From PNNL: “Oxygen: Not at All Random”

July 2015

Rejecting random diffusion, oxygen atoms create detailed architectures in uranium dioxide, radically altering our understanding of corrosion

Oxygen atoms follow a set pattern in corroding uranium dioxide, the primary component of fuel rods in nuclear reactors, not random diffusion. Understanding this pattern opens new doors for controlling corrosion. Image by Cortland Johnson, PNNL.

Results: Corrosion follows a different path when it comes to uranium dioxide, the primary component of the rods that power nuclear reactors, according to a new study by scientists at the Pacific Northwest National Laboratory, University of Chicago, and the Stanford Synchrotron Radiation Lightsource. In uranium dioxide, the oxygen atoms-key corrosion creators-do not diffuse randomly through the material. Rather, the oxygen atoms settle into the third, sixth, ninth, etc., layers. They space themselves within the layers and alter the structure by causing the layers of uranium atoms above and below to draw closer to the oxygen. The oxygen atoms essentially self-assemble into a highly structured array.

Why It Matters: Oxygen’s interactions can extensively corrode materials, whether it is a car in a field or a fuel canister in a nuclear reactor. Under certain conditions, oxygen corrodes fuel rods and causes them to swell by more than 30 percent, creating problems during both routine operations and emergency situations. Also, this swelling can be a problem for long-term storage of nuclear waste. The study shows atomic-level changes counter to those shown by the classical diffusion model that states most of the oxygen atoms are near the surface. The new study gives scientists accurate information to understand the start of corrosion, possibly leading to new ways to avoid corrosion-related failures.

See the full article here.

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Pacific Northwest National Laboratory (PNNL) is one of the United States Department of Energy National Laboratories, managed by the Department of Energy’s Office of Science. The main campus of the laboratory is in Richland, Washington.

PNNL scientists conduct basic and applied research and development to strengthen U.S. scientific foundations for fundamental research and innovation; prevent and counter acts of terrorism through applied research in information analysis, cyber security, and the nonproliferation of weapons of mass destruction; increase the U.S. energy capacity and reduce dependence on imported oil; and reduce the effects of human activity on the environment. PNNL has been operated by Battelle Memorial Institute since 1965.

From PNNL: “Scientists Discover Precise Location of Active Sites on Popular Catalyst”

PNNL Lab

August 2015
No Writer Credit

Experimental work with vanadium oxide catalysts relied on sophisticated spectroscopy and chemical structure calculations to establish a relationship between specific sites on the catalysts and the degree of activity they bring out in a reaction. The work was published in the July 2, 2015, issue of ACS Catalysis and featured on the cover. Posted with permission from ACS Catalysis, July 2, 2015, 5(7). Copyright 2015 American Chemical Society.

Results: If you want to change a situation, it’s often best to get to the heart of the matter. For chemists, this often means delving into the active sites of catalysts, which speed the reactions behind billions of dollars worth of chemicals and other products. Active sites are where the reaction actually happens. If active sites work slowly or fail quickly, the result is higher costs and lower production rates. To make better active sites, scientists need to see the sites. For the first time, a team led by researchers at Pacific Northwest National Laboratory saw the active sites on a well-known vanadium-based catalyst.

In addition to the PNNL staff, the team included experts from Washington State University, the University of Alabama, and the Dalian Institute of Chemical Physics, Chinese Academy of Sciences.

Why It Matters: Fast. Stable. Efficient. These are the hallmarks of a good catalyst, one that can produce needed products without excessive costs or wastes. The results from this study could help researchers design such catalysts. How? By finding ways to create more active sites or protect existing sites from degrading during such reactions — or both.

Methods: In the experiments, the researchers dispersed or spread the vanadium oxide catalyst on a support of titanium dioxide to create a relatively large surface area with more reactive sites. They used a magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy technology at EMSL, the Department of Energy’s Environmental Molecular Sciences Laboratory, to obtain detailed information about the structures of active species as they exist on the titanium dioxide support.

“Using an ultra-high magnetic field with fast spinning enabled the team to observe five types of surface vanadium oxide structures that exist when supported on the surfaces of titanium dioxide,” said Dr. Jian Zhi Hu, a PNNL scientist and the team’s lead.

The scientists correlated the various peaks observed in the NMR spectra with the catalysts’ reactivity for an oxidation reaction that removes a hydrogen atom from methanol. Next, using computational methods, they predicted which peaks in the NMR spectra corresponded with the specific vanadium oxide geometries. In this way, the scientists determined which structures on the vanadium oxide surface do the best job of initiating and sustaining reactions.

See the full article here.

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From EMSL: “A new material for transparent electronics”

EMSL

August 17, 2015
No Writer Credit

Specialized crystalline films revealed to be highly conductive and transparent

Scanning transmission electron micrograph of a p-Sr0.12La0.88 CrO3/n-SrTiO3(001) heterojunction.

Results: The performance of solar cells, flat panel displays, and other electronics are limited by today’s materials. A new material, created by modifying a transparent insulating oxide, replacing up to 25 percent of the lanthanum ions in the host material with strontium ions, offers considerable promise. The new perovskite film, with the formula SrxLa1-xCrO3, (x up to 0.25), conducts electricity more effectively than the unmodified oxide and yet retains much of the transparency to visible light exhibited by the pure material.

Why It Matters: Materials that are both electrically conductive and optically transparent are needed for more efficient solar cells, light detectors, and several kinds of electronic devices that are by nature transparent to visible light. Of particular importance are new materials that conduct electricity by using missing electrons, otherwise known as “holes.” The new perovskite film falls into this category.

Methods: The development of high-performance transparent conducting oxides (TCOs) is critical to many technologies ranging from flat panel displays to solar cells. Although electron conducting (n-type) TCOs are presently in use in many devices, their hole-conducting (p-type) counterparts have not been commercialized as candidate materials because they exhibit much lower conductivities. Scientists at Pacific Northwest National Laboratory along with collaborators at Binghamton University and the Paul Drude Institute in Berlin show that La1-xSrxCrO3 (LSCO) is a new p-type TCO with considerable potential. The researchers demonstrate that crystalline LSCO films deposited on SrTiO3(001) by molecular beam epitaxy show figures of merit which are highly competitive with best p-type TCOs reported to date, and yet are more stable and structurally compatible with the workhorse materials of oxide electronics, as seen in the image. Being structurally and chemically compatible with other perovskite oxides, perovksite LSCO offers considerable promise in the design of all-perovskite oxide electronics.

See the full article here.

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Welcome to EMSL. EMSL is a national scientific user facility that is funded and sponsored by DOE’s Office of Biological & Environmental Research. As a user facility, our scientific capabilities – people, instruments and facilities – are available for use by the global research community. We support BER’s mission to provide innovative solutions to the nation’s environmental and energy production challenges in areas such as atmospheric aerosols, feedstocks, global carbon cycling, biogeochemistry, subsurface science and energy materials.

A deep understanding of molecular-level processes is critical to gaining a predictive, systems-level understanding of the impacts of aerosols and terrestrial systems on climate change; making clean, affordable, abundant energy; and cleaning up our legacy wastes. Visit our Science page to learn how EMSL leads in these areas, through our Science Themes.

Team’s in Our DNA. We approach science differently than many institutions. We believe in – and have proven – the value of drawing together members of the scientific community and assembling the people, resources and facilities to solve problems. It’s in our DNA, since our founder Dr. Wiley’s initial call to create a user facility that would facilitate “synergism between the physical, mathematical, and life sciences.” We integrate experts across disciplines; experiment with theory; and our user program proposal calls with other user facilities.

We proudly provide an enriched, customized experience that allows users to connect with our people and capabilities in an environment where we focus on solving problems. We collaborate with researchers from academia, government labs and industry, and from nearly all 50 states and from other countries.

From U Washington: “Crystals form through a variety of paths, with implications for biological, materials and environmental research”

University of Washington

August 3, 2015
News and Information

Crystals play an important role in the formation of substances from skeletons and shells to soils and semiconductor materials. But many aspects of their formation are shrouded in mystery. Scientists have long worked to understand how crystals grow into complex shapes. Now, an international group of researchers has shown how nature uses a variety of pathways to grow crystals beyond the classical, one-piece-at-a-time route.

“Because crystallization is a ubiquitous phenomenon across a wide range of scientific disciplines, a shift in the picture of how this process occurs has far-reaching consequences,” said James De Yoreo, a materials scientist and physicist at the Department of Energy’s Pacific Northwest National Laboratory and affiliate UW professor of chemistry and materials science and engineering.

These conclusions, published July 31 in Science with De Yoreo as lead author, have implications for decades-old questions in crystal formation, such as how animals and plants form minerals into shapes that have no relation to their original crystal symmetry or why some contaminants are so difficult to remove from stream sediments and groundwater.

An artist’s rendition of the early crystallization process of calcium carbonate. Adam F. Wallace/University of Delaware/David J. Carey

Their findings crystalized during discussions among 15 scientists from diverse fields such as geochemistry, physics, biology and the earth and materials sciences. At their home institutions, these researchers conduct experiments, investigate animal skeletons, study soils and streams or use computer simulations to visualize how particles can form and attach. They met for a three-day workshop in Berkeley, California, that was sponsored by the Council on Geosciences from the Department of Energy’s Office of Basic Energy Sciences.

“Researchers across all disciplines have made observations of skeletons and laboratory-grown crystals that cannot be explained by traditional theories,” said senior author Patricia Dove, a professor of geosciences at Virginia Tech. “We show how these crystals can be built up into complex structures by attaching particles — as nanocrystals, clusters, or droplets — that become organized into complex shapes. Many scientists have contributed to identifying these particles and pathways to becoming a crystal — our challenge was to put together a framework to understand them.”

In animal and laboratory systems alike, the crystal formation process begins by constructing their constituent particles. These can be small molecules, clusters, droplets or nanocrystals. These particles are unstable and begin to combine with each other, nearby crystals and other surfaces. For example, nanocrystals prefer to orient themselves along the same direction as a larger crystal before attaching, much like adding Legos. In contrast, amorphous conglomerates can simply aggregate. Their atoms later become organized by “doing the wave” through the mass to rearrange into a single crystal.

“Because we largely show a community consensus on this topic, the study has the potential to define the directions of future research on crystallization,” said De Yoreo.

Aragonite crystals forming on calcium carbonate.Pacific Northwest National Laboratory/James De Yoreo

The authors say much work remains to understand the forces that cause these particles to move and combine. It is one of the driving forces behind new research.

“Particle pathways are tricky because they can form what appear to be crystals with the traditional faceted surfaces or they can have completely unexpected shapes and chemical compositions,” said Dove. “Our group synthesized the evidence to show these pathways to growing a crystal become possible because of interplays between of thermodynamic and kinetic factors.”

The implications of these discussions span diverse scientific fields. By understanding how animals form crystals into working structures such as shells, teeth and bones, scientists will have a bigger and better toolbox to interpret crystals formed in nature. These insights may also help design novel materials and explain unusual mineral patterns in rocks. In addition, knowledge of how pollutants are transported or trapped in the minerals of sediments has implications for environmental management of water and soil.

“How we think about the ways to crystallization impacts how we interpret natural crystallization processes in geochemical and biological environments, as well as how we design and control synthetic crystal growth processes,” said De Yoreo. “I was surprised at how widespread a phenomenon particle-mediated crystallization is and how easily one can create a unified picture that captures its many styles.”

The work was supported by the Council on Geosciences of the U.S. Department of Energy’s office of Science. All co-authors and their affiliations are listed on the paper.

See the full article here.

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From PNNL: “Playing ‘tag’ with pollution lets scientists see who’s It”

PNNL Lab

July 29, 2015
Mary Beckman

Snow and ice from the Tibetan Plateau and Himalayan range (upper left), an important source of water for many people, can be seen feeding rivers that flow down through India. Image courtesy of Jacques Descloitres, NASA

Using a climate model that can tag sources of soot from different global regions and can track where it lands on the Tibetan Plateau, researchers have determined which areas around the plateau contribute the most soot — and where. The model can also suggest the most effective way to reduce soot on the plateau, easing the amount of warming the region undergoes.

The work, which appeared in Atmospheric Chemistry and Physics in June, shows that soot pollution on and above the Himalayan-Tibetan Plateau area warms the region enough to contribute to earlier snowmelt and shrinking glaciers. A major source of water, such changes could affect the people living there. The study might help policy makers target pollution reduction efforts by pinpointing the sources that make the biggest difference when cut.

“If we really want to address the issue of soot on the Tibetan Plateau,” said Yun Qian, a study co-author at the Department of Energy’s Pacific Northwest National Laboratory, “we need to know where we should start.”

Overall, the work shows that, of worldwide sources, India’s wildfires, cooking fuel and fossil fuel burning contribute the most soot to the mountain range and plateau region, followed by fossil fuel burning in China and other East Asian countries.

However, the work also zooms in on regions of the plateau. In this close up, India contributes the greatest amount of soot to the most regions, especially the Himalayas and the central Plateau. China contributes the most soot to the northeast Plateau. Finally, sources in central Asia, the Middle East and Tibet are only important to the northwest Plateau.

The researchers identified where the soot went and also determined how much warming it caused there. In addition to confirming previous work that soot causes net warming over the entire Himalayan-Tibetan Plateau region, one area stood out. Soot increased the amount of warming on the snowy northwest Plateau in the spring by more than 10 times the annual average of the entire plateau.

“Soot on snow in the northwest plateau causes more warming than all other sources in the area,” said corresponding author Hailong Wang, an atmospheric scientist at PNNL. “It’s bigger than the effect of greenhouse gases and soot in the atmosphere. The strong heating caused by soot on snow and in the atmosphere can change air circulation over the Plateau, leading to a broader impact on climate.”

Third pole

Often called the Third Pole due to how much ice and snow accumulates there, the Himalayas and Tibetan Plateau are the source of major rivers in nearby countries and changes to them can affect the largest populations in China and India. The mass of frozen water also contributes to the global climate, which is changing as Earth’s temperature rises.

Although earlier work showed soot’s warming effect over the whole region, the researchers wanted to pinpoint what kind of sources contribute. The team looked specifically at fossil fuel sources, biofuel and biomass sources of soot. For example, people in the surrounding countries use much wood, grass and agricultural wastes to cook with, which the team categorized as biofuel.

To track the soot, the team developed a new way to tag the soot particles emitted from individual sources within a climate model. The method had advantages over other source-attribution methods, which either don’t completely isolate contributions from particular sources or require running the model many times to turn the sources off and on one at a time.

Essentially, the team “dyed” 16 sources of soot in a well-known climate model called the Community Atmosphere Model version 5, also known as CAM5. After running the model, the team compared the model’s results to actual soot data taken from seven sites in the Tibetan Plateau/Himalayan region and to satellite data of snow cover to see how well it represented soot and snowfall. The model performed well, and taking into consideration the strengths and weaknesses of the model, the team focused on the soot.

While the soot tracker showed where the soot fell or where it hovered in the air above ground, the tracker also showed the path the soot took to its ending position.

“We got a vertical and horizontal view of the pathways,” said Wang. “Not only where the soot came from, but also how the air moves it, and how much got removed on its path.”

Soot scooting boogie

By zooming in on the plateau, the scientists got a great bit of detail, more than would have shown up on a global map. In the close up, the majority of soot that arrives in the Himalayas and the central Plateau comes from biofuel and fossil fuel burning in India; soot arriving in the northeast Plateau in all seasons and the southeast Plateau in the summer come from fossil fuel and biomass burning in China. In the northwest Plateau, emissions from central Asia and the Middle East also contribute significantly.

Running the computer model in this way not only showed which source sent the most soot over, but also can determine which source would make the biggest impact if emissions are cut. The soot destination that changed the most was the northwest Plateau by cuts in central Asia’s fossil fuel burning. Cuts in South Asia can effectively reduce the soot level on the entire plateau, especially in the Himalayas.

“The model can be used to test how efficient it would be to cut any particular amount of worldwide emissions,” said Wang. “For example, if we wanted to cut global emissions by an eighth, our results can tell us where to cut from to make the biggest reduction on the Tibetan Plateau.”

The authors suggest this type of research could be helpful to policymakers interested in reducing the effects of climate change at the Third Pole.

This work was supported by the Department of Energy’s Office of Science, China Scholarship Fund, National Basic Research Program of China. Computing experiments used DOE’s Lawrence Berkeley National Laboratory’s NERSC computing resources, a DOE Office of Science user facility.

See the full article here.

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From PNNL: “Power grid forecasting tool reduces costly errors”

PNNL Lab

July 29, 2015
Dawn Zimmerman

PNNL’s Power Grid Integrator has demonstrated up to a 50 percent improvement in forecasting future electricity needs over several commonly used tools. Project lead Luke Gosink, right, consults on the use of the new tool, which could save millions in wasted electricity costs.

Accurately forecasting future electricity needs is tricky, with sudden weather changes and other variables impacting projections minute by minute. Errors can have grave repercussions, from blackouts to high market costs. Now, a new forecasting tool that delivers up to a 50 percent increase in accuracy and the potential to save millions in wasted energy costs has been developed by researchers at the Department of Energy’s Pacific Northwest National Laboratory.

Performance of the tool, called the Power Model Integrator, was tested against five commonly used forecasting models processing a year’s worth of historical power system data.

“For forecasts one-to-four hours out, we saw a 30-55 percent reduction in errors,” said Luke Gosink, a staff scientist and project lead at PNNL. “It was with longer-term forecasts — the most difficult to accurately make — where we found the tool actually performed best.”

The advancement is featured this week as a best conference paper in the power system modeling and simulation session at the IEEE Power & Energy Society general meeting in Denver.

A delicate balancing act

Fluctuations in energy demand throughout the day, season and year along with weather events and increased use of intermittent renewable energy from the sun and wind all contribute to forecasting errors. Miscalculations can be costly, put stress on power generators and lead to instabilities in the power system.

Grid coordinators have the daily challenge of forecasting the need for and scheduling exchanges of power to and from a number of neighboring entities. The sum of these future transactions, called the net interchange schedule, is submitted and committed to in advance. Accurate forecasting of the schedule is critical not only to grid stability, but a power purchaser’s bottom line.

“Imagine the complexity for coordinators at regional transmission organizations who must accurately predict electricity needs for multiple entities across several states,” Gosink noted. “Our aim was to put better tools in their hands.”

Five heads better than one

Currently, forecasters rely on a combination of personal experience, historical data and often a preferred forecasting model. Each model tends to excel at capturing certain grid behavior characteristics, but not necessarily the whole picture. To address this gap, PNNL researchers theorized that they could develop a method to guide the selection of an ensemble of models with the ideal, collective set of attributes in response to what was occurring on the grid at any given moment.

First, the team developed a statistical framework capable of guiding an iterative process to assemble, design, evaluate and optimize a collection of forecasting models. Researchers then used this patent-pending framework to evaluate and fine tune a set of five forecasting methods that together delivered optimal results.

The resulting Power Model Integrator tool has the ability to adaptively combine the strengths of different forecasting models continuously and in real time to address a variety scenarios that impact electricity use, from peak periods during the day to seasonal swings. To do this, the tool accesses short- and long-term trends on the grid as well as the historical forecasting performance of the individual and combined models. Minute by minute, the system adapts to and accounts for this information to form the best aggregated forecast possible at any given time.

“During these forecasting tasks, we noted that an ensemble of models, even those considered moderate performers, would routinely outperform individual, high-performing models,” Gosink said.

Researchers used PNNL’s Institutional Computing resources to develop and validate the tool, making it possible to process a year’s worth of historical grid data within a few days. High-performance computing also made it possible to evaluate the tool’s performance across multiple forecasting periods, ranging from 15, 30 and 60 minutes up to four hours. However, the tool also runs on standard computer workstations commonly used by the electric industry.

Flexibility in application

“The underlying framework is very adaptable, so we envision using it to create other forecasting tools for electric industry use,” Gosink said. “We also are exploring other applications, from the prediction of chemical properties studied in computational chemistry applications to the identification of particles for high-energy physics experiments.”

Initial development of the Power Model Integrator was funded by PNNL’s Future Power Grid Initiative and GridOPTICS.

See the full article here.

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From PNNL: “Tiny grains of rice hold big promise for greenhouse gas reductions, bioenergy”

PNNL Lab

July 28, 2015
Dawn Zimmerman

Rice serves as the staple food for more than half of the world’s population, but it’s also the one of the largest manmade sources of atmospheric methane, a potent greenhouse gas. Now, with the addition of a single gene, rice can be cultivated to emit virtually no methane from its paddies during growth. It also packs much more of the plant’s desired properties, such as starch for a richer food source and biomass for energy production, according to a study in Nature.

In addition to a near elimination of greenhouse gases associated with its growth, SUSIBA2 rice produces substantially more grains for a richer food source. The new strain is shown here (right) compared to the study’s control.
Image courtesy of Swedish University of Agricultural Sciences

With their warm, waterlogged soils, rice paddies contribute up to 17 percent of global methane emissions, the equivalent of about 100 million tons each year. While this represents a much smaller percentage of overall greenhouse gases than carbon dioxide, methane is about 20 times more effective at trapping heat. SUSIBA2 rice, as the new strain is dubbed, is the first high-starch, low-methane rice that could offer a significant and sustainable solution.

Researchers created SUSIBA2 rice by introducing a single gene from barley into common rice, resulting in a plant that can better feed its grains, stems and leaves while starving off methane-producing microbes in the soil.

The results, which appear in the July 30 print edition of Nature and online, represent a culmination of more than a decade of work by researchers in three countries, including Christer Jansson, director of plant sciences at the Department of Energy’s Pacific Northwest National Laboratory and EMSL, DOE’s Environmental Molecular Sciences Laboratory. Jansson and colleagues hypothesized the concept while at the Swedish University of Agricultural Sciences and carried out ongoing studies at the university and with colleagues at China’s Fujian Academy of Agricultural Sciences and Hunan Agricultural University.

“The need to increase starch content and lower methane emissions from rice production is widely recognized, but the ability to do both simultaneously has eluded researchers,” Jansson said. “As the world’s population grows, so will rice production. And as the Earth warms, so will rice paddies, resulting in even more methane emissions. It’s an issue that must be addressed.”
Channeling carbon

During photosynthesis, carbon dioxide is absorbed and converts to sugars to feed or be stored in various parts of the plant. Researchers have long sought to better understand and control this process to coax out desired characteristics of the plant. Funneling more carbon to the seeds in rice results in a plumper, starchier grain. Similarly, carbon and resulting sugars channeled to stems and leaves increases their mass and creates more plant biomass, a bioenergy feedstock.

In early work in Sweden, Jansson and his team investigated how distribution of sugars in plants could be controlled by a special protein called a transcription factor, which binds to certain genes and turns them on or off.

“By controlling where the transcription factor is produced, we can then dictate where in a plant the carbon — and resulting sugars — accumulate,” Jansson said.

To narrow down the mass of gene contenders, the team started with grains of barley that were high in starch, then identified genes within that were highly active. The activity of each gene then was analyzed in an attempt to find the specific transcription factor responsible for regulating the conversion of sugar to starch in the above-ground portions of the plant, primarily the grains.

The master plan

Upon discovery of the transcription factor SUSIBA2, for SUgar SIgnaling in BArley 2, further investigation revealed it was a type known as a master regulator. Master regulators control several genes and processes in metabolic or regulatory pathways. As such, SUSIBA2 had the ability to direct the majority of carbon to the grains and leaves, and essentially cut off the supply to the roots and soil where certain microbes consume and convert it to methane.

Researchers introduced SUSIBA2 into a common variety of rice and tested its performance against a non-modified version of the same strain. Over three years of field studies in China, researchers consistently demonstrated that SUSIBA2 delivered increased crop yields and a near elimination of methane emissions.

Next steps

Jansson will continue his work with SUSIBA2 this fall to further investigate the mechanisms involved with the allocation of carbon using mass spectrometry and imaging capabilities at EMSL. Jansson and collaborators also want to analyze how roots and microbial communities interact to gain a more holistic understanding of any impacts a decrease in methane-producing bacteria may have.

Funding for this research was provided by The Swedish University of Agricultural Sciences, the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, the National Natural Science Foundation of China and the Carl Tryggers Foundation.

See the full article here.

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From R&D: “How clouds get their brightness”

07/20/2015
Mary Beckman, PNNL

The Southern Ocean’s clouds can cool the Earth by reflecting sunlight that would otherwise be absorbed by the darker ocean below. Phytoplankton help with that. Image: NASA

How clouds form and how they help set the temperature of the earth are two of the big remaining questions in climate research. Now, a study of clouds over the world’s remotest ocean shows that ocean life is responsible for up to half the cloud droplets that pop in and out of existence during summer.

The study, which appears online in Science Advances, combines computer modeling with satellite data over the Southern Ocean, the vast sea surrounding Antarctica. It reveals how tiny natural particles given off by marine organisms—airborne droplets and solid particles called aerosols—nearly double cloud droplet numbers in the summer, which boosts the amount of sunlight reflected back to space. And for the first time, this study estimates how much solar energy that equates to over the whole Southern Ocean.

“It is a strong effect,” said climate scientist Susannah Burrows at the Dept. of Energy’s Pacific Northwest National Laboratory. “But it makes sense because most of the area down there is ocean, with strong winds that kick up a lot of spray and lots of marine microorganisms producing these particles. And continental aerosol sources are mostly so far away that they only have a limited impact. Really the marine aerosols are running the show there.”

Burrows and co-author Daniel McCoy at the Univ. of Washington worked with other colleagues from the Univ. of Leeds, Los Alamos National Laboratory, UW and PNNL to explore the atmospheric show-runners.

Ocean born

Although the Southern Ocean’s borders have yet to be settled on by the International Hydrographic Organization, it comprises the southernmost parts of the Atlantic, Pacific and Indian Oceans, and is one of the cloudiest places on Earth. Important to the Southern Hemisphere’s atmospheric and oceanic circulation, Southern Ocean clouds might also help determine how sensitive Earth is to the accumulation of greenhouse gases in its atmosphere.

But to understand that climate sensitivity, scientists need to improve their understanding of how tiny aerosol particles brighten clouds by serving as seeds for cloud droplets. Over land, aerosols arise from vegetative matter, pollution, and dust. Sea spray shoots sea salt—a large source of ocean aerosols—into the atmosphere, but marine organisms also produce aerosols, most of which evaporate into the air.

But studying marine aerosols has been hard because they get overpowered by man-made pollutants in measurements near coastlines. Even so, studying marine aerosols in the Southern Ocean has been difficult as well. Satellites can’t tell different kinds of aerosols apart, and past satellite measurements of cloud droplets in regions near the poles had seasonal issues.

Aerosols have their own issues. Sea salt is one aerosol, and the ocean harbors marine organisms called phytoplankton that ultimately yield two more kinds of aerosols important to cloud formation—sulfates and organic matter aerosols. Previous studies, however, only examined how cloud droplet numbers correlated with chlorophyll—an easy-to-measure molecule involved in photosynthesis that gives plants their green color—as a proxy for marine life and were unable to nail down the individual roles of actual aerosols.

To flesh out the role of different aerosols, Burrows and colleagues used computer models to simulate both organic matter and sulfates, as well as sea salt. In addition, Burrows, McCoy and colleagues turned to a new set of satellite [? what satellite] measurements of cloud droplets. The data set fixes the seasonal issues with the Southern Ocean and covers the latitudes between 35 degrees south and 55 degrees south.

“Satellite data allows us to observe events that occur over the course of months and on a scale of thousands of kilometers in the remotest regions on the planet,” said UW’s McCoy. “It really gives us an unparalleled glimpse of the Earth System’s complexity.”

Summer fun

The team gathered simulated data of the three aerosols separately, taking sulfates and sea salt concentrations from a suite of computer models called AeroCom. The organic matter aerosols were trickier, and they used a computer model that simulated the presence of organic matter within sea spray, rather than the aerosols themselves.

Comparing the concentrations of all three ocean-derived components with satellite measurements of cloud droplets allowed the researchers to write a new mathematical equation of how the sulfates and organic matter related to cloud droplet concentrations. Plugging simulated aerosol data into their new model, the researchers found it recreated the actual cloud droplet data well.

An analysis of this model suggested that sea salt was the biggest source of aerosols in the ocean, contributing the most aerosols around which cloud droplets formed. And it was also the most uniform, contributing about the same number all year round.

The organic matter and sulfate aerosols, however, yielded more cloud droplets over summer than winter, as expected since the ocean receives more sunlight for organisms to grow in the summer. The sulfates, in addition, had a bigger effect than organic matter.

“The return of light in the summer ignites an amazing flurry of activity in phytoplankton communities across the Southern Ocean. This seasonality leads to an enhancement in cloud brightness when it will be able to reflect the most sunlight,” said UW’s McCoy.

Lastly, the scientists also found that sulfates and organic matter work to some extent independently of each other to increase the concentration of cloud droplets.

Overall, the aerosols given off by marine organisms almost doubled the cloud droplet concentration during the summer. This in turn increased the amount of sunlight reflected back into space by about 4 watts per square meter over the course of the year. Understanding the amount of energy that clouds over the Southern Ocean reflect might help researchers assess how well climate models are able to capture the effects of these marine particles on clouds.

“Phytoplankton in the oceans are a really important source for cloud-droplet-forming aerosols in remote marine air, and we can see the effect they have on clouds is big,” said Burrows. “Southern Ocean clouds play a large role in the global climate, and hopefully this will help us get a better sense of how sensitive the Earth is to greenhouse gases.”

Because it’s harder to see the effects of marine aerosols in other parts of the world, the researchers will be able to use what they’ve learned about the mechanism and strength of the aerosol interactions with clouds to apply to studies in other regions.

See the full article here.

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From PNNL: “Duets by Molecules and Plasmons”

PNNL Lab

January 2015

Scientists examine the information content in nanoscale chemical images

Physical Sciences Division
Research Highlights

January 2015

Frequency resolved TERS images of the laser-irradiated region, reconstructed using four different Raman-allowed vibrations of DMS. The representative images are obtained from the same pass of the AFM probe through the laser-illuminated region of the substrate. Namely, this is the same image, reconstructed at four different energies. The 2D contours have a color bar starting at white (brightest signals), passing through yellow to black (lowest signals). Copyright 2014: American Chemical Society. Enlarge/expand Image.

Results: Light waves trapped on a metal’s surface can interrogate the nearby molecules about their chemical identity through the molecule’s characteristic vibrations, which act as fingerprints. Scientists at Pacific Northwest National Laboratory (PNNL) “saw” the interaction between the molecules and the trapped light waves or surface plasmons. Their fundamental endeavor could lead to breakthroughs in interpreting ultrasensitive chemical images for characterizing new materials with potential uses in catalysis and energy conversion.

The article is featured in the American Chemical Society (ACS) Editors’ Choice collection. The decision was made by the journal editors, who select one article a day from across the 55 ACS journals to appear in this special collection. As such, it was made freely available to the public. The article was the editors’ choice for November 12, 2014.

Why It Matters: To detect only a few molecules, researchers using ultrasensitive spectroscopic and microscopic techniques rely on localized surface plasmons. This is particularly the case when the molecular identity must be determined. These plasmons are essentially light waves trapped at the surface of nanoscale noble metal structures. In surface plasmon-enhanced vibrational spectroscopy, the recorded optical signals result from the interaction between molecular and plasmonic states. This was revealed by PNNL scientists, who set out to understand the information content encoded in nanoscale chemical images, recorded by taking advantage of the unique properties of localized surface plasmons. They found that each pixel in their recorded images reports on the distinct local environments in which each probed molecule resides.

“This is really fundamental science that takes us a step closer to understanding what one actually measures with this type of spectroscopy,” said Dr. Patrick El-Khoury, a PNNL chemical physicist who carried out the measurements.

User Facility: EMSL

Research Team: Patrick Z. El-Khoury, Dehong Hu, and Wayne P. Hess, Pacific Northwest National Laboratory; Tyler W. Ueltschi and Amanda L. Mifflin, University of Puget Sound

See the full article here.

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From PNNL: “How ionic: Scaffolding is in charge of calcium carbonate crystals”

PNNL Lab

January 26, 2015
Mary Beckman

Using a powerful microscope that lets researchers see the formation of crystals in real time, a team led by the Department of Energy’s Pacific Northwest National Laboratory found that negatively charged molecules — such as carbohydrates found in the shells of mollusks — control where, when, and how calcium carbonate forms.

These large macromolecules do so by directing where calcium ions bind in the scaffold. The negative charge on the macromolecules attract the positively charged calcium ions, placing them in the scaffold through so-called ion binding. Rather than these chemical interactions, researchers had previously thought the scaffold guides crystallization by providing the best energetic environment for the crystal.

Watch crystals grow

Illustration of a polypeptide macromolecule

“This whole story is different from what we had believed to be the case,” said lead researcher Jim De Yoreo at PNNL. “Ion binding defines a completely different mechanism for controlling crystallization than does making a perfect interface between the crystal and the scaffold. And it is one that should provide us with considerable control.”

Large charged molecules form a scaffold (red) that draw in calcium ions (blue) that guide carbonate (red and yellow) to form ACC (white spheres). No image credit.

Missing Piece

Previous work showed that calcium carbonate takes multiple routes to becoming a mineral. All of the common crystal forms, including calcite (found in limestone), aragonite (found in mother-of-pearl), and vaterite (found in gallstones), crystallized from solution, often at the same time. But in some cases, droplet-like particles of uncrystallized material known as amorphous calcium carbonate, or ACC, formed first and then transformed into either aragonite or vaterite.

Those experiments, however, lacked a crucial element found in the biological world, where minerals form within an organic scaffold. For example, pearls develop in the presence of negatively charged carbohydrates and proteins from the oyster.

In addition, biologically built minerals often start out as ACC. De Yoreo and his colleagues wondered what role macromolecules — carbs, proteins or other large molecules with a negative charge — play.

To find out, De Yoreo and team allowed calcium carbonate to mineralize under a specialized transmission electron microscope at the Molecular Foundry, a DOE Office of Science User Facility at DOE’s Lawrence Berkeley National Laboratory. Collaborators also hailed from Eindhoven University of Technology in The Netherlands.

But this time they added a negatively charged macromolecule, a polymer called polystyrene sulfonate. Without the polymer, they saw crystals of vaterite and a little calcite forming randomly under the microscope. With the polymer, however, ACC always appeared first and vaterite formed much later.

Because the polymer interfered with vaterite formation, the team looked a little closer at what the polymer was doing. When they mixed the polymer with the calcium first before introducing carbonate, they found globules of the polymer forming in the solution. They determined that the polymer had soaked up more than half of the calcium to form the globules.

When the researchers then added carbonate to the experimental chamber, ACC formed instead and it only appeared within these globules. The ACC grew in size until the supply of calcium ran out. The researchers concluded that calcium binding to the polymer is the key to forming the ACC and controlling where it forms.

Mineral Motivation

The team realized that controlling crystallization by attracting calcium ions to the macromolecules was not the way researchers had long thought it happened.

There are two main ways that calcium carbonate molecules might be persuaded to come together to form a mineral. One is by providing an environment where the atoms assemble in the crystal in the least energetic way possible, sort of like organizing a classroom full of schoolchildren by having them sit in seats arranged neatly in rows side-by-side in the corner of the room.

Another is via chemical binding — negatively or positively charged atoms or molecules called ions attract one another, sort of like waving popsicles in front of those kids to gather them in one spot.

Researchers had long suspected that organic scaffolds caused calcium carbonate to mineralize and find its most stable form, calcite, by creating low energy surfaces where the ions could easily arrange themselves in rows side-by-side. In fact, scientists had seen this previously with highly organized films of organic molecules.

But in this study, the polymer, like the popsicle, pulls in the calcium before minerals can form and turns it into ACC. This showed the researchers that ion binding can completely overwhelm any lower-energy advantage that crystallization on or outside of the polymer might confer.

“This is definitely another means of controlling nucleation,” said De Yoreo. “Carbonate ions follow the calcium into the globules. They don’t crystallize outside the globules because there’s not enough calcium there to make a mineral. It’s like bank robbers out for a heist. They go where the money is.”

“This work opens new avenues for the investigation of biomineralization. Can we extend these experiments beyond the simple polymers we used here? To what extent can we rebuild parts of the biological machinery inside the microscope?” said co-author Prof. Nico Sommerdijk of Eindhoven University of Technology. “Answering these questions may eventually allow us to understand the biological mineral formation and apply its principles to design green, sustainable routes for the production of advanced materials.”

This work was supported by the U.S. Department of Energy Office of Science and the Dutch Science Foundation.

See the full article here.

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