Using waste heat to power an environmentally sustainable future

City, University of London's Dr Martin White, explores a novel organic Rankine system for converting waste heat into electricity.

CITY UNIVERSITY LONDON

Research News

 

IMAGE: PERFORMANCE GAIN OBTAINED BY TWO-PHASE ORC SYSTEMS view more 

CREDIT: DR MARTIN WHITE

In his most recent published research, appearing in Applied Thermal Engineering, City, University of London's Dr Martin White explores a novel organic Rankine cycle system, based on a two-phase expansion through numerical simulations of the system.

His paper, Cycle and turbne optimisation for an ORC operating with two-phase expansion, considers the use of modern fluids whose properties could help to mitigate concerns around turbine damage, whilst allowing the benefits of two-phase expansion to be realised.

Waste heat from a range of industries, ranging from iron and steel to food and drink, is currently ejected into the environment. Thus, the recovery of this wasted energy could have a significant role in reducing the environmental footprint of the manufacturing sector and help to ensure future manufacturing practices are sustainable.

Dr White, a Lecturer in Thermal Power in the School of Mathematics, Computer Science and Engineering, says:

"One of the most promising groups of waste-heat recovery technologies are those that are able to convert this waste heat into electricity. However, current technologies, typically based on the organic Rankine cycle (ORC) - which is similar to a steam cycle but operates with a different fluid rather than water - typically have relatively poor thermodynamic performance and are associated with high costs."

In a conventional ORC system, power is produced by the turbine which is designed to operate completely with a fluid that is in a gaseous state. This is done to avoid the presence of liquid droplets within the turbine that could damage or erode the machine. However, previous investigations have suggested that the admission of a two-phase fluid, which is a combination of liquid and vapour, could enhance the power output from these systems.

Dr White believes that if a suitable turbine design intended for two-phase operation can be designed, the performance of ORC systems could be enhanced.

The simulations he has carried out indicate that for waste heat temperatures up to 250 degrees centigrade, the introduction of two-phase expansion could generate up to 28% more power than conventional single-phase systems. Moreover, candidate designs for the turbine are proposed which require further investigation in later studies.

The work was conducted by Dr White as part of his Research Fellowship, funded by the Royal Academy of Engineering.

Through his Fellowship, Dr White is investigating next-generation waste-heat recovery technologies based on two-phase expansion.

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Electromagnetic anomalies that occur before an earthquake

SHINSHU UNIVERSITY

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IMAGE: SCHEMATIC VIEW OF EXPERIMENTAL SET UP view more 

CREDIT: COPYRIGHT © 2021, YUJI ENOMOTO, SHINSHU UNIVERSITY

It has been documented over hundreds of years that various electromagnetic anomalies occur during a few weeks before the occurrence of a large earthquake. These electromagnetic anomalies are variations that appear in telluric current, geomagnetism, electromagnetic waves etc. before the earthquake.

Although there are various models to explain the mechanism, the large current generated at the source was not fully explained. For example, many researchers thought that the stress applied to the fault produced an electric current, but the stress applied to the fault takes place over hundreds or thousands of years before the occurrence of the earthquake. It is a common belief among seismologists that it is impossible for the stress to suddenly increase and generate a large current just before the earthquake, and therefore the mechanism had not yet been explained.

To resolve this mystery, Shinshu University and Genesis Research Institute, Inc. conducted a joint research project on earthquake-preceding phenomena under the leadership of Professor Emeritus of Shinshu University, Dr. Yuji Enomoto. The research group made the following hypothesis and conducted laboratory experiments on indoor rock fracture and gas-electric interactions to solve the mystery of electromagnetic anomalies.

In the area that is at the epicenter of a seismic fault, a fault-valve forms before the next earthquake occurs. It is believed that dense layers in the crust are formed over time. The fluid, including some gases such as water that springs up from the vicinity is trapped by the fault valve and stays there. When the shear stress applied to the fault or the pressure of the stagnant reserved fluid reaches criticality, the fault valve cracks, the high-pressure fluid rises along the fault, and the pressure gradually decreases.

As the pressure decreases, carbon dioxide or methane that are now dissolved in the fluid are degassed at once, expanding in volume and expanding the cracks. The model considers the fault becomes fragile and the rupture accelerates, leading to an earthquake. The gas becomes electrified in the process. That is, it is charged with electricity. The trapped electrons in the defects are suddenly released due to the thermal stimulus and attached to gas molecules. Because it is negatively charged, a current is generated as the gas moves.

In the lab, several types of rock, including granite, gabbro, quartz diorite and basalt were tested. A simple estimation found that there is a high possibility that a large current will be generated immediately before the earthquake, depending on the earthquake magnitude.

This supports the above-mentioned hypothesis that fault rupture progresses just before an earthquake, and the invading gas is charged and forms a large current, causing various electromagnetic anomalies. In the future, the group plan to carry out field observations to verify this model.

CAPTION

Proposed model

CREDIT

Copyright © 2021, Yuji Enomoto, Shinshu University

CAPTION

Experimental set up

CREDIT

Copyright © 2021, Yuji Enomoto, Shinshu University

COVID-19 infections were high among hospital staff but re-infection rates are very low

EUROPEAN LUNG FOUNDATION

Research News

 

A study of healthcare workers shows they were three times more likely to become infected during the COVID-19 pandemic compared to the general population. Around one in five of workers who were infected were asymptomatic and unaware they had COVID-19.

The study published in ERJ Open Research [1] also shows that it was not only frontline staff who faced the higher risk, suggesting that there was transmission between staff and within the wider community.

However, health care workers who had been infected were very unlikely to contract COVID-19 a second time in the following six months.

The research was led by Professor James Chalmers, a consultant respiratory physician from the University of Dundee, UK. He said: "We have always believed that front line health workers face a high risk of contracting COVID-19 and that's why we've tried to ensure they have the PPE needed to protect themselves. But many questions remain about the level of this risk and what other measures we can take to protect staff and reduce transmission of the disease."

The study included a total of 2063 staff working in a wide variety of healthcare roles in in the East of Scotland. Between May and September 2020, participants were given blood tests for antibodies against COVID-19. The presence of these antibodies is a very accurate indication that someone has been infected with COVID-19. Researchers also recorded whether any participants developed an infection in the following months.

Results from these health care workers were compared with a randomly selected control group of blood samples taken by local GPs during the same period of time.

The blood tests showed that 300 (14.5%) of the healthcare workers had been infected. This is more than three times higher than the proportion of people infected in the local population. The highest rates of infections among the workers were in dentistry (26%), health care assistants (23.3%) and hospital porters (22.2%). The rate among admin staff was the same as that of doctors (21.1%).

Rates among people working in areas of the hospital where COVID-19 patients were being treated were a little higher than those working in non-COVID areas (17.4% compare to 13.5%). However, the majority of infections were in staff who were not working directly with COVID-19 patients, suggesting transmission between staff or infections acquired in the community.

Among the 300 healthcare workers who tested positive, 56 (18.7%) did not think they ever had COVID-19 and were completely asymptomatic. The researchers say this is important since people without symptoms are likely to go to work and could potentially infect other people.

In the months following their blood tests, 39 workers developed a symptomatic COVID-19 infection, but only one of these was a worker who had previously tested positive. This equates to an 85% reduction in risk, which is similar to the protection provided by COVID-19 vaccines.

Professor Chalmers said: "A lot of attention during the pandemic has been around PPE for doctors and nurses but we found that dentists, healthcare assistants and porters were the staff most likely to test positive.

"We continued to monitor staff for up to seven months and found that having a positive antibody test gave 85% protection against a future infection. This is really good news for people who have already had COVID-19, as it means the chances of a second infection are very low."

The team hope to continue the research to see how long immunity lasts and how vaccination affects infections among healthcare workers.

Professor Anita Simonds, President of the European Respiratory Society and Consultant in Respiratory and Sleep Medicine at Royal Brompton Hospital, UK, was not involved in the research. She said: "This research shows the high levels of COVID-19 infection among all healthcare workers, with the highest evidence of infection in dentists, healthcare assistants and porters. Staff working in critical care, who are likely to have been protected by using personal protective equipment at all times, were not disproportionately affected.

"It should be noted that among administrative staff, 21.1% were found to have been infected with COVID-19, indicating that all those working directly with patients, and those working in other hospital roles are at risk, and vaccination and risk assessment for appropriate levels of PPE in all these frontline groups are crucial."

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COVID-19 infection rates of dentists remain lower than other health professionals

AMERICAN DENTAL ASSOCIATION

Research News

 

CHICAGO, May 24, 2021--More than a year after COVID-19 appeared in the U.S., dentists continue to have a lower infection rate than other front-line health professionals, such as nurses and physicians, according to a study published online ahead of the June print issue in the Journal of the American Dental Association. The study, "COVID19 among Dentists in the U.S. and Associated Infection Control: a six-month longitudinal study," is based on data collected June 9 - Nov. 13, 2020.

According to the study, based on the number of dentists with confirmed or probable COVID-19 infections over more than six months, the cumulative infection rate for U.S. dentists is 2.6%. The monthly incidence rate varied, ranging from 0.2% to 1.1% per month. By comparison, in June 2020, the cumulative COVID-19 prevalence rate for other U.S. health professionals ranged from 3.3% (Chicago-based hospital physicians) to 35.3% (U.S. based emergency medicine services).

"We're pleased to see that dentists have demonstrated continued low monthly incidence of disease despite several regional and national COVID-19 rate spikes during the study period," said American Dental Association (ADA) Science and Research Institute Chief Executive Officer Marcelo Araujo, D.D.S., M.S., Ph.D., the senior author of the report.

Dr. Araujo added, "This study shows high rates of pre-appointment screening of patients and appropriate infection control measures throughout the study period, demonstrating that adhering to very strict protocols for enhanced infection control helps protect their patients, their dental team and themselves."

In addition to Dr. Araujo, other authors of the report include researchers from the ADA Science and Research Institute and Health Policy Institute based in Chicago, as well as Maria L Geisinger, D.D.S., M.S. with University of Alabama at Birmingham in Birmingham, Ala., and Effie Ioannidou, D.D.S., M.D.S., with the University of Connecticut in Farmington, Conn., and a member of the ADA Council on Scientific Affairs.

This study is a continuation of the first large-scale report of incidence rates of COVID-19 among dentists in the U.S published in October 2020. The present six-month longitudinal study aimed to:

• Determine the cumulative prevalence rate of COVID-19 among dentists;

• Calculate the monthly incidence rate for the same population over the course of the study; and

• Assess the level of engagement in specific infection control practices among dentists over a six-month period of time.

The results of this present study, as well as the earlier study, show that prevalence and incidence rates among dentists continue to be very low when compared to the population as a whole and to other health care professionals.

"This study reinforces that the dental care sector is up and running safely," said Chief Economist and Vice President of the ADA Health Policy Institute Marko Vujicic, Ph.D. "Nowhere is this proof point more evident than by the fact that more than 90% of patients surveyed indicate they have already visited the dentist or soon will."

The authors plan future research projects on the barriers and facilitators to wearing Personal Protective Equipment (PPE) according to CDC recommendations, and levels of protection against COVID-19 provided by different levels of PPE use and infection control procedures.

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For more information on COVID-19 and dental visits, visit MouthHealthy.org.

Editor's Note: Reporters are invited to follow the ADA on Twitter @AmerDentalAssn

About the American Dental Association

The not-for-profit ADA is the nation's largest dental association, representing more than 163,000 dentist members. The premier source of oral health information, the ADA has advocated for the public's health and promoted the art and science of dentistry since 1859. The ADA's state-of-the-art research facilities develop and test dental products and materials that have advanced the practice of dentistry and made the patient experience more positive. The ADA Seal of Acceptance long has been a valuable and respected guide to consumer dental care products. The monthly The Journal of the American Dental Association (JADA) is the ADA's flagship publication and the best-read scientific journal in dentistry. For more information about the ADA, visit ADA.org. For more information on oral health, including prevention, care and treatment of dental disease, visit the ADA's consumer website MouthHealthy.org.

Ancient discovery could help us develop more disease resistant watermelons

UNIVERSITY OF SHEFFIELD

Research News

 

An ancient melon which is the closest relative and potential ancestor of the watermelon, has been discovered by scientists.

A team of scientists led by Dr Guillaume Chomicki, from the University of Sheffield, has discovered the potential progenitor of the domestic watermelon, the Kordofan melon, using DNA sequencing technologies and analyses with historical data and Ancient Egyptian iconography.

The discovery could explain why watermelons are so susceptible to disease as their analysis shows how key disease-resistant genes were lost as the melon was domesticated, and also help us to breed more disease-resistant watermelons in the future.

The findings show that the melon originates from North Eastern Africa, in the region of Kordofan in Sudan, settling decades old debate and giving us more insight into how the watermelon was domesticated.

Dr Guillaume Chomicki, from the University of Sheffield's Department of Animal and Plant Sciences, said: "The watermelon is one of the most important tropical fruits, with over 200 million tons produced every year, but it is also very susceptible to disease.

"There are specific watermelon diseases, such as the Watermelon mosaic virus and they are also very sensitive to fungal infections. In conventional agriculture, they are frequently treated with fungicides, and insecticides to limit virus transfer.

"Our analysis clearly shows that the Kordofan melon has more disease resistant genes, and different versions of those too. This means that the genome of the Kordofan melon has the potential to help us breed disease-resistant watermelons and allow non-GM gene editing. Achieving this would be reducing substantially pesticide use in watermelon farming."

The new research, published in the journal PNAS, also found that the wild progenitor of the watermelon was already non-bitter and farmers brought these naturally sweet forms into cultivation, this contrasts dramatically with other crop species in the same family such as cucumber or squash, in which the loss of bitterness is the result of domestication.

The genomic work, together with new interpretations of ancient Egyptian iconography by Dr Chomicki and colleagues shows that Egyptians were cultivating sweet watermelons at least 4,200 years ago.

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Notes to editors:

* The study will be available when the embargo breaks at: https://doi.org/10.1073/pnas.2101486118 to see an embargoed copy before then please contact the Media Relations Officer.

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A seedy slice of history: Watermelons actually came from northeast Africa

WASHINGTON UNIVERSITY IN ST. LOUIS

Research News

Just in time for picnic-table trivia, a new study published in the Proceedings of the National Academy of Sciences rewrites the origins of domesticated watermelons.

Using DNA from greenhouse-grown plants representing all species and hundreds of varieties of watermelon, scientists discovered that watermelons most likely came from wild crop progenitors in northeast Africa.

The study corrects a 90-year-old mistake that lumped watermelons into the same category as the South African citron melon. Instead, researchers, including a first author now at Washington University in St. Louis, found that a Sudanese form with non-bitter whitish pulp, known as the Kordofan melon (C. lanatus), is the closest relative of domesticated watermelons.

The genetic research is consistent with newly interpreted Egyptian tomb paintings that suggest the watermelon may have been consumed in the Nile Valley as a dessert more than 4,000 years ago.

"Based on DNA, we found that watermelons as we know them today -- with sweet, often red pulp that can be eaten raw -- were genetically closest to wild forms from west Africa and northeast Africa," said Susanne S. Renner, honorary professor of biology in Arts & Sciences at Washington University.

Renner is an evolutionary biologist who recently joined Washington University after 17 years working as a professor at Ludwig Maximilian University in Munich, Germany, where she also served as the director of the Munich Botanical Garden and Munich herbarium.

Her lab has long focused on honey melons and cucumbers, but for the past 10 years she has turned to watermelons and bitter gourds.

The genetic information published in the new study -- completed with colleagues from the U.S. Department of Agriculture in Ithaca, New York; the Royal Botanic Gardens, Kew in London; and the University of Sheffield -- could be useful for developing a more disease-resistant watermelon crop, Renner said.

"Today's watermelon comes from a very small genetic stock and is highly susceptible to diseases and insect pests, including various mildews, other fungi, viruses and nematodes [worms]," Renner said. "So far, we found variation in three disease resistance genes between the Kordofan melon and the domesticated watermelon. Breeders might use these and other insights from the genome."

But some of the greatest takeaways from this study, Renner said, are related to the mobility of people and their cultural connections.

"It was the Egyptian tomb paintings that convinced me that the Egyptians were eating cold watermelon pulp," Renner said. "Otherwise, why place those huge fruits on flat trays next to grapes and other sweet fruits?"

"Melons, cucumbers and watermelons were domesticated several times" across human history, she said. "But to place these domestications in space and name is much more difficult than I thought 10 to 15 years ago. DNA from ancient seeds is already beginning to help."

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FSU researchers find Greenland glacial meltwaters rich in mercury

FLORIDA STATE UNIVERSITY

Research News

 

IMAGE: NEW RESEARCH FROM FLORIDA STATE UNIVERSITY SHOWS THAT CONCENTRATIONS OF THE TOXIC ELEMENT MERCURY IN RIVERS AND FJORDS CONNECTED TO THE GREENLAND ICE SHEET ARE COMPARABLE TO RIVERS IN INDUSTRIAL... view more 

CREDIT: PHOTO COURTESY OF JADE HATTON/UNIVERSITY OF BRISTOL

New research from Florida State University shows that concentrations of the toxic element mercury in rivers and fjords connected to the Greenland Ice Sheet are comparable to rivers in industrial China, an unexpected finding that is raising questions about the effects of glacial melting in an area that is a major exporter of seafood.

"There are surprisingly high levels of mercury in the glacier meltwaters we sampled in southwest Greenland," said FSU postdoctoral fellow Jon Hawkings. "And that's leading us to look now at a whole host of other questions such as how that mercury could potentially get into the food chain."

The study was published today in Nature Geoscience.

Initially, researchers sampled waters from three different rivers and two fjords next to the ice sheet to gain a better understanding of meltwater water quality from the glacier and how nutrients in these meltwaters may sustain coastal ecosystems.

One of the elements they measured for was the potentially toxic element mercury, but they had no expectation that they would find such high concentrations in the water there.

Typical dissolved mercury content in rivers are about 1 - 10 ng L-1 (the equivalent of a salt grain-sized amount of mercury in an Olympic swimming pool of water). In the glacier meltwater rivers sampled in Greenland, scientists found dissolved mercury levels in excess of 150 ng L-1, far higher than an average river. Particulate mercury carried by glacial flour (the sediment that makes glacial rivers look milky) was found in very high concentrations of more than 2000 ng L-1.

With any unusual finding, the results raise more questions than answers. Researchers are unclear if the mercury levels will dissipate farther away from the ice sheet and whether this "glacier" derived mercury is making its way into the aquatic food web, where it can often concentrate further.

"We didn't expect there would be anywhere near that amount of mercury in the glacial water there," said Associate Professor of Earth, Ocean and Atmospheric Science Rob Spencer. "Naturally, we have hypotheses as to what is leading to these high mercury concentrations, but these findings have raised a whole host of questions that we don't have the answers to yet."

Fishing is Greenland's primary industry with the country being a major exporter of cold-water shrimp, halibut and cod.

The finding underscores the complicated reality of rapidly melting ice sheets across the globe. About 10 percent of the Earth's land surface is covered by glaciers, and these environments are undergoing rapid change as a result of rising temperatures. Scientists worldwide are working to understand how warming temperatures -- and thus more rapidly melting glaciers -- will affect geochemical processes critical to life on Earth.

"For decades, scientists perceived glaciers as frozen blocks of water that had limited relevance to the Earth's geochemical and biological processes," Spencer said. "But we've shown over the past several years that line of thinking isn't true. This study continues to highlight that these ice sheets are rich with elements of relevance to life."

Hawkings also said it was worth noting that this source of mercury is very likely coming from the Earth itself, as opposed to a fossil fuel combustion or other industrial source. That may matter in how scientists and policymakers think about the management of mercury pollution in the future.

"All the efforts to manage mercury thus far have come from the idea that the increasing concentrations we have been seeing across the Earth system come primarily from direct anthropogenic activity, like industry," Hawkings said. "But mercury coming from climatically sensitive environments like glaciers could be a source that is much more difficult to manage."

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Hawkings' and Spencer's co-authors come from an international team based in the United States (USGS, Woods Hole Oceanographic Institute, University of California Santa Cruz, Brigham Young University) United Kingdom (University of Bristol, University of Glasgow), Czechia (Charles University), Norway (UiT The Arctic University of Norway, UiO University of Oslo), Greenland (Greenland Climate Research Centre) and the Netherlands (Royal Netherlands Institute of Sea Research).

Hawkings was supported by a European Commission Horizon 2020 Marie Sklodowska-Curie Actions Fellowship and the Natural Environment Research Council (United Kingdom). Part of the research was conducted at the Florida State University-headquartered National High Magnetic Field Laboratory, funded by the National Science Foundation and the state of Florida.

Microscopic fossils record ancient climate conditions

UNIVERSITY OF UTAH

Research News

 

IMAGE: TRANSMISSION ELECTRON MICROSCOPE IMAGES OF MAGNETOFOSSILS WITH EXAMPLES OF CUBOCTAHEDRA (TOP CENTER, ROUNDED) AND ELONGATED PRISMS (BOTTOM CENTER, SQUARE). view more 

CREDIT: COURTNEY WAGNER/UNIVERSITY OF UTAH

Fifty-six million years ago, as the Earth's climate warmed by five to eight degrees C, new land mammals evolved, tropical forests expanded, giant insects and reptiles appeared and the chemistry of the ocean changed. Through it all, bacteria in the ocean in what is now New Jersey kept a record of the changes in their environment through forming tiny magnetic particles. Now, those particles and their record are all that's left of these microorganisms. Thanks to new research tools, that record is finally being read.

In research published in the journal Paleoceanography and Paleoclimatology, researchers including University of Utah doctoral student Courtney Wagner and associate professor Peter Lippert report the climate clues that can be found by analyzing the magnetic fossil particles, or magnetofossils.

"We interpret the relative abundances of these different populations of magnetofossils based on shape and size, which are a function of bacteria species, to encode environmental changes that are not as apparent in other fossil data sets or geochemical proxies," Lippert says.

Using their FORC method (which stands for first-order reversal curves, a way of magnetically measuring and statistically describing the magnetic signatures in a sample of rock or sediment) they teased out three different subsets of magnetofossils from ancient coastal marine sediments.

"Each of the magnetofossil populations tells us something a little different about the environment," Wagner says. One consists of "giant needle-shaped" magnetofossils, associated with increased iron and an expansion of a gradient between oxygenated and deoxygenated seawater. Another contains "equant" magnetofossils, which may record more stable, long-term conditions in the ocean and the last contains "elongated" magnetofossils, which may indicate seasonal conditions.

The results are important because they allow researchers to track the chemistry of the ocean throughout a global warming event similar to what the Earth is currently experiencing. For example, the results seem to show that the New Jersey coast rapidly declined in oxygen near the beginning of the ancient warming event and then oxygen levels fluctuated thereafter.

"All this has potential implications for understanding how climate change will affect these sensitive coastal ecosystems today and in the future," Wagner says.

CAPTION

Transmission electron microscope image of magnetofossils with examples of giant magnetofossils (giant bullets, in left cluster, and spindles, in right cluster).

CREDIT

Courtney Wagner/University of Utah

 

Researchers identify the causes of the extreme drought that affected the Pantanal

The study shows that the 2019-20 drought resulted from a natural meteorological phenomenon similar to the one that caused the 2014-16 critical water shortage in São Paulo state, Southeast Brazil.

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO

Research News

 

IMAGE: THE STUDY SHOWS THAT THE 2019-20 DROUGHT RESULTED FROM A NATURAL METEOROLOGICAL PHENOMENON SIMILAR TO THE ONE THAT CAUSED THE 2014-16 CRITICAL WATER SHORTAGE IN SÃO PAULO STATE, SOUTHEAST BRAZIL... view more 

CREDIT: JOSÉ MARENGO

The extreme drought suffered by the Pantanal in 2019-20, considered the worst in the last 50 years, was caused by natural climate conditions similar to those underlying the 2014-16 water crisis in São Paulo state. The Pantanal is one of the world’s largest wetlands. The Brazilian portion is located in the Center-West region, mainly Mato Grosso do Sul state.

The 2019-20 extreme drought was studied by researchers affiliated with the Natural Disaster Surveillance and Early Warning Center (CEMADEN), the National Space Research Institute (INPE) and São Paulo State University (UNESP) as part of a project supported by FAPESP under the aegis of its Research Program on Global Climate Change (RPGCC).

The results of the study are published in the journal Frontiers in Water.

“The recent drought in the Pantanal was caused by a meteorological phenomenon we call atmospheric blocking. A high-pressure area prevented the formation of rainclouds throughout the central-western portion of South America. Temperatures were very high and relative humidity very low,” José Marengo, a researcher at CEMADEN and principal investigator for the study, told Agência FAPESP.

“Lack of rain combined with high temperatures and very low humidity led to a heightened risk of fire, which extended to agricultural areas as well as natural parts of the biome.”

Deliberate burning of vegetation to clear land for cattle ranching contributed to the spread of wildfires throughout the region, and these were harder to control owing to the long period of drought. “Fires caused on one hand by warmer air and lack of rain in the Pantanal, and on the other by the burning of areas to clear the vegetation for cattle to graze, resulted in environmental disaster,” Marengo said.

Sources of observational data

To investigate the hydroclimatic causes of drought in the Pantanal, the researchers used an array of sources of observational hydrological data (on the level of the Paraguay River) as well as data on rainfall and hydroclimatic teleconnections (links between hydrological events and atmospheric circulation patterns causing weather phenomena). They also used information on land use and remote sensing data to characterize water stress and drought in the Pantanal.

Based on an analysis of all these datasets they were able to provide a clear description of the interannual variability of rainfall, river streamflow, and drought-related factors, concluding that the drought was caused by a complex combination of hydroclimatic teleconnections.

“The lack of rain during the summer in 2019 and 2020 in the Pantanal was due to a decrease in the flow of warm humid air from the Amazon,” Marengo said.

Part of the rain that falls on the Pantanal is brought by winds blowing from the North Atlantic to the Amazon, and from there to the Pantanal in Brazil’s Center-West region. The humidity coming down from the Amazon and cold fronts coming up from the South were prevented from reaching the Pantanal by a high-pressure bubble. As a result, masses of warmer and drier air contributed to the scarcity of rain during the summer at the peak of the monsoon season, typically characterized by changes in atmospheric circulation and precipitation in tropical and subtropical coastal regions due to asymmetric heating of land and sea.

The result was a prolonged extreme drought throughout the Pantanal, with severely adverse effects on the biome. “This phenomenon is natural and occurred in a similar manner in São Paulo during the 2014-16 drought,” Marengo said.

Amplified impact

According to Marengo, it is not yet possible to foresee whether the Pantanal will face more severe droughts in the years ahead. The problem can only be avoided if there is the right amount of rain at the right time. “It’s no use getting rain now, in March, at the end of the rainy season, and then between December this year and February 2022, for example,” he said. “This compromises the rainy season and increases the risk of more wildfires in the Pantanal.”

Drought in the Pantanal cannot be blamed solely on global climate change because it is a natural event and climate change is a long-term process. The recent drought differed from those seen in the 1950s and 1960s when the planet was cooler. “What’s happening now is that these natural droughts are suffering the effects of climate instability, and the effects are worse because back then there was a lot less human occupancy in the region. Its population is now more vulnerable to the impact of drought,” Marengo said.

The article “Extreme drought in the Brazilian Pantanal in 2019-2020: characterization, causes, and impacts” (doi: 10.3389/frwa.2021.639204) by Jose A. Marengo, Ana P. Cunha, Luz Adriana Cuartas, Karinne R. Deusdará Leal, Elisangela Broedel, Marcelo E. Seluchi, Camila Miranda Michelin, Cheila Flávia De Praga Baião, Eleazar Chuchón Ângulo, Elton K. Almeida, Marcos L. Kazmierczak, Nelson Pedro António Mateus, Rodrigo C. Silva and Fabiani Bender is at: www.frontiersin.org/articles/10.3389/frwa.2021.639204/full.

Pre-Columbus climate change may have caused Amazon population decline

Indigenous Amazonia populations may have been in decline prior to 'Great Dying'

UNIVERSITY OF READING

Research News

Climate change impacts felt in the Amazon rainforest prior to the arrival of European settlers after 1492 may have meant populations of indigenous people were already in decline before the 'Great Dying', new research has suggested.

Scientists studying fossil pollen and charcoal data from across the Amazon say it appears to show that human management of the rainforest may have peaked around 1200 AD, before some sites were abandoned, allowing reforestation of these areas.

The new research, involving University of Reading scientists and published in the journal Science, challenges the prior assumption that the largest population decrease in the Americas - known as the Great Dying - did not start until after European settlers carried new diseases to the continent.

Professor Frank Mayle, a tropical palaeoecology researcher at the University of Reading, and co-author of the study, said: "Our analysis raises the possibility that climate change caused the decline of some Amazonian societies several centuries before the Europeans arrived, especially the more complex societies which may have been too rigid to adapt.

"Although the introduction of European diseases, such as small pox, is still likely to have been the reason for the major population decline subsequently seen in the Americas, the research is a warning of the threat climate change poses to society. Knowledge of how different types of ancient society responded to past climate change may provide valuable clues to understanding the fate of today's diverse societies under 21st century global warming."

The research was led by Professor Mark Bush at Florida Tech, and included a team of international collaborators who are investigating how pre- and post-European people modified and managed Amazonian forests.

Analysis of fossilised pollen and charcoal revealed that many previously deforested lands have been recovering for over 800 years, rather than the 400 years previously supposed, indicating a pre-European population decline. The research team is now looking to assess the drivers and mechanisms of this population drop-off.

Finding signatures of initial forest regrowth following ancient human disturbance is important to ongoing discussions about the impact of Pre-Columbian people on Amazon rainforests and the extent to which modern forests exhibit legacies of past human activity.

This research also has implications for atmospheric and biosphere science. It was previously believed that the indigenous population collapse in Amazonia following European Contact, and subsequent reforestation, led to the sequestration of so much carbon dioxide that global atmospheric CO2 levels decreased markedly, an event known as the 'Orbis Spike'. Yet the team found no evidence that the Orbis Spike was caused by Amazonian reforestation.

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The research was funded by grants from the National Geographic Society and the National Science Foundation in the United States and the European Research Council and the Natural Environment Research Council in the United Kingdom.