Geoengineering to Neutralize Ocean Acidification

sealover wrote:

duncan61 wrote:
I used to do the museum tour at Hamelin Pool Telegraph station where the Stromatolites live.Have a look at the website its an interesting place.This is where the first oxygen came from,The microscopic bacteria can remove the Oxygen from sea water and poop it as bubbles.There was an aquarium with some living rocks and during the day you can see the bubbles randomly being emitted.Other life forms wiped them out a long time ago but the water in the shallows of East shark bay are hyper saline and these very old creatures are still there.South of Perth there are lakes near the coast that have Thrombolites that are very similar

This is basically all true, except the assertion that "This is where the first oxygen came from".

Oxygen isn't easy to make. An electric current can transform water into hydrogen and oxygen gas, but it costs energy. It is not spontaneous.

4000 million years ago the earth's crust was still very actively spewing reductants to the surface. Volcanic activity was widespread and frequent. The planet was still getting hit with the occasional massive asteroid. These asteroid strikes caused even more massive release of reductants to the surface. Indeed, they are the benchmark events for the big chert layers at the bottom of banded iron formation sequences.

By 3000 million years ago, things had calmed down. Volcanic active was much less intense than before. We were't getting hit by massive asteroids any more.
And the supply of high energy reductants such as hydrogen was being depleted.

The oldest banded iron formations, the "microbanded" ones have only two kinds of material in the repeating layers. Chert, (iron + sulfur) mineral, chert, (iron + sulfur) mineral, chert, and on and on and on. These older banded iron formations are useless as iron ore. The iron layers are barely a couple of millimeters thick. The repetition is so consistent that they were once believed to be "annual varves", representing yearly seasonal shifts in sediment deposition.

I'll have to get back to how intracellular photooxidation evolved into photosynthesis later. When microbanded banded iron formations were created, there were already at least two kinds of anoxygenic photosynthesis. At least two different kinds of anoxygenic photosynthetic communities were competing for reductants and sunlight.

During periods when hydrogen was most abundant, the photosynthetic community that used hydrogen as reductant for anoxygenic photosynthesis would win out. They got the most bang for the buck from the sunlight and they outcompeted the others. Their photosynthesis oxidized the hydrogen into water.
Water was the oxidized product of that photosynthesis.

When dihydrogen was less depleted by the photosynthetic bacteris, there was still plenty of hydrogen sulfide to use as reductant for anoxygenic photosynthesis. A different community of photosynthetic bacteria could then become competitive. Anoxygenic photosynthesis using hydrogen sulfide doesn't give as much bang for the buck from the sunlight, and they couldn't compete until the ones who depended on dihydrogen starved off.

Anoxygenic photosynthesis using hydrogen sulfide as reductant generates sulfate as the oxidized product of that photosynthesis. When the new community of H2S-based photosynthesis displaced the H2-based community, they changed the chemistry of the sea water by adding sulfate - an oxidant.

Anoxygenic photosynthesis using dihydrogen produces water as the oxidized product. Water isn't a very good oxidant. Anoxygenic photosynthesis using hydrogen sulfide produces sulfate as the oxidized product. Sulfate is a mediocre oxidant, but it changed everything.

Each time the earth belched up another massive release of hydrogen, the hydrogen oxidizing photosynthetic community became dominant. Their debris rained down on the sea floor, piling up organic carbon. And no good oxidants to do anything with it. Carbon piled up.

Each time photosynthesis eventually depleted the available hydrogen enough for the hydrogen sulfide oxidizing photosynthetic bacteria to become dominant, an oxidant became available to enable microorganisms to exploit carbon on the sea floor. Carbon still piled up. But some of it was being lost via sulfate reduction by bacteria. Iron pyrite, among others, was being formed among the organic carbon on the sea floor.

When the microbanded banded iron formation sediments were first deposited, they consisted of alternating layers. Pure organic matter, organic matter plus pyrite, pure organic matter, organic matter plus pyrite, etc.

Over geologic time these carbon deposits became fossilized.

No, it wasn't "fossil fuel". The carbon got replaced by silica. The pure-silica chert layers of the banded iron formations are the fossils of the dead organic matter in the ancient seafloor.

Hmm, this is supposed to be about oxygen, so I'll jump ahead another 1000 million years.

The excited skin of the earth has calmed down over the years. Fewer and fewer reductants are being spewed out. Photosynthetic bacteria have had to evolve to use weaker and weaker reductants.

Dihydrogen gas and hydrogen sulfide were the best ones available before, but they are getting harder to find.

Well, there are other forms of reduced sulfur besides hydrogen sulfide that could be used. And they were. Arsenic was widely available and arsenite was a good reductant. Ferrous iron was a pretty good reductant. New photosynthetic communities evolved to exploit the next best available reductants. Sulfate, arsenate, and ferric iron were the oxidized products of photosynthesis released into the environment.

Skip, Skip, Skip.... Well, now we're getting desperate. Harder and harder to find a good reductant for anoxygenic photosynthesis.

What about nitrite? That's a tough nut to crack. Gonna require a lot of voltage.
And somebody did it. Anoxygenic photosynthesis using nitrite as reductant generates nitrate as the oxidized product. Nitrate is a pretty powerful oxidant. But that took a lot of voltage from the photosystem to yank off its electron. Not much bang for the buck as far as energy captured during photosynthesis. But if nitrite is the only reductant in town, that's what you have to work with.

Anoxygenic photosynthesis using nitrite as reductant generated a powerful oxidant for microorganisms to exploit. Reductants that were too weak to be exploited using sulfate as oxidant could now be oxidized for profit using nitrate.

But even nitrite can be depleted. What's a photosynthetic bacteria to do? Well, that nitrite oxidizing photosystem generate a whole lot of voltage. Enough to oxidize water? Somebody did it. They used water as reductant in a photosystem that could generate so much voltage it could yank an electron right off a water molecule. The water falls apart and release oxygen. Oxygen is the oxidized product from using water as reductant for oxygenic photosynthesis.

Hardly any bang for the sunlight buck, compared to the old school anoxygenic photosynthesis using reductants much stronger than water. These oxygenic guys still can't compete in microsites where there is still enough hydrogen, hydrogen sulfide, (organic-S, elemental-S, sulfite), arsenite, ferrous iron, or nitrite to support anoxygenic photosynthesis.

Check out the switch hitter. A blue green bacteria that is perfectly capable of doing oxygenic photosynthesis. Put him in a hydrogen rich environment and he'll turn off one of his photosystems. He won't squander sun energy just to tear water apart. He'll just take up the hydrogen directly from the sea and get a whole lot more bang for the buck in photosynthesis.

sealover wrote:

duncan61 wrote:
Nice work.The very basic single cell lifeform known as Stromatolites were all over the shallow warm seas of most of the planet.When the sun shines they literally fart oxygen.This put oxygen in the atmosphere.They still exist in Shark bay as the shallow ocean has little movement and evaporates rapidly in the hot conditions that exist there nearly all year round.The hyper saline water did and still does not allow the snails and other lifeforms that developed later to consume the stromatolites that are still doing their thing.I have seen this in person.Look it up for yourself and stop picking on my mate Sealover.You will scare him away before I have my fun

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I totally respect your interest in paleobiogeochemistry.


So, banded iron formations are more than just the world's biggest deposits of iron ore.

They are among the oldest evidence of life on earth.

However, they represent photosynthetic ecosystem community succession.

Life was already pretty advanced by the time they formed.

The oldest banded iron formations are just shy of 4000 million years old.

They are the "microbanded" variety. No thick layers of high grade iron ore. Just a bunch of alternating thin (maybe 2 mm) layers.

They represent ecosystem community succession between just two types, back and forth. There are only two kinds of interlayered material. Pure chert and iron-and-sulfur-enriched chert.

The pure chert layer formed from sediment deposited following large release of hydrogen into the environment. Usually geologic activity, but sometimes following a big blow from an asteroid.

Anoxygenic photosynthesis using hydrogen as reductant does not generate any oxidant, just water.

When the hydrogen became depleted, a new photosynthetic community came in. They did anoxygenic photosynthesis using hydrogen sulfide as reductant. This generates sulfate. Sulfate is an oxidant.

When hydrogen was abundant, there was no sulfate being generated. Organic matter piled on the sea floor with virtually no oxidants available to decompose it.

When hydrogen was depleted and a new photosynthetic community used hydrogen sulfide as reductant, the sulfate they generated was used as an oxidant in the sea floor. Sulfate reduction generated pyrite.

The alternating layers were originally deposited as pure organic matter or organic matter plus pyrite. Fossilization replaced carbon with silica.

The earth was very active in those days. It never took very long before a wave of geologic activity resulted in an abundance of hydrogen again.


About 1000-2000 million years later, very different kinds of banded iron formations were created. This was a much more complex community succession. There were more than two kinds of layers.

They always begin at the bottom with layers of pure chert, just under layers of chert plus iron and sulfur.

But then there are overlying layers of increasing iron content, with iron in an increasingly oxidized state. What the miners coveted were the top layers of each sequence, massive deposits of the purest ore.

Every once in a while, a huge asteroid would still strike and begin another sequence.

But now there wasn't going to be a rapid resupply in the relatively near future.

Unlike the microbanded iron formations, there was enough time for the hydrogen sulfide to run out as the next best reductant for anoxygenic photosynthesis. When they had to resort to iron reduction, using ferrous iron as reductant, they generated ferric iron as the oxidized product.

Ferric iron is a more powerful oxidant than sulfate. The chemistry of the sediments in the banded iron formations reflects the presence of this more powerful oxidant. A third distinct layer type in every sequence.

When ferric iron ran out, they resorted to using arsenite or nitrite as reductants for anoxygenic photosynthesis. This generated arsenate and nitrate, which are more powerful oxidants than sulfate or ferric iron. A fourth distinct layer type in many sequences.

When all the available reductants ran out, photosynthetic communities had to resort to oxygenic photosynthesis. Oxygenic photosynthesis using water as reductant generates oxygen, a very powerful oxidant. The sediments deposited in the presence of this powerful oxidant are quite distinct from those that underly them.

Swan wrote:

sealover wrote:
Even under the best-case climate change mitigation scenarios, atmospheric concentrations of carbon will only gradually decline. Even if we cease all fossil fuel combustion tomorrow, ocean "acidification" (i.e. depletion of alkalinity) would continue to get worse for decades to come.

Direct human intervention to perform environmental chemotherapy and provide exogenous alkalinity to the sea by ourselves, dumping gigatons of lime or grinding up gigatons of rocks to transport and distribute to the sea is a non-starter. It is simply not humanly possible to provide the quantities required.

Coastal wetlands are the major source of new alkalinity entering many marine ecosystems, as submarine groundwater discharge.

Under the low oxygen conditions of wetland soil, bacteria use sulfate as oxidant to oxidize organic carbon and acquire energy. Sulfate reduction by bacteria generates inorganic carbon alkalinity rather than carbon dioxide as the oxidized carbon product.

If anyone is curious, there are three distinctly different geoengineering approaches that could be applied to increase the generation of alkalinity for the sea through oxidation of wetland sediment organic carbon via microbial sulfate reduction.

LOL who exactly would decide what the PH of the ocean should be and was before the industrial revolution?

You?

Whaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

Im a BM wrote:

Swan wrote:

sealover wrote:
Even under the best-case climate change mitigation scenarios, atmospheric concentrations of carbon will only gradually decline. Even if we cease all fossil fuel combustion tomorrow, ocean "acidification" (i.e. depletion of alkalinity) would continue to get worse for decades to come.

Direct human intervention to perform environmental chemotherapy and provide exogenous alkalinity to the sea by ourselves, dumping gigatons of lime or grinding up gigatons of rocks to transport and distribute to the sea is a non-starter. It is simply not humanly possible to provide the quantities required.

Coastal wetlands are the major source of new alkalinity entering many marine ecosystems, as submarine groundwater discharge.

Under the low oxygen conditions of wetland soil, bacteria use sulfate as oxidant to oxidize organic carbon and acquire energy. Sulfate reduction by bacteria generates inorganic carbon alkalinity rather than carbon dioxide as the oxidized carbon product.

If anyone is curious, there are three distinctly different geoengineering approaches that could be applied to increase the generation of alkalinity for the sea through oxidation of wetland sediment organic carbon via microbial sulfate reduction.

LOL who exactly would decide what the PH of the ocean should be and was before the industrial revolution?

You?

Whaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa

The term "pH" does not appear in the post anywhere.

The response refers ONLY to "PH" and makes no reference to alkalinity.

A typical sample of sea water has pH about 8.2, and 2300 microequivalents per liter alkalinity (acid neutralizing capacity).

One typical liter of sea water can neutralize 2300 microequivalents of acid in an alkalinity titration test.

Measuring the pH isn't very revealing, as the depletion of alkalinity only brings about very small change to pH.

The term "acidification" is put in quotation marks because the ocean isn't becoming "acidic" at all. The alkalinity is being depleted.

Alkalinity is a measurable parameter, but it is NOT pH.

Whether or not the pH is greater than 7 or less than 7 does not measure or determine alkalinity.

A substance is "alkaline" if the pH is greater than 7.

That is very different than alkalinity.

The statement "you cannot acidify an alkaline" is meaningless, because "alkaline" is an adjective, not a noun.

LOL who taught you to read so well that you could somehow see "PH"?

sealover wrote:
Even under the best-case climate change mitigation scenarios, atmospheric concentrations of carbon will only gradually decline. Even if we cease all fossil fuel combustion tomorrow, ocean "acidification" (i.e. depletion of alkalinity) would continue to get worse for decades to come.

Direct human intervention to perform environmental chemotherapy and provide exogenous alkalinity to the sea by ourselves, dumping gigatons of lime or grinding up gigatons of rocks to transport and distribute to the sea is a non-starter. It is simply not humanly possible to provide the quantities required.

Coastal wetlands are the major source of new alkalinity entering many marine ecosystems, as submarine groundwater discharge.

Under the low oxygen conditions of wetland soil, bacteria use sulfate as oxidant to oxidize organic carbon and acquire energy. Sulfate reduction by bacteria generates inorganic carbon alkalinity rather than carbon dioxide as the oxidized carbon product.

If anyone is curious, there are three distinctly different geoengineering approaches that could be applied to increase the generation of alkalinity for the sea through oxidation of wetland sediment organic carbon via microbial sulfate reduction.

sealover wrote:
Even under the best-case climate change mitigation scenarios,

sealover wrote:
atmospheric concentrations of carbon will only gradually decline.

sealover wrote:
Even if we cease all fossil fuel combustion tomorrow,

sealover wrote:
ocean "acidification" (i.e. depletion of alkalinity) would continue to get worse for decades to come.

sealover wrote:
Direct human intervention to perform environmental chemotherapy and provide exogenous alkalinity to the sea by ourselves, dumping gigatons of lime or grinding up gigatons of rocks to transport and distribute to the sea is a non-starter. It is simply not humanly possible to provide the quantities required.

sealover wrote:
Coastal wetlands are the major source of new alkalinity entering many marine ecosystems, as submarine groundwater discharge.

sealover wrote:
Under the low oxygen conditions of wetland soil, bacteria use sulfate as oxidant to oxidize organic carbon and acquire energy. Sulfate reduction by bacteria generates inorganic carbon alkalinity rather than carbon dioxide as the oxidized carbon product.

sealover wrote:
If anyone is curious, there are three distinctly different geoengineering approaches that could be applied to increase the generation of alkalinity for the sea through oxidation of wetland sediment organic carbon via microbial sulfate reduction.

sealover wrote:
There has been at least a 30% depletion of the ocean's alkalinity (acid neutralizing capacity, equivalents per liter).

sealover wrote:
Of particular concern is the reduction in carbonate ion available for shell formation.

sealover wrote:
Potential remediation could employ natural wetlands to increase their alkalinity input.

sealover wrote:
Drained wetlands could be managed to reduce their discharge of sulfuric acid, and increase discharge of alkalinity in submarine groundwater discharge.

sealover wrote:
Submerged wetlands could be managed to become a major source of new alkalinity (carbonate and bicarbonate ions) entering the sea.