New sensor enables 'smart diapers,' range of other health monitors

Peer-Reviewed Publication

PENN STATE

 

IMAGE: A PENN STATE-LED RESEARCH TEAM INTEGRATED FOUR HUMIDITY SENSORS BETWEEN THE ABSORBENT LAYERS OF A DIAPER TO CREATE A “SMART DIAPER,” CAPABLE OF DETECTING WETNESS AND ALERTING FOR A CHANGE. view more 

CREDIT: HUANYU “LARRY” CHENG/PENN STATE

UNIVERSITY PARK, Pa. — Waaahhh! While babies have a natural mechanism for alerting their parents that they need a diaper change, a new sensor developed by researchers at Penn State could help workers in daycares, hospitals and other settings provide more immediate care to their charges.

The new sensor — so cheap and simple to produce that it can be hand-drawn with a pencil onto paper treated with sodium chloride — could clear the way for wearable, self-powered health monitors for use not only in “smart diapers” but also to predict major health concerns like cardiac arrest and pneumonia.

“Our team has been focused on developing devices that can capture vital information for human health,” said Huanyu “Larry” Cheng, the James L. Henderson, Jr. Memorial Associate Professor of Engineering Science and Mechanics at Penn State. “The goal is early prediction for disease conditions and health situations, to spot problems before it is too late.”

Cheng is the lead author on a new study, published in the journal Nano Letters, which describes the design and fabrication process for a reliable, hand-drawn electrode sensor. The sensor is created using a pencil, drawn on paper treated with a sodium chloride solution. The hydration sensor is highly sensitive to changes in humidity and provides accurate readings over a wide range of relative humidity levels, from 5.6% to 90%.

Research into wearable sensors has been gaining momentum because of their wide-ranging applications in medical health, disaster warning and military defense, Cheng explained. Flexible humidity sensors have become increasingly necessary in health care, for uses such as respiratory monitoring and skin humidity detection, but it is still challenging to achieve high sensitivity and easy disposal with simple, low-cost fabrication processes, he added.

“We wanted to develop something low-cost that people would understand how to make and use — and you can’t get more accessible than pencil and paper,” said Li Yang, professor in the School of Artificial Intelligence at China’s Hebei University of Technology. “You don’t need to have some piece of multi-million-dollar equipment for fabrication. You just need to be able to draw within the lines of a pre-drawn electrode on a treated piece of paper. It can be done simply and quickly.”

The device takes advantage of the way paper naturally reacts to changes in humidity and uses the graphite in the pencil to interact with water molecules and the sodium chloride solution. As water molecules are absorbed by the paper, the solution becomes ionized and electrons begin to flow to the graphite in the pencil, setting off the sensor, which detects those changes in humidity in the environment and sends a signal to a smartphone, which displays and records the data.

Essentially, drawing on the pre-treated paper within pre-treated lines creates a miniaturized paper circuit board. The paper can be connected to a computer with copper wires and conductive silver paste to act as an environmental humidity detector. For wireless application, such as “smart diapers” and mask-based respiration monitoring, the drawing is connected to a tiny lithium battery which powers data transmission to a smartphone via Bluetooth.

For the respiration monitor, the team drew the electrode directly on a solution-treated face mask. The sensor easily differentiated mouth breathing from nose breathing and was able to classify three breathing states: deep, regular and rapid. Cheng explained that the data collected could be used to detect the onset of various disease conditions, such as respiratory arrest and shortness of breath and provide opportunities in the smart internet of things and telemedicine.

He added that respiratory rate is a fundamental vital sign and research has shown it to be an early indicator of a variety of pathological conditions such as cardiac events, pneumonia and clinical deterioration. It can also indicate emotional stressors like cognitive load, heat, cold, physical effort and exercise-induced fatigue.

Compared with breath, the human skin exhibits a smaller change in humidity, but the researchers were still able to detect changes using their pencil-on-paper humidity sensor, even after test subjects applied lotion or exercised. Skin is the body’s largest organ, Cheng explained, so if it is not processing moisture correctly, that could indicate that some other health issue is going on.

“Different types of disease conditions result in different rates of water loss on our skin,” he said. “The skin will function differently based on those underlying conditions, which we will be able to flag and possibly characterize using the sensor.”

The team also integrated four humidity sensors between the absorbent layers of a diaper to create a “smart diaper,” capable of detecting wetness and alerting for a change.

“That application was actually born out of personal experience,” said Cheng, who is the father of two young children. “There’s no easy way to know how wet is wet, and that information could be really valuable for parents. The sensor can provide data in the short-term, to alert for diaper changes, but also in the long-term, to show patterns that can inform parents about the overall health of their child.”

The applications of the humidity sensor go beyond “smart diapers” and monitoring for respiration and perspiration, Cheng explained. The team also deployed the sensor as a noncontact switch, which could sense the humidity changes in the air from the presence of a finger without the finger touching the sensor. The team used the noncontact switch to operate a small-scale elevator, play a keyboard and light up an LED array.

“The atoms on the finger don’t need to touch the button, they only need to be near the surface to diffuse the water molecules and trigger the signal,” Cheng said. “When we think about what we learned from the pandemic about the need to limit the body’s contact with shared surfaces, a sensor like this could be an important tool to stop potential contamination.”

Other authors on the study are Penn State doctoral candidate Ankan Dutta as well as Guangyu Niu, Zihan Wang, Ye Xue, Jiayi Yan, Xue Chen, Ya Wang, Chaosai Liu, Shuaijie Du Langang Guo of the Hebei University of Technology. Peng Zhou of Tianjin Tianzhong Yimai Technology Development Co. Ltd. also contributed to the research.

Cheng’s work was funded by the National Institutes of Health, the National Science Foundation and Penn State.

Illustration showing fabrication and application of the pencil-on-paper hydration sensor. Schematics showing the (a) fabrication processes and (b) the response mechanism of the flexible pencil-on-paper hydration sensor with (c) applications in health monitoring, noncontact switching, and skin characterizations.

CREDIT

Courtesy Huanyu “Larry” Cheng / Penn State

---

JOURNAL

Nano Letters

DOI

10.1021/acs.nanolett.2c04384 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Pencil-on-Paper Humidity Sensor Treated with NaCl Solution for Health Monitoring and Skin Characterization

Toxic metals in baby food: Researchers find ‘concerning’ gaps in U.S. regulations

Peer-Reviewed Publication

UNIVERSITY AT BUFFALO

BUFFALO, N.Y. – Rice cereal, formula, purees and puffs. They’re among the most popular products purchased from the baby food aisle. And they share one more thing in common: They likely contain toxic metals.

What’s more, the U.S. doesn’t have the kind of strict regulations for commercially produced baby foods that parents might expect. That’s according to the findings of a recent University at Buffalo-led study that outlined risk prevention strategies for parents and health care professionals.

“It is concerning that there are gaps in food contaminant federal guidelines, particularly for baby foods. Parents might expect and trust that their infant’s commercially produced baby food is automatically protected by tightly regulated guidelines, but that is just not the case,” said the study’s lead author, Sarah J. Ventre, MD, clinical assistant professor in the Department of Pediatrics in the Jacobs School of Medicine and Biomedical Sciences at UB.

Ventre and her co-authors decided to examine the issue after reports of toxic metals in baby foods became more widespread in 2019, prompting families to raise safety concerns. The researchers reviewed several recent studies, and an analysis commissioned by Healthy Babies Bright Futures, all of which have reported that toxic elements such as arsenic, lead, mercury and cadmium have been found in popular baby foods, in an effort to help parents, caregivers and health care professionals make sense of the potential risks and offer guidance.

“As a pediatrician, my goal is to provide parents with the tools to keep their children healthy and safe,” said Ventre, who is also part of UBMD Pediatrics and serves as co-medical director for the Buffalo Public Schools.

After the U.S. Food and Drug Administration (FDA) developed an action plan for reducing toxic metals in baby foods in 2019, it issued draft guidance for lead in juices in April 2022 and lead in baby foods just last month. But the FDA has not yet offered guidance for arsenic, mercury or cadmium, leading to concerns that regulatory changes may not be coming quickly enough.

Toxic elements can be consumed from a variety of sources, including water, baby formula, breast milk, homemade purees and baby foods like cereals, fruits and vegetables and fruit juices. When toxic elements are ingested with food or water, they are absorbed in the gastrointestinal tract and enter the bloodstream.

“A big concern is that the testing reveals multiple toxic elements in many of the foods, which means that we are dealing with multiple issues,” says study senior author Katarzyna Kordas, PhD, associate professor of epidemiology and environmental health in UB’s School of Public Health and Health Professions.

“If you add to this the pesticides that are intentionally used when growing foods, the problem becomes almost too large to think about – do you address one toxicant at a time? Try to deal with all of them at once? Which foods do you focus on?” adds Kordas, who studies the health effects of exposure to lead and other harmful metals and chemicals, particularly in children.

Infants and young children are especially vulnerable to the effects of exposure to toxic elements, the researchers note, adding that little research has been done to identify the extent to which toxic element exposure from diet contributes to the health effects that can be caused in children exposed to such metals early in life. Those effects include cognitive function deficits, lower socioeconomic status and difficult personality traits well into adulthood for children exposed to lead. Arsenic, meanwhile, is associated with lung and bladder cancers in adulthood.

“We know that a wide range of foods are contaminated and that higher consumption of those foods is related to body levels of those contaminants in children,” Kordas adds. “But does the exposure to contaminants specifically through foods harm the health of young children? We don’t know that for sure, and it is uncomfortable to have few definitive answers for parents.”

While some parents may want to completely eliminate certain food products because they fear they could be exposing their children to toxicants, the researchers say that’s not the best course of action. Instead, they suggest feeding children a varied diet consisting of many different foods and food types.

“It is important to focus on the fact that although foods have been found to contain toxic elements, several of these foods are rich in nutrients that are necessary for children’s growth and development,” says paper co-author Gauri Desai, PhD, clinical assistant professor of epidemiology and environmental health at UB. “Eliminating some foods from children’s diets may deprive them of the benefits that those foods have to offer.”

In addition to varying a child’s diet, the researchers also recommend ensuring clean drinking water, providing breast milk for the first 1-2 years if possible, and limiting juice intake.

When it comes to baby formula, while there is some data on which brands may have the lowest levels of heavy metals, it remains challenging to identify which formulas are safest, researchers say, adding that parents and health care providers can advocate for tighter U.S. Food and Drug Administration control parameters for infant formula.

“While providing guidance to parents and health care providers is important, the most conclusive way to protect the safety of food ingested by infants and children is through the establishment of stronger guidelines and enforcing those guidelines,” says Ventre.

---

JOURNAL

Current Problems in Pediatric and Adolescent Health Care

DOI

10.1016/j.cppeds.2022.101276 

ARTICLE TITLE

Toxic metal exposures from infant diets: Risk prevention strategies for caregivers and health care professionals

Abandoning wood cook stoves would be great for Africa, if families could afford it

Use of biomass-burning stoves has actually grown 50% in last two decades

Peer-Reviewed Publication

DUKE UNIVERSITY

 

IMAGE: A SMALL HOME IN MADAGASCAR CONTAINING A TYPICAL WOOD-FIRED COOKING AREA. INDOOR AIR QUALITY AND DEFORESTATION ARE HUGE CONSEQUENCES OF TRADITIONAL COOKING. view more 

CREDIT: CHARLES NUNN, DUKE UNIVERSITY

DURHAM, N.C. -- Replacing traditional biomass-burning cookstoves across sub-Saharan Africa could save more than 463,000 lives and US $66 billion in health costs annually, according to a new analysis of the most socially optimal cooking technologies in Africa.

But the promise of those outcomes alone may not be enough to hasten the adoption of cleaner alternatives, the researchers warn.

The study, published in the open source journal Nature Sustainability, used a geospatial model to determine the best cooking options by location across the continent, weighing factors such as availability and cost of fuel, time spent gathering fuels and preparing meals, and impacts on health and the environment. In the model, everyone using a traditional cookstove – around 83 percent of households in sub-Saharan Africa, comprising nearly 1 billion people – would switch to stoves that delivered more benefits to both households and society.

“From both a social perspective and a private perspective, it would be optimal for most of these households to use cleaner technologies,” says Marc Jeuland, Ph.D., an associate professor of global health and public policy at Duke who led the research. “And so that’s telling you that these polluting technologies are extremely damaging.”

Traditional stoves typically burn wood or other solid fuels, generating indoor air pollution and climate-altering emissions. Cooking regularly on such stoves can cause respiratory disease, as well as contribute to global warming and deforestation. Stoves fueled by electricity or even liquid petroleum gas (LPG) mitigate those risks while also offering efficiencies in time and labor. Many African households using traditional stoves spend more than an hour a day gathering fuel to prepare meals, Jeuland notes.

Despite those advantages, adoption of cleaner alternatives has been sluggish in Africa, which has lagged other regions in the transition away from polluting cooking technologies. In fact, according to the World Bank’s 2022 Energy Progress Report, the number of people using biomass-burning cookstoves actually increased by 50 percent between 2000 and 2020, as population growth outpaced conversion.

Jeuland and colleagues describe the situation as a “severe market failure” that calls for new policies and incentives to stimulate growth of cleaner technologies.

“Just because something may be beneficial from a social or private perspective doesn’t necessarily mean it’s affordable,” Jeuland says. The up-front cost of purchasing a new stove and ongoing fuel costs “are going to continue to be a barrier for many households in sub-Saharan Africa unless you really reduce those costs through subsidies of some form.”

Jeuland favors subsidies that would reduce the cost of conversion for most families to “close to zero.” He also believes wealthy nations should help foot the bill, since a wide-scale shift to cleaner cooking technologies would lessen a climate problem that those countries bear the most responsibility for creating.

“If rural Africans continue to harvest firewood for cooking, the contribution to climate change is pretty minimal. But because those damages are accumulating, the rich world should be paying to avoid them,” Jeuland says.

But affordability is not the only obstacle. Many parts of Africa do not have reliable electricity or infrastructure to deliver gas for LPG stoves, Jeuland says. The researchers’ model, designed by a team of energy systems engineers at the KTH Royal Institute of Technology in Sweden, accounted for regional infrastructure differences, picking the technology best suited for each location’s unique circumstances.

In the model selecting for the highest net benefits, about two-thirds of households across sub-Saharan Africa would be best off using LPG stoves, with another 30 percent, mostly in urban areas where grid power is available, using electric. Smaller populations in the poorest and most remote locations would use biogas or improved biomass stoves, which burn more cleanly than traditional cookstoves. Even when factoring only benefits to the household, the model suggests eight in ten people in sub-Saharan Africa should switch to cleaner technologies.

The results can help governments and nonprofits target their efforts to encourage conversion, Jeuland says. Doing more to inform people about the potential benefits of switching and developing technologies that are well-suited to local cultures and customs will also be critical, he adds.

But one other area Jeuland would like to explore is how to influence who is at the table when household cooking preferences are discussed. In traditional societies where women and children are exerting most of the cooking labor, men still often make most of the financial decisions.

“Women tend to not have as much bargaining power, and their preferences are down-weighted in these households,” Jeuland says. “And so we need to be thinking about how to empower women in these decisions.”

This research was partially supported by the Clean Cooking Alliance and The Royal Institute of Technology

CITATION: “A Geospatial Approach to Understanding Clean Cooking Challenges in Sub-Saharan Africa,” Babak Khavari, Camilo Ramirez, Merc Jeuland, Francesco Fuso Nerini. Nature Sustainability, Jan. 12, 2023. DOI: 10.1038/s41893-022-01039-8

---

JOURNAL

Nature Sustainability

DOI

10.1038/s41893-022-01039-8 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

People

ARTICLE TITLE

A geospatial approach to understanding clean cooking challenges in sub-Saharan Africa

Are plastics in the ocean as big a problem as widely believed?

Book Announcement

WORLD SCIENTIFI

 

IMAGE: COVER FOR "PLASTIC POLLUTION IN THE GLOBAL OCEAN" view more 

CREDIT: WORLD SCIENTIFIC

It is understood that plastic pollution is one of the great environmental problems of our time, but do we not know enough to solve it already? In Plastic Pollution in the Global Ocean, a number of foremost researchers in the field of environmental contamination, polar research, hydrology, oceanography, ecotoxicology and more, explore this complex topic in an accessible and engaging way; explaining why this issue is so challenging to tackle and how little we really understand the fate of these materials in the environment. Attention is given to the range of key areas and environments being considered by current research in this diverse field, highlighting the state of the art of the current research, as well as the breadth and importance of the projected and planned future investigations.

Plastics are fantastically useful materials. From automotives and technology, to healthcare and construction, plastics are a stalwart of modern life, and one which we could no longer do without. Calls to live ‘plastic-free’ are short sighted – do you wish to be without your mobile phone, your car and most of your clothes? Instead, it is important to determine where the real problems with plastics lie, and how these can be resolved without losing the incredible functionality of these materials. To this end, researchers are looking into how plastics enter the environment and degrade, which are the most hazardous plastics if they enter ecosystems (and why) and the real pros and cons of proposed solutions, including policies, biodegradable materials, and societal change. Banning plastics is neither practical nor desirable, and so learning to adapt the ways in which we use them to achieve maximum benefit with minimal harm is fundamental to retaining both a prosperous environment and society. Bringing together a range of expert contributions, this book details the recent advances in our knowledge of these essential materials, and how we can achieve all their benefits, while reducing or eliminating future environmental harm. This is one of the fundamental challenges of the modern age.

While this is a complex and nuanced issue, Plastic Pollution in the Global Ocean makes the topic accessible and digestible to established and new researchers alike, and is suitable for readers from undergraduate through to professor level who are entering this field, or who simply wish to learn more.

Written by contributors ranging from PhD scholars to world leading experts and researchers, from 20 leading institutions in the UK, China, Australia, Canada, the Netherlands, Vietnam Portugal and the USA, this review volume explores the wide range of the fundamental geographical, environmental and research areas that are central to understanding the context of plastic pollution in the global ocean. Addressing these key issues, this book should be a core text for anyone wishing to enter the field of plastics in the environment.

Plastic Pollution in the Global Ocean retails for US$148 / £130 (hardcover) and is also available in electronic formats. To order or know more about the book, visit http://www.worldscientific.com/worldscibooks/10.1142/12912.

###

About the Editor

Dr Alice A. Horton is a Principal Investigator of Anthropogenic Contaminants at the National Oceanography Centre, UK. She completed her PhD at Leiden University in the Netherlands in 2019. Her expertise lies in the fate and ecological effects of microplastics in aquatic environments. Her research focuses on how the connections between land, lakes, rivers and the ocean lead to the transport and accumulation of microplastics within the environment, their associations with organic chemicals, and how these processes influence the interactions and effects of microplastics on aquatic organisms. Dr Horton has published numerous papers and book chapters in this field, and has worked as a guest editor for the journal Environment International. She has chaired sessions and presented her work at a wide range of international conferences including MICRO, Society of Environmental Toxicology and Chemistry (SETAC), European Geosciences Union (EGU), World Water Week, and the Arctic Circle Assembly.

About World Scientific Publishing Co.

World Scientific Publishing is a leading international independent publisher of books and journals for the scholarly, research and professional communities. World Scientific collaborates with prestigious organisations like the Nobel Foundation and US National Academies Press to bring high quality academic and professional content to researchers and academics worldwide. The company publishes about 600 books and over 160 journals in various fields annually. To find out more about World Scientific, please visit www.worldscientific.com.

For more information, contact WSPC Communications at communications@wspc.com.

---

DOI

10.1142/12912 

Researchers team up to break down, upcycle low-quality, rejected plastic wastes

Grant and Award Announcement

IOWA STATE UNIVERSITY

 

IMAGE: IOWA STATE'S XIANGLAN BAI HOLDS A BEAKER OF SHREDDED, SINGLE-USE PLASTICS, WHILE GRADUATE STUDENTS WORK BEHIND HER IN THE BIORENEWABLES RESEARCH LABORATORY. view more 

CREDIT: PHOTO BY CHRISTOPHER GANNON/IOWA STATE UNIVERSITY.

AMES, Iowa – Researchers are integrating tried-and-true technologies (let’s unleash bacteria on the biodegradables then heat up the leftovers) and developing new ones (let’s try plasma that shoots “bullet” electrons) to break down waste plastics and convert them to useful materials.

“We’re learning about new technologies and helping to develop new ideas for more interdisciplinary approaches to solving these complex problems,” said Xianglan Bai, an Iowa State University associate professor of mechanical engineering and leader of two, $2-million-plus research projects supported by the U.S. Department of Energy.

The newest project, a three-year, $2.25 million grant administered by the Department of Energy’s Bioenergy Technologies Office, aims to convert the lowest-quality plastics in the waste stream, plastics now rejected for recycling, into materials for construction industries.

The first step is to feed the rejected, biodegradable fraction of the mixed wastes into an anaerobic digester where bacteria break it down to produce biogas, a sustainable, low-cost, low-carbon fuel that’s mostly methane (the same as natural gas).

Leftovers from the digester would be combined with the nonbiodegradable waste and heated without oxygen in a process called pyrolysis. That would produce bio-oils for asphalt-binding products plus charcoal-like biochars for carbon-sequestering concrete additives and reinforced biocomposites.

The big problem, Bai said, is that the rejected plastic waste is “very complex – there are too many things in there. It’s very heterogenous.”

So, the waste must be analyzed to understand what’s there. Then the researchers need to find technologies that can efficiently and economically convert the waste. And then they have to understand the resulting materials.

It takes a lot of expertise to work through all that, so Bai has assembled a large team of researchers for the project. (See sidebar.) Working together, they’ll develop a system that uses most of those rejected wastes and keeps them out of landfills.

Electron ‘bullets’ to break down plastics

The second project, a three-year, $2.5 million grant administered by the Department of Energy’s Advanced Manufacturing and Bioenergy Technologies offices, will develop new plasma technology to convert single-use plastics to biodegradable plastics.

Bai said the project is all about trying a hybrid of plasma and biological technologies to break down and upcycle single-use plastic films such as plastic bags, product packaging and food containers.

Bai has been developing novel, low-temperature plasma conversion technologies for adding value to biomass and waste plastics. The plasma is created by applying a strong electric field to a gas, which accelerates electrons and creates charged particles

“The free electrons are like bullets,” Bai said. “They speed up and hit other things. These ‘attacks’ can break down chemical bonds.”

By using the plasma with carbon dioxide, the researchers can break down decontaminated plastic films, creating a fermentable liquid. That liquid can be fermented to produce biodegradable polymers, with the fermentation creating carbon dioxide that can be looped back into the plasma reactor.

The result? Conversion of waste plastic film into biodegradable plastics in a process that lowers energy use, carbon emissions and production costs.

Bai has assembled another big team of researchers to develop this hybrid idea for reusing plastic wastes. (See sidebar.)

“These two projects are using very different approaches,” she said. “Both are using an interdisciplinary approach to solve the problems and understand what is happening at the molecular level.”

Bai is looking forward to breaking down the complexity of both projects.

“We’re going to learn and figure this out – it’s a great feeling when you figure it out.”

Researchers are working to convert these shredded, single-use, waste plastics into useful materials.

CREDIT

Photo by Christopher Gannon/Iowa State University.

Research team for converting rejected wastes to value-added construction materials:

Principal investigator, Xianglan Bai, Iowa State University

Co-principal investigators, Keith Vorst, Iowa State; Christopher Williams, Iowa State; Kejin Wang, Iowa State; Bradley Wahlen, Idaho National Laboratory; Xianhui Zhao, Oak Ridge National Laboratory (Tennessee); Soydan Ozcan, Oak Ridge National Laboratory; Yebo Li, quasar energy group (Ohio)

Research team for upcycling single-use plastic films to biodegradable polymers:

Principal investigator, Xianglan Bai, Iowa State University

Co-principal investigators, Keith Vorst, Iowa State; Mark Mba-Wright, Iowa State; Hui Hu, Iowa State; Greg Curtzwiler, Iowa State; Caixia “Ellen” Wan, University of Missouri; Nils Hansen, Sandia National Laboratories (California); Yebo Li, quasar energy group (Ohio); Xumeng Ge, quasar energy group

Study reveals new clues about how 'Earth's thermostat' controls climate

Peer-Reviewed Publication

PENN STATE

 

IMAGE: RESEARCHERS IN THE WOODS INVESTIGATING RATES OF WEATHERING IN PENNSYLVANIA. view more 

CREDIT: PENN STATE

UNIVERSITY PARK, Pa. – Rocks, rain and carbon dioxide help control Earth’s climate over thousands of years — like a thermostat — through a process called weathering. A new study led by Penn State scientists may improve our understanding of how this thermostat responds as temperatures change.

“Life has been on this planet for billions of years, so we know Earth’s temperature has remained consistent enough for there to be liquid water and to support life,” said Susan Brantley, Evan Pugh University Professor and Barnes Professor of Geosciences at Penn State. “The idea is that silicate rock weathering is this thermostat, but no one has ever really agreed on its temperature sensitivity.”

Because many factors go into weathering, it has been challenging to use results of laboratory experiments alone to create global estimates of how weathering responds to temperature changes, the scientists said.

The team combined laboratory measurements and soil analysis from 45 soil sites around the world and many watersheds to better understand weathering of the major rock types on Earth and used those findings to create a global estimate for how weathering responds to temperature.

“When you do experiments in the laboratory versus taking samples from soil or a river, you get different values,” Brantley said. “So what we tried to do in this research is look across those different spatial scales and figure out how we can make sense of all this data geochemists around the world been accumulating about weathering on the planet. And this study is a model for how we can do that.”

Weathering represents part of a balancing act of carbon dioxide in Earth’s atmosphere. Volcanoes have emitted large amounts of carbon dioxide through Earth’s history, but instead of turning the planet into a hot house, the greenhouse gas is slowly removed via weathering.

Rain takes the carbon dioxide from the atmosphere and creates a weak acid that falls to Earth and wears away silicate rocks the surface. The byproducts are carried by streams and rivers to the ocean where the carbon is eventually locked away in sedimentary rocks, the scientists said.

“It has long been hypothesized that the balance between carbon dioxide entering the atmosphere from volcanoes and being pulled out by weathering over millions of years holds the temperature of the planet relatively constant,” Brantley said. “The key is when there is more carbon dioxide in the atmosphere and the planet gets hotter, weathering goes faster and pulls more carbon dioxide out. And when the planet is cooler, weathering slows down.”

But much remains unknown about how sensitive weathering is to changing temperatures, partly because of the long spatial and time scales involved.

“In a soil profile, you are seeing a picture of soil where the camera shutter was open for sometimes a million years — there are integrated processes happening for a million years and you’re trying to compare that with a two-year flask experiment,” Brantley said.

Brantley said the field of critical zone science — which examines landscapes from the tallest vegetation to the deepest groundwater — has helped scientists better understand the complex interactions that influence weathering.

For example, rocks must fracture for water to get in cracks and start breaking down the materials. For that to happen, the rock must have large, exposed surface areas, and that is less likely to happen in regions where soil is deeper.

“It’s only when you start crossing spatial and time scales that you start seeing what’s really important,” Brantley said. “Surface area is really important. You can measure all the rate constants you want for that solution in the lab, but until you can tell me how does surface area form out there in the natural system, you are never going to be able to predict the real system.”

The scientists reported in the journal Science that temperature sensitivity measurements in the laboratory were lower than estimates from soils and rivers in their study. Using observations from the lab and field sites, they upscaled their findings to estimate the global temperature dependance of weathering.

Their model may be helpful for understanding how weathering will respond to future climate change, and in evaluating man-made attempts to increase weathering to draw more carbon dioxide from the atmosphere — like carbon sequestration.

“One idea has been to enhance weathering by digging up a lot of rock, grinding it, transporting it and putting it out in the fields to let weathering happen,” Brantley said. “And that will work — it’s already working. The problem is, it’s a very slow process.”

Though warming may speed up weathering, pulling all the carbon dioxide out of the atmosphere that humans have added could take thousands or hundreds of thousands of years, the scientists said.

Other Penn State researchers who participated on the study were Andrew Shaughnessy, doctoral candidate in the Department of Geosciences and Marina Lebedeva and Victor Balashov, senior scientists in the Earth and Environmental Systems Institute.

The National Science Foundation and the Hubert L. Barnes and Mary Barnes Professorship supported this work.

---

JOURNAL

Science

DOI

10.1126/science.add2922 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

How temperature-dependent silicate weathering acts as Earth’s geological thermostat

Study reveals salps play outsize role in damping global warming

Jelly plankton blooms can offset as much CO2 as emitted by millions of cars

Peer-Reviewed Publication

VIRGINIA INSTITUTE OF MARINE SCIENCE

 

IMAGE: VIMS PROFESSOR DEBORAH STEINBERG PREPARES TO PROCESS A SAMPLE OF SALPS COLLECTED DURING THE 2018 EXPORTS EXPEDITION TO THE NORTHEASTERN PACIFIC. EACH SALP IS ABOUT THE SIZE OF A KIWI FRUIT. view more 

CREDIT: © JASON GRAFF/OREGON STATE UNIVERSITY

Humans continue to amplify global warming by emitting billions of tons of carbon dioxide into the atmosphere each year. A new study reveals that a distant human relative plays an outsize role in damping the impacts of this greenhouse gas by pumping large amounts of carbon from the ocean surface to the deep sea, where it contributes nothing to current warming.

The study, led by Dr. Deborah Steinberg of William & Mary’s Virginia Institute of Marine Science, appeared in the latest issue of Global Biogeochemical Cycles. It reports on research conducted as part of EXPORTS, a 4-year, multi-institutional field program funded by NASA. Co-authors hail from marine institutes in Maine, Bermuda, California, Newfoundland, British Columbia, and Alaska.

The goal of EXPORTS, for EXport Processes in the Ocean from RemoTe Sensing, is to combine shipboard and satellite observations to more accurately quantify the global impact of the “biological pump.” This is a suite of biological processes that transport carbon and other organic matter from sunlit surface waters to the deep sea, effectively removing carbon dioxide from the surface ocean and atmosphere. Tiny drifting animals called zooplankton play a key role in the pump by eating phytoplankton, which incorporate carbon from carbon dioxide into their tissues during photosynthesis, then exporting that carbon to depth.

During a month-long EXPORTS expedition to the northeast Pacific Ocean in 2018, Steinberg and colleagues chanced upon a large bloom of a poorly studied player in the biological pump: a species of gelatinous zooplankton named Salpa aspera. Like other salps, these “jelly barrels” begin life with a notochord—the structure that develops into the spinal cord in humans and other vertebrates—and as adults drift through the world’s oceans like tiny transparent whales, filtering microscopic plants afloat in the water. 

Three features keyed the team’s interest in salps, and S. aspera in particular. One is that these organisms can reproduce asexually, rapidly cloning into immense blooms under the right conditions. Second is that S. aspera is bigger and filters more water than most other zooplankton, thus producing larger, heavier fecal pellets. Third is that it migrates up and down through the water each day, rising to feed on phytoplankton during the cover of night and jetting to the perpetual darkness of the deep sea during sunlit hours to avoid its own predators, which include sea turtles, marine birds, and fishes.

Together, these features had led researchers to suspect that salps might play an important role in the biological pump, as large blooms of these relatively bulky zooplankton could effectively transport carbon to depth through their heavy, fast-sinking fecal pellets; vertical migrations that give those pellets a head start on their journey to depth; and the sinking of countless salp carcasses during a bloom (individual salps live only a few weeks).

But the proof is in the pudding, and the ephemeral life cycle and uneven distribution of salps has long challenged efforts to study their role in carbon export and deep-sea food webs. “Salps follow a ‘bloom or bust’ life cycle,” says Steinberg, “with populations that are inherently patchy in space and time. That makes it hard to observe or model their contribution to the export of carbon to the deep sea.”

During the 2018 EXPORTS expedition to the Pacific, Steinberg and colleagues were able to overcome these challenges by deploying a wide range of ocean-observation tools, from traditional plankton nets and sediment traps to underwater video recorders and sonar-based computer models. Moreover, by using two research vessels—the 277-ft Roger Revelleand the 238-ft Sally Ride—the scientists were able to observe conditions not only inside the salp bloom but in surrounding waters, providing a broader geographic context for their study.

The results of the team’s unprecedented field campaign were clear. “High salp abundances, combined with unique features of their ecology and physiology, lead to an outsized role in the biological pump,” says Steinberg. 

To put things in perspective, the observed salp bloom covered more than 4,000 square miles (~11,000 km2), about the size of Connecticut. With onboard experiments showing salps capable of exporting a daily average of 9 milligrams of carbon through each square meter at 100 meters below the bloom, the amount of carbon exported to the deep sea was about 100 metric tons per day. For comparison, a typical passenger car emits 4.6 metric tons per year. Comparing these values shows the carbon removed from the climate system each day of the bloom is equal to taking 7,500 cars off the road. Adjusting these values using the team’s highest measured rate of salp-mediated export (34 mg of C per day) increases the carbon offset to more than 28,000 vehicles.

Moving forward, the team calls for increased recognition of the key role that salps play in global carbon export. “Blooms like the one we observed often go undetected,” says Steinberg, “and their contributions to the biological pump are rarely quantified, even in some of the best-studied regions of the world's oceans.” Incorporation of salp dynamics into a recent carbon-cycle model illustrates the potential of salp-mediated export. In this global model, salps and other tunicates exported 700 million metric tons of carbon to the deep sea each year, equal to emissions from more than 150 million cars. 

“Greater use of new technologies, such as adding video imaging systems to autonomous floats, would help detect these salp blooms,” says Steinberg. “Our study serves as a ‘call to arms’ to better detect and quantify these processes, using technology and sampling schemes that enable their inclusion in measurements and models of the biological carbon pump.”

A snorkeler swims through a salp bloom off the coast of New Zealand. Salps resemble jellyfish but are more closely related to humans. VIMS-led research reveals they play an outsized role in the ocean’s biological carbon pump.

CREDIT

Paul Caiger

JOURNAL

Global Biogeochemical Cycles

DOI

10.1029/2022GB007523 

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

The outsized role of salps in carbon export in the subarctic Northeast Pacific Ocean