Following the people and events that make up the research community at Duke

Category: Environment/Sustainability Page 1 of 11

Saving Africa’s Biggest Trees to Help Earth Breathe

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Like wine, cheese, and savvy financial investments, many tropical trees become more valuable with age. This is particularly true when it comes to carbon storage, because old trees are often the biggest trees and the larger the tree, the more carbon it stores.

The value of big, old trees in combating climate change was underscored in a recent study of Gabon’s forests, led by the Nicholas School of the Environment’s John Poulsen. The team’s striking finding — that half of Gabon’s wealth of carbon is found in the largest 5% of trees — has implications that reach far beyond the sparsely populated Central African country’s borders.

Nicholas School Ph.D. student Graden Froese admires a forest giant in Ivindo National Park, Gabon.

Tropical forests play a key role in the global carbon cycle by keeping carbon out of the atmosphere. Trees take in CO2 — one of the infamous, heat-trapping greenhouse gases — during photosynthesis and use the carbon to grow, making new leaves, thicker and taller trunks, and more expansive root systems.

Scientists can estimate how much carbon a tree holds by measuring its trunk. So, like rainforest tailors, trained technicians traveled to all corners of the country to measure the girth and height of tens of thousands of trees.

This extraordinary two-year long effort was one of the first nationwide forest inventories in the tropics, making Gabon a leader in comprehensive forest monitoring.

John Poulsen is an associate professor of tropical ecology.

Poulsen and collaborators used the tree measurements to estimate the amount of carbon stored in Gabon’s forests and to determine why some forests hold more carbon than others.

“The field techs deserve all the credit”, Poulsen explained, “as they often walked for days through thick forest, traversing swamps and enduring humid, buggy conditions to measure trees. We turned their sweat and toil into information that could be used by Gabon’s government to prioritize areas for conservation.”

Who needs ladders, when you have colleagues? The field team collaborates to measure a forest giant.

The team analyzed a suite of environmental factors to see their effects on carbon storage. Of the natural factors, only soil fertility had a noticeable positive effect on tree biomass. Much more important was the impact of humans. As human activities such as agriculture and logging tend to target large trees, more heavily human-disturbed forests had a much different structure than pristine forests. The farther a study area was from human settlements, the more likely it was to host large trees and consequently, higher amounts of carbon.

The paper notes that Gabon stands out as a country with “one of the highest densities of aboveground forest carbon.” In fact, Gabon’s undisturbed forests store more carbon than those in the Amazon, which have been referred to as the lungs of the planet.

According to Poulsen, “Gabon is the second most forested country in the world with 87% forest cover, a deforestation rate near zero…” Because of its impressive forest cover and its location straddling the equator, Gabon’s forests host an incredibly diverse array of plants and animals, including many threatened and endangered species. Rural communities depend on these forests for their livelihoods.

Unfortunately, even Gabon’s ‘small’ trees make for spectacular felled logs.

However, Gabon’s impressive forests are valuable to more than just wildlife, climate researchers, and local communities. The logging industry also sees these forests as a chance for profit. More than half (about 67%) of Gabon’s forests are under contract with logging companies to harvest timber, putting them at risk of losing many of their carbon-storing giants.

Poulsen’s study highlights the importance of a more nuanced approach to forest conservation in Gabon. One that doesn’t simply focus on stopping deforestation or promoting restoration, as is prescribed in many international climate change plans, but an approach that recognizes the necessity of preserving high conservation value, old growth forests.

Anna Nordseth

Guest Post by Anna Nordseth, a graduate student in the Nicholas School of the Environment.

Following In The Footsteps of Elephants

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Imagine for a moment that you’re 6,000 pounds, living in one of the wildest places on Earth, with no schedule, nowhere to be. How do you decide where to spend your time? Where to go next? Do you move where food is most plentiful? Is water your main priority?

Amelia Meier in the field.

These are some of the questions addressed by Duke Ph.D. candidate Amelia Meier and former postdoctoral researcher Dr. Chris Beirne in Dr. John Poulsen’s lab. Their recent study published in Trends in Ecology and Evolution focused on the African forest elephant–the slightly smaller yet still undeniably huge cousin of the savanna elephant.  

The team wanted to know what influences certain aspects of elephant behavior. Specifically, how much climate and resource availability drives elephant movement and influences their diet. To do this, the team looked at fruit abundance (a high-energy staple of elephants’ diets), water availability from rainfall, and elephant identity and how those factors affect how an individual moves and eats.

One might think that such a massive animal is easy to spot in the forest. However, the dense vegetation of Central African rainforests can be an impenetrable wall, allowing the massive animals to move unseen through the forest, leaving broken branches and steaming dung piles in their wake.

To better track them, the researchers fitted individual elephants with GPS collars that turn an iPhone into an elephant-tracking tool. This also allowed trackers to follow the elephants at a distance and avoid conflict with the sometimes temperamental animals.

Collared elephant, Marijo, (left) enjoying the rich minerals found at the Langoue Bai forest clearing.

Meier, Beirne, and colleagues also wanted to know more about the diets of the tracked elephants to see if what they ate changed with how much fruit is available. This less-than-glamorous job was done by dissecting fresh dung piles, estimating the proportions of leafy and woody material, and counting the number of seeds in each one.

Tropical rainforests are lush, yet have patchy resources, making it important for many frugivores to have flexible diets. Some trees only produce fruit in the wet season. Others fruit every other year. To gauge fruit availability, the research team conducted “fruit-walks” at the beginning and end of each day of following an elephant, in which trackers counted all of the ripe fruit on the ground.

A key finding of the study was that the most important factor driving movement was an elephant’s individuality; some respond to food or water availability differently and some simply move around more than others.

Field researcher Marius Edang getting the straight poop on elephant diets.

Interestingly, elephants appear to be affected by resources differently depending on the timescale the authors looked at. Water was important on both a day-to-day and month-to-month basis. Yet on a daily basis, fruit and water were more equally matched, with water still maintaining a slight lead.

Fruit availability was also critical in determining how much elephants moved and what they ate. When there was more fruit available, the elephants ate more fruit, as evidenced by the proportion of seeds in dissected dung piles.

Aside from being an awe-inspiring species, forest elephants are important to the health of their native ecosystems. They are unwitting gardeners, planting seeds of the fruits they consume in piles of dung and giving those seeds a better chance of survival. That’s part of why understanding what motivates forest elephant movement is more than the satisfaction of an elephant enthusiast’s curiosity; it is critical to managing and conserving a species that is vulnerable to multiple threats from humans.

Meier’s dissertation research focuses on elephant social behavior and the effects of human disturbance on elephant social groups, allowing her to pursue her long-term interest in animal behavior with a practical conservation application.

“I was living in Congo and I knew I wanted to keep working in the region. There, you have elephants–this amazing, highly intelligent, social species that is surrounded by conflict.”

Poachers seek elephants for their ivory tusks, which are valuable on the black market. The pachyderms are also prone to conflict with humans when they start foraging in village plantations, destroying crops and damaging livelihoods.

The team’s findings open the way for new questions about why different elephants exhibit different patterns of movement. What underlying factors affect behavior, and why? Does it have to do with age? Sex? Their social environment?

These questions remain unanswered for now, but the work of Meier and colleagues represents a critical step in understanding elephant behavior to improve forest elephant management and conservation strategies.

Guest Post by Anna Nordseth, a Ph.D. Candidate in the Nicholas School of the Environment

Contaminated Drinking Water in Our Backyard

About 70% of the human body is made up of water. Water is something we consume on a daily basis. Therefore, when a community’s water source is threatened or contaminated it can be extremely detrimental. 

In 2017, it became apparent that there was water contamination in eastern North Carolina. Specifically, PFAS or per- and polyfluoroalkyl Alkyl chemicals were found in the water supply. As a result, several legislative mandates were issued in 2018 establishing a PFAS Testing Network to investigate the contamination.

Lee Ferguson, an Associate Professor of Civil and Environmental Engineering at Duke and Kathleen Gray, a professor at UNC’s Institute for the Environment, are testing PFAS water contamination and communicating any risks to the public. 

Gray is part of the network’s risk communication team. She explained that PFASs are hard to address because the health effects are unknown and they have yet to determine a standard or guideline for these substances. However, because this water contamination affects the lives of everyone connected to the water supply it is extremely important to communicate risk to the affected community but without eliciting panic. 

Gray explained that people often ask, “Are my family and I safe?” “What can I do to protect myself and my family?” “Why did this happen?” and “Why wasn’t it prevented?”

In the last year Ferguson and his research team have tested 409 sites in North Carolina for PFAS compounds.

He explained that PFAS substances are particularly dangerous because they are non-degradable, potentially toxic and constantly changing. Long-chain PFASs are being replaced by fluorinated alternatives.

Ferguson described this phenomenon as “playing environmental ‘whack-a-mole’ with different substances.”

Ferguson and his testing team have found two contaminated water supply sites in North Carolina. Dangerous contamination is based on the EPA health advisory level of 70ng/Liter. The exceedances were found in Maysville and Orange Water and Sewer Authority. Maysville was able to switch to the Jones County water source once the problem was identified.

New data that came in within the last couple weeks found high month-to-month variability in PFAS in the Haw River near Pittsboro. Ferguson and his team predict that it is coming downstream from a waste treatment plant. 

Brunswick County is shown having the worst PFAS concentrations. However, Dr. Ferguson and his team have recently found that the contamination in Haw River is even worse.

While all of this information may seem very alarming, Gray and Ferguson both reiterated that it is not necessary to panic. Instead, people should make sure they are drinking filtered water or invest in a water filter. 

Ferguson added, “The best choice is reverse osmosis.”

Gray and Ferguson presented their work at a SciComm Lunch-and-Learn, a monthly event sponsored by Duke Science & Society Initiative that explores interesting and innovative aspects of science communication. The event is free and open to anyone in the Duke community.

By Anna Gotskind

How Do You Engineer a Microbial Community?

This is the first of several posts written by students at the North Carolina School of Science and Math as part of an elective about science communication with Dean Amy Sheck.

Claudia Gunsch, the Theodore Kennedy distinguished associate professor in the department of civil and environmental engineering, wants to know how to engineer a microbial community. An environmental engineer with a fascination for the world at the micro level, Gunsch takes a unique approach to solving the problem of environmental pollution: She looks to what’s already been done by nature.

Claudia Gunsch, Ph.D.

Gunsch and her team seek to harness the power of microbes to create living communities capable of degrading contamination in the environment.

“How can you engineer that microbial community so the organisms that degrade the pollutant become enriched?” she asks. “Or — if you’re thinking about dangerous pathogenic organisms — how do you engineer the microbial community so that those organisms become depressed in that particular environment?”

The first step, Gunsch says, is to figure out who’s there. What microbes make up a community? How do these organisms function? Who is doing what? Which organisms are interchangeable? Which prefer to live with one another, and which prefer not living with one another?

“Once we can really start building that kind of framework,” she says, “we can start engineering it for our particular purposes.”

Yet identifying the members of a microbial community is far more difficult than it may seem. Shallow databases coupled with vast variations in microbial communities leave Gunsch and her team with quite a challenge. Gunsch, however, remains optimistic.

Map of U.S. Superfund Sites (2013)

“The exciting part is that we have all these technologies where we can sequence all these samples,” she says. “As we become more sophisticated and more people do this type of research, we keep feeding all of this data into these databases. Then we will have more information and one day, we’ll be able to go out and take that sample and know exactly who’s there.”

“Right now, it’s in its infancy,” she says with a smile. “But in the long-term, I have no doubt we will get there.”

Gunsch is currently working on Duke’s Superfund Research Center designing bioremediation technologies for the degradation of polycyclic aromatic hydrocarbon (PAH) contamination. These pollutants are extremely difficult to break down due to their tendency to stick strongly onto soil and sediments. Gunsch and her team are searching for the right microbial community to break these compounds down — all by taking advantage of the innate capabilities of these microorganisms.

A photo montage from Dr. Gunsch’s lab page.

Step one, Gunsch says, has already been completed. She and her team have identified several different organisms capable of degrading PAHs. The next step, she explains, is assembling the microbial communities — taking these organisms and getting them to work together, sometimes even across kingdoms of life. Teamwork at the micro level.

The subsequent challenge, then, is figuring out how these organisms will survive and thrive in the environment they’re placed in, and which microbial seeds will best degrade the contamination when placed in the environment. This technique is known as “precision bioremediation” — similar to precision medicine, it involves finding the right solution in the right amounts to be the most effective in a certain scenario.

“In this particular case, we’re trying to figure out what the right cocktail of microbes we can add to an environment that will lead to the end result that is desired — in this case, PAH degradation,” Gunsch says.

Ultimately, the aim is to reduce pollution and restore ecological health to contaminated environments. A lofty goal, but one within sight. Yet Gunsch sees applications beyond work in the environment — all work dealing with microbes, she says, has the potential to be impacted by this research.

“If we understand how these organisms work together,” she says, “then we can advance our understanding of human health microbiomes as well.”

Post by Emily Yang, NCSSM 2021

A Research Tour of Duke’s Largest Lab

“Lightning is like a dangerous animal that wants to go places. And you can’t stop it,” smiled Steve Cummer, Ph.D. as he gestured to the colorful image on the widescreen TV he’d set up outside his research trailer in an open field in Duke Forest.

Cummer, the William H. Younger Professor of electrical and computer engineering at Duke, is accustomed to lecturing in front of the students he teaches or his peers at conferences. But on this day, he was showing spectacular videos of lightning to curious members of the public who were given exclusive access to his research site on Eubanks Road in Chapel Hill, about 8 miles west of campus.

Steve Cummer shows a time-lapse video of lightning to the visitors on the annual Duke Forest Research Tour in the Blackwood Division of the Duke Forest.

More than two dozen members of the community had signed up for a tour of research projects in the Blackwood Division of Duke Forest (which recently expanded), a research-only area that is not normally open to the public. Cummer’s research site was the last stop of the afternoon research tour. The tour also covered native trees, moths and geological features of the Blackwood Division with biologist and ecologist Steve Hall, and air quality monitoring and remote sensing studies with John Walker and Dave Williams, from the U.S. Environmental Protection Agency.

The Hardwood Tower in the Blackwood Division is used for air quality monitoring and remote sensing studies. Researchers frequently climb the 138 foot tall tower to sample the air above the tree canopy.

Cummer’s research on lightning and sprites (electrical discharges associated with lightning that occur above thunderstorm clouds) sparked a lively question and answer session about everything from hurricanes to how to survive if you’re caught in a lightning storm. (Contrary to popular belief, crouching where you are is probably not the safest solution, he said. A car is a great hiding spot as long as you don’t touch anything made of metal.)

Cummer kept his tone fun and casual, like a live science television host, perched on the steps of his research trailer, referring to some of the scientific equipment spread out across the field as “salad bowls,” “pizza pans” and “lunar landers,” given their odd shapes. But the research he talked about was serious. Lightning is big business because it can cause billions of dollars in damage and insurance claims every year.

An ash tree (Fraxinus spp.) being examined by one of the visitors on the Duke Forest Research tour. Blackwood Division ash trees are showing signs of the highly destructive emerald ash borer invasion.

Surprisingly little is known about lightning, not even how it is first formed. “There are a shocking number of things,” he said, pausing to let his pun sink in, “that we really don’t understand about how lightning works. Starting with the very beginning, nobody knows exactly how it starts. Like, really the physics of that.”  But Cummer loves his research and has made some advances in this field (like devising more precise sensor systems), “When you’re the first person to understand something and you haven’t written about it yet or told anyone about it… that’s the best feeling.”

The Duke Forest hosted 49 research projects last year, which —with less than half of the projects reporting—represented over a million dollars of investment in Duke Forest-based work. 

“The Duke Forest is more than just a place to walk and to jog. It’s an outdoor classroom. It’s a living laboratory. It’s where faculty and teachers and students of all ages come to learn and explore,” explained Sara Childs, Duke Forest director.

The Duke Forest offers their research tour every year. Members of the public can sign up for the email newsletter to be notified about future events.

Post by Véronique Koch

Republican to RepublicEn: Climate Change for Conservatives

My mom’s calling—we talk every day. She asks me if I’ve eaten, and I complain about the usual: essays, exams, horrifying clumps of hair on the shower floor. 

Bob Inglis, former Congressman and speaker at the Change My Mind Symposium during Duke Energy Week.

I sit on the steps of the chapel, a warm yellow against a silent sky. Durham is chilly tonight. Cloudy, starless, I feel rain coming. My fingers — naked, against my phone and ear —fare worst, somewhere between cold and numb. They crave my pocket’s warmth, and I tell my mother goodbye.

“Wait, Mom, before I go, did you see the climate change report?”

And with a single sentence, cordial relations are over, and little things like “familial love” fall away. Constructed arguments become a battle of volume. Mom, if we don’t do anything, millions will die. But, Jeremy, she says, climate change is natural — and these summits, they’re PR moves, politicians don’t actually care. In the ring, it’s Me vs. Mother, Ali vs. Frazier, Democrat vs. Republican. An hour in, I’ve forgotten the cold — hell, I’m sweating in self-righteous anger.

These little spats parallel increasingly intense partisanship in the United States. Hot-button topics fuel the divide, with gun control, abortion rights, and impeachment splitting Democrats and Republicans along party lines. Particularly contentious is climate change. While 84% of Democrats “consider climate change a ‘major threat,’” only a fourth of Republicans feel the same. 

Enter Bob Inglis, former US Congressman and 1981 Duke alumnus. Inglis represented South Carolina’s 4th House district, one of the reddest regions in the nation. Initially, he wasn’t so hot on global warming himself. “For years, I was in Congress saying climate change was nonsense,” he says, laughing. “I didn’t know anything about it except that Al Gore was for it.

But what changed his mind?

“Inglis 2.0,” as he calls it, began with his son in 2004, who pushed him to adopt greener policies. Next was the increasing body of evidence that proved climate change undeniable. But it would take a spiritual awakening to transform Inglis’s views. On a snorkeling trip to the Great Barrier Reef, Inglis met oceanographer Scott Heron. The two were kindred spirits, and in Heron’s conservation work, Inglis saw a love for God. For Inglis, “Conservation became loving God and loving people,” he says.        

Inglis addresses free-enterprise solutions to climate change
(Source: Duke University Energy Initiative)

In 2009, he introduced the “Raise Wages, Cut Carbon Act” designed to curb global warming. Central to the bill was a carbon tax, which puts a price on carbon-based fuel use. Voter backlash was swift. “They were having a Tea Party— and I was specifically uninvited,” Inglis chuckles. In the 2010 election, he was soundly defeated in a primary race against Trey Gowdy, largely in response to the carbon tax. 

But Inglis didn’t stop there. In 2012, he founded republicEn, an organization that promotes free enterprise solutions to global warming. republicEn targets a right-wing audience—those most hesitant to accept global warming. 

The core of republicEn is its online community. Thousands of members convene in local events and write letters to Congress advocating a carbon tax solution. Dedicated spokespeople also tour the nation to promote the need for conservative leadership. Both benefit from republicEn’s media wing, which gives conservative voices a platform for climate change.

Inglis firmly believes that conservative solutions are key to fighting climate change. Citing the explosion of smartphones, he poses a question: would the cell phone industry have grown as rapidly had it been intensely regulated? He doubts it. Similarly, he sees free market solutions as the fastest way to slow global warming.

republicEn has no set timeline, no five-year plan. But Inglis is hopeful: “You weren’t there when we marched in Selma, but you can be there when we solve climate change.” 

Post by Jeremy Jacobs

Responding to the Climate Crisis Through Dance

Kimerer LaMothe began her talk in an unconventional way, by singing a song. As she reached the refrain she repeated the words “everybody dances” and invited the audience to join her. 

She then posed an intriguing question: How can dance be a response to the climate crisis? In the western world, dance is usually seen as a recreational activity and here LaMothe was asking how it could be used as a tool or even as the solution to one of the largest issues of our time. I was definitely a little skeptical. 

Image by Geoffry Gee

The talk was a part of Duke’s Ruby Fridays organized by the staff of Duke Arts and the Rubenstein Arts Center. LaMothe was invited to contribute to the series which features casual art talks with the intention of connecting art across a multitude of disciplines.

Her response to the climate crisis began with a discussion about the body. LaMothe explained that for three and a half billion years after the planet was formed, there were no complex bodies on the planet, just microbes. She said they developed multicellular bodies because they needed to move.

“We build our knowledge of the world through the bodily movements we make,” she said.

The idea is that a body’s ability to move and interact with the world around it is a form of dance. This is especially demonstrated by how human babies interact with their caregivers. Human babies, unlike many other animals, are extremely reliant on their caregivers and must find a way to communicate with them. Thus, they use movement to garner attention. They have an impulse to connect and use patterns of movement like a smile or a snuggle to make sure they are taken care of. What results is something like a dance.

LaMothe described it as, “A vital human expression of kinectivity.”

Using movement and dance as a way to connect or interact, however, is important to human life past infancy. Many different cultures around the world use dance as the primary ritual of their community.

One example LaMothe gave was the healing dance practiced by the Bushmen of the African Kalahari. They use dance to “stir energy” and understand any pain. As the dancing intensifies the energy grows. 

LaMothe explained that this allows them to “enter what they call first creation, a perception of reality where everything is changed and everything is changing.”

Through this, the healer can see the capacity of that pain to change and help the members release the pain. The idea is that to dance is to heal both themselves and the earth. 

Still, the question remains: How does dance heal the earth? The earth that is facing ecosystem collapse, species extinction, and overexploitation. The past five hundred years have exponentially brought us to the brink of the climate crisis. These are the same centuries that Europeans traveled around the world colonializing and overtaking native lands. One of the main ways colonists tried to make native people civilized was by stopping them from dancing.

LaMothe stated, “Native communities were told to stop dancing and instead make “progress towards civilization.”

In many places, it actually became a crime to dance. In fact, until 1932 it was against the law for native people to engage in ceremonial dances in the United States. Furthermore, in efforts to “civilize” people, a focus was placed on learning through reading and forsaking movement as a way to gain knowledge. This “civilized” culture also abandoned the awareness and respect native communities showed towards the environment around them. Dance not only allowed them to connect with each other but with the earth. This connection was reflected in the other parts of their life resulting in sustainable living and caring for the earth.

In LaMothe’s words, “dance can catalyze a sensory awareness of our own movement making.” 

An Image from LaMothe’s Presentation Featuring People Participating in
Climate Conscious Dance

She explained that through climate-conscious dance we can reconnect ourselves with the environment and help restore the earth.

One example she gave of how to do this is through events like Global Water Dances where people can participate in events all over the world to dance and raise consciousnesses about how to protect water.

In 2005 after teaching at both Brown and Harvard, LaMothe moved to a farm with her family so she could write and dance in an environment closer to nature. She has written six books, created several dance concerts and even a full-length musical titled “Happy If Happy When.” She spends her time writing, singing, dancing, and tending to the farm alongside her family.

Post by Anna Gotskind

These Microbes ‘Eat’ Electrons for Energy

The human body is populated by a greater number of microbes than its own cells. These microbes survive using metabolic pathways that vary drastically from humans’.

Arpita Bose’s research explores the metabolism of microorganisms.

Arpita Bose, PhD, of Washington University in St. Louis, is interested in understanding the metabolism of these ubiquitous microorganisms, and putting that knowledge to use to address the energy crisis and other applications.

Photoferrotrophic organisms use light and electrons from the environment as an energy source

One of the biggest research questions for her lab involves understanding photoferrotrophy, or using light and electrons from an external source for carbon fixation. Much of the source of energy humans consume comes from carbon fixation in phototrophic organisms like plants. Carbon fixation involves using energy from light to fuel the production of sugars that we then consume for energy.

Before Bose began her research, scientists had found that some microbes interact with electricity in their environments, even donating electrons to the environment. Bose hypothesized that the reverse could also be true and sought to show that some organisms can also accept electrons from metal oxides in their environments. Using a bacterial strain called Rhodopseudomonas palustris TIE-1 (TIE-1), Bose identified this process called extracellular electron uptake (EEU).

After showing that some microorganisms can take in electrons from their surroundings and identifying a collection of genes that code for this ability, Bose found that this ability was dependent on whether a light source was also present. Without the presence of light, these organisms lost 70% of their ability to take in electrons.   

Because the organisms Bose was studying can rely on light as a source of energy, Bose hypothesized that this dependence on light for electron uptake could signify a function of the electrons in photosynthesis.  With subsequent studies, Bose’s team found that these electrons the microorganisms were taking were entering their photosystem.

To show that the electrons were playing a role in carbon fixation, Bose and her team looked at the activity of an enzyme called RuBisCo, which plays an integral role in converting carbon dioxide into sugars that can be broken down for energy. They found that RuBisCo was most strongly expressed and active when EEU was occurring, and that, without RuBisCo present, these organisms lost their ability to take in electrons. This finding suggests that organisms like TIE-1 are able to take in electrons from their environment and use them in conjunction with light energy to synthesize molecules for energy sources.  

In addition to broadening our understanding of the great diversity in metabolisms, Bose’s research has profound implications in sustainability. These microbes have the potential to play an integral role in clean energy generation.

Post by undergraduate blogger Sarah Haurin
Post by undergraduate blogger Sarah Haurin

Nature Shows a U-Turn Path to Better Solar Cells

The technical-sounding category of “light-driven charge-transfer reactions,” becomes more familiar to non-physicists when you just call it photosynthesis or solar electricity.

When a molecule (in a leaf or solar cell) is hit by an energetic photon of light, it first absorbs the little meteor’s energy, generating what chemists call an excited state. This excited state then almost immediately (like trillionths of a second) shuttles an electron away to a charge acceptor to lower its energy. That transference of charge is what drives plant life and photovoltaic current.

A 20 Megawatt solar farm ( Aerial Innovations via wikimedia commons)

The energy of the excited state plays an important role in determining solar energy conversion efficiency. That is, the more of that photon’s energy that can be retained in the charge-separated state, the better. For most solar-electric devices, the excited state rapidly loses energy, resulting in less efficient devices.

But what if there were a way to create even more energetic excited states from that incoming photon?

Using a very efficient photosynthesizing bacterium as their inspiration, a team of Duke chemists that included graduate students Nick Polizzi and Ting Jiang, and faculty members David Beratan and Michael Therien, synthesized a “supermolecule” to help address this question.

“Nick and Ting discovered a really cool trick about electron transfer that we might be able to adapt to improving solar cells,” said Michael Therien, the William R. Kenan, Jr. Professor of Chemistry. “Biology figured this out eons ago,” he said.

“When molecules absorb light, they have more energy,” Therien said. “One of the things that these molecular excited states do is that they move charge. Generally speaking, most solar energy conversion structures that chemists design feature molecules that push electron density in the direction they want charge to move when a photon is absorbed. The solar-fueled microbe, Rhodobacter sphaeroides, however, does the opposite. What Nick and Ting demonstrated is that this could also be a winning strategy for solar cells.”

Ting Jiang
Nick Polizzi

The chemists devised a clever synthetic molecule that shows the advantages of an excited state that pushes electron density in the direction opposite to where charge flows. In effect, this allows more of the energy harvested from a photon to be used in a solar cell. 

“Nick and Ting’s work shows that there are huge advantages to pushing electron density in the exact opposite direction where you want charge to flow,” Therien said in his top-floor office of the French Family Science Center. “The biggest advantage of an excited state that pushes charge the wrong way is it stops a really critical pathway for excited state relaxation.”

“So, in many ways it’s a Rube Goldberg Like conception,” Therien said. “It is a design strategy that’s been maybe staring us in the face for several years, but no one’s connected the dots like Nick and Ting have here.”

In a July 2 commentary for the Proceedings of the National Academy of Sciences, Bowling Green State University chemist and photoscientist Malcom D.E. Forbes calls this work “a great leap forward,” and says it “should be regarded as one of the most beautiful experiments in physical chemistry in the 21st century.”

Here’s a schematic from the paper.
(Image by Nick Polizzi)

CITATION: “Engineering Opposite Electronic Polarization of Singlet and Triplet States Increases the Yield of High-Energy Photoproducts,” Nicholas Polizzi, Ting Jiang, David Beratan, Michael Therien. Proceedings of the National Academy of Sciences, June 10, 2019. DOI: 10.1073/pnas.1901752116 Online: https://www.pnas.org/content/early/2019/07/01/1908872116

Don’t Drink the Tap

Have you ever questioned the quality of the water you drink every day? Or worried that cooking with tap water might be dangerous? For most of us, the answer to these questions is probably no. However, students from a Bass Connections team at Duke say we may want to think otherwise.

Image result for image of water

From bottle refilling stations to the tap, drinking water is so habitual and commonplace that we often take it for granted. Only in moments of crisis do we start worrying about what’s in the water we drink daily. The reality is that safe drinking water isn’t accessible for a lot of people.

Image result for pink hog farm water
Pig waste discoloring lagoon water

Images like this hog farm motivated the Bass Connections project team DECIPHER to take a closer look at the quality of water in North Carolina. On April 16 they presented their concerning findings from three case studies looking at lead contamination, coal ash impoundments, and aging infrastructure at the Motorco Music Hall.

Motorco in Durham. The talk was inside, though.

Nadratun Chowdhury, a Ph.D. student in Civil and Environmental Engineering, investigated lead contamination in water. Lead is an abundant and corrosion-resistant material, making it appealing for use in things like paint, batteries, faucets and pipes. While we’ve successfully removed lead from paint and gasoline, a lot of old water pipes in use today are still fashioned from lead. That’s not good – lead is very toxic and can leach into the water.

Just how toxic is it? Anything over a blood-lead level concentration of fifty parts per billion – fifty drops of water in a giant Olympic swimming pool – is considered dangerous. According to Duke graduate student Aaron Reuben, this much lead in one’s blood is correlated with downward social mobility, serious health concerns, diminished capacity to regulate thoughts and emotions, and hyperactivity. Lower income and minority areas are more at risk due to the higher likelihood of owning contaminated older homes.

Rupanjali Karthik, a Master of Laws student, conducted research on the intersection of water and aging infrastructure in Orange County. Breaks in water pipes are common and can result in serious consequences, like the loss of 9 million gallons of drinkable water. Sometimes it takes 8 or 9 months just to find the location of a broken pipe. In 2018, the UNC-Chapel Hill water main break caused a huge shortage on campus and at the medical center.

Excess fluoridation is also an issue caused by aging infrastructure. In February 2017, a combination of human and machine error caused an excessive fluoride concentration coming out of an Orange County Water Treatment Plant. People were advised not to use their water even to shower. A UNC basketball game had to move locations, and stores were completely swept of bottled water.

Another issue is that arsenic, a known carcinogen, is often used as the fluoridation agent. We definitely don’t want that in our drinking water. Fluoridation isn’t even that necessary these days when we have toothpaste and mouthwash that supports our dental health.

Tommy Lin, an undergraduate studying Chemistry and Computer Science, topped off the group’s presentation with findings surrounding coal ash in Belmont, NC. Coal ash, the residue after coal is burned in power plants, can pollute rivers and seep into ground water, affecting domestic wells of neighboring communities. This creates a cocktail of highly concentrated heavy metals and carcinogens. Drinking it can cause damage to your nervous system, cancer, and birth defects, among other things. Not so great.

The group’s presentation.

Forty-five plastic water bottles. That’s how much water it takes Laura, a Belmont resident, to cook her middle-sized family Thanksgiving. She knows that number because it’s been her family’s tradition the past three years. The Allen Plant Steam Station is a big culprit of polluting water with coal ash. Tons of homes nearby the station, like Laura’s, are told not to use the tap water. You can find these homes excessively stockpiled with cases on cases of plastic water bottles.

These issues aren’t that apparent to people unless they have been directly impacted. Lead, aging infrastructure, and coal ash all pose real threats but are also very invisible problems. Kathleen Burns, a Ph.D. student in English, notes that only in moments of crisis will people start to care, but by then it may be too late.

So, what can people do? Not much, according to the Bass Connections team. They noted that providing clean water is very much a structural issue which will require some complex steps to be solved. So, for now, you may want to go buy a Brita.

Will Sheehan
Post by Will Sheehan

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