Categories
ScienceDaily

Scientists probe the chemistry of a single battery electrode particle both inside and out

The particles that make up lithium-ion battery electrodes are microscopic but mighty: They determine how much charge the battery can store, how fast it charges and discharges and how it holds up over time — all crucial for high performance in an electric vehicle or electronic device.

Cracks and chemical reactions on a particle’s surface can degrade performance, and the whole particle’s ability to absorb and release lithium ions also changes over time. Scientists have studied both, but until now they had never looked at both the surface and the interior of an individual particle to see how what happens in one affects the other.

In a new study, a research team led by Yijin Liu at the Department of Energy’s SLAC National Accelerator Laboratory did that. They stuck a single battery cathode particle, about the size of a red blood cell, on a needle tip and probed its surface and interior in 3D with two X-ray instruments. They discovered that cracking and chemical changes on the particle’s surface varied a lot from place to place and corresponded with areas of microscopic cracking deep inside the particle that sapped its capacity for storing energy.

“Our results show that the surface and the interior of a particle talk to each other, basically,” said SLAC lead scientist Yijin Liu, who led the study at the lab’s Stanford Synchrotron Radiation Lightsource (SSRL). “Understanding this chemical conversation will help us engineer the whole particle so the battery can cycle faster, for instance.”

The scientists describe their findings in Nature Communications today.

Damage both inside and out

A lithium-ion battery stores and releases energy by moving lithium ions through an electrolyte back and forth between two electrodes, the anode and the cathode. When you charge the battery, lithium ions rush into the anode for storage. When you use the battery, the ions leave the anode and flow into the cathode, where they generate a flow of electrical current.

Each electrode consists of many microscopic particles, and each particle contains even smaller grains. Their structure and chemistry are key to the battery’s performance. As the battery charges and discharges, lithium ions seep in and out of the spaces between the particles’ atoms, causing them to swell and shrink. Over time this can crack and break particles, reducing their ability to absorb and release ions. Particles also react with the surrounding electrolyte to form a surface layer that gets in the way of ions entering and leaving. As cracks develop, the electrolyte penetrates deeper to damage the interior.

This study focused on particles made from a nickel-rich layered oxide, which can theoretically store more charge than today’s battery materials. It also contains less cobalt, making it cheaper and less ethically problematic, since some cobalt mining involves inhumane conditions, Liu said.

There’s just one problem: The particles’ capacity for storing charge quickly fades during multiple rounds of high-voltage charging – the type used to fast-charge electric vehicles.

“You have millions of particles in an electrode. Each one is like a rice ball with many grains,” Liu said. “They’re the building blocks of the battery, and each one is unique, just like every person has different characteristics.”

Taming a next-gen material

Liu said scientists have been working on two basic approaches for minimizing damage and increasing the performance of particles: Putting a protective coating on the surface and packing the grains together in different ways to change the internal structure. “Either approach could be effective,” Liu said, “but combining them would be even more effective, and that’s why we have to address the bigger picture.”

Shaofeng Li, a visiting graduate student at SSRL who will be joining SLAC as a postdoctoral researcher, led X-ray experiments that examined a single needle-mounted cathode particle from a charged battery with two instruments — one scanning the surface, the other probing the interior. Based on the results, theorists led by Kejie Zhao, an associate professor at Purdue University, developed a computer model showing how charging would have damaged the particle over a period of 12 minutes and how that damage pattern reflects interactions between the surface and interior.

“The picture we are getting is that there are variations everywhere in the particle,” Liu said. “For instance, certain areas on the surface degrade more than others, and this affects how the interior responds, which in turn makes the surface degrade in a different manner.”

Now, he said, the team plans to apply this technique to other electrode materials they have studied in the past, with particular attention to how charging speed affects damage patterns. “You want to be able to charge your electric car in 10 minutes rather than several hours,” he said, “so this is an important direction for follow-up studies.”

Go to Source
Author:

Categories
ScienceDaily

Scientists have modeled Mars climate to understand habitability

A Southwest Research Institute scientist modeled the atmosphere of Mars to help determine that salty pockets of water present on the Red Planet are likely not habitable by life as we know it on Earth. A team that also included scientists from Universities Space Research Association (USRA) and the University of Arkansas helped allay planetary protection concerns about contaminating potential Martian ecosystems. These results were published this month in Nature Astronomy.

Due to Mars’ low temperatures and extremely dry conditions, a droplet of liquid water on its surface would instantly freeze, boil or evaporate, unless the droplet had dissolved salts in it. This brine would have a lower freezing temperature and would evaporate more slowly than pure liquid water. Salts are found across Mars, so brines could form there.

“Our team looked at specific regions on Mars — areas where liquid water temperature and accessibility limits could possibly allow known terrestrial organisms to replicate — to understand if they could be habitable,” said SwRI’s Dr. Alejandro Soto, a senior research scientist and co-author of the study. “We used Martian climate information from both atmospheric models and spacecraft measurements. We developed a model to predict where, when and for how long brines are stable on the surface and shallow subsurface of Mars.”

Mars’ hyper-arid conditions require lower temperatures to reach high relative humidities and tolerable water activities, which are measures of how easily the water content may be utilized for hydration. The maximum brine temperature expected is -55 F — at the boundary of the theoretical low temperature limit for life.

“Even extreme life on Earth has its limits, and we found that brine formation from some salts can lead to liquid water over 40% of the Martian surface but only seasonally, during 2% of the Martian year,” Soto continued. “This would preclude life as we know it.”

While pure liquid water is unstable on the Martian surface, models showed that stable brines can form and persist from the equator to high latitudes on the surface of Mars for a few percent of the year for up to six consecutive hours, a broader range than previously thought. However, the temperatures are well below the lowest temperatures to support life.

“These new results reduce some of the risk of exploring the Red Planet while also contributing to future work on the potential for habitable conditions on Mars,” Soto said.

Story Source:

Materials provided by Southwest Research Institute. Note: Content may be edited for style and length.

Go to Source
Author:

Categories
ScienceDaily

How drones can hear walls

One drone, four microphones and a loudspeaker: nothing more is needed to determine the position of walls and other flat surfaces within a room. This has been mathematically proved by Prof. Gregor Kemper of the Technical University of Munich and Prof. Mireille Boutin of Purdue University in Indiana, USA.

Can walls and flat surfaces be recognized using sound waves? Mathematicians have been studying this question from a theoretical standpoint for quite some time.

“The basic scenario is a room with flat walls, and maybe a ceiling and a floor,” explains Prof. Gregor Kemper of the Chair of Algorithmic Algebra at TUM. The room is not assumed to be rectangular. It is also possible to measure the slope of the walls. Several microphones and a loudspeaker are contained in the room.

Speaker and microphones are placed on a drone

Previous studies have already mathematically proven that four microphones and a loudspeaker are sufficient to pinpoint the walls and also calculate their inclination. To prepare for this, the microphones have to be brought into the room at random positions, which will take quite some time and in some situations will be altogether impossible.

That is why Kemper and Boutin took the idea one step further. In their theoretical approach, they mounted the loudspeaker and four microphones on a drone — making measurement much more practical, because the equipment does not have to be installed in the room.

The algorithm can match echoes to a wall

The basic principle remains unchanged in the current approach: When the loudspeaker sends out a sound impulse, the waves bounce back from the walls. These direct reflections of the impulse are referred to as first order echoes. The biggest problem arising in the mathematical feasibility study: “Every microphone detects a large number of echoes. We need to be able to decide with certainty which echoes are coming from which wall,” says Kemper.

The transit time — the time delay between emitting the sound pulse and receiving its echo — can be determined very precisely using the microphones. All transit times from a given wall have a specific relationship with one another. Kemper and Boutin developed a new algorithm that uses this relationship to assign individual echoes to a particular wall.

Once the echoes have been assigned to the right walls, the position and inclination of the walls are calculated using a geometric approach similar to that used by GPS when determining location data.

Ghost walls can be created by chance

The calculation can go wrong, however. That is because some echoes might satisfy the conditions of the mathematical relationship by chance. This leads to the identification of walls that are actually not there, so-called ghost walls.

“Naively, the probability of ghost walls would be expected to be higher when the microphones are mounted on a drone,” explains Kemper. “This is because, in contrast to microphones mounted freely in space, they have less freedom of movement due to their rigid mounting on the drone. Instead of twelve, they have only six degrees of freedom.”

Drone in ideal position for measurements

The question of how likely it is for such ghost walls to arise in the measurement process leads to the core statement of the paper: Kemper and Boutin have proved that the drone’s freedom of motion is sufficient for the probability of placing it in a “good” position — meaning a position where no ghost walls are detected — to be equal to 1. In other words, such a placement is a near certainty.

“The six degrees of freedom of the drone are sufficient for the microphones to be almost certainly in an optimal position for the measurement,” says Kemper. The only prerequisite is that the microphones are not arranged in a common plane on the drone.

A first step towards practical applications

In a next step, the researchers’ scenario will become more realistic: They hope to find a mathematical solution for when errors or inaccuracies occur during measurement. They also intend to study configurations with the loudspeaker and microphones mounted on ground-based vehicles.

Go to Source
Author:

Categories
ScienceDaily

Scientists learn more about the first hours of a lithium-ion battery’s life

The first hours of a lithium-ion battery’s life largely determine just how well it will perform. In those moments, a set of molecules self-assembles into a structure inside the battery that will affect the battery for years to come.

This component, known as the solid-electrolyte interphase or SEI, has the crucial job of blocking some particles while allowing others to pass, like a tavern bouncer rejecting undesirables while allowing in the glitterati. The structure has been an enigma for scientists who have studied it for decades. Researchers have tapped multiple techniques to learn more but never — until now — had they witnessed its creation at a molecular level.

Knowing more about the SEI is a crucial step on the road to creating more energetic, longer-lasting and safer lithium-ion batteries.

The work published Jan. 27 in Nature Nanotechnology was performed by an international team of scientists led by researchers at the U.S. Department of Energy’s Pacific Northwest National Laboratory and the U.S. Army Research Laboratory. Corresponding authors include Zihua Zhu, Chongmin Wang and Zhijie Xu of PNNL and Kang Xu of the U.S. Army Research Laboratory.

Why lithium-ion batteries work at all: the SEI

The solid-electrolyte interphase is a very thin film of material that doesn’t exist when a battery is first built. Only when the battery is charged for the very first time do molecules aggregate and electrochemically react to form the structure, which acts as a gateway allowing lithium ions to pass back and forth between the anode and cathode. Crucially, the SEI forces electrons to take a detour, which keeps the battery operating and makes energy storage possible.

It’s because of the SEI that we have lithium-ion batteries at all to power our cell phones, laptops and electric vehicles.

But scientists need to know more about this gateway structure. What factors separate the glitterati from the riffraff in a lithium-ion battery? What chemicals need to be included in the electrolyte, and in what concentrations, for the molecules to form themselves into the most useful SEI structures so they don’t continually sop up molecules from the electrolyte, hurting battery performance?

Scientists work with a variety of ingredients, predicting how they will combine to create the best structure. But without more knowledge about how the solid-electrolyte interphase is created, scientists are like chefs juggling ingredients, working with cookbooks that are only partially written.

Exploring lithium-ion batteries with new technology

To help scientists better understand the SEI more, the team used PNNL’s patented technology to analyze the structure as it was created. Scientists used an energetic ion beam to tunnel into a just-forming SEI in an operating battery, sending some of the material airborne and capturing it for analysis while relying on surface tension to help contain the liquid electrolyte. Then the team analyzed the SEI components using a mass spectrometer.

The patented approach, known as in situ liquid secondary ion mass spectrometry or liquid SIMS, allowed the team to get an unprecedented look at the SEI as it formed and sidestep problems presented by a working lithium-ion battery. The technology was created by a team led by Zhu, building on previous SIMS work by PNNL colleague Xiao-Ying Yu.

“Our technology gives us a solid scientific understanding of the molecular activity in this complex structure,” said Zhu. “The findings could potentially help others tailor the chemistry of the electrolyte and electrodes to make better batteries.”

U.S. Army and PNNL researchers collaborate

The PNNL team connected with Kang Xu, a research fellow with the U.S. Army Research Laboratory and an expert on electrolyte and the SEI, and together they tackled the question.

The scientists confirmed what researchers have suspected — that the SEI is composed of two layers. But the team went much further, specifying the precise chemical make-up of each layer and determining the chemical steps that occur in a battery to bring about the structure.

The team found that one layer of the structure, next to the anode, is thin but dense; this is the layer that repels electrons but allows lithium ions to pass through. The outer layer, right next to the electrolyte, is thicker and mediates interactions between the liquid and the rest of the SEI. The inner layer is a bit harder and the outer later is more liquidy, a little bit like the difference between undercooked and overcooked oatmeal.

The role of lithium fluoride

One result of the study is a better understanding of the role of lithium fluoride in the electrolyte used in lithium-ion batteries. Several researchers, including Kang Xu, have shown that batteries with SEIs richer in lithium fluoride perform better. The team showed how lithium fluoride becomes part of the inner layer of the SEI, and the findings offer clues about how to incorporate more fluorine into the structure.

“With this technique, you learn not only what molecules are present but also how they’re structured,” Wang says. “That’s the beauty of this technology.”

The PNNL portion of the research published in Nature Nanotechnology was funded by PNNL, DOE’s Office of Energy Efficiency and Renewable Energy’s Vehicle Technologies Office, and the U.S.-Germany Cooperation on Energy Storage. Kang Xu’s work was funded by DOE’s Office of Science Joint Center for Energy Storage Research. The liquid SIMS analysis was done at EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science user facility located at PNNL.

In addition to Xu, Wang and Zhu, PNNL authors include Yufan Zhou, Mao Su, Xiafei Yu, Yanyan Zhang, Jun-Gang Wang, Xiaodi Ren, Ruiguo Cao, Wu Xu, Donald R. Baer and Yingge Du.

Go to Source
Author:

Categories
ScienceDaily

New optical technique captures real-time dynamics of cement setting

Researchers have developed a nondestructive and noninvasive optical technique that can determine the setting times for various types of cement paste, which is used to bind new and old concrete surfaces. The new method could aid in the development of optimized types of cement with less impact on the environment.

“Our noninvasive optical method characterizes and determines the setting time of cement, which is a very important parameter for the construction industry,” said José Ortiz-Lozano, a member of the research team from Universidad Autónoma de Aguascalientes, Tecnológico Nacional de México and Centro de Investigaciones en Óptica, in Mexico. “It can also precisely assess the cement hydration process in real-time. This information is crucial for both the study of physical chemistry and the quantitative characterization of the nanomechanical properties of cement-based materials.”

In the Optical Society’s (OSA) journal Applied Optics, the researchers describe the new method, which combines laser-based technology with an optical model to calculate the dynamic behavior of the cement paste. The researchers show that their approach can accurately calculate both the initial setting time — the time available for mixing the cement and placing it in position — and the final setting time, when the cement reaches its full strength.

“Our group is trying to enhance the performance of cement-based materials, such as cement pastes, mortars and concrete,” said Ortiz-Lozano. “New material characterization methods, such as the one we report here, can be used to improve the behavior and performance of cement by optimizing its constituents. This could lead to new types of cement that use less water and raw materials like limestone and clay, which would make them more environmentally friendly.”

Studying cement with light

Although a variety of techniques exist to study the dynamics of setting cement, they come with various drawbacks such as being destructive, invasive or influenced by human factors. The new method uses the optical properties of cement paste to directly calculate the initial and final cement setting time by measuring the diffuse light that reflects off the cement.

As the cement sets, the diffuse light reflection changes as it reacts with water and the spaces between the cement particles change. The amount of water present and the protective surface layer at each setting stage also influence the diffuse reflection properties. The researchers combined the diffuse reflection measurements with the Kubelka-Munk model, which is used to describe diffuse reflection of opaque samples.

“This new optical method was developed using tools, components and materials common among the optical industry,” said Ortiz-Lozano. “It would be, therefore, quite simple and economic to implement in cement quality control laboratories. It can be applied to any type of cement once the appropriate calibration is performed with the Kubelka-Munk model.”

The researchers applied the new technique to six cement samples and found that the results for all the samples were repeatable and agreed well with measurement techniques commonly used today.

“This laser-based technique gives continuous and accurate assessment of cement hydration process with high repeatability and reproducibility, showing its potential for studying the physical chemistry properties of cement,” said Ortiz-Lozano.

Next, the researchers plan to acquire more data using more types of cement, mortars, concretes as well as additional water to cement ratios and cement pastes that contain chemical and/or mineral admixtures. They are also planning to perform the work required to normalize the method as a standard.

Story Source:

Materials provided by The Optical Society. Note: Content may be edited for style and length.

Go to Source
Author:

Categories
ScienceDaily

Visualizing chemical reactions, e.g. from H2 and CO2 to synthetic natural gas

Infrared (IR) thermography is used to determine the temperature of humans and objects with high precision and without interfering with the system. A single image taken with an IR camera can capture the same amount of information as hundreds to millions of thermocouples (temperature sensors) at once. Furthermore, modern IR cameras can achieve fast acquisition frequencies of over 50 Hz, which allows the investigation of dynamic phenomena with high resolution.

Now, scientists at EPFL have designed a reactor that can use IR thermography to visualize dynamic surface reactions and correlate it with other rapid gas analysis methods to obtain a holistic understanding of the reaction in rapidly changing conditions. The research was led by Robin Mutschler and Emanuele Moioli at the lab of Andreas Züttel (EPFL and Empa) and they collaborated with researchers at the Polytechnic University of Milan.

The scientists applied their method to catalytic surface reactions between carbon dioxide and hydrogen, including the Sabatier reaction, which can be used to produce synthetic methane from renewable energy by combining CO2 from the atmosphere and H2 from water splitting, thus enabling the synthesis of renewable synthetic fuels with similar properties to their fossil counterparts which is why the Sabatier reaction has attracted a lot of attention recently. A catalyst is required in the Sabatier reaction to activate the relatively inert CO2 as a reactant.

In particular the EPFL researchers focused on the investigation of dynamic reaction phenomena occurring during the reaction activation from different initial catalyst states.

“The reaction on the catalyst is favored by a hydrogenated surface while an exposure to CO2 poisons the catalyst and inhibits a fast reaction activation,” says Mutschler.

“Thanks to this new approach, we could visualize new dynamic reaction phenomena never observed before,” says Moioli.

In their work they showed the catalyst working and responding to the changes in the feed gas composition and during its activation from different initial states in real time for the first time. By means of their results, the reaction startup and activation behavior are now better understood and it can lead to optimized reactor and catalyst designs to improve the performance of these reactor systems working in dynamic conditions.

This is crucial since renewable energy typically provides energy and reactants stochastically and therefore the reactors converting renewable energy to fuels have to be adapted to work in dynamic conditions under certain circumstances.

Story Source:

Materials provided by Ecole Polytechnique Fédérale de Lausanne. Original written by Nik Papageorgiou. Note: Content may be edited for style and length.

Go to Source
Author:

Categories
IEEE Spectrum

CES 2020: Bzigo Laser System Detects and Tracks Mosquitoes So You Can Destroy Them

As far as I know, the current state of the art in indoor mosquito management is frantically trying to determine where that buzzing noise is coming from so that you can whack the damn bug before it lands and you lose track of it.

This “system” rarely works, but at CES this week, we found something better: Israeli startup Bzigo (the name of both the company and the product), which makes a mosquito detection and tracking system that combines an IR camera and laser designator with computer vision algorithms that follows mosquitoes as they fly and tells you exactly where they land to help you smash them. It’s not quite as deadly as the backyard star wars system, but it’s a lot more practical, because you’ll be able to buy one.

Bzigo’s visual tracking system can reliably spot mosquitoes at distances of up to 8 meters. A single near-IR (850nm) camera with a pair of IR illuminators and a wide angle lens can spot mosquitoes over an entire room, day or night. Once a bug is detected, an eye-safe laser will follow it until it lands and then draws a box around it for you so you can attack with your implement of choice.

At maximum range, you run into plenty of situations where the apparent size of a mosquito can be less than a single pixel. Bzigo’s AI relies on a mosquito’s motion rather than an identifiable image of the bug itself, and tracking those potentially intermittent and far-off pixel traces requires four 1GHz cores running at 100% continuously (all on-device). That’s a lot of oomph, but the result is that false positives are down around 1%, and 90% of landings are detected. This is not to say that the system can only detect 90% of bugs— since mosquitoes take off and land frequently, they’re almost always detected after just a few flight cycles. It’s taken Bzigo four years to reach this level of accuracy and precision with detection and tracking, and it’s impressive.

The super obvious missing feature is that this system only points at mosquitoes, as opposed to actually dealing with them in a direct (and lethal) way. You could argue that it’s the detection and tracking that’s the hard part (and it certainly is for humans), and that automated bug destruction is a lower priority, and you’d probably be right.

Or at least, Bzigo would agree with you, because that’s the approach they’ve taken. However, there are plans for a Bzigo V2, which adds a dedicated mosquito killing feature. If you guessed that said feature would involve replacing the laser designator with a much higher powered laser bug zapper, you’d be wrong, because we’re told that the V2 will rely on a custom nano-drone to destroy its winged foes at close range.

Bzigo has raised one round of funding, and they’re currently looking to raise a bit more to fund manufacturing of the device. Once that comes through, the first version of the system should be available in 12-14 months for about $170.

Categories
ScienceDaily

LED lighting in greenhouses helps but standards are needed

While LED lighting can enhance plant growth in greenhouses, standards are needed to determine the optimal intensity and colors of light, according to Rutgers research that could help improve the energy efficiency of horticultural lighting products.

Many lighting companies market their LED (light-emitting diode) products with claims of delivering an optimal “light recipe” that often consists of a combination of wavelengths and color ratios, such as a 4-to-1 red to blue ratio on the spectrum (colors of a rainbow). Plant scientists often use this information to evaluate the potential effects of lamps on plant growth and development. But standardized procedures on how to calculate these ratios are lacking, according to a study soon to be published in the journal Acta Horticulturae.

“The more efficient supplemental lighting sources are, the less electric power growers need to finish their crops,” said senior author A.J. Both, a professor and extension specialist in controlled environment engineering in the Department of Environmental Sciences in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick. “We hope to help make indoor crop production more sustainable and affordable.”

Increased energy efficiency can have a big impact on the bottom line, and information about new crop lighting strategies will help the burgeoning indoor farming industry, Both said.

In greenhouses and controlled environments, electric lamps are used to supplement sunlight and extend lighting times to produce horticultural crops, such as vegetables, flowers and herbs, according to a previous study led by Both. Recent advances in energy-efficient LED technology provide the horticultural industry with multiple lighting options. But growers can’t easily compare technologies and LED options because of a lack of independent data on how lamps perform. That study led to a proposed standardized product label allowing for comparisons of lamps across manufacturers.

Both and colleagues continue to focus on independently assessing performance metrics such as power consumption, efficiency, light intensity and the light distribution pattern and relaying that information to commercial growers. Recent advancements have provided opportunities to precisely control the light from LED lamps and study their impacts on plant growth and development, according to Both’s research. Both and his team work closely with plant scientists who study the impact of light on plants grown for food or ornamental crops.

The new study recommends using a spectroradiometer, an instrument that measures light output across a specific range of wavelengths. Using such an instrument, various light ratios can be calculated. The researchers reported substantial differences in light ratios comparing sunlight with common lamps, including LED, high-pressure sodium, incandescent and fluorescent lamps used for plant lighting. The researchers hope that their work will contribute to the development of standard definitions for specific wavebands (ranges of wavelengths) that are important for plant growth and development.

The lead author of the new study is Timothy Shelford, a part-time research specialist at Rutgers who also works at Cornell University. Claude Wallace, a Rutgers graduate and part-time employee, also contributed to the study.

Story Source:

Materials provided by Rutgers University. Note: Content may be edited for style and length.

Go to Source
Author:

Categories
3D Printing Industry

Can 3D printing challenge China’s position as a manufacturing leader?

Belgian software and 3D printing service provider Materialise has conducted a survey to determine the interest and attitudes of Chinese manufacturing companies towards 3D printing.  From the results of the survey, it is suggested that China is doubtful about 3D printing’s readiness for manufacturing end products. Instead, the country is focused on utilizing the technology for prototyping […]

Go to Source
Author: Anas Essop

Categories
ScienceDaily

Why did the turtles cross the highway? They didn’t, but they still might be impacted

Ohio University researchers set out to determine the impact of the Route 33 bypass through Wayne National Forest on the local box turtle population. The answers were not exactly what they expected.

Roads define the very fabric of our civilization, and very few places in North America remain road-less. As an integral part of the landscape, roads and their vehicle traffic also have unintended consequences for wildlife: many animals die as a result of vehicle strikes, and some strikes pose a risk to human lives. Think about the consequences of hitting a moose, bear or deer on the highway at 70 mph.

These types of events capture a lot of attention, and management agencies work hard to minimize the chance of wildlife-vehicle strikes through mitigation structures such as wildlife fences and overpasses.

However, the effects of roads are not limited to animals dying on roads. Roads may affect the way animals use their habitat. They may bisect important connections between habitats and populations, or they may deter animals altogether and increase their stress levels because of traffic noise, light or vibration.

These types of effects are what former Ohio University Biological Sciences graduate student Marcel Weigand in Dr. Viorel Popescu’s Conservation Ecology Lab sought to investigate and have recently been published in the European Journal of Wildlife Research.

Eastern Box Turtle — Threatened by Road Mortality

With a passion for reptiles, Weigand asked how new high-traffic roads affect the ecology, behavior and physiology of Eastern Box Turtles, a species of concern in Ohio, threatened by road mortality. Weigand found the perfect study setting, the new Nelsonville Bypass (U.S. 33), cutting through Wayne National Forest, and opened to vehicle traffic in 2013. Several other wildlife studies have been under way in the same location, investigating the success of mitigation structures to reduce road mortality for deer, snakes, and amphibians, so focusing on turtles would paint a more complete picture on the effects of the new highway on road-naïve wildlife.

Weigand also scouted a roadless study site, not far from the Bypass, on the Hocking College and Wayne National Forest lands; this would serve as a control test site, against which any potential effects of the Bypass could be compared.

For two years (2017-18), Weigand, aided by a horde of undergraduate OHIO and Hocking College students, tracked 30 Box Turtles (15 along the Bypass and 15 at the roadless site) via VHF telemetry on a daily basis between March, when turtles come out of hibernation, and October, when they dig down deep for their long winter sleep.

They first captured and collected the turtles with the help of turtle detection dogs, specially trained to sniff out and find the domed critters even under feet-deep leaf litter. After attaching a small transmitter that would provide data on their movements and habitat use, all turtles were treated with a pedicure.

By clipping a couple millimeters of their nails, the OHIO researchers could learn about their stress levels in the previous several months, as the stress hormone corticosterone accumulates in the nail keratin. To evaluate corticosterone levels, Weigand forged a collaboration with Ohio State University avian ecologist and physiologist Dr. Chris Tonra, with his new endocrinology lab offering the equipment and know-how for performing state-of-the-art hormone bioassays.

“Tracking turtles was hard, but fun work. It turns out that turtles liked to hang out (a lot) in fun places like thick patches of greenbrier and multiflora rose,” says Weigand. “Overall, we found that turtles at both roadless and roadside sites used similar habitats, with high volumes of downed woody debris and thick understory, so our initial hypothesis that the bypass was affecting how turtles selected habitat was not validated.”

Adapting to Road, but Not Crossing?

However, the researchers discovered something rather puzzling — while many turtles used the open roadside habitat created by the new highway for thermoregulation and nesting, with several female turtles spending many weeks during summer within a few feet of the pavement, no turtles attempted to cross the road.

“We were confident that we would see crossing attempts, as Box Turtles crossing roads are a common sighting in this part of Ohio. Instead, the new highway acted as a complete barrier to turtle movements; so, in the absence of crossing structures, such as underpasses, the highway has the potential to completely separate the local Box Turtle population,” Popescu says. “Interestingly, a four-foot wide culvert underneath the highway was available to Bypass turtles for reaching the other side, but no turtle accessed this mitigation structure. Cutting gene flow may have long-term negative impacts on the viability of turtle populations and decrease their ability to cope with other threats.”

Another unexpected result was the lack of a difference in nail keratin corticosterone concentrations between animals at Bypass and roadless sites. “This came as a surprise, as we expected that the road-naïve population along the Bypass would exhibit higher stress levels due to proximity to the busy highway; corticosterone levels were not higher even in animals that spent weeks in very close proximity to the highway,” adds Weigand. “This result, along with the lack of differences in habitat use and home range sizes, show that Box Turtles have the capacity to rapidly adapt to new habitat conditions.”

Weigand’s study also offered the opportunity for many OHIO and Hocking College undergraduates to learn new field skills, such as VHF telemetry, habitat sampling and field data collection, GPS orientation and much more. Ryan Wagner, a wildlife and conservation major supported by OHIO’s Program to Aid Career Exploration (PACE), was Wiegand’s sidekick throughout the study.

“This was my first exposure to wildlife field research, and it gripped me. I love reptiles, and having the opportunity to participate in all aspects of this study, from capturing, tagging and tracking turtles, to stress hormone lab work, data analysis and manuscript writing, set the stage for my next career move, graduate school,” Wagner said. Besides being an enthusiastic researcher, Wagner is also an accomplished photographer, and his photo of a Garter Snake was selected for the 2018 Ohio Wildlife Legacy Stamp among hundreds of submissions.

Overall, this study opens many other questions about the long-term impacts of barriers on the genetic makeup of turtle populations, their physiology, as well as their population viability. It suggests wildlife management techniques that could make certain areas more attractive to turtle populations without putting them at risk of exposure to roads. It also highlights the importance of designing and implementing the types of road mitigation structures that maintain population connectivity. “This research is a prime example of collaboration between academia, Wayne National Forest, Ohio Department of Transportation and local environmental groups (Rural Action).

“My hope is that our work will provide transportation and wildlife management agencies additional knowledge and tools to ensure that the anthropogenic march of progress does not rest on the backs of turtles,” Weigand said.

Go to Source
Author: