Geoengineering to Neutralize Ocean Acidification
| RE: hexavalent chromium contaminated soil remediation with polyphenols05-06-2023 09:41 | |
| Im a BM★★★☆☆ (595) |
sealover wrote: A word of caution about coastal desert chemistry. You won't have to wait for the live wetland ecosystem to establish before you'll generate a whole lot of alkalinity. Rewetting a dry desert soil with sea water could result in extremely high initial pH. A toxic witch's brew will be the immediate result, although capable of rapid self attenuation. An exceptionally high pH initial mix could contain toxic concentrations of arsenic, boron, selenium, even hexavalent chromium (of natural origin). Within seconds of initial contact between the dry desert soil and applied sea water, the soil becomes a high pH chemical trap for CO2. The pH will decline soon as alkali hydroxides absorb CO2 to become carbonates. Self attenuation with decreasing pH as CO2 is absorbed will soon sequester arsenic, borate, etc. out of solution.[/quote] __________________________________________________________ Naturally-occurring hexavalent chromium can be found beneath desert soils. It is usually limited to the margins where the last inputs of groundwater dried up as it became desert. Hexavalent chromium is not our friend. Trivalent chromium is common in many soils. It is benign, and not easily transformed into the carcinogenic hexavalent form. The overwhelming majority of chromium in desert soil is trivalent Cr(III) occluded within the crystal lattice of rock minerals. A small amount of chromium(III) is present in material coating the surface of larger particles. Before becoming desert, photosynthesis once provided the soil with organic carbon. The most enduring fraction of that soil organic matter were humic acids coating soil particle surfaces. Humic acids have cation exchange capacity to adsorb chromium(III) into tightly bound complexes. Occluded within the humic coating, the chromium(III) was never exposed to oxidation into hexavalent chromium. Also cycled along with chromium(III), manganese adsorbed to humic acid cation exchange sites as a tightly bound complex. Manganese(II) is far more soluble than the oxidized form, manganese(IV). Manganese(II) is the mobile form that adsorbed to humic coatings on soil particle surfaces. With its reactive sites occluded from oxidation by formation of inner sphere complexes with organic ligands, manganese(II) remained intact in its chemically reduced form. It's not easy to oxidize chromium(III) into hexavalent chromium. Oxygen isn't a powerful enough oxidant to do it. Hexavalent chromium rarely occurs in nature. But there is an oxidant generated as a by-product during manganese oxidation, far more powerful than oxygen. Under aerobic conditions, some bacteria acquire their energy by oxidizing manganese(II) into manganese(IV). These chemoautotrophic can use carbon dioxide as their carbon source and manganese oxidation as their energy source. During oxidation of manganese(II) to manganese(IV), a tiny bit of highly oxidized manganese(VII) is generated as by product. Manganese(VII) is a strong enough oxidant to turn chromium(III) into hexavalent chromium through purely abiotic mechanisms. Manganese(II) and chromium(III) lived happily side-by-side within organic carbon matrix of humic coatings for centuries. When the land became desert, input of new organic carbon ceased. As the chromium(III)/manganese(II) bearing humic coatings decomposed, they no longer had the cation exchange capacity of the organic matrix to hold them or prevent their oxidation. As manganese(II) oxidized to manganese(IV) by oxygen, by product manganese(VII) oxidized chromium(III) to hexavalent chromium. ---------------------------------------- Government Oversight and Mandated Remediation Caused Hex Chrome Hazard. Naturally occurring hexavalent chromium is limited to the margins of deserts. Anthropogenic hexavalent chromium can have a complex life cycle. Picture a Superfund site. A former laboratory that once handled extremely hazardous substances. The lab has been shut down for decades. That laboratory used to drain their sinks into a septic tank on site. None of the deadly stuff went down the drain. Just the usual lab sink waste. That laboratory waste water included hexavalent chromium, commonly used as an oxidant in laboratory procedures. It also included organic carbon, some of which came in from the toilets. When the hexavalent chromium entered the septic tank, it was highly soluble and mobile. It traveled into the leaching field and along subsurface flow paths. The hexavalent chromium had a very short half life after it left the laboratory. After it stalled somewhere along the subsurface flow path and was adsorbed by soil organic matter, it was reduced to Cr(III). Organic carbon is a good reductant. For decades the input of organic carbon and chromium continued. Subsurface flow paths were loaded up with organic carbon, chromium(III) and manganese(IV). When the lab sewer system was taken out of service, the supply of new organic carbon was cut off. Like the desert margin, as the organic matter decomposed and exposed chromium and manganese to oxidation, hexavalent chromium was generated. -------------------------------------------------------------------------------- Naturally-occurring hexavalent chromium, created as a result of the activity of microorganisms, isn't something that gets much attention. Mainly, because environmental conditions where it happens are rare, and they are never sites where ground water would be used for human consumption. Or even for irrigating crops. It is only recently that we are finding it closer to home, in sites where human beings have controlled the inputs of both organic carbon and chromium. In the context of this thread, transforming coastal deserts into saltwater wetlands would be in one of the rare environments where naturally occurring hexavalent chromium would be expected. And in the context of how do we remediate the hexavalent chromium that we are now finding in ground water much closer to home than the nearest desert. Xiaofeng Jiang et al. 2023. Reductive transformation of Cr(VI) in contaminated soil by polyphenols: The role of gallic acid and tannic acid. Ecotoxicology and Environmental Safety. Volume 255 11 4807 This method for remediating hexavalent chromium contaminated soils involves application of soluble polyphenols. The polyphenols, including gallic acid and tannic acid, act as reducing agents. Indeed, chemical tests to measure polyphenols often measure their capacity to reduced ferric iron(III) to ferrous iron(II). Polyphenols reduce hexavalent chromium Cr(VI) to trivalent chromium Cr(III). Sooner or later, someone with genuine interest in this thread topic will see this. This paper is still very new. I intend to communicate with the authors. In part, it will be to thank them for citing my polyphenol research to inform their investigation. Mainly, it will be to offer them advice for their next paper. I will encourage them to follow the polyphenols on a longer time scale. Most of the added polyphenols will become stable soil humic acids with very long residence time. These will sequester trivalent chromium from solution and seal it off from potential contact with manganese Mn(VII). Other reducing agents used to remediate hexavalent chromium are much more short lived in their effectiveness. To the new viewer, I'm the guy who gets cited in the hexavalent chromium papers, such as the new one referenced above. Hopefully, this distinguishes me from someone who simply cuts and pastes material without actually understanding any of it. |
| 05-06-2023 19:44 | |
Into the Night ★★★★★(21599) |
You are spamming. You are cutting and pasting yourself. Buzzwords are not chemistry. You don't understand acid-base chemistry or anything about pH. |
| 06-06-2023 21:20 | |
IBdaMann ★★★★★(14414) |
sealover wrote:Inorganic Carbon versus Organic Carbon OK, I'm listening ... sealover wrote: ORGANIC CARBON is in chemically reduced state. Organic carbon can yield energy by being oxidized. Diamonds? sealover wrote:INORGANIC CARBON is in a chemically oxidized state. Inorganic carbon cannot yield energy by being oxidized. Charcoal? |
| 07-06-2023 08:33 | |
| sealover★★★★☆ (1249) |
[quote]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. |
| 07-06-2023 08:33 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: One geoengineering approach to enable wetlands to generate and discharge alkalinity to the ocean is simply to better manage them. Rising sea level and drainage for agriculture has greatly decreased the output of alkalinity from coastal wetlands. As sea level rises, the distance between low tide and ground surface elevation is reduced. There is now less hydraulic gradient during the drainage phase to drive sulfate into low oxygen, organic carbon rich sediments. Tidal pumping is no longer as effective as it used to be to extract alkalinity from coastal wetlands. Once the rising sea level completely submerges the coastal wetland, there is no longer any hydraulic gradient or tidal pumping at all to allow sulfate to enter the low oxygen, carbon rich sediment. When wetlands are drained for agriculture the hydraulic gradient completely shifts. Water is continuously drained from the topsoil into deep drainage ditches, then pumped uphill into adjacent surface water. The elevation of the recharge water is higher than the water table in the field below the aerobic topsoil. There is upward pressure from recharge water pushing groundwater up toward the drained topsoil, to then be intercepted, drained off, and pumped up to the river. When wetland soils are drained, buried pyrite is exposed to oxygen. Sulfur oxidizing bacteria then generate sulfuric acid. These "acid sulfate soils" develop very low pH. They also export a lot of acidity, salinity, and dissolved organic matter to surface waters. Wetlands that previously generated alkalinity for the sea as groundwater discharge now export sulfuric-acid-enriched drainage to surface water. |
| 07-06-2023 08:34 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: One geoengineering approach to use coastal wetlands to generate alkalinity for the sea would also sequester atmospheric carbon dioxide. Coastal deserts could be farmed for alkalinity by pumping sea water into them. Constructed wetlands have been employed for more than 50 years to neutralize acid mine drainage. Constructed saltwater wetlands could use the same biogeochemical mechanisms to neutralize ocean acidification. It could be as simple as a low earthen dam across a dry river outlet. Wind-driven or sea-wave powered pumps could give sea water the slight lift uphill. As the water drains back to the sea, it carries the alkalinity acquired from sulfate reduction in the low oxygen sediment. Continuous pumping of sea water in would balance with continuous drainage and evaporation to establish a steady state of hypersalinity in the constructed, upland saltwater wetland. A high enough rate of continuous sea water input could establish a steady state of only slightly elevated salinity, tolerable for aquaculture. The resources are already available on site at little or no cost. Unproductive land could be transformed into a sink to sequester atmospheric carbon dioxide, as well as a source of new alkalinity for the sea. |
| 07-06-2023 08:35 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Geoengineering to acquire alkalinity for the sea from carbon stored in wetlands can be done offshore. The waterlogged, low oxygen soil conditions of wetlands prevent aerobic oxidation of organic matter by micro organisms. Dead organic matter in the wetland soil has centuries long residence time. Centuries of peat accumulation and carbon rich sediment can pile up to great depth. Rising sea level has submerged large areas of coastal wetlands. These submerged lands no longer support wetland photosynthesis to sequester carbon dioxide from the atmosphere. They no longer pile up new organic matter. They no longer discharge alkalinity to the sea from groundwater flows. However, these areas are still an enormous reservoir of organic carbon stored in shallow sediments just below the surface of the sea. These deposits of pre-fossil fuel (i.e. wetland soil carbon not yet transformed by the earth into coal) contain many, many gigatons of stored organic carbon. Offshore drilling of these pre-fossil fuel deposits could enable their exploitation as a nearly limitless source of alkalinity for the sea. Sea water could be pumped into the underlying sediments under pressure. This will drive sulfate in to the low oxygen, carbon rich sediment. Sulfate reduction will generate alkalinity which would be driven out into the sea as submarine groundwater discharge to marine ecosystems. Sufficient alkalinity for the sea could be generated long before the pre-fossil fuel runs out. |
| 07-06-2023 08:36 | |
| sealover★★★★☆ (1249) |
sealover wrote: Groundwater is not a discharge. [quote] There are always two sides to a disagreement. A good reality check would be to Google "submarine groundwater discharge" It would be too exhausting to have to defend the definition of terms. About 75% of the alkalinity discharged from coastal wetlands via groundwater is comprised of bicarbonate ions, and much lesser amounts of bicarbonate ions. The other 25% of the alkalinity in groundwater discharge from coastal wetlands is comprised of ORGANIC alkalinity. Organic alkalinity is the acid neutralizing capacity that arises from anions of deprotonated organic acids. Organic alkalinity is of ecological significance because organic anions often have metal complexing capacity. Organic alkalinity can form chelation complexes with iron to keep it soluble and bioavailble. Inorganic carbon alkalinity (bicarbonate or carbonate) cannot do this. Organic alkalinity in submarine groundwater discharge from coastal wetlands is accompanied by organically-complexed ferric or ferrous iron, essential for the nutrition of marine ecosystems |
| 07-06-2023 08:37 | |
| sealover★★★★☆ (1249) |
sealover wrote: A word of caution about coastal desert chemistry. You won't have to wait for the live wetland ecosystem to establish before you'll generate a whole lot of alkalinity. Rewetting a dry desert soil with sea water could result in extremely high initial pH. A toxic witch's brew will be the immediate result, although capable of rapid self attenuation. An exceptionally high pH initial mix could contain toxic concentrations of arsenic, boron, selenium, even hexavalent chromium (of natural origin). Within seconds of initial contact between the dry desert soil and applied sea water, the soil becomes a high pH chemical trap for CO2. The pH will decline soon as alkali hydroxides absorb CO2 to become carbonates. Self attenuation with decreasing pH as CO2 is absorbed will soon sequester arsenic, borate, etc. out of solution. |
| 07-06-2023 08:38 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Hopefully, it does not cause too much confusion that "sea water" and "sulfate" are interchangeable as a name for the input of sulfate bearing sea water into low oxygen wetland sediment. Sea water contains from 2650-2690 ppm sulfate. In contrast, sea water contains from 8-11 ppm oxygen. The energy yield for microorganisms who make their living oxidizing organic carbon is greatest when oxygen is used as oxidant (aerobic respiration). Aerobic respiration of (reduced) organic carbon generates carbon dioxide as the (oxidized) inorganic carbon product. Much lower energy yield is acquired when sulfate is used by bacteria to oxidize organic carbon. Sulfate reduction generates alkalinity as the (oxidized) inorganic carbon product. At only 8-11 ppm, oxygen gets depleted very quickly in carbon rich sediment. With 2650-2950 ppm sulfate remaining when the oxygen runs out, the next best available oxidant is most abundant, albeit for a much smaller energy yield. One mole of organic carbon generates two moles of alkalinity when sulfate is used as oxidant by sulfate reducing bacteria |
| 07-06-2023 08:40 | |
| sealover★★★★☆ (1249) |
Naturally-occurring hexavalent chromium can be found beneath desert soils. It is usually limited to the margins where the last inputs of groundwater dried up as it became desert. Hexavalent chromium is not our friend. Trivalent chromium is common in many soils. It is benign, and not easily transformed into the carcinogenic hexavalent form. The overwhelming majority of chromium in desert soil is trivalent Cr(III) occluded within the crystal lattice of rock minerals. A small amount of chromium(III) is present in material coating the surface of larger particles. Before becoming desert, photosynthesis once provided the soil with organic carbon. The most enduring fraction of that soil organic matter were humic acids coating soil particle surfaces. Humic acids have cation exchange capacity to adsorb chromium(III) into tightly bound complexes. Occluded within the humic coating, the chromium(III) was never exposed to oxidation into hexavalent chromium. Also cycled along with chromium(III), manganese adsorbed to humic acid cation exchange sites as a tightly bound complex. Manganese(II) is far more soluble than the oxidized form, manganese(IV). Manganese(II) is the mobile form that adsorbed to humic coatings on soil particle surfaces. With its reactive sites occluded from oxidation by formation of inner sphere complexes with organic ligands, manganese(II) remained intact in its chemically reduced form. It's not easy to oxidize chromium(III) into hexavalent chromium. Oxygen isn't a powerful enough oxidant to do it. Hexavalent chromium rarely occurs in nature. But there is an oxidant generated as a by-product during manganese oxidation, far more powerful than oxygen. Under aerobic conditions, some bacteria acquire their energy by oxidizing manganese(II) into manganese(IV). These chemoautotrophic can use carbon dioxide as their carbon source and manganese oxidation as their energy source. During oxidation of manganese(II) to manganese(IV), a tiny bit of highly oxidized manganese(VII) is generated as by product. Manganese(VII) is a strong enough oxidant to turn chromium(III) into hexavalent chromium through purely abiotic mechanisms. Manganese(II) and chromium(III) lived happily side-by-side within organic carbon matrix of humic coatings for centuries. When the land became desert, input of new organic carbon ceased. As the chromium(III)/manganese(II) bearing humic coatings decomposed, they no longer had the cation exchange capacity of the organic matrix to hold them or prevent their oxidation. As manganese(II) oxidized to manganese(IV) by oxygen, by product manganese(VII) oxidized chromium(III) to hexavalent chromium. ---------------------------------------- Government Oversight and Mandated Remediation Caused Hex Chrome Hazard. Naturally occurring hexavalent chromium is limited to the margins of deserts. Anthropogenic hexavalent chromium can have a complex life cycle. Picture a Superfund site. A former laboratory that once handled extremely hazardous substances. The lab has been shut down for decades. That laboratory used to drain their sinks into a septic tank on site. None of the deadly stuff went down the drain. Just the usual lab sink waste. That laboratory waste water included hexavalent chromium, commonly used as an oxidant in laboratory procedures. It also included organic carbon, some of which came in from the toilets. When the hexavalent chromium entered the septic tank, it was highly soluble and mobile. It traveled into the leaching field and along subsurface flow paths. The hexavalent chromium had a very short half life after it left the laboratory. After it stalled somewhere along the subsurface flow path and was adsorbed by soil organic matter, it was reduced to Cr(III). Organic carbon is a good reductant. For decades the input of organic carbon and chromium continued. Subsurface flow paths were loaded up with organic carbon, chromium(III) and manganese(IV). When the lab sewer system was taken out of service, the supply of new organic carbon was cut off. Like the desert margin, as the organic matter decomposed and exposed chromium and manganese to oxidation, hexavalent chromium was generated. |
| 07-06-2023 08:41 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Microorganisms have evolved to use multiple oxidants and multiple reductants to acquire energy. Some oxidants are much stronger than others. Same for reductants. The highest energy yield comes from coupling the strongest available oxidant to the strongest available reductant. Aerobic hydrogen oxidizing bacteria get the most energy by using oxygen to oxidize hydrogen and generate water. Hydrogen is such a strong reductant that even a very weak oxidant can be used to yield energy. Ancient methanogenic bacteria used carbon dioxide as oxidant for hydrogen. They generated methane gas for a slight energetic payoff. Oxygen is such a strong oxidant that even a very weak reductant can be used to yield energy. Oxygen is the only naturally available oxidant strong enough to oxidize nitrite to nitrate by nitrifying bacteria, for a slight energetic payoff. The most commonly used reductants in nature, in order of strength: H2 > H2S > elemental-S > organic-S > iron(II) = Mn(II) > ammonia > nitrite An even weaker reductant is used for most photosynthesis. Water is oxidized to oxygen gas in order to reduce carbon dioxide into organic carbon. The most commonly used oxidants in nature, in order of strength: O2 > nitrate > nitrite > iron(III) = Mn(IV) > sulfate > carbon dioxide Competitive advantage goes to the organism that can best exploit the available reductants and oxidants. So long as oxygen is available, nitrate reducers, iron/manganese reducers, sulfate reducers, methanogens, etc, are at a disadvantage. So long as hydrogen is available, sulfur oxidizers, iron/manganese oxidizers, nitrogen oxidizers, etc., are all at a disadvantage. This is just a short list of elements used by microorganisms for oxidation/reduction reactions. The complete list includes everything from arsenic to selenium. |
| 07-06-2023 08:43 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: There has been life on earth for at least 4000 million years. There was no photosynthesis in the earliest days. There was an abundance of energy-rich reductants available in the environment. Hydrogen gas for example. All a bacteria needed was an oxidant to take advantage of it. Oxidants were scarce in those days. No oxidants had yet been generated by photosynthesis. The earth did provide a few. There was some nitrate here and there, some sulfate, some iron and manganese in oxidized state. But not much. A few localized niches for nitrate reducers, sulfate reducers, etc., where the earth provided oxidants. One very weak oxidant that was abundant was carbon dioxide. The first methanogenic bacteria evolved to couple hydrogen oxidation to carbon dioxide reduction. The product of their metabolism was methane gas. The earth had no ozone shield to protect from ultraviolet. Manganese was particularly sensitive to photo oxidation by sunlight. Where sunlight photooxidized manganese(II) to manganese(IV), that manganese(IV) could then be used by microorganisms as oxidant. After they used the manganese(IV) to oxidize (hydrogen, hydrogen sulfide, sulfur, iron, carbon, etc., they had manganese(II) leftover as a waste product. Somehow, a bacteria had manganese(II) inside the cell that got photooxidized to manganese(IV). Somehow it evolved into recycling the manganese within the cell, reoxidizing it with sunlight over and over. Somehow it evolved into an organic matrix structure to hold the manganese atom in place. It wasn't photosynthesis. It was just intracellular photoxidation to generate an oxidant. Somehow, that organic structure to hold the manganese atom expanded into a light harvesting apparatus. Able to use blue light rather than ultraviolet, and be competitive in zones of lower light intensity. Expanded further to even be able to use red light, making it competitive in even dimmer environments. But still not photosynthesis. It was only generating oxidant, not reducing carbon. The sunlight wasn't the source of energy for the bacteria. It was just the spark that allowed the bacteria to exploit other sources of energy, such as the oxidation of hydrogen. Well, it's getting late. I'll pick it up tomorrow, get into anoxygenic photosynthesis and banded iron formations, finally oxygenic photosynthesis which provided the oxygen that changed everything. |
| 07-06-2023 08:44 | |
| sealover★★★★☆ (1249) |
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. |
| 07-06-2023 08:46 | |
| sealover★★★★☆ (1249) |
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. |
| 07-06-2023 08:47 | |
| sealover★★★★☆ (1249) |
Millions sickened by arsenic poisoning. The hazards of good intentions. In the 1970s to 1980s, well intentioned public health programs sought to improve the lives of millions of the world's most impoverished people living in densely populated delta regions. River water used for human consumption was infested with parasites and pathogens. Many thousands of shallow tube wells were installed to provide safe drinking water. In the Ganges delta, the Mekong delta, the Red River delta, etc. The water was somewhat salty and worthless for irrigation. But it didn't have parasites or pathogens. What the shallow delta groundwater from the wells did have was arsenic. It took years before the problem was identified. By then, literally millions of people had been sickened with "blackfoot disease" and arsenic-related cancers. The intentions were good. It was a reasonable goal to improve public health. What was missing? There was not a recognition among policy makers that expertise in biogeochemistry was needed. Why would there be arsenic in groundwater? They didn't even know how to ask the right questions. They didn't think the questions needed to be asked. |
| 07-06-2023 08:50 | |
| sealover★★★★☆ (1249) |
Today, in wealthy nations such as the United States, there are indeed environmental regulations that require such testing to certify a well. In the delta backwaters of South Asia and Southeast Asia in the 1970s, regulation wasn't so strict. They didn't even have the infrastructure to do any such testing or any kind of certification process. And who could have predicted the seasonal variability in groundwater arsenic biogeochemistry? Samples from the initial wells, airlifted for testing abroad, showed no problem. That would remain true for the few samples from new wells they could afford to test. Only a small minority of wells would eventually prove to have high arsenic all year round. Many other wells that were actually tested were caught at the wrong time of year to reveal any problem. Relatively few wells could be tested. It just wasn't an option. And many of those that they did test, revealing low arsenic, would turn out to have much higher arsenic during the season when new well boring and testing was too difficult due to heavy rain. Acute arsenic poisoning is a rapid process. People show symptoms very quickly. When "agent blue" was sprayed over rice paddies of Viet Nam to kill the crops as part of the "food denial" program, people died immediately of acute arsenic poisoning. The chemical form of arsenic in herbicides and pesticides is very different than the arsenic found in groundwater. It took years of drinking the water day after day before people accumulated enough arsenic to make them sick. |
| 07-06-2023 08:51 | |
| sealover★★★★☆ (1249) |
Viet Nam - Anthropogenic AND Natural Arsenic Poisoning Some poor peasants in the Mekong delta got arsenic poisoning twice during their lifetime. They survived subacute arsenic poisoning when "agent blue" rained down into their water supply. Years later they got sick from arsenic again, after drinking too much of it from shallow well water. The first arsenic poisoning, arguably a war crime, was acute toxicity from highly reactive chemical forms of arsenic in anthropogenic herbicide. That herbicide didn't remain poisonous in the rice paddies for very long. The arsenic was rapidly transformed and attenuated as arsenate strongly bound to the soil. It would never hurt anybody again. The second arsenic poisoning, a tragic mistake and not an act of war, was from drinking water that historically people knew better than to use. There was no preexisting data set from shallow delta wells used for drinking water in the past. Such wells never existed before. There was very little preexisting data for delta groundwater, period. Arsenic has no taste, although the water was saltier than one might like. You don't know you are sick until years too late to imagine it was the water. |
| 07-06-2023 08:53 | |
| sealover★★★★☆ (1249) |
Reductive dehalogenenation is the process by which bacteria remove atoms of chlorine, fluorine, bromine, or iodine from an organic carbon compound. These halogenated organics include everything from teflon to DDT. No microorganism is capable of degrading these things for profit. It costs more to make the enzymes to degrade them and make the carbon available for oxidation than they can get from oxidizing the carbon. The stuff just hangs out in the environment for the longest time. However, if we provide the right anaerobic bacteria with a source of energy (usually carbohyrate) to do it and provide extreme hypoxia conditions, they can tear the chlorine, fluorine, bromine or iodine off the xenobiotic. The halogen is chemically reduced to chloride, fluoride, bromide, or iodide ion. The remaining carbon can later be degraded for profit by (different) aerobic bacteria when oxygen is allowed to return. Proven fact. It's already a success story, not a theory. Contracting microorganisms to do our dirty work for us offers hope for how we can detoxify xenobiotics and facilitate their degradation |
| 07-06-2023 08:56 | |
| sealover★★★★☆ (1249) |
XENOBIOTICS include PLASTIC. We synthesized a lot of materials that no organism ever evolved to degrade. Many bacteria and fungi produce the right kind of enzymes, or are capable of carrying out detoxifying redox reactions, but cannot degrade xenobiotics unless they are supplied. But it can be as simple and flooding the soil with beer brewery waste to create extreme low oxygen with an energy source for reductive dehalogenation and other xenobiotic degradation reactions. And we can use a model from Mother Nature. Chitin degradation. 3-way symbiosis: Plant-fungi-bacteria. Chitin is what arthropod (insects, etc.) exoskeletons are made of. There is a lot of it in soil communities. It is a great source of nitrogen, but it's tough to degrade. Some bacteria make enzymes that can degrade chitin. But they can't make a living at it. They can tear apart the chitin to mobilize the nitrogen. They could then oxidize the remaining organic carbon. But there's no profit in it. Almost all plants have symbiotic mycorrhizal fungi associated with their roots. Plants provide organic carbon to the fungi. The fungi with its extensive network of fine hyphae, contacts about 50 times as much soil surface area as the roots of its plant partner. The fungal hyphae can reach far and wide, using the food provided by the plant. They can then transfer to the plant nutrients acquired from the soil. Fungi are biochemical wizards are far as producing enzymes to degrade decomposing organic matter. But chitin is a tough nut to crack even for a fungi. Besides, many fungi include chitin in their own structure. Producing a self-digesting enzyme is hazardous. Bacteria can degrade chitin, but it's generally not worth it. Unless they are truly starving for nitrogen. But let's connect the three to see the model nature provides for degrading xenobiotics. The tree gives its mycorrhizal fungi some organic carbon. Go get me some nitrogen. The fungi has a monolayer of bacteria on the tips of its hyphae. The fungi gives some of the organic carbon it got from the tree and gives it to the bacteria. Go get me some nitrogen. The bacteria produces chitinase. Just far enough away from the fungi not to digest it too. Soil chitin is degraded by the chitinase from the bacteria. The mycorrhizal fungi pick up the nitrogen mobilized by the bacteria and pass it back up to the tree. We can use those guys to break down things besides chitin. We can selectively breed bacteria to degrade things that Mother Nature has never seen before. Maybe even throw in a little genetic engineering. |
| 07-06-2023 08:57 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Paleobiogeochemistry time again! The banded iron formations reveal that life has been present on earth for 4000 million years. The geologic record revealed that there was a time before the earth had oxygen in the atmosphere. The banded iron formations revealed a major shift in oxidation-reduction conditions, where iron was fully oxidized. It was known that oxygen is deadly to microorganisms adapted exclusively to low oxygen conditions. So, there must been an "oxygen catastrophe". A mass extinction must have occurred. One little flaw in the theory was that there wasn't just one band of oxidized iron in the banded iron formations. The "oxygen catastrophe" must have happened over and over. And over and over and over again, over a period of 2000 million years. The quantities of oxidized iron in the banded iron formations represent at least a 1000 million years of oxygenic photosynthesis. And this was before enough of the iron in the earth's crust had oxidized that it became possible for free oxygen to accumulate in the atmosphere. There was no "oxygen catastrophe". There were 2000 million years during which oxygen was at least sometimes present under otherwise prevailing reducing conditions. Oxygen was not a poison. It was a coveted resource. It was the most powerful oxidant nature ever provided. It released more energy than any other oxidant when used to oxidize hydrogen, hydrogen sulfide, reduced sulfur of all forms, manganese(II), ferrous iron, and all the other reductants. And, of course, carbon. Oxygen got the most bang for the buck when a microorganism used it to oxidize organic carbon. Sulfur gave a lot more energy than carbon, using oxygen to burn it. Sulfur oxidizing bacteria parked next to the photosynthetic cyanobacteria. They wanted to catch the oxygen as soon as it came out. They left us some distinct fossil layers to prove it. |
| 07-06-2023 09:00 | |
| sealover★★★★☆ (1249) |
pH is commensurate with hydrogen ion ACTIVITY, but not necessarily hydrogen ion CONCENTRATION. Before we go there, let's start with the basics. Actually it IS possible to measure the pH of the oceans. That probably doesn't require too much suspension of disbelief. But when they measure pH, what are they even measuring. I used the word "commensurate" rather than "proportional" because the pH scale is logarithmic. pH is the negative of the logarithm of hydrogen ion activity. Before we get into "activity" rather than "concentration", make sure we got the "logarithm" part right. pH 7 is where the activity of hydrogen ions is equal to the activity of hydroxide. 10 to the minus 7 power is a tiny number. 0.000001 pH 6 translates to 0.00001 a unit change of just 1 represents tens times as much hydrogen activity. Why "activity"? To illustrate, let's look at ferric iron. Put some ferric iron into our pH 7 solution and nearly all of it precipitates. Equilibrium activity of labile ferric ion is extremely low at pH 7. A measure of iron concentration would show extremely low. Now make a pH 7 solution of ascorbic acid (vitamin C) and add ferric iron to it. The concentration of iron in solution can be orders of magnitude higher at pH 7 than the pH 7 water with no vitamin C. Concentration is not activity. When the ferric iron was chelated by vitamin C, its reactive sites were occluded by attachment to organic ligands. These iron atoms have very low chemical activity, compared to ferric iron not chelated by vitamin C. The same level of total chemical activity can support a much much higher concentration of iron in solution, if each iron atom atom has low chemical activity. But you could still calculate iron concentration based on pH if you have the right activity coefficient for iron in vitamin C chelation complexes. And by the way, the fact that chelated ferric iron is so soluble, it means that even at SEA WATER pH it remains soluble and bioavailable. |
| 07-06-2023 09:03 | |
| sealover★★★★☆ (1249) |
sealover wrote: I am enjoying the comments from sealover. New life has been breathed into Climate Debate Questions for this solution... Would it be hazardous to one's health, to breathe in the air near the constructed saltwater wetlands? How long would it take to sequester arsenic, borate, etc. out of the solution? |
| 07-06-2023 09:05 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Alkalinity and alkaline sound very similar but have little in common. Alkaline refers to the extent above pH of a solution. Bicarbonate is less alkaline than carbonate less alkaline than hydroxide. "You can't acidify an alkaline" It's either or pH > 7, alkaline, or pH < 7, acid. But alkalinity is quite different, not at all interchangeable with alkaline. Alkalinity is acid neutralizing capacity. A solution can have pH < 7, yet have very high alkalinity. A solution can have pH > 7, yet have very low alkalinity. Try not to get them mixed up. It's a common mistake. |
| 07-06-2023 09:08 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Pyrite at the beach - Bacterial sulfate reduction? Spongy Iris asked about the "fool's gold" one often sees at the beach. Was that pyrite in the sand formed by bacterial sulfate reduction? Not most of it. Most of the pyrite eroded off the mountains and washing down to the sea was not formed by bacteria. It is the same chemical compound, formed by abiotic mechanisms in geochemical processes millions of years ago. It was in the rocks before erosion. But walk around to the right part of the beach and you can find enormous crystals of pyrite formed in place by bacteria, during your lifetime. The rising sea level created a new layer of pyrite in the nearby mud flat. You don't have to dig deep at all to find them in the sediment. Some of those chunks of "fool's gold" are HUGE! ------------------------------------------------------------------------------- [quote]sealover wrote: Thank you, Spongy Iris, for a meaningful contribution to a rational discussion. You mentioned that one approach to mitigating the "rotten egg" smell is simply to aerate. Bubbling oxygen in. That is your easiest, cheapest, best quick fix. Entry of oxygen accomplishes two things. It allows sulfur oxidizing bacteria to transform hydrogen sulfide into sulfuric acid. Maybe that doesn't sound better than rotten eggs, but it really is. Entry of oxygen also prevents further generation of H2S. Some microorganisms are adapted to exclusively low-oxygen conditions, and oxygen will simply kill them. Others, like many sulfate reducers won't be killed by oxygen. But they will be STARVED by the presence of oxygen. They just can't compete if oxygen is around. Aerobic microorganisms will get much much greater payoff by using oxygen, rather than sulfate, as oxidant to get energy from the oxidation of organic carbon. The aerobic population will quickly outnumber the sulfate reducers and starve them out. Back to the sulfuric acid generated when H2S is oxidized using oxygen. Some sewer systems built of concrete get dissolved by the stuff. Hydrogen sulfide, H2S, emitted from the anaerobic sewage by sulfate reducing bacteria under low oxygen conditions, floats up into the air. Sulfur oxidizing bacteria on the concrete walls of the sewer catch the H2S and turn it into sulfuric acid. That sulfuric acid then reacts with the calcium carbonate (lime) in the concrete. The acid neutralizing capacity (alkalinity) of the lime comes into play. Sulfuric acid + calcium carbonate = calcium sulfate + carbon dioxide + water Back to bubbling oxygen to prevent anaerobic generation of stink and such. During dredging operations, anaerobic sediment is exposed to oxygen. It often contains a lot of H2S that is released. Dredging use to occasionally cause big fish kills. Then they learned to use industrial scale injection of air bubbles in the process. Rather than get fish kills, they get fish feeding frenzies. Thank you again, Spongy Iris for bringing relevant information and knowledge that makes a valuable contribution to the discussion! |
| 07-06-2023 09:10 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Inorganic Carbon versus Organic Carbon Some of the important differences. ORGANIC CARBON is in chemically reduced state. INORGANIC CARBON is in a chemically oxidized state. Organic carbon can yield energy by being oxidized. Inorganic carbon cannot yield energy by being oxidized. Inorganic carbon is a very weak oxidant. Ancient methanogens used to combine hydrogen gas with carbon dioxide to generate methane, water, and a very small amount of energy. Organic carbon is a weaker reductant than many others in nature, such as hydrogen, hydrogen sulfide, and other reduced forms of sulfur. If stronger reductants than organic carbon are available in the presence of oxygen, microorganisms that use the stronger reductants have a competitive advantage. Such as the sulfur oxidizers who competed to get the oxygen from ancient cyanobacteria in a time when oxygen was a coveted and limited resource. Sulfur oxidation yielded so much more energy than carbon oxidation, the carbon oxidizers didn't have a chance until the sulfur ran out. Inorganic carbon oxyanions bicarbonate and carbonate provide the vast majority of alkalinity in the sea. Organic carbon anions of deprotonated organic acids (citrate, acetate, etc.) provide more of the sea's alkalinity than previously recognized. ORGANIC ALKALINITY can be one fourth of the total alkalinity in submarine groundwater discharge from wetlands. |
| 07-06-2023 09:11 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Oxygen Limitation - Evolution of Mitochondrial Symbiosis. When the first oxygenic photosynthetic cyanobacteria stumbled on to a way to generate hydrogen for reduction of inorganic carbon, using water as the source of hydrogen, it changed biology, ecology, and the very chemistry of the land, sea, and air. Oxygenic photosynthesis generated oxygen gas, a powerful oxidant. A whole new niche opened up for anyone who could grab the oxygen as soon as it came off, and use it oxidize some reductant from somewhere else. One consequence were the layered fossils, NOT banded iron formations, showing the earliest adaptations. Hydrogen sulfide was the second strongest reductant out there, after hydrogen. Hydrogen sulfide was much heavier than hydrogen H2. Big bursts of geologic activity could fill the atmosphere with hydrogen gas. But the earth's gravity couldn't keep it on the planet very long. After the hydrogen floated off to space, taking its reducing power and potential energy off with it, the heavy hydrogen sulfide remained as the next most powerful reductant. The most profitable transaction out there for a bacteria was to get the oxygen from the cyanobacteria and use to oxidize hydrogen sulfide. There were plenty of other reductants around to oxidize for whoever got the oxygen first. Especially organic carbon. There was tons of it EVERYWHERE. It just didn't pay as well to use weaker reductants, with the oxygen. The hydrogen sulfide oxidizing bacteria had a competitive advantage. They formed a dense layer immediately below the photosynthetic bacteria at the surface. When the sulfur oxidizing bacteria use oxygen as oxidant, it generates sulfuric acid. Sulfuric acid, hydrogen sulfate, contains sulfate. Sulfate is a divalent oxyanion that can be used to oxidize organic carbon during sulfate reduction. Top layer. Cyanobacteria making oxygen oxidant. Middle layer. Sulfur oxidizing bacteria making sulfate oxidant. Bottom layer. Sulfate reducing bacteria turn organic carbon to inorganic carbon oxyanion. The chemistry of the fossil is consistent with the three layers of microbial communities. |
| 07-06-2023 09:13 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Organic Alkalinity - Carboxylic and Phenolic groups on organic acids. Historically, organic alkalinity was not recognized as an important component in the alkalinity of the ocean. It was known that oxyanions of deprotonated organic acid existed. It was known that they contributed acid neutralizing capacity (alkalinity). Few people had any idea how much of them there was in sea water, and how important this unique "pool" of alkalinity is. Most alkalinity in sea water arises from phenol carboxylic acids, such as "humic" acids. These are often large molecules that act as polydentate ligands with multiple binding sites provided by carboxylic and phenolic functional groups. Carboxylic acids are the most familiar organic acids. Vinegar, citric acid, vitamin C, lactic acid. They all have a carboxylic group. A carbon double bonded to one oxygen, and single bonded to a second oxygen in a hydroxyl (-OH) group. Carboxylic acids typically have pKa in the ballpark of 4.5. This means that at near pH 4.5, they are half deprotonated and half in acid form. The alkalinity of organic acid buffers can be calculated knowing the pH of the solution and the pKa of the organic acid. One thing that organic carbon alkalinity can do that inorganic carbon alkalinity cannot is to form organometallic complexes with transition metals such as iron. Often tightly bound as inner sphere chelation complexes, organic anions are a major controller on the behavior of metals in solution. Organic alkalinity is finally getting the attention it deserves in the new research. |
| 07-06-2023 09:15 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: CORRECTION (organic alkalinity) and role of phenolic groups. I mistakenly said that organic alkalinity supplied most of the seas alkalinity. WRONG. Not even close. Bicarbonate and carbonate supply the overwhelming majority of the sea's acid neutralizing capacity (alkalinity). ORGANIC ALKALINITY IS HUGELY IMPORTANT IN SUBMARINE GROUNDWATER DISCHARGE FROM WETLANDS - ABOUT ONE FOURTH OF TOTAL ALKALINITY. Phenolic groups, a hydroxyl group attached to an aromatic ring, also provide alkalinity. Phenolic acids are much weaker acids than carboxylic acids. They do not deprotonate until much higher pH, compared to carboxylic acids. Much higher pKa. The most important functional group pairings within the organic alkalinity oxyanions are Ortho di carboxylic - Two adjacent carboxylic groups capable of forming chelation complex with transition metals. Ortho hydric phenol carboxylic - adjacent phenolic and carboxylic groups on an aromatic ring, capable of forming chelation complex with transition metals. Ortho di hydric phenolic - adjacent phenolic groups on an aromatic ring, capable of forming chelation complex with transition metals. |
| 07-06-2023 09:17 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: CORRECTION: BENZOIC ACIDS (aromatic carboxylic) The most common organic acids in nature are carboxylic acids. Deprotonation of the carboxylic group yields an organic carbon oxyanion. Organic carbon oxyanions contribute alkalinity. Some carboxylic groups on organic acids occur on aromatic rings. This combination of aromatic carboxylic is known as BENZOIC ACID. As in it is on a BENZENE aromatic ring. The pKas of benzoic acids range substantially more widely than the aliphatic carboxylic acids with pKas typically near 4. Phenolic acids, hydroxylic groups on aromatic benzene ring, are much weaker acids than carboxylic acids. Furthermore, phenolics pKa is closer to 10. They don't deprotonate until high pH. The combination of aliphatic carboxylic, benzoic, phenol carboxylic, and polyphenolic functional results in four distinct pH ranges where naturally occurring organic alkalinity has peak buffering capacity. The two biggest peaks are near pH 4.5 and pH 10. Maximum resistance to pH shift in response to addition or neutralization of protons occurs near pH 4.5 and pH 10. Organic anions with adjacent acidic functional groups can form chelation complexes with metals, forming ring structure 2-bond complex. Dicarboxylic, ortho phenol benzoic, and ortho dihydric phenolic acids all have two adjacent acidic groups to act as polydentate ligands. |
| 07-06-2023 09:19 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: 3 layer fossil, adaptation to new oxygen. The banded iron formations formed from sea floor deposits. There was a layer of sea water between the photosynthetic community on the surface and the sea floor. The three-layer fossil described here is very different from banded iron formation. The three layers lived side by side simultaneously. The top layer needed only sunlight, and water as reductant for oxygenic photosynthesis. It was not being eroded away or buried in sediment. It remained intact year after year, generating oxygen and organic carbon. The middle layer needed only oxygen. The hydrogen sulfide continuously came up from below. An energy-rich reductant could be combined with a powerful oxidant. The input of oxygen from above was as was he input of Hydrogen sulfide from below. The sulfur oxidizers could just sit in the middle and take it in from both ends. One small catch. It constantly generated sulfuric acid. The bottom layer needed only sulfate from above. They were sitting on an accumulation of more organic carbon than they could ever use. Sulfate wasn't that great an oxidant, but it made exploitation of the organic carbon possible. Sulfate reduction generated alkalinity in the bottom layer. Exactly enough to neutralize the sulfuric acid that brought the sulfate. Sulfate reduction in the bottom layer also generated hydrogen sulfide to bubble back up to the sulfur oxidizers. Sulfur going back and forth, being used as reductant in the form of sulfide, and then being used as oxidant in the form of sulfate. Acid generated, acid neutralized. Sustainable with no input besides sunlight for nearly forever. Every last drop of oxygen generated by photosynthesis was captured immediately by sulfur oxidizers. It would be at least two thousand million years of this before enough iron would eventually start to rust away, allowing for the accumulation of free oxygen in the atmosphere. ----------------------------------------------------------- [quote]sealover wrote: Oxygen Limitation - Evolution of Mitochondrial Symbiosis. When the first oxygenic photosynthetic cyanobacteria stumbled on to a way to generate hydrogen for reduction of inorganic carbon, using water as the source of hydrogen, it changed biology, ecology, and the very chemistry of the land, sea, and air. Oxygenic photosynthesis generated oxygen gas, a powerful oxidant. A whole new niche opened up for anyone who could grab the oxygen as soon as it came off, and use it oxidize some reductant from somewhere else. One consequence were the layered fossils, NOT banded iron formations, showing the earliest adaptations. Hydrogen sulfide was the second strongest reductant out there, after hydrogen. Hydrogen sulfide was much heavier than hydrogen H2. Big bursts of geologic activity could fill the atmosphere with hydrogen gas. But the earth's gravity couldn't keep it on the planet very long. After the hydrogen floated off to space, taking its reducing power and potential energy off with it, the heavy hydrogen sulfide remained as the next most powerful reductant. The most profitable transaction out there for a bacteria was to get the oxygen from the cyanobacteria and use to oxidize hydrogen sulfide. There were plenty of other reductants around to oxidize for whoever got the oxygen first. Especially organic carbon. There was tons of it EVERYWHERE. It just didn't pay as well to use weaker reductants, with the oxygen. The hydrogen sulfide oxidizing bacteria had a competitive advantage. They formed a dense layer immediately below the photosynthetic bacteria at the surface. When the sulfur oxidizing bacteria use oxygen as oxidant, it generates sulfuric acid. Sulfuric acid, hydrogen sulfate, contains sulfate. Sulfate is a divalent oxyanion that can be used to oxidize organic carbon during sulfate reduction. Top layer. Cyanobacteria making oxygen oxidant. Middle layer. Sulfur oxidizing bacteria making sulfate oxidant. Bottom layer. Sulfate reducing bacteria turn organic carbon to inorganic carbon oxyanion. The chemistry of the fossil is consistent with the three layers of microbial communities. |
| 07-06-2023 09:24 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Mitochondria: A parasite became a partner in respiration. When cyanobacteria began to supply the earth with oxygen, it created a new niche for microorganisms to exploit a powerful new oxidant. Cyanobacteria could generate oxygen ANYWHERE THERE WAS SUNLIGHT. Unlike other oxidants, oxygen availability was not limited to geologic seeps and vents, or places where photooxidized manganese washed down into the sea. For the first time, it became profitable for microorganisms to oxidize ammonium into nitrite, and to oxidize nitrite into nitrate. The relatively low energy yield from oxidation of organic carbon could be boosted using this new, powerful oxidant - oxygen. Everybody wanted a piece of it. The hydrogen oxidizers could push everyone else out of the way, if hydrogen were seeping or bubbling into the microsite. They could get so much more bang for the buck from every oxygen molecule they use, the other microorganisms would be quickly outgrown and overrun. The more common situation was for hydrogen sulfide to be the strongest available reductant to combine with oxygen. Sulfur oxidizers could outgrow and overrun any competition for oxygen. Sometimes ferrous iron or manganese(II) were the next strongest available reductant. Some massive deposits of manganese(IV) or ferric iron resulted. And organic carbon was piling up everywhere. The protomitochondria didn't come aboard to offer his assistance to the cyanobacteria. He burrowed in as a parasite. Organic carbon was everywhere, but oxygen was very scarce. The protomitochondria evolved a good trick to be able to oxidize organic carbon via aerobic respiration, generating carbon dioxide as the oxidized carbon product. The protomitochondria couldn't compete well for the oxygen coming out of the cyanobacteria. Others who oxidized stronger reductants would always win. On the other hand, INSIDE the source of the oxygen there was also organic carbon. Burrow up inside there and you have a monopoly on both the oxidant and the reductant. The original arrangement was probably short lived. Probably only so long you can survive with someone inside you burning up your organic carbon with the oxygen you make. The parasite honed its skills to keep the host alive a little longer. The parasite honed its skills to ensure the host was healthy enough to feed him. The parasite started sharing some of the ATP it was making with the host. Before long, it became a mutually beneficial relationship that changed the course of biology. |
| 07-06-2023 09:26 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Target audience buzzword challenge. Chemoautotrophic bacteria. I continue to rest assured that the target audience will recognize my correct use of buzzwords. Scientists who play word games can pick apart the ones they don't know and make a good guess. Many of the bacteria I have been speaking of are chemoautotrophs. Chemo"autotrophs". NOT chemo heterotrophs. "Chemo"autotrophs. NOT photo autotrophs. Chemoautotrophic bacteria feed themselves, reducing inorganic carbon with the energy of chemical oxidation/reduction reactions. Many of them oxidize minerals found in rocks - litho trophic chemoautotrophs Like sulfur oxidizers, iron oxidizers, manganese oxiders, nitrogen oxidizers, arsenic oxidizers, selenium, phosphorous, molybdenum, boron, and on and on. |
| 07-06-2023 09:28 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Photosynthetic oxygen from WATER not CARBON DIOXIDE. Photosynthesis was a tough one for scientists to figure out. The plant was taking in carbon dioxide and water. The plant was putting out oxygen and synthesizing carbohydrate. CO2 plus H20 go in. O2 and C6H12O6 come out. Well, it looks like the O2 must have come off the CO2. It looks like the H20 attached to the C to make the equivalent of CH2O. But that's not what happened at all. The oxygen came from the water. It was a purple sulfur photosynthetic bacteria who taught us that. This guy takes in hydrogen sulfide, H2S, for photosynthesis. The purple sulfur bacteria put out sulfate instead of oxygen. The purple sulfur anoxygenic photosynthetic bacteria didn't have to take in water to make carbohydrate, just hydrogen sulfide. And this guy is a throw back to ancient ancient times when there was no oxygen in the atmosphere. He can still outcompete cyanobacteria quite well in microsites where hydrogen sulfide is available, along with sunlight. They proved that the source of oxygen in oxygenic photosynthesis came from tearing apart water, not from tearing apart carbon dioxide apart. |
| 07-06-2023 09:31 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Voltage required to oxidize nitrite in anoxygenic photosynthesis. The basic photosystem required for intracellular photooxidation of manganese didn't require much voltage to make it work. Manganese(II) needed only to be oxidized to manganese(IV). It was EASY with ultraviolet. It took a light harvesting apparatus to be able to create that low voltage in bright blue visible light. It took a far more elaborate light harvesting apparatus to be able to create that voltage in dim red visible light. Still just enough voltage to yank off just those two electrons, to oxidize manganese(II) to manganese(IV). But now that elaborate light harvesting apparatus for dim red light could be brought to the bright surface to generate much higher voltage. Manganese has multiple oxidation states. Manganese(II) and manganese(IV) are just two of them. Manganese(VII), a highly oxidized by product of manganese(II) oxidation by manganese oxidizing bacteria, is a VERY POWERFUL OXIDANT. Manganese(VII) is a much more powerful oxidant than oxygen, O2. Manganese(VII) can oxidize chromium(III) to hexavalent chromium, abiotically. A photosystem that generates enough voltage to turn manganese(II) to manganese(VII) could yank an electron off nitrite to make nitrate. Nitrite could be used as a last resort reductant reductant for anoxygenic photosynthesis, generating nitrate, a powerful oxidant. And a photosystem that could generate that much voltage for manganese oxidation was almost ready to be able to oxidize water and generate oxygen gas. Then you would never need to depend on the environment to supply chemical reductants for photosynthesis. A lot of sun energy was wasted just to crank up the voltage enough to oxidize water. But now a photosynthetic bacteria could grow anywhere that had sun and water. |
| 07-06-2023 09:33 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Arsenic Based Anoxygenic Photosynthesis - Mono Lake, California The use of arsenic by bacteria at Mono Lake was cause for a genuine scandal in science. Arsenic is VERY similar to phosphorus in its chemical properties and behavior. Many of the things organisms need phosphorus for, such as the phospholipids in membranes, can be made with arsenic instead. SO MANY of the things that phosphorus does can be replaced by arsenic that a very controversial paper was published in the journal NATURE. She claimed to have shown a bacteria from Mono Lake was able to survive, grow, and reproduce with NO PHOSPHORUS WHATSOEVER. It was a lie. She had to add just a smidgeon of phosphorus to keep them alive. But hardly any! This was an organism adapted to survive in an arsenic rich ecosystem. Who else lived there? How about an oxygenic photosynthetic bacteria that uses arsenite as reductant and puts out arsenate as the oxidant product of photosynthesis? It's a much better deal than using nitrite. More bang for the sunlight buck. With so much arsenite around, the oxygenic photosynthetic competitors don't have a chance. No cyanobacteria here. They were outgrown and overrun. And it provided a source of arsenate as an oxidant for microbial ecosystems. Arsenate is a better oxidant than many, except for nitrate and oxygen, and a few others. |
| 07-06-2023 09:34 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Ferrous Iron as Reductant for Anoxygenic photosynthesis. Made in the shade! One way that bacteria evolved to carry out anoxygenic photosynthesis is to use ferrous iron as reductant. Using ferrous iron as reductant, ferric iron is the oxidant product of this pathway for anoxygenic photosynthesis. Using ferrous iron in anoxygenic photosynthesis gives higher energy yield than using something like nitrite. And if ferrous iron is available, these iron oxidizing photosynthetic bacteria can out compete cyanobacteria nicely. Especially in the shade. There are places where ferrous iron seeps up into marine ecosystems from below. At the surface where the cyanobacteria and others compete for sunlight, there is just too much oxygen around for ferrous iron to be available at sufficient concentration to support anoxygenic photosynthesis. But IMMEDIATELY BELOW the top layer is a dense layer of photosynthetic bacteria thriving in the shade. There is enough more bang for the buck using ferrous iron rather than water as reductant for photosynthesis, it more than makes up for the difference having dimmer light. These guys have it made in the shade, even in today's oxygen rich world. |
| 07-06-2023 09:36 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Rock Hound Bacteria? They ARE Lithophiles! Give me an unambiguous definition for the term lithophile? It kind of depends on the context. It is either a person who loves rocks, a "rock hound", or... It is a BACTERIA that loves rocks so much that they can't live without them. Lithophilic bacteria are chemoautotrophs. They are capable of synthesizing their own organic carbon starting with carbon dioxide, bicarbonate, or carbonate. They get their energy from the aerobic oxidation of rock minerals. Sulfur, iron, manganese, ammonium, and the list goes on and on. All a rock hound bacteria really needs is oxygen, inorganic carbon (CO2, HCO3, or CO3), and a rock mineral with chemically reduced form of the element they are specialized at oxidizing. Many rock hound bacteria CAN use pre-formed organic carbon that they acquire from the environment. Why not? It's already there and it's FREE. But they don't have to. They can get by just on inorganic carbon if required. Rock hound bacteria played a role in the eutrophication, hypoxia, and fish kills. Ammonium was trapped in the mineral structure of the rocks in this narrow zone of the richest gold deposits in California Gold Rush history. It was, literally, the Mother Lode. The rocks of the Mother Lode used to be sea floor off the California coast, long long ago. A lot of organic nitrogen piled up in the sea floor debris. When plate tectonics shoved the sea floor of the coastal shelf up under the mountains of the coast, that organic nitrogen got buried among the sediment layers. The material in these sediments was never subjected to severe metamorphosis. They are metasedimentary rocks, but they didn't meta very much. The nitrogen remained intact as ammonium, rather than getting baked out or pressed out as nitrogen gas. By the time it became the Mother Lode, these buried sediments were no longer under the coast range. A whole new mountain range was now building on the coast, and there was a huge valley in between them. The Mother Lode was now in the foothills of the Sierra Nevada. When the ancient buried ammonium-rich rock was exposed to oxygen, rock hound bacteria fed upon it. Two kinds. The first ones used oxygen to oxidize ammonium (NH4+) to nitrite (NO2-). The second ones used oxygen to oxidize nitrite (NO2-) to nitrate (NO3-). And nitrate then percolated down into groundwater. Flowed down along sub surface flow paths. And seeped back up into stream water and reservoir water. And fertilized too much algae. And killed too many fish. |
| 07-06-2023 09:37 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Phenotypic Plasticity as a Mechanism of Adaptive Radiation. Adaptive radiation is when a species is able to move into new niches owing to a new adaptation. Becoming warm blooded allowed an animal species to be competitive in niches that were previously too cold for it to survive. Adaptive radiation also allows a population to survive when the niche to which it is adapted changes. Becoming warm blooded allowed an animal to stay competitive even as the niche to which it had adapted becomes colder. One way to facilitate adaptive radiation is to have a lot of genetic variability among progeny. Most of the mutant freaks will die because the genetic variation made them LESS competitive. One of the mutant freaks will survive where no others could because the genetic variation made it MORE competitive. A tree might have fruit bats dropping its seeds far and wide. Some of those seeds will fall into soil conditions to which the seed tree is not adapted. Genetic variability among the seeds could mean that one of them IS adapted to the different soil condition. This would be adaptive radiation facilitated by genetic variation. But what if you don't want to have to make so many seeds in order for them to be able to have variability of traits for adaptive radiation? PHENOTYPIC PLASTICITY! A single genotype can code for multiple phenotypes, depending on environmental conditions. A single genotype in a fish species could allow that fish to survive in a broad range of salinity, if it has phenotypic plasticity. In saltier water, that fish will grow differently, have different physiology, and live a different lifestyle than the same fish genotype growing in less salty water. Phenotypic plasticity to change physiology, morphology, and behavior in response to changing environmental conditions is a superb mechanism of adaptive radiation. Some of my vegetable friends are really good at it. Beech. Fagus sylvatica. Drop one of their seeds into an acidic, siliceous soil, and they will grow one way. They will grow slowly, become very woody, hang on to their leaves as long as possible, concentrate their roots near the surface, allocate much if not most of their photosynthate to mycorrhizal fungi, and produce exceptionally high concentrations of polyphenols. Leaf litter will accumulate at the surface as distinct layers in different stages of decomposition. Detritivores such as earthworms will find the litter unpalatable and will not eat it or mix it into the mineral soil during the process of eating it. Drop another genetically identical beech seed into a calcareous, neutral pH soil, and it will grow VERY differently. They will grow rapidly, not become so woody, shed and replace their leaves frequently, distribute roots deep into the soil with few at the surface, allocate very little of their photosynthate to mycorrhizal fungi, and produce only low concentrations of polyphenols. Leaf litter will decompose rapidly and get mixed into the mineral soil as detritivores devour it. Other plants, you won't even recognize them when they grow in a different niche. Phenotypic plasticity facilitates adaptive radiation of a population out into new niches. Phenotypic plasticity also facilitates a population remaining in place when the niche changes. Plants are pretty good at it. |
| 07-06-2023 09:39 | |
| sealover★★★★☆ (1249) |
[quote]sealover wrote: Familiar Phenotypic Plasticity. Ants, termites, wasps, and bees. Phenotypic plasticity, the ability of a single phenotype to express multiple phenotypes, is more familiar to you than you may know. Some termite larvae are given a lot of hormones at the right stage of development to grow into guards. They have the same genes as the other termites, but they sure don't look the same. Their jaws are HUGE. They cannot eat with those jaws. Someone has to spit pre-chewed food into their mouth for them to keep them alive. With ants, bees, and wasps, how much royal jelly a larvae gets determines what it grows into. Queens, drones, guards, and soldiers.. Phenotypic plasticity is something you knew about your whole life! |
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