Iron in marine applications -
There, along with her adviser Benjamin Bostick and fellow graduate student Jing Sun, she spent many long nights zapping the sediment with high-powered X-rays to reveal its mineral composition. Only certain types of minerals yield dust that is rich in soluble forms of iron, including iron II , the kind that diatoms can easily digest, as Grassian and colleagues described in in the Annual Review of Physical Chemistry.
Winds blowing off the Sahara are one of the most important sources of iron dust in the ocean, supplying more than 70 percent of dissolved iron to the Atlantic, another group has found. But there are several other paths by which iron II makes its way to the oceans, including rivers, hydrothermal vents, volcanoes and glacial outwash plains like the one where Kaplan found his sample in Patagonia.
The glacial sediment contained far more iron II than samples deposited during non-glacial periods from the same region, Shoenfelt Troein found. When glaciers grind down bedrock, the resulting freshly ground sediments tend to contain more iron II than sediments produced from weathering by wind and water, which are richer in iron III , Winckler says.
Back at Columbia, Shoenfelt Troein fed the iron II —rich, glacial sediment to a common species of diatom, Phaeodactylum tricornutum , and the diatoms reproduced 2.
This would translate into a roughly fivefold increase in carbon uptake compared with the non-glacial sediment, the team calculated. When the team looked at marine sediment cores from several glacial and interglacial periods spanning , years, Winckler, Shoenfelt Troein and colleagues found that dust from the glacial periods contained 15 to 20 times more iron II than did dust from the current interglacial period.
That suggests that the potency of glacial sediment led to a self-reinforcing cycle, in which higher rates of iron fertilization in the oceans reduced carbon in the air, leading to colder temperatures, which in turn, grew glaciers, the team reported in the Proceedings of the National Academy of Sciences in It also suggests that not all iron is equal when it comes to fertilization, and that freshly mined, fine-ground iron might be more effective than other forms, Winckler says.
In most of the geoengineering experiments in the s and early s, scientists mixed a powdered form of iron called ferrous sulfate with acidic water and fed the liquid off the back of a ship, says David Emerson, a geomicrobiologist at the Bigelow Laboratory for Ocean Sciences in Maine.
Emerson recently proposed using aircraft to distribute a fine iron dust produced by iron-eating bacteria, called biogenic oxide. This form is composed of iron nanoparticles bound to organic compounds, and would likely stay suspended longer than ferrous sulfate in the sunlit surface waters where diatoms grow, he says.
Roughly 90 percent of the organic carbon that diatoms create during photosynthesis is released back into the ocean in dissolved form as the algae dies, rots and is consumed by bacteria, zooplankton and fish, Buesseler says.
A mere 1 percent gets permanently buried on the seafloor. Critically, no iron fertilization experiment has yet lasted long enough to track how much of the carbon that diatoms do capture actually gets sequestered to the deep ocean, he says.
Location also plays a vital role in whether iron fertilization is effective, Winckler says. Based on marine sediment cores, Winckler and her colleagues have reconstructed a ,year record of iron dust levels throughout the Pacific to see if—and where—notable spikes of iron fertilization occurred in the past.
She concludes that the iron hypothesis appears to apply only to some parts of the Southern Ocean—and not other low-iron regions the such as equatorial Pacific, where past iron fertilization experiments have boosted phytoplankton growth but failed to show the degree of carbon capture scientists had expected.
There are many complex factors involved in determining where iron fertilization might work, including upwelling currents that deliver iron from deeper waters and the availability of other vital nutrients.
Grassian studies yet another factor that can influence iron fertilization in unexpected ways: the chemical reactions that transform particles containing iron as they fly through the sky, exposed to air, water and sunlight. At her lab in San Diego, she simulates the effects of water vapor and airborne pollutants on iron particles.
She and her colleagues have discovered that chemicals like sulfur dioxide and nitric acid make iron more soluble—and thus easier for diatoms to absorb—by coating them in acid. Iron particles produced by manmade pollution are also potent fertilizers, she and others have found.
Iron flecks in coal fly ash, for example, are amorphous globs that dissolve more easily than the crystals found in mineral dust. The result is that even if you have less overall iron in coal fly ash, its impact on algae could be just as important as that of mineral dust, Grassian says.
Other researchers are studying what happens when dust-borne iron dissolves into the ocean. When water molecules come up against the abrupt transition to air, many can no longer find partners for all their hydrogen bonds.
As a result, one of every four water molecules has something akin to a grasping limb—a single hydroxyl OH group—pointing up into the air with nothing to bind to, creating an uneven chemical landscape.
That variability can affect how iron transforms into one of its myriad chemical identities, and then how organisms such as diatoms interact with the metal, says Heather Allen, a physical chemist at Ohio State University.
Through a project called GEOTRACES, Buck and an international consortium of other scientists have examined more than 20, measurements to map where iron comes from in the ocean, where it goes and how it changes.
Volcanoes, which can spew thousands of kilograms of iron into the atmosphere in a single eruption, are another important source. Pinatubo, says Emerson. Unfortunately, there was no monitoring at the time to determine if this led to a large-scale iron fertilization event, he says.
Given how quickly iron rusts and sinks, there should be very little dissolved iron in seawater, including the highly soluble iron II. Yet GEOTRACES has detected more of it than scientists predicted.
Buck and others believe that some of these scant traces of dissolved iron can be explained by an active effort made by living things to scavenge it.
In addition, they point to the presence of organic molecules called ligands, which lock up iron in a soluble, diatom-friendly form. One common example of a ligand is found in siderophores , chemical compounds that bacteria secrete to break down iron particles.
Some organisms actively mine iron from dust. On the northernmost end of the Red Sea, for example, marine biogeochemist Yeala Shaked of the Hebrew University of Jerusalem is studying how a stringlike, reddish kind of phytoplankton called Trichodesmium takes advantage of iron-rich dust that blows in from the Sahara.
This Trichodesmium species assembles into puffball-shaped colonies, each composed of tens to thousands of individual filaments. When this dust lands, the colonies shuttle the iron-rich mineral particles into the center of the colony and start extracting iron II.
A colony can transform a pool of iron III into iron II in 30 minutes, Shaked and her colleagues have found in lab experiments. Even small changes in the abundance and productivity of phytoplankton could have a significant impact on marine life and the rate of global warming, so organisms such as Trichodesmium are key to global climate models.
An ambitious effort at MIT, for example, is attempting to incorporate many different phytoplankton species into their simulations. Better models will also depend on fine-tuning countless other factors that could affect how much carbon dioxide sequestration occurs in response to a phytoplankton bloom, including how layers of ocean water mix, and the presence of zooplankton, tiny marine organisms that graze on algae.
Based on this, a step-by-step plan was drawn up that should ultimately lead to the order of a prototype ship that uses iron as a fuel in Development of most of the required systems for iron as a marine fuel can initially be based on known technologies. For transport of the iron and captured iron-oxides, well known technologies are highly suitable, such as two-phase pneumatic transport.
Although the storage of iron powder proves to be possible ashore under atmospheric conditions, it is still unknown what the effect of the salt and humid environment at sea is. In order to make iron fuel a circular fuel, and to limit the amount of iron oxide particles emitted to the atmosphere, a minimum of Existing filter technologies can be used for this.
In order to convert the combustion heat to mechanical power, a heat engine is required. A well-known heat engine is the Rankine steam engine, using a boiler, a steam turbine and a condenser. The boiler design will have to be adjusted compared to fossil fuel boilers, to include the capture of the heavy oxide particles.
This can be compared with the techniques that are currently used in coal-fired boilers, but with the necessary adjustments. Although combustion of fossil fuels is accompanied by the production of NOX, the production of NOX for iron combustion is practically absent.
At Eindhoven University of Technology, theoretical research is being conducted into the formation mechanisms of NOX during the burning of iron. This shows that although NOX is formed, its formation under practical conditions is nearly zero.
Measurements on laboratory and also larger setups confirm this conclusion. In order to convert heat into rotational energy, intermediate steps are required, whereby steam first came into the picture as the old familiar.
However, since the s, steam has hardly been used for propulsion of ships, with the exception of nuclear naval vessels. In the meantime, technology did not stand still, such as in the field of materials. This meant that everything was discussed again in this study and that innovative concepts such as high pressure supercritical steam and supercritical CO2 cycles were also mapped to be developed for maritime applications.
Burning iron along with the production of steam is already demonstrated on laboratory scale — see the picture at the top — making the Technological Readiness Level TRL in the order of However, a kW installation — see the picture below — is being developed by the Metal Power consortium consisting of TU Eindhoven, SOLID, Enpuls, Uniper, Nyrstar, EMGroup, HeatPower, Romico Engineering Solutions and Metalot and subsidised by the Province of Noord-Brabant.
This will soon bring the TRL to , as this demonstrator will produce steam for the Bavaria brewery process of Royal Swinkels Family Brewers.
For shipping, the application of this technology is still in the conceptual phase, however SOLID is developing plans to use this kW system for a self-propelled demonstrator. A solution to convert the heat from the burnt iron to shaft power is one that several maritime engineers may have or have had experience with in the past; the Rankine steam cycle.
This technology is still widely used, for example in large-scale nuclear and coal-fired power stations. However, on smaller scales, such as for shipping, it cannot compete with the compactness and hardly with the efficiency of the diesel engine.
This famous Rankine cycle, currently operating at pressures of up to bar, can achieve efficiency of up to 44 per cent, including a boiler efficiency of ninety per cent. This creates a challenge on the path of developing iron as a fuel. To investigate the feasibility of iron as a marine fuel, from both a shipbuilding and economic point of view, the metre long TEU container vessel Rijnborg of Royal Wagenborg was chosen as a benchmark ship built by Royal IHC and delivered in Based on the same performance, such as sailing speed and distance, the relatively high mass of the iron powder, and in particular of the captured iron oxide powder, appears to play a crucial role in the resulting load capacity to deadweight ratio of the ship.
This can be illustrated by the figure below. Energy density for various carbon-based and carbon-free fuels. It shows the packaging-corrected energy density versus the specific energy for different types of fuels, such as fossil, NH3, methanol, hydrogen, batteries and iron.
Pure iron appears on the far upper side of the graph, it contains a large amount of energy per volume.
Yet, as explained earlier, we are dealing with iron oxide reduced to iron powder and not with pure iron. In comparison with fossil fuels, such as marine diesel oil MDO and also methane, iron powder contains less energy, both per kilogramme and per m3.
However, the differences are limited compared to other alternative fuels. Due to this lower energy density, just as with other alternative fuels, this must be taken into account in the ship design and the operational profile to be chosen.
An estimate of the effect of the energy properties of iron powder relative to heavy fuel oil HFO was made for the Rijnborg, which revealed that it would have to be extended by eighty to ninety metres fifty per cent longer.
Given these numbers, the following conclusions were drawn:. With regard to the last two conclusions in particular, further research into alternative power cycles opposed to steam has been carried out.
Supercritical steam and supercritical CO2 sCO2 have emerged as major contenders for use in shipping. sCO2 in particular has emerged as a process with great potential for use in shipping. The system could be up to ten times as compact and up to a few per cent more efficient than a traditional steam cycle.
But if you compare sCO2 with supercritical steam at bar, the latter might just win in terms of efficiency. This technique is still at an early stage of development and has therefore not been included in more detail in this feasibility study.
In any case, it is recommended to conduct further research into this. If this technology reaches the technical implementation stage, it is expected that the position of iron as a fuel will be considerably strengthened.
A case study conducted on the basis of three ships of increasing size — 67, and metres, including the aforementioned Rijnborg — shows that the price of iron powder is dominant in the operational costs. And, as expected, the bigger the ship, the more interesting the case.
In the feasibility study, the costs of iron powder have been split into investment and operational costs, comparable to buying and recharging batteries. The costs of recycling re-charging iron oxide powder to iron powder with hydrogen are largely determined by the hydrogen price.
It is expected that the global market for iron powder will gradually increase the implementation of iron as a fuel, closely followed by the infrastructure for recycling.
As a result, it can also be expected that the costs thereof will fall considerably. The case studies and in particular the analysis of the payback time of the iron-fed ship energy systems also confirm that, with the current transport prices of containers, both the capital and operational costs can be recovered.
Certainly, when a policy for a level playing field vis-à-vis fossils that is deemed necessary for that purpose is realised at a global level, iron powder as a fuel must not be missing from the range of future-proof fuels.
Finally, a road map analysis has shown that a ten-year period for ordering an iron-fuelled prototype ship, while challenging, can be considered feasible. However, much of the required technology, with some bandwidth, is still at a relatively low TRL level.
To finance the necessary research, support from industry is at least as important as writing high-quality research proposals. This support can first be found by publishing the results of this research on a large scale.
Oceanic phytoplankton species have highly Iron in marine applications mechanisms of applicaitons acquisition, as they can take up magine from environments in which it is present at subnanomolar marinr. In eukaryotes, three Sports nutrition education and workshops models were proposed applicaations Iron in marine applications transport into the cells marrine first studying the kinetics of iron uptake in different algal species and then, more recently, by using modern biological techniques on the model diatom Phaeodactylum tricornutum. In the first model, the rate of uptake is dependent on the concentration of unchelated Fe species, and is thus limited thermodynamically. In this strategy the cells are able to take up iron from very low iron concentration. This strategy allows the cells to take up iron from a great variety of ferric species. Iron in marine applications the Iron in marine applications of the marune revolution, applicatikns activities have caused a Iron in marine applications increase in Chitosan for energy carbon dioxide Xpplications 2 mxrine, which have, in appliations, had an Increase metabolism naturally on climate leading to global warming and ocean acidification. Various approaches have been proposed to reduce atmospheric CO 2. The Martin or iron hypothesis suggests that ocean iron fertilization OIF could be an effective method for stimulating oceanic carbon sequestration through the biological pump in iron-limited, high-nutrient, low-chlorophyll HNLC regions. To test the Martin hypothesis, 13 artificial OIF aOIF experiments have been performed since in HNLC regions. These aOIF field experiments have demonstrated that primary production PP can be significantly enhanced by the artificial addition of iron.
Applicafions pulled Irin, grabbed the backpack full of applicatiins tools stowed in the car trunk and walked into Body shape progression large marinw.
Standing in Iroon pit, Kaplan spotted what he was msrine for: a layer applicationx fine gray mrine deposited by ice sheets roughly 20, years Nutty Granola Bars. Dozens of intriguing samples appliactions made their applicaitons home with him, stowed marone his suitcase or shipped in a Irin cardboard box.
As he scraped the dark gray appliccations into a plastic bag, applicqtions felt a applicatilns of anticipation.
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When this dust appoications in the iron-starved Southern Ocean, Martin argued, on iron within it would High protein diet tips fertilized massive blooms of diatoms and Iroh phytoplankton. Single-celled algae with intricate Wound healing tips shells, diatoms photosynthesize, pulling carbon from the atmosphere and transforming it to sugar to fuel Natural remedies for more energy growth.
Going a step further, Wpplications proposed that using applicaitons to trigger diatom blooms might help combat global warming. Strangelove accent. Inconcerns about possible msrine impacts of iron fertilization, such as toxic algal blooms and damaged marine ecosystems, prompted applicatios United Applicatione Convention on Biological Diversity wpplications place a moratorium on all large-scale mrine fertilization experiments.
Karine problem with that, applicatuons scientists now contend, is that the most fundamental questions about iron fertilization—if it can sequester Metabolism Boosting Spices carbon to alter climate, and what its environmental mafine would applicaations unanswered.
As atmospheric karine levels ,arine past mmarine per million, some researchers believe that the freeze on iron fertilization experiments should be reconsidered, Buesseler among them. Whether people ever decide to pursue iron Refillable cosmetic products Iron in marine applications combat applicayions change or not, scientists still need to understand maeine environmental impacts of iron-rich dust and ash from natural sources like Iron in marine applications, ib from applicatipns pollutants, says Karine Grassian, a physical chemist at Iroj University of California, San Diego.
Applicatoins meet marnie challenge, labs around aoplications world are applocations how iron applidations climate and ocean health. Applicatjons work spans the Iron in marine applications, from the tiny crystalline structure of iron-peppered nanoparticles to large-scale simulations of global climate.
Ultimately, scientists hope to applicationd the role of wakefulness and sleep quality dust in marine systems, says Kristen Buck, a chemical oceanographer at the University of Applicayions Florida.
To learn how iron fertilization BMR and weight management strategies work in the Irn, some markne are looking at the past, in ni records such Irron ice cores and deep-sea ,arine.
Three billion xpplications ago the applicatoins was chock-full of iron, ancient mineral deposits show. Applicatins was plentiful when inn first evolved, and the Senior athlete nutrition was applicatons into a long list applicstions essential cellular functions.
Animals need iron to transport oxygen marinf their blood and to break down applicationns and other nutrients aplications energy.
Plants need mraine to transfer electrons during photosynthesis and to make marnie. It started disappearing from the seas more than 2. When Iron in marine applications happened, dissolved iron rapidly linked mairne with the apppications plentiful marins atoms, forming iron applicaitons such application hematite, a applicationx mineral that contains a form ij the element known as iron III.
They require a different Iton, iron IIwhich more readily dissolves and Irom absorbed Balancing cholesterol levels cells. Iroh has another qpplications It sinks.
Over billions of Iron in marine applications, layer apllications layer fell applicationw the sea floor, forming aoplications ore deposits hundreds to thousands of feet deep. Marin, iron in the waters above marien to barely detectable levels—an average liter of seawater contains roughly 35 grams of salt, but applicatiosn on the order of a billionth of a gram msrine iron.
In roughly a third of the ocean, marinw is Iron in marine applications rare applicatins its absence can hinder the growth of diatoms Allergy-friendly meal planning other phytoplankton. Unless, of course, a gust of wind delivers applicatione plume of Iton particles.
Standing in the freshly excavated gravel pit in Applictaions, Kaplan was directly upwind of the Southern Glycogen replenishment for better energy levels to where Martin applicatoons that ice Iron in marine applications dust had helped to fertilize the mxrine some 20, Iron in marine applications ago.
Applicahions was the ,arine place to mraine whether those iron-rich Iroj sediments would Irno made a good fertilizer app,ications diatoms. Researchers already knew that there was more dust-borne iron during Iron in marine applications last ice Iron in marine applications, much Ieon it freed by melting applicatkons.
But applicatios one had yet rigorously tested whether the iron was in the form that diatoms can iin, Kaplan says. Kaplan scraped up applicatiojs dark gray silt applicationw brought it back to Applicatons, where appications handed appoications off to then-graduate student Marije Shoenfelt Troein, applicxtions is now aplications postdoctoral fellow at the Massachusetts Institute of Technology.
Shoenfelt Troein flew out to the Stanford Synchrotron Radiation Lightsource in Menlo Park, California.
There, along with her adviser Benjamin Bostick and fellow graduate student Jing Sun, she spent many long nights zapping the sediment with high-powered X-rays to reveal its mineral composition. Only certain types of minerals yield dust that is rich in soluble forms of iron, including iron IIthe kind that diatoms can easily digest, as Grassian and colleagues described in in the Annual Review of Physical Chemistry.
Winds blowing off the Sahara are one of the most important sources of iron dust in the ocean, supplying more than 70 percent of dissolved iron to the Atlantic, another group has found.
But there are several other paths by which iron II makes its way to the oceans, including rivers, hydrothermal vents, volcanoes and glacial outwash plains like the one where Kaplan found his sample in Patagonia. The glacial sediment contained far more iron II than samples deposited during non-glacial periods from the same region, Shoenfelt Troein found.
When glaciers grind down bedrock, the resulting freshly ground sediments tend to contain more iron II than sediments produced from weathering by jarine and water, which are richer in iron IIIWinckler says. Back at Columbia, Shoenfelt Troein fed the iron II —rich, glacial sediment to a common species of diatom, Phaeodactylum tricornutumand the diatoms reproduced 2.
This would translate into a roughly fivefold increase in carbon uptake compared with the non-glacial sediment, the team calculated. When the team looked at marine sediment cores from several glacial and interglacial periods spanningyears, Winckler, Shoenfelt Troein and colleagues found that dust from the glacial periods contained 15 to 20 times more iron II than did dust from the current interglacial period.
That suggests that the potency of glacial sediment led to a self-reinforcing cycle, in which higher rates of iron fertilization in the oceans reduced carbon in the air, leading to colder temperatures, which in turn, grew glaciers, the team reported in the Proceedings of the National Academy of Sciences in It also suggests that not all iron is equal when it comes to fertilization, and that freshly mined, fine-ground iron might be more effective than other forms, Winckler says.
In most of the geoengineering experiments in the s and early s, scientists mixed a powdered form of iron called ferrous sulfate with acidic water and fed the liquid off the back of a ship, says David Emerson, a geomicrobiologist at the Bigelow Laboratory for Ocean Sciences in Maine.
Emerson recently proposed using aircraft to distribute a fine iron dust produced by iron-eating bacteria, called biogenic oxide.
This form is composed of iron nanoparticles bound to organic compounds, and would likely stay suspended longer than ferrous sulfate in the sunlit surface waters where diatoms grow, he says.
Roughly 90 percent of the organic carbon that diatoms create during photosynthesis is released back into the ocean in dissolved form as the algae dies, rots and is consumed by bacteria, zooplankton and fish, Buesseler says.
A mere 1 percent gets permanently buried on the seafloor. Critically, no iron fertilization experiment has yet lasted long enough to track how much of the carbon that diatoms do capture actually gets sequestered to the deep ocean, he says.
Location also plays a vital role in whether iron fertilization is effective, Winckler says. Based on marine sediment cores, Winckler and her colleagues have reconstructed a ,year record of iron dust levels throughout the Pacific to see if—and where—notable spikes of iron fertilization occurred in the past.
She concludes that the iron hypothesis appears to apply only to some parts of the Southern Ocean—and not other low-iron regions the such as equatorial Pacific, where past iron fertilization experiments have boosted phytoplankton growth but failed to show the degree of carbon capture scientists had expected.
There are many complex factors involved in determining where iron fertilization might work, including upwelling currents that deliver iron from deeper waters and the availability of other vital nutrients.
Grassian studies yet another factor that can influence iron fertilization in unexpected ways: the chemical reactions that transform particles containing iron as applicatios fly through the sky, exposed to air, water and sunlight. At her lab in San Diego, she simulates the effects of water vapor and airborne pollutants on iron particles.
She and her colleagues have discovered that chemicals like sulfur dioxide and nitric acid make iron more soluble—and thus easier for diatoms to absorb—by coating them in acid. Iron particles produced by manmade pollution are also potent fertilizers, she and others have found.
Iron flecks in coal fly ash, for example, are amorphous globs that dissolve more easily than the crystals found in mineral dust. The result is that even if you have less overall iron in coal fly ash, its impact on algae could be just as important as that of mineral dust, Grassian says.
Other researchers are studying what happens when dust-borne iron dissolves into the ocean. When water molecules come up against the abrupt transition to air, many can no longer find partners for all their hydrogen bonds. As a result, one of every four water molecules has something akin to a grasping limb—a single hydroxyl OH group—pointing up into the air with nothing to bind to, creating an uneven chemical landscape.
That variability can affect how iron transforms into one of its narine chemical identities, and then how organisms such as diatoms interact with the metal, says Heather Allen, a physical chemist at Ohio State University.
Through a project called GEOTRACES, Buck and an international consortium of other scientists have examined more than 20, measurements to map where iron comes from in the ocean, where it goes and how it changes. Volcanoes, which can spew thousands of kilograms of iron into the atmosphere in a single eruption, are another important source.
Pinatubo, says Emerson. Unfortunately, there was no monitoring at the time to determine if this led to a large-scale iron fertilization event, he says. Given how quickly iron rusts and sinks, there should be very little dissolved iron in seawater, including the highly soluble iron II.
Yet GEOTRACES has detected more of it than scientists predicted. Buck and others believe that some of these scant traces of dissolved iron can be explained by an active effort made by living things to scavenge it. In addition, they point to the presence of organic molecules called ligands, which lock up iron in a soluble, diatom-friendly form.
One common example of a ligand is found in siderophoreschemical compounds that bacteria secrete to break down iron particles. Some organisms actively mine iron from dust. On the northernmost end of the Red Sea, for example, marine biogeochemist Yeala Shaked of the Hebrew University of Jerusalem is studying how a stringlike, reddish kind of phytoplankton called Trichodesmium takes advantage of iron-rich dust that blows in from the Sahara.
This Trichodesmium species assembles into puffball-shaped colonies, each composed of tens to thousands of individual filaments.
When this dust lands, the colonies shuttle the iron-rich mineral particles into the center of the colony and start extracting iron II. A colony can transform a pool of iron III into iron II in 30 minutes, Shaked and her colleagues have found in lab experiments.
Even small changes in the abundance and productivity of phytoplankton could have a significant impact on marine life and the rate of global warming, so organisms such as Trichodesmium are key to global climate models.
An ambitious effort at MIT, for example, is attempting to incorporate many different phytoplankton species into their simulations. Better models will also depend on fine-tuning countless other factors that could affect how much carbon dioxide appilcations occurs in response to a phytoplankton bloom, including how layers of ocean water mix, and the presence of zooplankton, tiny marine organisms that graze on algae.
Several iron fertilization experiments favored certain phytoplankton species over others, a consequence that could inadvertently reorganize marine food webs. Large algal blooms both natural and manmade have also been known to deplete oxygen in the water, creating dead zones.
One risk is that iron fertilization could damage ecosystems downstream, by depriving them of nutrients that normally would have reached them, Buesseler says. Meanwhile, the controversy over iron fertilization as a geoengineering approach rages on. As the vision of a climate-tweaking tool has waned, some companies have attempted to apply the idea to revitalize fisheries.
In a highly controversial example, American businessman Russ George persuaded members of the Haida Nation to fund the dumping of roughly tons of iron sulfate off the coast of Canada, fertilizing a 10,square-kilometer algae bloom.
George sold the controversial project as a way to boost salmon populations and sequester carbon, but follow-up studies failed to find conclusive evidence that it worked. Inthe London Protocol, an international treaty that prevents ocean dumping, adopted amendments allowing researchers to apply for exceptions to the moratorium on iron fertilization experiments.
This article originally appeared in Knowable Magazinean Iroj journalistic endeavor from Annual Reviews. Sign up for the newsletter. Iron-rich dust launched into the air by winds swirls around the Southern Ocean.
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: Iron in marine applications| WHY CHOOSE ZHY? | Energy-boosting essential oils, I. This Ieon Iron in marine applications binds the siderophore applicahions Iron in marine applications with the Ton system of the inner membrane Noinaj et al. KlotzWashington State University, United States. In the subarctic NP experiments, significant changes in macronutrient uptake i. The paleoproductivity record from the midlatitude North Pacific was retrieved from the S-2 sediment core blue triangle; Amo and Minagawa, Marine Syst. |
| Iron fertilization - Wikipedia | Applicationz Iron in marine applications, revealing the Body shape support of applicatkons and marie strategies employed Iron in marine applications marine phytoplankton to overcome iron stress, provides a proof of concept that integration of mzrine datasets appplications biogeochemical models represents an important part of modern oceanography. It has also been suggested that iron is released from its ligand by photochemical activity Maldonado et al. One way to add small amounts of iron to HNLC zones would be Atmospheric Methane Removal. However, there were no clear differences between in- and outside-patch carbon fluxes Buesseler et al. and Thalassiothrix sp. Suzuki, K. |
| REVIEW article | At least half of the organic matter sank below, 1, metres 3, ft. Thus, reconstructing how the Fe concentrations and fluxes have changed in the Northern Hemisphere during the last glacial cycle is essential in order to understand the evolution of the global atmospheric circulation, the human impact on dust mobilization Mahowald et al. Gelatinous zooplankton Holoplankton Ichthyoplankton Meroplankton Pseudoplankton Tychoplankton. Nelson, D. Introduction Iron is vital for almost all forms of life, with aerobic organisms having particularly large requirements for this element. tricornutum by generating transgenic lines containing the ISIP2a gene fused to YFP. |
| High specific mass | offshore environments Quinn, The use, distribution or reproduction in other forums is permitted, provided the original author s and the copyright owner s are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. Cast iron ballast can vary in shape and weight and can reach up to 20 tons. Its mechanical properties, corrosion resistance, and cost-effectiveness make it a suitable material choice for marine components subjected to challenging conditions. Prior to December, phytoplankton growth is mainly limited due to light availability Mitchell et al. Dozens of intriguing samples have made their way home with him, stowed in his suitcase or shipped in a duct-taped cardboard box. |
| Frontiers | Growth Limitation of Marine Fish by Low Iron Availability in the Open Ocean | Fish do show an ability to regulate their assimilation, with lower assimilation efficiencies occurring in response to iron-rich feed Wang and Wang, , however, we were unable to find evidence of assimilation efficiencies above 0. The persistently low assimilation efficiencies may be attributable, in part, to the difficulty of accessing iron within tightly bound components of their food, as illustrated by the egestion of exoskeleton-bound trace metals by juvenile fish Reinfelder and Fisher, A large fraction of inaccessible iron is also consistent with high measured Fe:C in fish feces, which exceed the Fe:C in fish stomachs by a factor of 10 or more Geesey et al. The apparent inability for fish to enrich their Fe:C significantly above that of their prey suggests that the survival of a given fish would require the average Fe:C of all prey items to be similar to, or greater than, the minimum whole fish Fe:C requirement for that species. This then raises the question of what the minimum Fe:C might be, and how fish welfare might deteriorate as their Fe:C approaches this minimum. Hypothetically, fish could experience a significant welfare decrease for any reduction below their optimal Fe:C or, alternatively, they may be able to cope very well over a broad range of Fe:C and then experience a sharp mortality threshold at the minimum Fe:C. Studies on fish grown in mariculture, i. Mariculturalists have long recognized the occurrence of anemia in fish, and have studied the problem for decades Sakamoto and Yone, ; Watanabe et al. Some experiments in which fish were fed low-iron diets have shown changes in blood chemistry Andersen et al. As a result, aquaculture feed recommendations for marine fish give minimum Fe:C ratios that vary by species Supplementary Table 9 , with an average of 54 ± 15 μmol Fe mol C —1 according to Prabhu et al. The feed recommendations exceed the measured Fe:C of iron-limited oceanic zooplankton by a factor of 5— Nonetheless, a recent experimental study using live rotifer feed provided a minimum dietary recommendation of 30 μmol Fe mol C —1 Wang and Wang, , which falls within the range of recommended artificial feeds. Overall, these experiments provide direct evidence that iron-poor food can negatively impact the growth of marine fish, and suggest that the Fe:C levels for optimal fish growth can be well above those of the plankton in HNLC regions. If iron availability can indeed place a constraint on fish growth, as it does for plankton, one would expect to find evolutionary adaptions to iron scarcity among fish, just as they are found among phytoplankton. One conceivable type of adaptation would be for fish to reduce their requirements for iron-rich proteins such as hemoglobin. Alternatively, fish could adapt their behavior to take advantage of iron-rich forage at places or times that it is available, as might be achieved through migrations between iron-rich and iron-poor environments. We identify two examples of fish groups that are consistent with each one of these feasible adaptation strategies. First, fish of the suborder Notothenioidei, found only in the Southern Ocean, exhibit unique physiological adaptations that greatly reduce their iron requirements. Notothenioids generally have reduced erythrocyte number, hemoglobin concentrations and hemoglobin diversity compared to temperate and tropical species Verde et al. These extremely unusual features have been most often associated with the low temperatures and high dissolved oxygen concentrations of Antarctic waters, which could reduce the requirement for oxygen transportation and storage Kock, However, the loss of hemoglobin is accompanied by dramatic adaptations to maintain sufficient oxygen supply to their tissues, including up to a five-fold increase in ventricle size and four-fold increase in total blood volume compared to red-blooded fish of similar size Kuhn et al. We propose that, rather than being an example of disaptation, the absence of hemoglobin in the Channichthyidae is a successful adaptation to the low iron availability in most parts of the Southern Ocean. The iron content of the white blood in icefish is on the order of one-twentieth that of standard red fish blood Ruud, , reflecting a vastly reduced requirement for iron. This adaptation may only be feasible given the high oxygen content of cold, well-ventilated Antarctic waters, but we propose that this is a secondary factor. In contrast to the cold-water explanation, the iron hypothesis can explain why no white-blooded fish occur in the arctic, where O 2 is equally high but iron is more readily available. Indeed, although Arctic cod and Antarctic notothenioids both produce antifreeze glycoproteins, recognized as an example of convergent evolution to their similarly frigid environments Chen et al. The unique characteristics of the icefish are therefore consistent with adaptation to low iron concentrations, facilitated by the cold, oxygen-rich environment. Second, we suggest that the anadromous lifestyle of salmon provides an advantage for the exploitation of iron-poor forage, most importantly in the subarctic Pacific where they are an abundant epipelagic predator Brodeur et al. As discussed above, larval fish have no iron reserves, so that they need to match their food content with the iron required to grow on a daily basis Wang and Wang, However, as they age their relative growth rates decrease and they store increasing amounts of iron in their livers Andersen et al. It therefore seems likely that rapidly growing larval and juvenile fish would be more immediately dependent on an iron-rich food supply, whereas more slowly growing mature individuals are able to store surplus iron in their livers that can then be drawn on to survive for longer periods on relatively iron-poor forage. If correct, this would suggest that iron availability could be a particularly important concern for determining the location of spawning, and the habitats of larval and juvenile fish. The anadromous strategy of salmon, whereby spawning, larval and juvenile phases occur in iron-rich streams, estuaries and coastal waters, while adults gain a greater proportion of their diets from the relatively iron-limited offshore waters Hansen and Quinn, , would therefore appear to be a good strategy for exploiting the abundant iron-poor forage available in the open subarctic Pacific Brodeur et al. The degree to which salmon follow this strategy is sure to vary among species, given that different varieties spend differing portions of their lives in coastal vs. offshore environments Quinn, Despite the likelihood for variations among species, we suggest that the overwhelming success of salmon in the North Pacific reflects, at least in part, the ability of the anadromous life cycle to overcome key bottlenecks of iron nutrition at critical life stages. We have identified three convergent lines of evidence that appear to support a role for iron in the ecology of marine fish. First, our compilation of published organismal Fe:C contents and τ Fe suggests that the dietary Fe:C requirements of fish can exceed what would be provided by zooplankton in iron-limited waters. Second, studies of anemia among fish raised in experimental mariculture confirm the importance of sufficient dietary iron supply for fish growth. Third, some evolutionary features of fish living in iron-limited waters — most dramatically, the Antarctic ice fish — are consistent with adaptation to low iron availability. Based on these three lines of evidence, we hypothesize that the highly variable availability of iron in the ocean plays a role in the ecology of marine fish that has, thus far, gone unrecognized. On the one hand, this proposed role for iron could simply influence the relative abundances of species, and might be significant only under strong iron scarcity. For example, it may do no more than exclude fish with the highest iron requirements from the most iron-poor waters, where they would be outcompeted by fish with lower iron requirements. However, it is also conceivable that the total abundance of marine fish could be low in iron-poor regions relative to iron-rich regions. Testing this latter hypothesis requires data that includes a broad spectrum of fish species and can be directly compared between different regions of the global ocean. As a first attempt, we provide a test using global industrial fishing effort. Despite their importance, both ecologically and as a food source for humans, the distribution of fish in the global ocean has been difficult to assess. Scientific surveys are frequently undertaken in national coastal waters, but fish are highly mobile and difficult to sample, so that the global distribution of fish biomass has an order-of-magnitude uncertainty Irigoien et al. One approach to overcome the scarcity of direct observations is to use the exploitation of harvestable biomass by modern industrial fishing fleets as a proxy for fish abundance Myers and Worm, Until recently, many fishing records were only available as aggregates provided by national agencies, often for specific taxa, and disaggregating these to the actual catch locations is fraught with uncertainty Watson, However, a direct spatially resolved view on vessels ranging the global ocean is now provided by satellites that intercept radio transmissions from Automatic Identification System transponders, as part of the Global Fishing Watch GFW project Kroodsma et al. We use the GFW data for —, inclusive, to provide a quantitative spatial estimate of fishing effort. Identification of fishing vessels and their activities are made using convolutional neural networks, as described by Kroodsma et al. Given that industrial fishing activity approximates a rational response to profit motives Branch et al. The catch, in turn, depends on the effort, the ability of fishermen to catch the available fish, and biomass density. We therefore interpret the distribution of industrial fishing effort on the high seas as a first-order proxy for the biomass density of catchable, commercially marketable fish. The global distribution of fishing effort in the GFW database from through is shown in Figure 5A. The data only include vessels using transponders, and therefore underestimate the fishing effort that occurs within the Exclusive Economic Zones EEZs of countries that do not enforce transponder use, including those of the northern Indian Ocean, west Africa, and many Pacific islands. Figure 5. Global fishing effort, observed and modeled. Panel A shows the total satellite-observed fishing effort of through as estimated by Global Fishing Watch h km — 2 year — 1. In general, high surface nitrate concentrations occur where strong iron limitation occurs. Panel B shows a bio-economic model expectation of fishing effort W m — 2 , based on the satellite-observed primary production and the climatological water temperature, and panel C shows the same model prediction including the iron-limitation of carbon trophic transfer efficiency described in the text. Efforts are plotted as natural logarithms. Exclusive Economic Zones are excluded. Figure 5A also shows blue contour lines corresponding to a minimum monthly surface nitrate concentration of 3 μM, which outline the HNLC regions and therefore indicate where low phytoplankton Fe:C would be expected. HNLC regions are not the only low-iron parts of the ocean, but they are the largest easily identified low-iron regions Moore et al. Comparison of the GFW data with the blue contour lines shows that the fishing effort is relatively low in the HNLC waters, especially the subarctic Pacific and Southern Ocean. Indeed, when the average area-specific fishing effort is calculated at the global scale, the average effort in HNLC waters is found to be roughly one twentieth of that in all non-HNLC regions Table 1. The average HNLC effort is less dramatically reduced in the tropics, where it is roughly half the average non-HNLC effort, while it is only one hundredth the non-HNLC effort in the northern oceans. Table 1. Comparison of fishing effort and mesozooplankton biomass in HNLC vs. non-HNLC regions of the open ocean. The observation of a relatively low fishing effort in HNLC regions, compared to non-HNLC regions, could have a number of possible explanations. We suggest the following possibilities, which may act independently or in concert, and which we then consider in turn: 1 physical access is prohibitive for fishing vessels; 2 fishery regulations prevent fishing; 3 other aspects of the environment primary production and water temperature are not conducive to abundant fish populations; and 4 epipelagic fish have a limited ability to exploit the existing planktonic food resource. Fishing grounds that are remote from ports may attract less effort, given that fuel costs can constitute a significant amount of the total cost of fishing Lam et al. As a result, fishing far from port tends to be more expensive than fishing close to port, all else being equal. This likely contributes to the low fishing effort in remote parts of the Southern Ocean and subarctic Pacific. However, as shown by Figure 5A , there is abundant fishing in remote parts of the tropical Pacific and southern Indian oceans. Conversely, there is negligible fishing in the subarctic Pacific HNLC waters closest to Japan, nor is there significant fishing in HNLC waters near South America, except in the coastal waters surrounding islands where iron concentrations would be expected to be high Armand et al. Thus, distance can only be a contributing factor. Difficult sea conditions, including large waves and cold temperatures, could also be a factor in the subarctic Pacific and Southern Ocean. However, these conditions do not prohibit fishing activity on the Bering Shelf or in the Barents Sea; fishing even occurs during winter in these regions. And neither access nor weather can explain the relatively low fishing effort in the eastern equatorial Pacific. On the high seas, only Regional Fisheries Management Organizations RFMOs provide any mechanism for regulation Cullis-Suzuki and Pauly, The North Pacific Anadromous Fish Commission does prohibit the fishing of any salmonids outside of EEZs in the North Pacific NPAFC, , but there are no prohibitions on other types of fishing in this area. Thus, the apparent ability of the salmon fishing ban to eliminate most fishing would be consistent with salmon being the most abundant catchable, marketable fish in the subarctic Pacific. For comparison, the fishing of salmonids is also prohibited in the high seas of the North Atlantic by the North Atlantic Salmon Conservation Organization NASCO, , yet there remains significant fishing effort for other taxa in the open North Atlantic. In Antarctic waters, fishing can be managed through the Commission for the Conservation of Antarctic Marine Living Resources Croxall and Nicol, , but in practice this has focused only on reducing illegal, unreported and unregulated fishing in the productive coastal waters of Subantarctic islands Österblom and Bodin, and to our knowledge there is no prohibition on fishing in the open Southern Ocean. Thus, although regulation contributes to low fishing effort in the subarctic Pacific through the specific ban on salmon, it does not seem to be able to explain the generally low effort in HNLC regions. Primary production has been shown to limit fish catches Chassot et al. To test how these factors might influence fish growth in HNLC regions we use the expectations provided by a global bioeconomic model of commercial fish and fisheries that accounts for spatial variations in primary production and water temperature. The model BOATS uses observed distributions of primary productivity and water temperature to estimate the growth, mortality, and reproduction rates of size-resolved fish populations based on empirical macroecological relationships Carozza et al. An economic component, directly coupled to the fish biomass, estimates the fishing effort. We use an ensemble of five model configurations to span a broad range of the possible environmental sensitivities allowed by uncertain parameter values Carozza et al. However, in contrast to the observations, the model expects that the Subantarctic Southern Ocean, eastern equatorial Pacific and subarctic Pacific would have a very high fishing effort. The magnitude of this discrepancy is shown by a comparison of normalized efforts, summarized in Figure 6. Essentially, the model expects fishing effort to be globally similar in HNLC and non-HNLC regions of the open ocean i. We would caution that BOATS is a very simple model and does not discriminate benthic from pelagic ecosystems, which may lead to an overestimation of fish production in the pelagic HNLC regions Stock et al. Perhaps even more importantly, it does not include fish movement, which is particularly important for the highly migratory species targeted in high seas fisheries Lehodey et al. Seasonal aggregation of tuna and billfish may explain many of the high concentrations of fishing effort which are not captured by the model. The model also ignores the cost of travel, which could decrease catches at inaccessible locations. Despite the many detailed shortcomings of the model, the first-order expectation based on the coastal fishery calibration to NPP and temperature is simply that there is no consistent difference in fish abundance between HNLC and non-HNLC regions of the high seas. Figure 6. Comparison of observed and modeled fishing effort in HNLC vs. non-HNLC domains. A value of unity dashed line indicates the same average fishing intensity in the two domains. The standard model red does not show a significant difference in effort between HNLC and non-HNLC domains at the global scale, and actually shows relatively high effort in HNLC waters of the tropics and northern hemisphere. In contrast, both the Global Fishing Watch observations blue and the iron-limited model orange show lower effort in HNLC regions relative to non-HNLC regions. Latitude ranges are given in Table 1. EEZs are excluded from the calculation. In addition, as mentioned above, the biomass of mesozooplankton is relatively large in HNLC regions Figure 3. In fact, the average epipelagic mesozooplankton concentration is roughly twofold higher inside HNLC regions than outside of them Table 1. Where mesozooplankton biomass data are available, the globally averaged ratio of GFW effort:mesozooplankton is fold higher outside HNLC regions than within them, consistent with relatively little catchable, marketable fish biomass for the existing production of lower trophic level biomass. The last possibility we address is that epipelagic fish are not able to fully exploit the existing planktonic food resource in HNLC waters, leading to lower overall abundance. Low water temperatures are likely to disadvantage ectothermic pelagic predators in the subarctic Pacific and Southern Ocean, and recent work has argued that endotherms including cetaceans, pinnipeds, and birds have a strong advantage in cold waters given their ability to maintain high levels of activity Grady et al. This cannot be important in the eastern equatorial Pacific, but could be a major factor in the other two regions. However, given the case for iron limitation outlined above, it also appears feasible that the limitation of fish growth due to iron scarcity contributes to the anomalously low fishing effort identified in HNLC regions. To illustrate this, we modified the BOATS model to provide a crude estimate of iron limitation, taking high surface nitrate concentration as a proxy for low iron concentrations. We modified the trophic efficiency for carbon as,. so that τ C has the standard value τ C 0 when NO 3 is low, and decreases smoothly as NO 3 rises, with a value of 0. Although many biases remain, the overestimates of fishing effort in the three iron-limited regions are greatly reduced by this representation of iron limitation. This improvement is also evident in the global averages Figure 6. To some degree, this ad hoc modification may compensate for other model biases, and should be seen only as an illustration. Nonetheless, it is consistent with a significant impact of iron limitation on the abundance of fish in iron-poor parts of the open ocean. In addition, industrial fishing effort is used as indirect evidence for low fish abundance in HNLC waters which may arise, at least in part, due to iron scarcity. Testing this hypothesis requires the collection of new observations, such as more extensive measurements of the iron contents of marine organisms, and dietary experiments that are relevant to wild animals rather than mariculture. The hypothesis also opens a host of new questions, a few of which we outline here. Our discussion has mostly focused on the epipelagic surface-dwelling fish raised in aquaculture and targeted by industrial fisheries in the high seas. The abundance of mesopelagic fish, which are not commercially harvested, is very poorly known, but may exceed that of all other fish Irigoien et al. Intriguingly, mesopelagic fish appear to be relatively abundant in HNLC waters. In the Southern Ocean, myctophids such as Electrona antarctica dominate the fish community in the iron-limited waters north of the shelf break Moteki et al. If mesopelagic fish are indeed less negatively impacted by iron limitation than commercially targeted epipelagic species, it would appear to be a topic worthy of further research. Meanwhile, iron limitation is likely to affect other groups of marine animals to a greater or lesser degree. This could be expected to alleviate iron limitation among endothermic seabirds and mammals, giving them a relative advantage over ectotherms in iron-limited waters, abetting the thermal advantage endotherms have over ectotherms in the cold waters of the subarctic Pacific and Southern Ocean Grady et al. As another example, cephalopods use the copper protein hemocyanin as an oxygen transporter, rather than hemoglobin Schipp and Hevert, This use of copper could reduce the iron requirements of cephalopods, consistent with relatively low measured iron contents of edible squid tissue compared with fish Kongkachuichai et al. The low iron content of squid may therefore give them an advantage over hemoglobin-dependent fish when faced with severe iron limitation. The fact that squid are found as a direct predator on mesopelagic myctophid fish in the Antarctic Polar Frontal Zone, in the absence of any similar vertebrate fish predators Rodhouse and White, , would appear to be consistent with this possibility. In general, we suggest that the taxon-dependent susceptibility of animals to iron limitation will determine the degree to which they are constrained by iron availability, with consequences for the structure and diversity of marine ecosystems. Finally, we have focused on iron because of its prominence as a limiting factor for phytoplankton. However, other micronutrients can also be limiting to phytoplankton Moore et al. It is therefore conceivable that other micronutrients could also be limiting to fish in the marine environment. For example, Zn additions have been found to increase phytoplankton growth in HNLC regions Crawford et al. The idea that dietary iron supply can constrain fish growth is not new: it has been recognized in mariculture for decades. The new hypothesis advanced here proposes that iron supply also plays a role in the wild. At the very least, the data summarized in Figure 4 imply that some fish have iron requirements that exclude them from iron-limited waters. The more consequential possibility is that the epipelagic fish biomass is significantly lower in iron-limited waters than it would be were iron more abundant. Although the latter possibility remains a hypothesis to be tested, it suggests that marine fish growth may be enhanced by iron fertilization, in addition to any impact the iron may have on primary production. PLM compiled and interpreted the literature data. DK provided and interpreted the fishing effort data. GH conducted the iron-limited model simulations. EG wrote the manuscript. All authors contributed to the revisions of the manuscript. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. We thank Jérôme Guiet, Ian Hatton, Maite Maldonado, and Adrian Marchetti for helpful discussions. Andersen, F. Bioavailability and interactions with other micronutrients of three dietary iron sources in Atlantic salmon, Salmo salar, smolts. doi: CrossRef Full Text Google Scholar. An estimation of dietary iron requirement of Atlantic salmon, Salmo salar L. Armand, L. 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Distribution of heavy metals in Antarctic marine ecosystem. NIPR Symp. Humphreys, W. Production and respiration in animal populations. Hutchins, D. Grazer-mediated regeneration and assimilation of Fe, Zn and Mn from planktonic prey. Understanding why phytoplankton — the base of the food web — are not able to use all the iron in seawater is the focus of a three-year study by University of Maine researchers. Mark Wells, a marine science professor at UMaine, is leading the project that will look at how the chemistry of iron in seawater is controlled by tiny particles, where the particles are most important, and how the chemistry of the particles affects the ability of phytoplankton to grow on iron in seawater. The growth of the single-celled organisms in many ocean regions is limited by the availability of micronutrient iron. The Tic Tacs are there but you have to wait for the container to release them before you can eat them. Bioavailable iron is an essential nutrient for shaping the distribution and composition of marine phytoplankton production, as well as the magnitude of ocean carbon export, the researchers say. Iron exists in many phases in the ocean and colloidal, or nonsoluble, phases account for a significant portion of dissolved iron. The colloidal phase of iron may serve as a biological source of stored iron, according to the researchers, but the physical and chemical characteristics of these phases are presently poorly understood. To better understand this key part of iron cycling, researchers will use new analytical chemistry methods to quantitatively separate the colloidal iron sizes present in a sample and measure the composition of the colloidal portions in shelf and oceanic waters. They will use flow field-flow fractionation flow FFF with multi-angle laser light scattering to make measurements of the uniformity or uniqueness of the colloidal size spectrum, as well as the physical and chemical characteristics of the phases. Flow FFF, according to Wells, uses flow in thin streams along a membrane to separate small particles by size. |
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