Research

Subterms

    More stories

    • 88 Shares129 Views

      in Energy

      Overcoming a bottleneck in carbon dioxide conversion

      by

      If researchers could find a way to chemically convert carbon dioxide into fuels or other products, they might make a major dent in greenhouse gas emissions. But many such processes that have seemed promising in the lab haven’t performed as expected in scaled-up formats that would be suitable for use with a power plant or other emissions sources.

      Now, researchers at MIT have identified, quantified, and modeled a major reason for poor performance in such conversion systems. The culprit turns out to be a local depletion of the carbon dioxide gas right next to the electrodes being used to catalyze the conversion. The problem can be alleviated, the team found, by simply pulsing the current off and on at specific intervals, allowing time for the gas to build back up to the needed levels next to the electrode.

      The findings, which could spur progress on developing a variety of materials and designs for electrochemical carbon dioxide conversion systems, were published today in the journal Langmuir, in a paper by MIT postdoc Álvaro Moreno Soto, graduate student Jack Lake, and professor of mechanical engineering Kripa Varanasi.

      “Carbon dioxide mitigation is, I think, one of the important challenges of our time,” Varanasi says. While much of the research in the area has focused on carbon capture and sequestration, in which the gas is pumped into some kind of deep underground reservoir or converted to an inert solid such as limestone, another promising avenue has been converting the gas into other carbon compounds such as methane or ethanol, to be used as fuel, or ethylene, which serves as a precursor to useful polymers.

      There are several ways to do such conversions, including electrochemical, thermocatalytic, photothermal, or photochemical processes. “Each of these has problems or challenges,” Varanasi says. The thermal processes require very high temperature, and they don’t produce very high-value chemical products, which is a challenge with the light-activated processes as well, he says. “Efficiency is always at play, always an issue.”

      The team has focused on the electrochemical approaches, with a goal of getting “higher-C products” — compounds that contain more carbon atoms and tend to be higher-value fuels because of their energy per weight or volume. In these reactions, the biggest challenge has been curbing competing reactions that can take place at the same time, especially the splitting of water molecules into oxygen and hydrogen.

      The reactions take place as a stream of liquid electrolyte with the carbon dioxide dissolved in it passes over a metal catalytic surface that is electrically charged. But as the carbon dioxide gets converted, it leaves behind a region in the electrolyte stream where it has essentially been used up, and so the reaction within this depleted zone turns toward water splitting instead. This unwanted reaction uses up energy and greatly reduces the overall efficiency of the conversion process, the researchers found.

      “There’s a number of groups working on this, and a number of catalysts that are out there,” Varanasi says. “In all of these, I think the hydrogen co-evolution becomes a bottleneck.”

      One way of counteracting this depletion, they found, can be achieved by a pulsed system — a cycle of simply turning off the voltage, stopping the reaction and giving the carbon dioxide time to spread back into the depleted zone and reach usable levels again, and then resuming the reaction.

      Often, the researchers say, groups have found promising catalyst materials but haven’t run their lab tests long enough to observe these depletion effects, and thus have been frustrated in trying to scale up their systems. Furthermore, the concentration of carbon dioxide next to the catalyst dictates the products that are made. Hence, depletion can also change the mix of products that are produced and can make the process unreliable. “If you want to be able to make a system that works at industrial scale, you need to be able to run things over a long period of time,” Varanasi says, “and you need to not have these kinds of effects that reduce the efficiency or reliability of the process.”

      The team studied three different catalyst materials, including copper, and “we really focused on making sure that we understood and can quantify the depletion effects,” Lake says. In the process they were able to develop a simple and reliable way of monitoring the efficiency of the conversion process as it happens, by measuring the changing pH levels, a measure of acidity, in the system’s electrolyte.

      In their tests, they used more sophisticated analytical tools to characterize reaction products, including gas chromatography for analysis of the gaseous products, and nuclear magnetic resonance characterization for the system’s liquid products. But their analysis showed that the simple pH measurement of the electrolyte next to the electrode during operation could provide a sufficient measure of the efficiency of the reaction as it progressed.

      This ability to easily monitor the reaction in real-time could ultimately lead to a system optimized by machine-learning methods, controlling the production rate of the desired compounds through continuous feedback, Moreno Soto says.

      Now that the process is understood and quantified, other approaches to mitigating the carbon dioxide depletion might be developed, the researchers say, and could easily be tested using their methods.

      This work shows, Lake says, that “no matter what your catalyst material is” in such an electrocatalytic system, “you’ll be affected by this problem.” And now, by using the model they developed, it’s possible to determine exactly what kind of time window needs to be evaluated to get an accurate sense of the material’s overall efficiency and what kind of system operations could maximize its effectiveness.

      The research was supported by Shell, through the MIT Energy Initiative. More

    • 100 Shares199 Views

      in Environment

      Courtney Lesoon and Elizabeth Yarina win Fulbright-Hays Scholarships

      by

      Two MIT doctoral students in the MIT School of Architecture and Planning have received the prestigious Fulbright-Hays Scholarship for Doctoral Dissertation Research Award. Courtney Lesoon and Elizabeth “Lizzie” Yarina are the first awardees from MIT in more than a decade.

      The fellowship provides opportunities for doctoral students to engage in full-time dissertation research abroad. The program, funded by the U.S. Department of Education, is designed to contribute to the development and improvement of the study of modern foreign languages and area studies. Applicants anticipate pursuing a teaching career in the United States following completion of their dissertation. There were 138 individuals from 47 institutions named scholars for the 2021 cycle.

      Courtney Lesoon

      Lesoon is a doctoral candidate in the Aga Khan Program for Islamic Architecture, in the History, Theory and Criticism Section of the Department of Architecture. Lesoon earned her BA from College of the Holy Cross and was a 2012-13 Fulbright U.S. Student grantee to the United Arab Emirates, where her research concerned contemporary art and emerging cultural institutions. Her dissertation is titled “Spatializing Ahl al-ʿIlm: Learning and the Rise of the Early Islamic City.” Losoon’s fieldwork will be done in Morocco, Egypt, and Turkey.

      “Courtney’s project presents an innovative idea that has not, to my knowledge, been investigated before,” says Nasser Rabbat, professor and director of the MIT Aga Khan Program. “How did the emergence and evolution of a particularly Islamic learning system affect the development of the city in the early Islamic period? Her work enriches the thinking about premodern urbanism and education everywhere by theorizing the intricate relationship between traveling, learning, and the city.”

      “I’ll be working in different manuscripts collections in Morocco, Egypt, and Turkey to investigate where and how scholars were learning inside of the early Islamic city before the formal institutionalization of higher education,” says Lesoon. “I’m interested in how learning — as a set of social practices — informed urban life. My project speaks to two different fields; Islamic urbanism and Islamic intellectual history. I’m really excited about my time on Fulbright-Hays; it will be a really fruitful time for my research and writing.”

      Before arriving at MIT, Lesoon worked as a research assistant in the Art of the Middle East Department at the Los Angeles County Museum of Art. Recently, she was awarded the 2021 Margaret B. Ševčenko Prize for “the best unpublished essay written by a junior scholar” for her paper “The Sphero-conical as Apothecary Vessel: An Argument for Dedicated Use.” Lesoon earned her MA from the University of Michigan at Ann Arbor, where her thesis investigated an 18th-century “Damascus Room” and its acquisition as a collected interior in the United States.

      Lizzie Yarina

      Yarina is a doctoral candidate in the MIT Department of Urban Studies and Planning (DUSP) and a research fellow at the MIT Norman B. Leventhal Center for Advanced Urbanism. She is presently co-editing a volume on the relationship between climate models and the built environment with a multidisciplinary team of editors and contributors. Yarina was a research scientist at the MIT Urban Risk Lab, where she was part of a team examining alternatives to the Federal Emergency Management Agency’s post-disaster housing systems; she also conducted research on disaster preparedness in Japan. Her award supports her doctoral research under the title “Modeling the Mekong: Climate Adaptation Imaginaries in Delta Regions,” which will include fieldwork in Vietnam, the Netherlands, Thailand, and Cambodia.

      “Lizzie’s research brings together three dimensions critical to global well-being and sustainability: adapting to the inevitability of changing ecosystems wrought by the climate crisis; questioning the equity, appropriateness, and relationality of adaptation planning models spanning the global North and the global South; and understanding how to develop durable and just climate futures,” says Christopher Zegras, professor of mobility and urban planning and department head for DUSP. “Her work will be an important contribution toward the long-term health of our planet and of communities working to justly adapt to climate change.”

      Previously, Yarina was awarded a U.S. Scholarship Fulbright to New Zealand to research spatial mapping and policy implications of Pacific Islander migration to New Zealand.

      “My dissertation project looks at climate adaptation planning in delta regions,” she says. “My focus is on Vietnam’s Mekong River Delta, but I’m also looking at how models that are used in delta adaptation planning move between different deltas, including the Netherlands Rhine Delta and the Mississippi Delta.”

      Working on her masters at MIT, Yarina had a teaching fellowship in Singapore, where she conducted research on climate adaptation plans in four major cities in Southeast Asia.

      “Through that process I learned about the role of Dutch experts and Dutch models in shaping how climate adaptation planning was taking place in Southeast Asia,” she says. “This project expands on that work from looking at a single city to examining a regional plan at the scale of a delta.”

      Yarina holds a joint masters in architecture and masters of city planning from MIT, and a BS in architecture from the University of Michigan. More

    • 150 Shares169 Views

      in Environment

      A dirt cheap solution? Common clay materials may help curb methane emissions

      by

      Methane is a far more potent greenhouse gas than carbon dioxide, and it has a pronounced effect within first two decades of its presence in the atmosphere. In the recent international climate negotiations in Glasgow, abatement of methane emissions was identified as a major priority in attempts to curb global climate change quickly.

      Now, a team of researchers at MIT has come up with a promising approach to controlling methane emissions and removing it from the air, using an inexpensive and abundant type of clay called zeolite. The findings are described in the journal ACS Environment Au, in a paper by doctoral student Rebecca Brenneis, Associate Professor Desiree Plata, and two others.

      Although many people associate atmospheric methane with drilling and fracking for oil and natural gas, those sources only account for about 18 percent of global methane emissions, Plata says. The vast majority of emitted methane comes from such sources as slash-and-burn agriculture, dairy farming, coal and ore mining, wetlands, and melting permafrost. “A lot of the methane that comes into the atmosphere is from distributed and diffuse sources, so we started to think about how you could take that out of the atmosphere,” she says.

      The answer the researchers found was something dirt cheap — in fact, a special kind of “dirt,” or clay. They used zeolite clays, a material so inexpensive that it is currently used to make cat litter. Treating the zeolite with a small amount of copper, the team found, makes the material very effective at absorbing methane from the air, even at extremely low concentrations.

      The system is simple in concept, though much work remains on the engineering details. In their lab tests, tiny particles of the copper-enhanced zeolite material, similar to cat litter, were packed into a reaction tube, which was then heated from the outside as the stream of gas, with methane levels ranging from just 2 parts per million up to 2 percent concentration, flowed through the tube. That range covers everything that might exist in the atmosphere, down to subflammable levels that cannot be burned or flared directly.

      The process has several advantages over other approaches to removing methane from air, Plata says. Other methods tend to use expensive catalysts such as platinum or palladium, require high temperatures of at least 600 degrees Celsius, and tend to require complex cycling between methane-rich and oxygen-rich streams, making the devices both more complicated and more risky, as methane and oxygen are highly combustible on their own and in combination.

      “The 600 degrees where they run these reactors makes it almost dangerous to be around the methane,” as well as the pure oxygen, Brenneis says. “They’re solving the problem by just creating a situation where there’s going to be an explosion.” Other engineering complications also arise from the high operating temperatures. Unsurprisingly, such systems have not found much use.

      As for the new process, “I think we’re still surprised at how well it works,” says Plata, who is the Gilbert W. Winslow Associate Professor of Civil and Environmental Engineering. The process seems to have its peak effectiveness at about 300 degrees Celsius, which requires far less energy for heating than other methane capture processes. It also can work at concentrations of methane lower than other methods can address, even small fractions of 1 percent, which most methods cannot remove, and does so in air rather than pure oxygen, a major advantage for real-world deployment.

      The method converts the methane into carbon dioxide. That might sound like a bad thing, given the worldwide efforts to combat carbon dioxide emissions. “A lot of people hear ‘carbon dioxide’ and they panic; they say ‘that’s bad,’” Plata says. But she points out that carbon dioxide is much less impactful in the atmosphere than methane, which is about 80 times stronger as a greenhouse gas over the first 20 years, and about 25 times stronger for the first century. This effect arises from that fact that methane turns into carbon dioxide naturally over time in the atmosphere. By accelerating that process, this method would drastically reduce the near-term climate impact, she says. And, even converting half of the atmosphere’s methane to carbon dioxide would increase levels of the latter by less than 1 part per million (about 0.2 percent of today’s atmospheric carbon dioxide) while saving about 16 percent of total radiative warming.

      The ideal location for such systems, the team concluded, would be in places where there is a relatively concentrated source of methane, such as dairy barns and coal mines. These sources already tend to have powerful air-handling systems in place, since a buildup of methane can be a fire, health, and explosion hazard. To surmount the outstanding engineering details, the team has just been awarded a $2 million grant from the U.S. Department of Energy to continue to develop specific equipment for methane removal in these types of locations.

      “The key advantage of mining air is that we move a lot of it,” she says. “You have to pull fresh air in to enable miners to breathe, and to reduce explosion risks from enriched methane pockets. So, the volumes of air that are moved in mines are enormous.” The concentration of methane is too low to ignite, but it’s in the catalysts’ sweet spot, she says.

      Adapting the technology to specific sites should be relatively straightforward. The lab setup the team used in their tests consisted of  “only a few components, and the technology you would put in a cow barn could be pretty simple as well,” Plata says. However, large volumes of gas do not flow that easily through clay, so the next phase of the research will focus on ways of structuring the clay material in a multiscale, hierarchical configuration that will aid air flow.

      “We need new technologies for oxidizing methane at concentrations below those used in flares and thermal oxidizers,” says Rob Jackson, a professor of earth systems science at Stanford University, who was not involved in this work. “There isn’t a cost-effective technology today for oxidizing methane at concentrations below about 2,000 parts per million.”

      Jackson adds, “Many questions remain for scaling this and all similar work: How quickly will the catalyst foul under field conditions? Can we get the required temperatures closer to ambient conditions? How scaleable will such technologies be when processing large volumes of air?”

      One potential major advantage of the new system is that the chemical process involved releases heat. By catalytically oxidizing the methane, in effect the process is a flame-free form of combustion. If the methane concentration is above 0.5 percent, the heat released is greater than the heat used to get the process started, and this heat could be used to generate electricity.

      The team’s calculations show that “at coal mines, you could potentially generate enough heat to generate electricity at the power plant scale, which is remarkable because it means that the device could pay for itself,” Plata says. “Most air-capture solutions cost a lot of money and would never be profitable. Our technology may one day be a counterexample.”

      Using the new grant money, she says, “over the next 18 months we’re aiming to demonstrate a proof of concept that this can work in the field,” where conditions can be more challenging than in the lab. Ultimately, they hope to be able to make devices that would be compatible with existing air-handling systems and could simply be an extra component added in place. “The coal mining application is meant to be at a stage that you could hand to a commercial builder or user three years from now,” Plata says.

      In addition to Plata and Brenneis, the team included Yale University PhD student Eric Johnson and former MIT postdoc Wenbo Shi. The work was supported by the Gerstner Philanthropies, Vanguard Charitable Trust, the Betty Moore Inventor Fellows Program, and MIT’s Research Support Committee. More

    • 163 Shares169 Views

      in Energy

      Seeing the plasma edge of fusion experiments in new ways with artificial intelligence

      by

      To make fusion energy a viable resource for the world’s energy grid, researchers need to understand the turbulent motion of plasmas: a mix of ions and electrons swirling around in reactor vessels. The plasma particles, following magnetic field lines in toroidal chambers known as tokamaks, must be confined long enough for fusion devices to produce significant gains in net energy, a challenge when the hot edge of the plasma (over 1 million degrees Celsius) is just centimeters away from the much cooler solid walls of the vessel.

      Abhilash Mathews, a PhD candidate in the Department of Nuclear Science and Engineering working at MIT’s Plasma Science and Fusion Center (PSFC), believes this plasma edge to be a particularly rich source of unanswered questions. A turbulent boundary, it is central to understanding plasma confinement, fueling, and the potentially damaging heat fluxes that can strike material surfaces — factors that impact fusion reactor designs.

      To better understand edge conditions, scientists focus on modeling turbulence at this boundary using numerical simulations that will help predict the plasma’s behavior. However, “first principles” simulations of this region are among the most challenging and time-consuming computations in fusion research. Progress could be accelerated if researchers could develop “reduced” computer models that run much faster, but with quantified levels of accuracy.

      For decades, tokamak physicists have regularly used a reduced “two-fluid theory” rather than higher-fidelity models to simulate boundary plasmas in experiment, despite uncertainty about accuracy. In a pair of recent publications, Mathews begins directly testing the accuracy of this reduced plasma turbulence model in a new way: he combines physics with machine learning.

      “A successful theory is supposed to predict what you’re going to observe,” explains Mathews, “for example, the temperature, the density, the electric potential, the flows. And it’s the relationships between these variables that fundamentally define a turbulence theory. What our work essentially examines is the dynamic relationship between two of these variables: the turbulent electric field and the electron pressure.”

      In the first paper, published in Physical Review E, Mathews employs a novel deep-learning technique that uses artificial neural networks to build representations of the equations governing the reduced fluid theory. With this framework, he demonstrates a way to compute the turbulent electric field from an electron pressure fluctuation in the plasma consistent with the reduced fluid theory. Models commonly used to relate the electric field to pressure break down when applied to turbulent plasmas, but this one is robust even to noisy pressure measurements.

      In the second paper, published in Physics of Plasmas, Mathews further investigates this connection, contrasting it against higher-fidelity turbulence simulations. This first-of-its-kind comparison of turbulence across models has previously been difficult — if not impossible — to evaluate precisely. Mathews finds that in plasmas relevant to existing fusion devices, the reduced fluid model’s predicted turbulent fields are consistent with high-fidelity calculations. In this sense, the reduced turbulence theory works. But to fully validate it, “one should check every connection between every variable,” says Mathews.

      Mathews’ advisor, Principal Research Scientist Jerry Hughes, notes that plasma turbulence is notoriously difficult to simulate, more so than the familiar turbulence seen in air and water. “This work shows that, under the right set of conditions, physics-informed machine-learning techniques can paint a very full picture of the rapidly fluctuating edge plasma, beginning from a limited set of observations. I’m excited to see how we can apply this to new experiments, in which we essentially never observe every quantity we want.”

      These physics-informed deep-learning methods pave new ways in testing old theories and expanding what can be observed from new experiments. David Hatch, a research scientist at the Institute for Fusion Studies at the University of Texas at Austin, believes these applications are the start of a promising new technique.

      “Abhi’s work is a major achievement with the potential for broad application,” he says. “For example, given limited diagnostic measurements of a specific plasma quantity, physics-informed machine learning could infer additional plasma quantities in a nearby domain, thereby augmenting the information provided by a given diagnostic. The technique also opens new strategies for model validation.”

      Mathews sees exciting research ahead.

      “Translating these techniques into fusion experiments for real edge plasmas is one goal we have in sight, and work is currently underway,” he says. “But this is just the beginning.”

      Mathews was supported in this work by the Manson Benedict Fellowship, Natural Sciences and Engineering Research Council of Canada, and U.S. Department of Energy Office of Science under the Fusion Energy Sciences program.​ More

    • 88 Shares189 Views

      in Energy

      Helping to make nuclear fusion a reality

      by

      Up until she served in the Peace Corps in Malawi, Rachel Bielajew was open to a career reboot. Having studied nuclear engineering as an undergraduate at the University of Michigan at Ann Arbor, graduate school had been on her mind. But seeing the drastic impacts of climate change play out in real-time in Malawi — the lives of the country’s subsistence farmers swing wildly, depending on the rains — convinced Bielajew of the importance of nuclear engineering. Bielajew was struck that her high school students in the small town of Chisenga had a shaky understanding of math, but universally understood global warming. “The concept of the changing world due to human impact was evident, and they could see it,” Bielajew says.

      Bielajew was looking to work on solutions that could positively impact global problems and feed her love of physics. Nuclear engineering, especially the study of fusion as a carbon-free energy source, checked off both boxes. Bielajew is now a fourth-year doctoral candidate in the Department of Nuclear Science and Engineering (NSE). She researches magnetic confinement fusion in the Plasma Science and Fusion Center (PSFC) with Professor Anne White.

      Researching fusion’s big challenge

      You need to confine plasma effectively in order to generate the extremely high temperatures (100 million degrees Celsius) fusion needs, without melting the walls of the tokamak, the device that hosts these reactions. Magnets can do the job, but “plasmas are weird, they behave strangely and are challenging to understand,” Bielajew says. Small instabilities in plasma can coalesce into fluctuating turbulence that can drive heat and particles out of the machine.

      In high-confinement mode, the edges of the plasma have less tolerance for such unruly behavior. “The turbulence gets damped out and sheared apart at the edge,” Bielajew says. This might seem like a good thing, but high-confinement plasmas have their own challenges. They are so tightly bound that they create edge-localized modes (ELMs), bursts of damaging particles and energy, that can be extremely damaging to the machine.

      The questions Bielajew is looking to answer: How do we get high confinement without ELMs? How do turbulence and transport play a role in plasmas? “We do not fully understand turbulence, even though we have studied it for a long time,” Bielajew says, “It is a big and important problem to solve for fusion to be a reality. I like that challenge,” Bielajew adds.

      A love of science

      Confronting such challenges head-on has been part of Bielajew’s toolkit since she was a child growing up in Ann Arbor, Michigan. Her father, Alex Bielajew, is a professor of nuclear engineering at the University of Michigan, and Bielajew’s mother also pursued graduate studies.

      Bielajew’s parents encouraged her to follow her own path and she found it led to her father’s chosen profession: nuclear engineering. Once she decided to pursue research in fusion, MIT stood out as a school she could set her sights on. “I knew that MIT had an extensive program in fusion and a lot of faculty in the field,” Bielajew says. The mechanics of the application were challenging: Chisenga had limited internet access, so Bielajew had to ride on the back of a pickup truck to meet a friend in a city a few hours away and use his phone as a hotspot to send the documents.

      A similar tenacity has surfaced in Bielajew’s approach to research during the Covid-19 pandemic. Working off a blueprint, Bielajew built the Correlation Cyclotron Emission Diagnostic, which measures turbulent electron temperature fluctuations. Through a collaboration, Bielajew conducts her plasma research at the ASDEX Upgrade tokamak in Germany. Traditionally, Bielajew would ship the diagnostic to Germany, follow and install it, and conduct the research in person. The pandemic threw a wrench in the plans, so Bielajew shipped the diagnostic and relied on team members to install it. She Zooms into the control room and trusts others to run the plasma experiments.

      DEI advocate

      Bielajew is very hands-on with another endeavor: improving diversity, equity, and inclusion (DEI) in her own backyard. Having grown up with parental encouragement and in an environment that never doubted her place as a woman in engineering, Bielajew realizes not everyone has the same opportunities. “I wish that the world was in a place where all I had to do was care about my research, but it’s not,” Bielajew says. While science can solve many problems, more fundamental ones about equity need humans to act in specific ways, she points out. “I want to see more women represented, more people of color. Everyone needs a voice in building a better world,” Bielajew says.

      To get there, Bielajew co-launched NSE’s Graduate Application Assistance Program, which connects underrepresented student applicants with NSE mentors. She has been the DEI officer with NSE’s student group, ANS, and is very involved in the department’s DEI committee.

      As for future research, Bielajew hopes to concentrate on the experiments that make her question existing paradigms about plasmas under high confinement. Bielajew has registered more head-scratching “hmm” moments than “a-ha” ones. Measurements from her experiments drive the need for more intensive study.

      Bielajew’s dogs, Dobby and Winky, keep her company through it all. They came home with her from Malawi. More

    • 88 Shares199 Views

      in Environment

      Predator interactions chiefly determine where Prochlorococcus thrive

      by

      Prochlorococcus are the smallest and most abundant photosynthesizing organisms on the planet. A single Prochlorococcus cell is dwarfed by a human red blood cell, yet globally the microbes number in the octillions and are responsible for a large fraction of the world’s oxygen production as they turn sunlight into energy.

      Prochlorococcus can be found in the ocean’s warm surface waters, and their population drops off dramatically in regions closer to the poles. Scientists have assumed that, as with many marine species, Prochlorococcus’ range is set by temperature: The colder the waters, the less likely the microbes are to live there.

      But MIT scientists have found that where the microbe lives is not determined primarily by temperature. While Prochlorococcus populations do drop off in colder waters, it’s a relationship with a shared predator, and not temperature, that sets the microbe’s range. These findings, published today in the Proceedings of the National Academy of Sciences, could help scientists predict how the microbes’ populations will shift with climate change.

      “People assume that if the ocean warms up, Prochlorococcus will move poleward. And that may be true, but not for the reason they’re predicting,” says study co-author Stephanie Dutkiewicz, senior research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “So, temperature is a bit of a red herring.”

      Dutkiewicz’s co-authors on the study are lead author and EAPS Research Scientist Christopher Follett, EAPS Professor Mick Follows, François Ribalet and Virginia Armbrust of the University of Washington, and Emily Zakem and David Caron of the University of Southern California at Los Angeles.

      Temperature’s collapse

      While temperature is thought to set the range of Prochloroccus and other phytoplankton in the ocean, Follett, Dutkiewicz, and their colleagues noticed a curious dissonance in data.

      The team examined observations from several research cruises that sailed through the northeast Pacific Ocean in 2003, 2016, and 2017. Each vessel traversed different latitudes, sampling waters continuously and measuring concentrations of various species of bacteria and phytoplankton, including Prochlorococcus. 

      The MIT team used the publicly archived cruise data to map out the locations where Prochlorococcus noticeably decreased or collapsed, along with each location’s ocean temperature. Surprisingly, they found that Prochlorococcus’ collapse occurred in regions of widely varying temperatures, ranging from around 13 to 18 degrees Celsius. Curiously, the upper end of this range has been shown in lab experiments to be suitable conditions for Prochlorococcus to grow and thrive.

      “Temperature itself was not able to explain where we saw these drop-offs,” Follett says.

      Follett was also working out an alternate idea related to Prochlorococcus and nutrient supply. As a byproduct of its photosynthesis, the microbe produces carbohydrate — an essential nutrient for heterotrophic bacteria, which are single-celled organisms that do not photosynthesize but live off the organic matter produced by phytoplankton.

      “Somewhere along the way, I wondered, what would happen if this food source Prochlorococcus was producing increased? What if we took that knob and spun it?” Follett says.

      In other words, how would the balance of Prochlorococcus and bacteria shift if the bacteria’s food increased as a result of, say, an increase in other carbohydrate-producing phytoplankton? The team also wondered: If the bacteria in question were about the same size as Prochlorococcus, the two would likely share a common grazer, or predator. How would the grazer’s population also shift with a change in carbohydrate supply?

      “Then we went to the whiteboard and started writing down equations and solving them for various cases, and realized that as soon as you reach an environment where other species add carbohydrates to the mix, bacteria and grazers grow up and annihilate Prochlorococcus,” Dutkiewicz says.

      Nutrient shift

      To test this idea, the researchers employed simulations of ocean circulation and marine ecosystem interactions. The team ran the MITgcm, a general circulation model that simulates, in this case, the ocean currents and regions of upwelling waters around the world. They overlaid a biogeochemistry model that simulates how nutrients are redistributed in the ocean. To all of this, they linked a complex ecosystem model that simulates the interactions between many different species of bacteria and phytoplankton, including Prochlorococcus.

      When they ran the simulations without incorporating a representation of bacteria, they found that Prochlorococcus persisted all the way to the poles, contrary to theory and observations. When they added in the equations outlining the relationship between the microbe, bacteria, and a shared predator, Prochlorococcus’ range shifted away from the poles, matching the observations of the original research cruises.

      In particular, the team observed that Prochlorococcus thrived in waters with very low nutrient levels, and where it is the dominant source of food for bacteria. These waters also happen to be warm, and Prochlorococcus and bacteria live in balance, along with their shared predator. But in more nutrient-rich enviroments, such as polar regions, where cold water and nutrients are upwelled from the deep ocean, many more species of phytoplankton can thrive. Bacteria can then feast and grow on more food sources, and in turn feed and grow more of its shared predator. Prochlorococcus, unable to keep up, is quickly decimated. 

      The results show that a relationship with a shared predator, and not temperature, sets Prochlorococcus’ range. Incorporating this mechanism into models will be crucial in predicting how the microbe — and possibly other marine species — will shift with climate change.

      “Prochlorococcus is a big harbinger of changes in the global ocean,” Dutkiewicz says. “If its range expands, that’s a canary — a sign that things have changed in the ocean by a great deal.”

      “There are reasons to believe its range will expand with a warming world,” Follett adds.” But we have to understand the physical mechanisms that set these ranges. And predictions just based on temperature will not be correct.” More

    • 100 Shares99 Views

      in Security

      Scientists build new atlas of ocean’s oxygen-starved waters

      by

      Life is teeming nearly everywhere in the oceans, except in certain pockets where oxygen naturally plummets and waters become unlivable for most aerobic organisms. These desolate pools are “oxygen-deficient zones,” or ODZs. And though they make up less than 1 percent of the ocean’s total volume, they are a significant source of nitrous oxide, a potent greenhouse gas. Their boundaries can also limit the extent of fisheries and marine ecosystems.

      Now MIT scientists have generated the most detailed, three-dimensional “atlas” of the largest ODZs in the world. The new atlas provides high-resolution maps of the two major, oxygen-starved bodies of water in the tropical Pacific. These maps reveal the volume, extent, and varying depths of each ODZ, along with fine-scale features, such as ribbons of oxygenated water that intrude into otherwise depleted zones.

      The team used a new method to process over 40 years’ worth of ocean data, comprising nearly 15 million measurements taken by many research cruises and autonomous robots deployed across the tropical Pacific. The researchers compiled then analyzed this vast and fine-grained data to generate maps of oxygen-deficient zones at various depths, similar to the many slices of a three-dimensional scan.

      From these maps, the researchers estimated the total volume of the two major ODZs in the tropical Pacific, more precisely than previous efforts. The first zone, which stretches out from the coast of South America, measures about 600,000 cubic kilometers — roughly the volume of water that would fill 240 billion Olympic-sized pools. The second zone, off the coast of Central America, is roughly three times larger.

      The atlas serves as a reference for where ODZs lie today. The team hopes scientists can add to this atlas with continued measurements, to better track changes in these zones and predict how they may shift as the climate warms.

      “It’s broadly expected that the oceans will lose oxygen as the climate gets warmer. But the situation is more complicated in the tropics where there are large oxygen-deficient zones,” says Jarek Kwiecinski ’21, who developed the atlas along with Andrew Babbin, the Cecil and Ida Green Career Development Professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “It’s important to create a detailed map of these zones so we have a point of comparison for future change.”

      The team’s study appears today in the journal Global Biogeochemical Cycles.

      Airing out artifacts

      Oxygen-deficient zones are large, persistent regions of the ocean that occur naturally, as a consequence of marine microbes gobbling up sinking phytoplankton along with all the available oxygen in the surroundings. These zones happen to lie in regions that miss passing ocean currents, which would normally replenish regions with oxygenated water. As a result, ODZs are locations of relatively permanent, oxygen-depleted waters, and can exist at mid-ocean depths of between roughly 35 to 1,000 meters below the surface. For some perspective, the oceans on average run about 4,000 meters deep.

      Over the last 40 years, research cruises have explored these regions by dropping bottles down to various depths and hauling up seawater that scientists then measure for oxygen.

      “But there are a lot of artifacts that come from a bottle measurement when you’re trying to measure truly zero oxygen,” Babbin says. “All the plastic that we deploy at depth is full of oxygen that can leach out into the sample. When all is said and done, that artificial oxygen inflates the ocean’s true value.”

      Rather than rely on measurements from bottle samples, the team looked at data from sensors attached to the outside of the bottles or integrated with robotic platforms that can change their buoyancy to measure water at different depths. These sensors measure a variety of signals, including changes in electrical currents or the intensity of light emitted by a photosensitive dye to estimate the amount of oxygen dissolved in water. In contrast to seawater samples that represent a single discrete depth, the sensors record signals continuously as they descend through the water column.

      Scientists have attempted to use these sensor data to estimate the true value of oxygen concentrations in ODZs, but have found it incredibly tricky to convert these signals accurately, particularly at concentrations approaching zero.

      “We took a very different approach, using measurements not to look at their true value, but rather how that value changes within the water column,” Kwiecinski says. “That way we can identify anoxic waters, regardless of what a specific sensor says.”

      Bottoming out

      The team reasoned that, if sensors showed a constant, unchanging value of oxygen in a continuous, vertical section of the ocean, regardless of the true value, then it would likely be a sign that oxygen had bottomed out, and that the section was part of an oxygen-deficient zone.

      The researchers brought together nearly 15 million sensor measurements collected over 40 years by various research cruises and robotic floats, and mapped the regions where oxygen did not change with depth.

      “We can now see how the distribution of anoxic water in the Pacific changes in three dimensions,” Babbin says. 

      The team mapped the boundaries, volume, and shape of two major ODZs in the tropical Pacific, one in the Northern Hemisphere, and the other in the Southern Hemisphere. They were also able to see fine details within each zone. For instance, oxygen-depleted waters are “thicker,” or more concentrated towards the middle, and appear to thin out toward the edges of each zone.

      “We could also see gaps, where it looks like big bites were taken out of anoxic waters at shallow depths,” Babbin says. “There’s some mechanism bringing oxygen into this region, making it oxygenated compared to the water around it.”

      Such observations of the tropical Pacific’s oxygen-deficient zones are more detailed than what’s been measured to date.

      “How the borders of these ODZs are shaped, and how far they extend, could not be previously resolved,” Babbin says. “Now we have a better idea of how these two zones compare in terms of areal extent and depth.”

      “This gives you a sketch of what could be happening,” Kwiecinski says. “There’s a lot more one can do with this data compilation to understand how the ocean’s oxygen supply is controlled.”

      This research is supported, in part, by the Simons Foundation. More

    • 88 Shares189 Views

      in Environment

      MIT in the media: 2021 in review

      by

      From Institute-wide efforts to address the climate crisis to responding to Covid-19, members of the MIT community made headlines this year for their innovative work in a variety of areas. Faculty, students, and staff were on the front lines of addressing many pressing issues this year, raising their voices and sharing their findings. Below are highlights of news stories that spotlight the many efforts underway at MIT to help make a better world.

      Fireside chat: Tackling global challenges with a culture of innovationPresident L. Rafael Reif and Linda Henry, CEO of Boston Globe Media Partners, took part in a wide-ranging fireside chat during the inaugural Globe Summit, touching upon everything from the urgent need to address the climate crisis to MIT’s response to Covid-19, the Institute’s approach to artificial intelligence education and the greater Boston innovation ecosystem.Full discussion via Globe Summit

      A real-world revolution in economicsProfessor Joshua Angrist, one of the winners of the 2021 Nobel Prize in economic sciences, spoke with The Economist’s Money Talks podcast about the evolution of his research and how his work has helped bring the field of economics closer to real life. “I like to tell graduate students that a good scholar is like a good hitter in baseball,” says Angrist of his advice for economics students. “You get on base about a third of the time you’re doing pretty well, which means you strike out most of the time.”Full story via The Economist

      Paula Hammond guest edits C&EN’s 2021 Trailblazers issueC&EN’s 2021 Trailblazers issue, curated by guest editor Paula Hammond, celebrated Black chemists and chemical engineers. “As we learn from several of the personal stories highlighted in this issue,” writes Hammond, “that first connection to science and research is critical to engage and inspire the next generation.” Helping propel the issue’s message about the importance of mentorship was a one-on-one with Professor Kristala Prather about her career path and a wide-ranging interview with Hammond herself on building a home at MIT.Full issue via C&EN

      Can fusion put the brakes on climate change? MIT’s new Climate Action Plan for the Decade calls for going as far as we can, as fast as we can, with the tools and methods we have now — but also asserts that ultimate success depends on breakthroughs. Commercial fusion energy is potentially one such game-changer, and a unique collaboration between MIT and Commonwealth Fusion Systems (CFS) is pursuing it. As Joy Dunn ’08, head of manufacturing at CFS, explains to the New Yorker’s Rivka Galchen: “When people ask me, ‘Why fusion? Why not other renewables,’ my thinking is: This is a solution at the scale of the problem.”Full story via New Yorker

      The genius next door: Taylor Perron discusses landscape evolutionProfessor and geomorphologist Taylor Perron, a recipient this year’s MacArthur Fellowships, joined Callie Crossley of GBH’s Under the Radar to discuss his work studying the mechanisms that shape landscapes on Earth and other planets. “We try to figure out how we can look at landscapes and read them, and try to figure out what happened in the past and also anticipate what might happen in the future,” says Perron.Full story via GBH

      How the pandemic “re-imagined how we can exhibit” Hashim Sarkis, dean of the School of Architecture and Planning and curator of this year’s Venice Architecture Biennale, spoke with Cajsa Carlson of Dezeen about how the field of architecture is transforming due to climate change, the Covid-19 pandemic, and efforts to increase diversity and representation. “Talent and imagination are not restricted to advanced development economically,” says Sarkis. “I hope this message comes across in this biennale.”Full story via Dezeen

      10 years at the top of the QS World University RankingsProvost Martin Schmidt spoke with TopUniversities.com reporter Chloe Lane about how MIT has maintained its position as the top university in the world on the QS World University Rankings for 10 consecutive years. “The Institute is full of a diverse community of people from all corners of the globe dedicated to solving the world’s most difficult problems,” says Schmidt. “Their efforts have a demonstrable impact through ambitious high-impact activities.”  Full story via TopUniversities.com

      Tackling Covid-19 and the Impact of a Global PandemicIn 2021, MIT researchers turned their attention to addressing the widespread effects of a global pandemic, exploring everything from supply chain issues to K-12 education.Massachusetts Miracle: “There are a lot of potential Modernas”Boston Globe columnist Shirley Leung spotlighted how the development of the Moderna Covid-19 vaccine demonstrates the success of the Massachusetts life sciences sector. “For more than half a century, the Massachusetts Institute of Technology has been the epicenter of that curiosity, with a focus on molecular biology — initially to find a cure for cancer,” writes Leung.Full story via The Boston Globe

      Weak links in the supply chainProfessor Yossi Sheffi spoke with David Pogue of CBS Sunday Morning about what’s causing supply chain breakdowns. “The underlying cause of all of this is actually a huge increase in demand,” says Sheffi. “People did not spend during the pandemic. And then, all the government help came; trillions of dollars went to households. So, they order stuff. They order more and more stuff. And the global markets were not ready for this.”Full story via CBS News

      Recruiting students and teachers to rethink schoolsA report co-authored by Associate Professor Justin Reich proposed a new path forward for rethinking K-12 schools after Covid-19, reported Paul Darvasi for KQED. “The report recommends that educators build on the positive aspects of their pandemic learning experience in the years ahead,” notes Darvasi, “and supports increased student independence to cultivate a safe and healthy environment that is more conducive to learning.”Full story via KQED

      This staff member has been quietly curating a flower box at the Collier MemorialResearch Specialist Kathy Cormier’s dedication to tending a flower planter at the Collier Memorial throughout the pandemic captured the hearts of many in the MIT community. “Here’s something that’s empty that I can fill, and make myself feel better and make other people — hopefully — feel better,” she says.Full story via The Boston Globe

      Amazing Alumni MIT alumni made headlines for their efforts to change the world, both here on Earth and in outer space. NASA selects three new astronaut candidates with MIT rootsMarcos Berríos ’06, Christina Birch PhD ’15 and Christopher Williams PhD ’12 were selected among NASA’s 10-member 2021 astronaut candidate class, reported WBUR’s Bill Chappell. “Alone, each candidate has ‘the right stuff,’ but together they represent the creed of our country: E pluribus unum — out of many, one,” said NASA Administrator Bill Nelson.Full story via WBUR

      Ngozi Okonjo-Iweala named WTO director-generalNgozi Okonjo-Iweala MCP ’78, PhD ’81, a former Nigerian finance minister, was named director-general of the World Trade Organization, reported William Wallace for the Financial Times. “Okonjo-Iweala sees an opportunity for the organization to rediscover some of its original purpose of raising living standards across the board and to bring its outdated rule book up to date at a time of accelerating change,” notes Wallace.Full story via Financial Times

      She doesn’t think skateboarding’s a sport, but she competed for a medalAlexis Sablone MArch ’16 spoke with Washington Post reporter Les Carpenter about street skateboarding, competing at this year’s Olympic Games, and why she is uncomfortable with being defined. “To me, I’m just always like trying to be myself and do things that I love to do and not try to fit into these categories in ways that I don’t feel comfortable with,” says Sablone.Full story via The Washington Post

      Applauding the culture of aerospace engineeringTiera Fletcher ’17, a structural design engineer working on building NASA’s Space Launch System, and her husband Myron Fletcher spoke with the hosts of The Real about what inspired them to pursue careers in aerospace engineering and their organization Rocket with the Fletchers, which is aimed at introducing youth to the field of aerodynamics.Full story via The Real

      Addressing the Climate CrisisThe urgent need to take action on climate change became more apparent in 2021. MIT researchers across campus answered the call and are unleashing innovative ideas to help address the biggest threat of our time.

      Why closing California’s last nuclear power plant would be a mistake The Washington Post Editorial Board highlighted a report co-authored by MIT researchers that found keeping the Diablo Canyon nuclear power plant in California open would help the state reach its climate goals.Full story via The Washington Post

      What will the U.S. do to reach emission reduction targets?Sergey Paltsev, deputy director of the MIT Joint Program on the Science and Policy of Global Change, spoke with Brian Cheung of Yahoo Finance about climate change, the path to net-zero emissions, and COP26. Paltsev was a lead author of the Fifth Assessment Report Intergovernmental Panel on Climate Change or IPCC. Full story via Yahoo News

      Lithium battery costs have fallen by 98% in three decadesA study by Professor Jessika Trancik and postdoc Micah Ziegler examining the plunge in lithium-ion battery costs finds “every time output doubles, as it did five times between 2006 and 2016, battery prices fall by about a quarter,” reports The Economist, which highlighted the work in its popular “Daily chart” feature. (Trancik’s research detailing carbon impacts of different cars was also cited by The Washington Post as a climate-change innovation helping respond to calls for action.)Full story via The Economist

      MIT students display a “climate clock” outside the Green BuildingBoston Globe reporter Matt Berg spotlights how a team from the MIT D-Lab created a climate clock, which was projected on the exterior of the Green Building at MIT in an effort to showcase key data about climate change. “The display highlights goals of the fight against climate change, such as limiting the annual temperature increases to no more than 2.7 degrees Fahrenheit,” writes Berg.Full story via The Boston Globe

      Social Impact

      MIT community members increasingly sought to address social issues around the world, from the spread of misinformation to ensuring marginalized communities could share their experiences. At MIT, arts, humanities and STEM fields forge an essential partnershipWriting for Times Higher Ed, Agustín Rayo, interim dean of MIT’s School of Humanities, Arts and Social Sciences, and Hashim Sarkis, dean of the School of Architecture and Planning, underscore the importance of the arts, humanities, and design fields as “an essential part of an MIT education, critical to the Institute’s capacity for innovation and vital to its mission to make a better world.” They add that “the MIT mission is to serve humankind, and the arts and humanities are essential resources for knowledge and understanding of the human condition.”Full story via Times Higher Ed

      Helping Bostonians feel heard with MIT’s “Real Talk” portalAn MIT initiative called “Real Talk for Change” launched a new online portal of more than 200 audio stories collected from Boston residents as part of an effort to “help prompt future community dialogues about the lived experiences of everyday Bostonians, particularly those in marginalized communities,” reported Meghan E. Irons for The Boston Globe.Full story via Boston Globe

      Why nations fail, America editionProfessor Daron Acemoglu spoke with Greg Rosalsky of NPR’s Planet Money about his book, “Why Nations Fail,” and whether the attack on the U.S. Capitol signals difficulties for U.S. institutions, and how politicians can create more shared prosperity through a “good jobs” agenda. “We are still at a point where we can reverse things,” Acemoglu says. “But I think if we paper over these issues, we will most likely see a huge deterioration in institutions. And it can happen very rapidly.”Full story via Planet Money

      Why confronting disinformation spreaders online only makes it worseA study by MIT researchers found that correcting people who were spreading misinformation on Twitter led to people retweeting and sharing even more misinformation, reported Matthew Gault for Motherboard. Professor David Rand explains that the research is aimed at identifying “what kinds of interventions increase versus decrease the quality of news people share. There is no question that social media has changed the way people interact. But understanding how exactly it’s changed things is really difficult.” Full story via Motherboard

      Out of This WorldFrom designing a new instrument that can extract oxygen out of Martian air to investigating gravitational waves, MIT community members continued their longstanding tradition of deepening our understanding of the cosmos. MOXIE pulled breathable oxygen out of thin Martian airMichael Hecht of MIT’s Haystack Observatory spoke with GBH’s Edgar Herwick about how the MIT-designed MOXIE instrument successfully extracted oxygen out of Martian air. “I’ve been using the expression ‘a small breath for man, a giant leap for humankind,’” says Hecht, who is the principal investigator for MOXIE.Full story via GBH

      The down-to-Earth applications of spaceAssistant Professor Danielle Wood joined Bloomberg TV to discuss her work focused on using space technologies as a way to advance the U.N. Sustainable Development Goals. She emphasizes how space “is a platform for serving the broad public. We use satellites to observe the environment and the climate, we use satellites to connect people across different parts of the Earth, and they give us information about our positions and our weather. All of these are broad public goods that really can serve people across the world all at once.”Full story via Bloomberg TV

      How Perseverance is hunting for life on MarsIn a conversation with New Scientist reporter Jonathan O’Callaghan, Professor Tanja Bosak discussed her work with the NASA Perseverance rover’s rock reconnaissance mission. “In the middle of a pandemic, I think we needed something good to happen, and that’s why so many people wanted all the science and engineering that goes into landing a rover on Mars to succeed,” says Bosak.Full story via New Scientist

      What scientists have learned from hidden ripples in spacetimeNergis Mavalvala, dean of the School of Science, spoke with Becky Ferreira of Motherboard’s “Space Show” about LIGO’s 2015 discovery of gravitational waves and what researchers in the field have learned since then. “Every one of these observations tells us a little bit more about how nature has assembled our universe,” says Mavalvala. “Really, in the end, the question we’re asking is: ‘How did this universe that we observe come about?’” Full story via MotherboardJoining the Conversation

      MIT authors contributed nearly 100 op-eds and essays to top news outlets this year, along with research-focused deep dives in The Conversation.

      Building on Vannevar Bush’s “wild garden” to cultivate solutions to human needsPresident L. Rafael Reif examined Vannevar Bush’s groundbreaking 1945 “Science, the Endless Frontier” report and considered how our needs today have changed. “To meet this moment, we need to ensure that our federally sponsored research addresses questions that will enhance our competitiveness now and in the future,” writes Reif. “Our current system has many strengths … but we must not allow these historical advantages to blind us to gaps that could become fatal weaknesses.”Full story via Issues in Science and Technology

      Good news: There’s a labor shortageWriting for The New York Times, Professor David Autor explored how the current labor shortage provides an opportunity to improve the quality of jobs in the U.S. “The period of labor scarcity, then, is an opportunity to catalyze better working conditions for those who need them most,” writes Autor.Full story via New York Times

      Opening the path to biotechIn an editorial for Science, Professor Sangeeta Bhatia, Professor Emerita Nancy Hopkins, and President Emerita Susan Hockfield underscored the importance of addressing the underrepresentation of women and individuals of color in tech transfer. “The discoveries women and minority researchers are making today have great potential as a force for good in the world,” they write, “but reaching that potential is only possible if paths to real-world applications are open to everybody.”Full story via Science

      To protect from lab leaks, we need “banal” safety rules, not anti-terrorism measuresMIT Professor Susan Silbey and Professor Ruthanne Huising of Emlyon Business School made the case that to prevent lab leaks, there should be a greater emphasis placed on biosafety. “The global research community does not need more rules, more layers of oversight, and more intermediary actors,” they write. “What it needs is more attention and respect to already known biosafety measures and techniques.”Full story via Stat

      Boston: The Silicon Valley of longevity?Writing for The Boston Globe, AgeLab Director Joseph Coughlin and Research Associate Luke Yoquinto explored how Greater Boston could serve as an innovation hub for aging populations. “By making groundbreaking creativity and inventiveness for older adults both seen and felt, Greater Boston and New England will be able to offer the world a new vision of old age,” they write.Full story via The Boston Globe

      More of the latest MIT In the Media summaries, with links to the original reporting, are available at news.mit.edu/in-the-media. More