering pH in land mammals and that free calcium ions simultaneously are tightly regulated and not directly used to move that number for the blood in short time frames. That actually fits perfectly well with my mental models that cellular acidosis is a more fundamental problem that fuels acidosis of bodily fluids.
If anyone has any good sources that might clarify this relationship for me, that would be cool.
Except that’s not what’s going on.
The Wikipedia article lays it out. The amount of hydrogen ions someplace is what PH means, so controlling PH is controlling the number of hydrogen ions.
The same thing happens with calcium, but rather than doing the buffering it’s the number of calcium ions being controlled. Calcium buffering is controlling the number of calcium ions.
> Calcium buffering describes the processes which help stabilise the concentration of free calcium ions within cells, in a similar manner to how pH buffers maintain a stable concentration of hydrogen ions.[1] The majority of calcium ions within the cell are bound to intracellular proteins, leaving a minority freely dissociated.[2] When calcium is added to or removed from the cytoplasm by transport across the cell membrane or sarcoplasmic reticulum, calcium buffers minimise the effect on changes in cytoplasmic free calcium concentration by binding calcium to or releasing calcium from intracellular proteins. As a result, 99% of the calcium added to the cytosol of a cardiomyocyte during each cardiac cycle becomes bound to calcium buffers, creating a relatively small change in free calcium.[2]
In layman's terms, pH is a scale for measuring alkalinity vs acidity. Calcium is supposedly alkaline and high levels of intracellular calcium is associated with cell death (apoptosis).
So, for example, some people with CF avoid calcium because they think excess calcium causes cell death. But I think most likely excess calcium -- along with high levels of intracellular glutathione -- are a desperate attempt to buffer against something, including but not limited to excess acid.
So that's really what I'm interested in understanding. And also would love to see confirmation that calcium stores helped life leave the ocean and that wasn't something stupid and stated in error.
Though people with CF also likely misprocess sodium bicarbonate, in addition to being prone to very early onset osteoporosis (as early as their teens).
More precisely, calcium is an alkali earth metal (second column from the left in the periodic table), and those metals are so named because the compounds in which they were first discovered were alkalis. But that does not mean all calcium compounds are alkalis. For example, calcium citrate, which is a common way to convey calcium in supplements, can be weakly acidic in water solution (because of the citrate ion).
Most reliable sources of information describing calcium as alkaline stem from PRAL (potential renal acid load) and other kidney literature. Combined with the right chemicals (as you find in the kidneys), calcium does reduce acidity (contrasted with a buffering agent, the formulae are more linear, and a linear amount of other shit requires a linear amount of calcium or other alkalizing compounds to compensate) in the kidneys.
As something of a fun aside, most "alkaline diets" recommend a diet of weakly to strongly acidic foods which have an alkalizing effect on the kidneys and nearly no pH impact anywhere else in the body.
No comment on the rest. I just want to reiterate that acid/alkaline in one context (most commonly a description of the hydrogen concentration or other related ions) absolutely does not translate without extra effort and math and chemistry to other contexts (like anything describing calcium as alkaline). When those two ideas are mixed in presentation, a correct interpretation absolutely requires you to understand the details of what/where/why an author means when they refer to pH as something other than hydrogen/hydroxide concentration.
HN != YC.
Breathing air came with challenges, though. A major one was getting rid of the air's carbon dioxide, which, when it builds up, reacts with water in the body and forms an acid.
Insects and friends manage to live on land just fine without any calcium bones.
What works once life is established on land can be different from what it took to transition to land and that's what I'm asking about.
https://forces.si.edu/atmosphere/02_02_06.html says
> As plants became firmly established on land, life once again had a major effect on Earth’s atmosphere during the Carboniferous Period. Oxygen made up 20 percent of the atmosphere—about today’s level—around 350 million years ago, and it rose to as much as 35 percent over the next 50 million years.
The high oxygen levels you mentioned occurred long after life had successfully made its way on land.
I'll take wikipedia as a reference (with reservations), but children's television shows?
Most land animals don't have a skeleton. Most land animals are insects and similar critters.
Well, the other reason sea life doesn't require rigid bones is that water provides a lot more buoyancy than air. Jellyfish work fine in the water; on land they're immobile puddles of glop.
The real question is why the sea isn't saltier. Why is the Dead Sea so salty? (Because the Dead Sea is enclosed and in a hot location, so evaporation happens faster.) Why aren't the oceans as salty as the Dead Sea? What is cause of equilibrium? The article briefly mentions (a) "organisms" using the salts, and (b) concentrations continuing to rise (!). So is the ocean on its way to being as dead as the Dead Sea, just really slowly, or what?
Edit: Our blood has the same salt concentration the ocean had when our ancestors formed or split off or something. Someone with actual knowledge will surely come along and enlighten us with a comment.
Perhaps it's deep sea flour shenanigans keeping it at some stable level.
So whatever process produces the mineable deposits will necessarily remove salt from the wider oceans.
> The two ions that are present most often in seawater are chloride and sodium.
This makes it sound like sodium and chloride are the most common ions because they're not used by the organisms in the ocean, unlike all the other dissolved ions. But that's not correct, is it? The ocean is salty because we don't need salt? But we do.
So why is there so much salt in the ocean? Do sodium and chloride simply happen to be the most common elements on Earth that are able to dissolve in water?
Although this graph of the abundance of elements[0] puts sodium with the rock-forming elements (and chloride just inside, but on the edge). So doesn't that mean they should also form insoluble minerals?
[0] https://en.wikipedia.org/wiki/File:Elemental_abundances.svg
(wow, there are a lot of different minerals https://www.mindat.org/element/Sodium .. ah, 50% of the earth's rocks are feldspars which contain some sodium. https://www.imerys.com/minerals/feldspar )
There's more than enough to go round?
(Feldspars in particular need aluminum, so once that's all bound up you aren't going to get more feldspar even if there is surplus sodium. Think of the sea as the leftovers in a non-stochiometric reaction.)
Water is truly a near-infinite resource. If we can master desalination then humanity is in a great spot in regards to fresh water.
It also frames the challenge well. Desalinating a cubic mile gives you 120 million tons of leftovers. Another extremely difficult challenge.
With all the chemical processing that would be needed to stabilize the salts, mechanical filtering and such, I think we're better off continuing to use bricks and ground sourced gravel and cement. At least the holes we dig can be repurposed into sanitary landfills.
Regardless, a polyp adds about 1mm to 1cm to the reef a year. You can get that right now just by throwing a shovel at the ground where I live.
Sodium is potentially useful towards two applications, off the top of my head. (1) Na2O is used in glassmaking, and it's possible that there are -- or that there can be discovered -- Na2O-enriched glasses that can be used in construction and as a filler substance, i.e. reduced to powder and added to cement. (2) Sodium-based zeolites can potentially be useful for carbon capture. Production of zeolites, however, also requires lots of alumina and silica.
I struggle to think of any large-scale application for all of that chlorine, though. Maybe vinyl chloride production? But the world doesn't need that much PVC...
https://www.energymonitor.ai/tech/can-desalination-save-a-dr...
A quick search popped up https://pubs.acs.org/doi/10.1021/acs.jchemed.0c01194
For example, desalinating seawater with a typical seawater salt concentration of 35 g L–1 (corresponding osmotic pressure of 29.7 bar) and 50% water recovery (i.e., 50% of the feed stream becomes purified water and 50% becomes brine)
requires at least 1.1 kWh per cubic meter of purified water.
Regardless of the desalination technology, it is impossible to desalinate water using less energy than that determined by eq 12.
There are so many examples in our collective technical history of overcoming these types of limitations not with brute force, but with finesse.
In this case, I expect it will be a combination of improved pumps, improved RO membrane technology, and finding synergies like making sea salt from the brine, collecting other useful minerals front the brine,etc. All of these things help to pay for the energy and development costs.
It's not a hard physics limit like the rule if squares or the speed of light. It's a complex engineering system that has may different dynamics and interactions between those dynamics, all opportunity for improvement.
Trying to pull gold out of the ocean to pay for pulling salt out of the ocean is --again not a chemist but-- probably thermodynamically worse.
Of course I'm not saying we need to break the laws of thermodynamics, in my house we obey the laws of thermodynamics.
In this case, the work needed is defined by the features of the RO membrane. It's conceivable that we could develop a RO membrane that requires less pressure or energy to operate. In fact they have been.
In that case, we would gain a more efficient process, while still obeying the laws of thermodynamics
It could easily be the case that RO is going to see only marginal improvements for the next decade or two (except perhaps some test membranes that are too expensive), and modern RO already uses energy recovery in the process.
Equation 12 is the energy you need to counteract the effect of the entropy of the ions in solution and separate the initial solution into one that does not have the ions. It’s pretty much a thermodynamic limit and does not depend on process or technology.
They explicitly assume that they have a perfect membrane when they introduce the equation. The floor will never be zero, it is a physical limit.
The energy required happents to go into separating the bonds between the salt ions and the water molecules. Those bonds are quite strong, so it takes some energy to break them.
The engineering problem is more one about capital investment. The price of water, vs the price of electricity are not what block desalination. It is the cost (and maintenance) of the machines that you need to earn back. That cost is what tends to make desalination un-economical. And that is an area where engineering has a lot of space to improve.
Don't forget that we actually mine salt, a lot of which ends up in the sea. A million years from now we might regret that ;-)
The world's freshwater need is about 950 cubic miles a year. (https://www.wolframalpha.com/input?i=worldwide+water+use+in+...)
You can just put the leftovers back without worrying much about it.
Yes, just not all in one place/time. Separating seawater into pure water in one place and pure brine in another, you don’t want to let that brine out all at once in one spot, it’ll kill a lot of ocean life. Most desal plants that are attempting to do this right, will pump the brine into pipes that diffuse it over a wide area to avoid oversalinating. And it still kills a lot of ocean life.
Or we could have a premix station where we pump in sea water and mix it with brine at a certain ratio and then return that to the sea.
And with your second process, you still end up with a higher concentration of salt / brine around where it's returned to the sea, still killing animals.
I'm thinking of pumping the brine onto large evaporation lakes and harvest the salt or whatever - which also already happens to produce sea salt.
And if there's too much salt for the market, just stockpile it. Like underground salt mines.
The big problem with making salt from sea water is evaporating the water. It either takes a lot of energy, or a lot of time and area.
It takes a lot of time for the salt to just diffuse out over the ocean.
I think the best way to pay for X, is to use energy from an external source. External from the Earth. I'm obviously talking about the Sun.
We could use the removed material as a general filler. I'm sure we can get creative about it. I think the problem is lack of incentives and misalignment of goals amongst people.
I truly think if we can figure out how to how to use the most out of the Sun's rays - i.e. as most directly as possible - we will solve all our needs. The energy is truly free to the Earth.
There's a thermodynamic fundamental lower limit on the amount of energy needed to desalinate water, but it's absurdly small. Much smaller than the amount of energy we use in practice with current technologies.
(Just like there's a thermodynamic lower limit on how much energy a computer needs. But it's also extremely low. See https://en.wikipedia.org/wiki/Landauer%27s_principle )
Edit, found in another comment : For example, desalinating seawater with a typical seawater salt concentration of 35 g L–1 (corresponding osmotic pressure of 29.7 bar) and 50% water recovery (i.e., 50% of the feed stream becomes purified water and 50% becomes brine) requires at least 1.1 kWh per cubic meter of purified water. Regardless of the desalination technology, it is impossible to desalinate water using less energy than that determined by eq 12.
1.1 KWh per cubic meter is very much NOT a negligible amount, so the landauer analogy is incorrect.
I stand corrected in that case.
I'm confident that in our generation we'll see mass migrations due to water shortages in the west. California is already at risk, I gathered.
It's not the water that is in the wrong place. People are not supposed to live in places that can't sustain their numbers.
Israel even turned into a water exported thanks to the technology.
See eg https://www.timesofisrael.com/how-israel-became-a-water-supe... and https://blogs.worldbank.org/water/israel-how-meeting-water-c...
The sea is salty because it
remembers the taste of the land.It is the solubility of sparingly soluble phases such as CaCO3 that controls much of the seawater composition: surface seawater is close to saturation with respect to CaCO3 (calcite, aragonite). Because halite (rock salt, NaCl) is highly soluble, seawater is, conversely, fairly concentrated with respect to these ions. Seawater must be extensively evaporated to remove the far more soluble (evaporite) minerals. Over geologic time, the composition of seawater has changed, reflecting the relative pace of the various processes listed above that deliver and remove components from solution.
Why? Well fresh water is pretty boring. Seawater, with all those polar ions in it, enables and facilitates all sorts of interesting (i.e. useful) chemistry.
One of the reasons we can't drink seawater is that our body needs to maintain homeostasis on the blood so the chemistry continues to work properly. If you drink a lot of seawater the kidneys can't excrete the salt fast enough. For that matter, if you drink too much fresh water the opposite happens and you die too.
https://www2.atmos.umd.edu/~dankd/MessinianWeb/_private/HOME...
Source for that claim?
Mediterranian is still more salty than oceans because of the high evaporation rate.
There is much more water in an ocean for the salt to disperse than in a creek, somehow I can drink from it, but not from the ocean.
I think the real answer is that these elements (sodium and chloride) easily dissolve in water, and there's no process that removes them from the ocean, so they linger and accumulate.
In the oceans, this accumulates, but the water evaporates. Hence the salt content goes up whilst the water volume remains constant (ignoring ice melt) which means the salt concentration goes up.
Earth’s oceans contain a combined volume of 320 million cubic miles, according to Wikipedia.
Why is the ocean salty? - https://news.ycombinator.com/item?id=16129786 - Jan 2018 (90 comments)
https://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth...
I'm also surprised to see that Nitrogen is relatively rare compared to its neighbours Carbon and Oxygen, despite making up 80% of the atmosphere. Or maybe that's why? Are we losing nitrogen to space?
Nitrogen is less reactive than Oxygen, doesn't form as many compounds as Carbon and has a molecule too fat to easily escape into space.
This is one of the best sales pitches for the metric system that I've ever seen.
It's equally silly to try to convey the size of a cubic mile of water in gallons, just as much as it is to convey the size of a cubic kilometer in liters. The numbers are just round in the latter case.
In other words, both:
1,101,117,147,000
1,000,000,000,000
Edit: now a trillion, that's getting beyond comprehension. Just multiply each side by 10.
Edit edit: that "1 billion" would make for a good conversation piece. Or, easier, a container with 1 billion small grains in it.
You're right that large numbers are hard to comprehend, but being able to summarise them and convert to other measures easily helps convey meaningful information.
Saying you want to process a billion tonnes of something is immediately grokable as vastly different to wanting to process a million tonnes.
Being able to immediately convert that into a conversation about processing a trillion litres vs a billion litres is similarly valuable.
If I can process 1 tonne of water per unit time, then I know that the cubic km will take 1000 times longer than a billion litres / million tonnes.
> are equally meaninglessly
> large to any lay reader.
It contains however many liters of water are in that cubic kilometer after you subtract everything else in the ocean, it'll be close to a trillion liters, but not quite.
Of course the article may be using "water" in the loose sense.
But if it's not the metric version would implicitly provide you with an easily inferred percentage of how much of a cubic kilometer of ocean is made up of other stuff.
Whereas in imperial units you won't know that at a glance, you'll need to either repeat the calculation, or memorize various conversions.
Because the land didn't wave back
Because it's full of seamen
Because it's full of <name of game> players