Tag Archives: #pollution

Aerosols From Pollution, Desert Storms, and Forest Fires May Intensify Thunderstorms (Earth Science)

Researchers identify a mechanism by which small particles in the atmosphere can generate more frequent thunderstorms.

Observations of Earth’s atmosphere show that thunderstorms are often stronger in the presence of high concentrations of aerosols — airborne particles too small to see with the naked eye.

MIT scientists have discovered a new mechanism by which aerosols may intensify thunderstorms in tropical regions. © MIT

For instance, lightning flashes are more frequent along shipping routes, where freighters emit particulates into the air, compared to the surrounding ocean. And the most intense thunderstorms in the tropics brew up over land, where aerosols are elevated by both natural sources and human activities.

While scientists have observed a link between aerosols and thunderstorms for decades, the reason for this association is not well-understood.

Now MIT scientists have discovered a new mechanism by which aerosols may intensify thunderstorms in tropical regions. Using idealized simulations of cloud dynamics, the researchers found that high concentrations of aerosols can enhance thunderstorm activity by increasing the humidity in the air surrounding clouds.

This new mechanism between aerosols and clouds, which the team has dubbed the “humidity-entrainment” mechanism, could be incorporated into weather and climate models to help predict how a region’s thunderstorm activity might vary with changing aerosol levels.

“It’s possible that, by cleaning up pollution, places might experience fewer storms,” says Tim Cronin, assistant professor of atmospheric science at MIT. “Overall, this provides a way that humans may have a footprint on the climate that we haven’t really appreciated much in the past.”

Cronin and his co-author Tristan Abbott, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences, have published their results today in the journal Science.

Clouds in a box

An aerosol is any collection of fine particles that is suspended in air. Aerosols are generated by anthropogenic processes, such as the burning of biomass, and combustion in ships, factories, and car tailpipes, as well as from natural phenomena such as volcanic eruptions, sea spray, and dust storms. In the atmosphere, aerosols can act as seeds for cloud formation. The suspended particles serve as airborne surfaces on which surrounding water vapor can condense to form individual droplets that hang together as a cloud. The droplets within the cloud can collide and merge to form bigger droplets that eventually fall out as rain.

But when aerosols are highly concentrated, the many tiny particles form equally tiny cloud droplets that don’t easily merge. Exactly how these aerosol-laden clouds generate thunderstorms is an open question, although scientists have proposed several possibilities, which Cronin and Abbott decided to test in high-resolution simulations of clouds.

For their simulations, they used an idealized model, which simulates the dynamics of clouds in a volume representing Earth’s atmosphere over a 128-kilometer-wide square of tropical ocean. The box is divided into a grid, and scientists can observe how parameters like relative humidity change in individual grid cells as they tune certain conditions in the model.

In their case, the team ran simulations of clouds and represented the effects of increased aerosol concentrations by increasing the concentration of water droplets in clouds. They then suppressed the processes thought to drive two previously proposed mechanisms, to see if thunderstorms still increased when they turned up aerosol concentrations.

When these processes were shut off, the simulation still generated more intense thunderstorms with higher aerosol concentrations.

“That told us these two previously proposed ideas weren’t what were producing changes in convection in our simulations,” Abbott says.

In other words, some other mechanism must be at work.

Video: A simulation of one day of cloud formation in a region of low aerosol concentration. The colored surface represents the air temperature at the surface. Many of the clouds (in grey) are 10 to 15 kilometers tall, reaching at or above the cruising altitudes of most aircraft. These simulated clouds are similar in size to clouds that produce thunderstorms in the real-world tropics. © MIT

Driving storms

The team dug through the literature on cloud dynamics and found previous work that pointed to a relationship between cloud temperature and the humidity of the surrounding air. These studies showed that as clouds rise they mix with the clear air around them, evaporating some of their moisture and as a result cooling the clouds themselves.

If the surrounding air is dry, it can soak up more of a cloud’s moisture and bring down its internal temperature, such that the cloud, laden with cold air, is slower to rise through the atmosphere. On the other hand, if the surrounding air is relatively humid, the cloud will be warmer as it evaporates and will rise more quickly, generating an updraft that could spin up into a thunderstorm.

Cronin and Abbott wondered whether this mechanism might be at play in aerosols’ effect on thunderstorms. If a cloud contains many aerosol particles that suppress rain, it might be able to evaporate more water to the its surroundings. In turn, this could increase the humidity of the surrounding air, providing a more favorable environment for the formation of thunderstorms. This chain of events, therefore, could explain aerosols’ link to thunderstorm activity.

They put their idea to the test using the same simulation of cloud dynamics, this time noting the temperature and relative humidity of each grid cell in and around clouds as they increased the aerosol concentration in the simulation. The concentrations they set ranged from low-aerosol conditions similar to remote regions over the ocean, to high-aerosol environments similar to relatively polluted air near urban areas.

They found that low-lying clouds with high aerosol concentrations were less likely to rain out. Instead, these clouds evaporated water to their surroundings, creating a humid layer of air that made it easier for air to rise quickly through the atmosphere as strong, storm-brewing updrafts.

“After you’ve established this humid layer relatively low in the atmosphere, you have a bubble of warm and moist air that can act as a seed for a thunderstorm,” Abbott says. “That bubble will have an easier time ascending to altitudes of 10 to15 kilometers, which is the depth clouds need to grow to to act as thunderstorms.”

This “humidity-entrainment” mechanism, in which aerosol-laden clouds mix with and change the humidity of the surrounding air, seems to be at least one explanation for how aerosols drive thunderstorm formation, particularly in tropical regions where the air in general is relatively humid.

“We’ve provided a new mechanism that should give you a reason to predict stronger thunderstorms in parts of the world with lots of aerosols,” Abbott says.

This research was supported, in part, by the National Science Foundation.

Provided by MIT

Polymer To Capture Ammonia Pollution Realized At the Niels Bohr Institute (Material Science)

Researchers at the Niels Bohr Institute and the Department of Chemistry at University of Copenhagen, have recently designed a porous polymer aiming for the capture of small molecules. Ammonia is a toxic gas widely used as a reagent in industrial processes or resulting from agricultural activities, causing irritation in the throat, eye damage and even death to humans. Being able to capture it with this new method could have huge health benefits. The result is now published in ACS Applied Materials & Interfaces.

Working in the lab can be a bit messy. This shot is from the actual production of the polymer at the chemistry lab. But like Heloisa Bordallo’s students say: “Clean lab = nobody is working!” © Neil Bohr Institute

Associate professor at the Niels Bohr Institute, Heloisa Bordallo, explains: “If we want to use this material in a real application to solve an important societal problem like ammonia pollution, it is important to explain how ammonia is captured by the porous network in the polymer. This implies that we needed to come up with a technique that allows us to find out exactly how the interaction between the polymer and ammonia takes place. Being successful in answering this question, will make us able to understand better how this or other polymers can be efficient in multidisciplinary domains, including nanomedicine and protective coatings. If scaled up – which is not a simple process – this could have a significant positive impact on the working environment of many people all over the globe”.

The polymer showed surprisingly good characteristics already at the outset

Assistant professor Jiwoong Lee at the Chemistry Department and Rodrigo Lima, a former postdoc at the Niels Bohr Institute, synthesized 2 grams of the polymer, which doesn’t sound like a lot, but it is actually substantial, considering the amounts chemists normally work with is only a few milligrams. After this first step, the team used a lot of different techniques to characterize the material. Assistant professor Jiwoong Lee explains: “The synthesis process often involves washing the material with solvents and it was a nice surprise to realize that the porous polymer actually kept a portion of these solvents inside. This was indicative of the material’s ability to perhaps capture other pollutants, such as ammonia.”

The researchers performed experiments at the ISIS Neutron and Muon Source part of the STFC Rutherford Appleton Laboratory in the UK, where the dynamics of the hydrogen bonds was investigated by collecting neutron scattering data at low pressure to get ammonia into the polymer. Neutron scattering is a technique able to describe where the atoms are located and at the same describe how the atoms are moving inside a material. Afterwards, Rodrigo Lima, former postdoc at the Niels Bohr Institute, set up an experiment at the thermal analysis laboratory at the Niels Bohr Institute and demonstrated that ammonia was not only captured, but attached to the porous materials. “This was a real surprise! The polymer binds ammonia very strongly”, he says.

Characterizing the amorphous polymer turned out to be a challenge in itself

“In order to be able to explain this seemingly strong connection between the polymer and the ammonia, we needed to know the structure of the polymer. But since this particular polymer is amorphous, it is difficult to fully characterize its structure. In a way you could say that we had ticked the box of capturing the ammonia, but we still needed to explain how this happens – and for that we needed a better view of the structure, which was unattainable. Quite a dilemma to have full success in one part of the project, and not be able to explain exactly why”. Heloisa Bordallo explains.

The researchers made different combinations of the polymer building blocks and were able to calculate a spectra, using a computational modelling method called DFT, from a combination that came closest to being similar to the measurements in the real sample. This, finally, made them able to “tick the box” of interpreting how the polymer binds.

“There are numerous applications for a polymer that captures ammonia”, Jiwoong Lee explains. “It would be useful in labs, as coating for masks to wear for personal safety, as ammonia is toxic and also very corrosive. It could be used as filters, reducing the spread of ammonia released through the exhausts from many types of industry. Thinking ahead, it is possible that the polymer technique could be applied to other types of polluents as well.”

Machine learning and artificial intelligence

Heloisa Bordallo wishes to apply machine learning to amorphous systems. For this experiment, she and her colleagues made the experiment “by hand”, so to speak, but it is perhaps a more viable way to go about this process to use machine learning and artificial intelligence. Applying deep learning algorithms can help in accurately classifying amorphous materials and in characterizing their structural features. “Then by combining Machine Learning with theoretical calculations we will be able to analyze the neutron scattering data in a much more elegant way”, she says.

References: Rodrigo J. S. Lima, Denis V. Okhrimenko, Svemir Rudić, Mark T. F. Telling, Victoria García Sakai, Dasol Hwang, Gokhan Barin, Juergen Eckert, Ji-Woong Lee, and Heloisa N. Bordallo, “Ammonia Storage in Hydrogen Bond-Rich Microporous Polymers”, ACS Appl. Mater. Interfaces 2020. https://pubs.acs.org/doi/full/10.1021/acsami.0c18855# https://doi.org/10.1021/acsami.0c18855

Provided by Neil Bohr Institute

Pandemic Brings Record Fall in Global CO2 Emissions (Nature)

The Global Carbon Project, of which LMU geographer Julia Pongratz is a leading member, reports an unprecedented drop in the level of carbon emissions since the onset of the coronavirus pandemic, although the overall concentration of CO2 in the atmosphere continues to rise.

In the USA and the EU reductions in the use of coal were complemented by the effects of the restrictions imposed in response to the coronavirus pandemic. Photo: imago images / Sven Simon

According to the latest figures published by the Global Carbon Project (GCP), the current coronavirus pandemic has led to a significant reduction in global CO2 emissions. The GCP is an international collaboration of climate researchers, which includes LMU geographers Julia Pongratz, Selma Bultan and Kerstin Hartung as contributors. The group monitors both the amounts of greenhouse gases released into Earth‘s atmosphere and the quantities absorbed by the world’s oceans and sequestered in vegetation on land.

The latest report issued by the GCP shows that, 5 years after the conclusion of the Paris Agreement, the rate of increase in global CO2 emissions has slowed. In the decade from 2010 to 2019, CO2 emissions from fossil sources decreased significantly in 24 countries whose economies had grown over the same period. This result suggests that policies intended to mitigate climate change may be having an effect. Over the course of this year – in part owing to the measures introduced in response to the coronavirus pandemic – global emissions of fossil carbon are estimated to have fallen to 34 billion tons (34 Gt CO2). This figure represents a decrease of some 2.4 Gt from the previous year. This is a considerably larger drop than previous dips in the emission record for the years 1981 and 2009 (0.5 Gt), 1992 (0.7 Gt) and 1945 (0.9 Gt). In order to achieve the goals set out in the Paris Agreement, CO2 emissions must fall by between 1 and 2 Gt annually between now and 2030.

The decrease was particularly notable in the USA (-12%) and in member states of the EU (-11%). “In both cases, reductions in the use of coal were complemented by the effects of the restrictions imposed in response to the coronavirus pandemic,” says Pongratz. “In 2019, the rate of increase in CO2 emissions was slower than in previous years. As a consequence of the pandemic, emissions have now fallen significantly. This makes 2020 a crucial year, but whether it marks the start of a trend strongly depends on how the measures taken to stimulate the economy unfold around the world. We are already seeing signs that the emission rate is climbing back toward the level observed for 2019.”

The transport sector accounts for most of the fall

Most of the decrease recorded for 2020 can be attributed to a drop in the carbon footprint of the transport sector. In December 2020, emissions due to road and air traffic still were lower by about 10% and 40%, respectively, relative to 2019 values. The authors of the report emphasize that it is not yet possible to assess whether the rate of global emissions will continue to fall in the coming years. Following the decrease in emissions in the aftermath of the global financial crisis in 2008, emissions rebounded a massive 5% in 2010, as the global economy recovered. The fear is that this could happen also in 2021.

Overall, total emissions of CO2 – from fossil sources and land use – for 2020 are estimated to be on the order of 39 Gt, which approximately corresponds to the value recorded for the year 2012. This caused the CO2 concentration of the atmosphere to continue rising, and the average concentration for the current year is expected to set a new record of 412 ppm (parts per million). This corresponds to a rise of 48% relative to the pre-industrial level. The authors of the new report point out that the atmospheric CO2 level, and consequently the world’s climate, will only stabilize when global CO2 emissions are near zero.

The overall amount of CO2 absorbed by carbon sinks on land and in the oceans continues to rise, and in 2020, they sequestered some 54% of all anthropogenic CO2 emissions.

No significant decrease in emissions from land use change

Julia Pongratz is particularly interested in the impact of changes in land use on the global carbon balance. While unusually high level of emissions from these sources were estimated for 2019 – which were exacerbated by extraordinarily dry conditions in Indonesia and the highest rate of deforestation in the Amazon Basin since 2008 – the value for 2020 is lower again and equivalent to the mean level for the decade as a whole.

“For the first time, we were able to estimate the gross CO2 emissions and removals through land use changes on the global carbon budget in 2020,” Pongratz says. She and her colleagues come to the conclusion that this factor – largely attributable to deforestation – accounts for the release of around 16 Gt of CO2 per year during the past decade. On the other hand, removals of CO2 such as through the abandonment of agricultural lands, over the same period resulted in an estimated increase of nearly 11 Gt in CO2 sequestration capacity. The net balance of +6 Gt for 2020 is similar to the values for previous years. “We have not found a reduction in carbon emissions in this sector yet. Deforestation continues at a rapid pace, especially in tropical regions, and public awareness of the impact of agricultural emissions has been muted owing to the influence of Covid,” Pongratz says. “Effective measures to improve land management could not only curb deforestation, they could also contribute to an increase in CO2 uptake from the atmosphere by allowing for the regrowth of natural vegetation.”

The team of 86 climate researchers from all parts of the world publishes its study in the peer-reviewed journal Earth System Science Data. The Global Carbon Budget 2020 is the 15th edition of the annual update that started in 2006. Besides Julia Pongratz, Selma Bultan und Kerstin Hartung, scientists from 7 other German institutions contributed — the Alfred-Wegener-Institut (Bremerhaven), the Max Planck Institute for Meteorology (Hamburg), the Max Planck Institute for Biogeochemistry (Jena), the Karlsruhe Institute of Technology, the GEOMAR Helmholtz Centre for Ocean Research (Kiel) and the Leibniz-Institut für Ostseeforschung (Warnemünde).

Further information
Data and Figures 
Data Atlas 
Estimated Daily Emission Rates 

Provided by LMU Munich

Pollution From Cooking Remains in Atmosphere For Longer (Food)

Particulate emissions from cooking stay in the atmosphere for longer than previously thought, making a prolonged contribution to poor air quality and human health, according to a new study.

credit: James Sutton/Unsplash

Researchers at the University of Birmingham succeeded in demonstrating how cooking emissions – which account for up to 10 per cent of particulate pollution in the UK – are able to survive in the atmosphere over several days, rather than being broken up and dispersed.

The team collaborated with experts at the University of Bath, the Central Laser Facility and Diamond Light Source to show how these fatty acid molecules react with molecules found naturally in the earth’s atmosphere. During the reaction process, a coating, or crust is formed around the outside of the particle that protects the fatty acid inside from gases such as ozone which would otherwise break up the particles.

This is the first time scientists have been able to recreate the process in a way that enables it to be studied in laboratory conditions by using the powerful X-ray beam at Diamond Light Source to follow the degradation of thin layers of molecules representative of these cooking emissions in minute detail. The results are published in the Royal Society of Chemistry’s Faraday Discussions.

The ability of these particles to remain in the atmosphere has a number of implications for climate change and human health. Because the molecules are interacting so closely with water, this affects the ability of water droplets to form clouds. In turn this may alter the amount of rainfall, and also the amount of sunlight that is either reflected by cloud cover or absorbed by the earth – all of which could contribute to temperature changes.

In addition, as the cooking emission particles form their protective layer they can also incorporate other pollutant particles, including those known to be harmful to health such as carcinogens from diesel engine emissions. These particles can then be transported over much wider areas.

Lead author, Dr Christian Pfrang, of the University of Birmingham’s School of Geography, Earth and Environmental Sciences, said: “These emissions, which come particularly from cooking processes such as deep fat frying, make up a significant proportion of air pollution in cities, in particular of small particles that can be inhaled known as PM2.5 particles. In London it accounts for around 10 per cent of those particles, but in some of the world’s megacities for example in China it can be as much as 22 per cent with recent measurements in Hong Kong indicating a proportion of up to 39%.

“The implications of this should be taken into account in city planning, but we should also look at ways we can better regulate the ways air is filtered – particularly in fast food industries where regulations do not currently cover air quality impacts from cooking extractor emissions for example.”

The research was supported by the Science and Technology Facilities Council (STFC) and the Natural Environment Research Council (NERC).

Reference: Adam Milsom, Adam M. Squires, Ben Woden, Nicholas J. Terrill, Andrew D. Ward and Christian Pfrang (2020). ‘The persistence of a proxy for cooking emissions in megacities: a kinetic study of the ozonolysis of self-assembled films by simultaneous Small & Wide Angle X-ray Scattering (SAXS/WAXS) and Raman microscopy.’ Faraday Discussions. https://pubs.rsc.org/en/Content/ArticleLanding/2020/FD/D0FD00088D#!divAbstract

Provided by University of Birmingham

Smog Exposure Linked to Higher Risk of Cardiac Arrest (Cardiology / Medicine)

Exposure to ozone, the main ingredient in smog—even at levels below federal safety standards—may increase the risk of going into cardiac arrest, new research shows.


Researchers analyzed records of air pollution concentrations in the neighborhoods of more than 187,000 people who had cardiac arrests outside the hospital in 28 states between 2013 and 2018. They compared two types of pollution, ozone and fine particulate matter, from two weeks before a person’s cardiac arrest to levels on the day their heart suddenly stopped beating. They found that as ozone levels rose, so did sudden cardiac arrests.

“There’s been a lot of evidence showing that air pollutants cause cardiovascular disease,” said Dr. Ali Malik, a cardiology fellow at Saint Luke’s Mid-America Heart Institute in Gladstone, Missouri. “We wanted to address the worst thing that can happen outside the hospital, which is to just drop dead from cardiac arrest, and how air pollutants play a role in that. We found that on days when ozone was high in ambient air, the risk of having an out-of-hospital cardiac arrest was higher.”

The findings were recently presented at the American Heart Association’s virtual Resuscitation Science Symposium. The study is considered preliminary until published in a peer-reviewed journal.

Air pollution contributes to an estimated 6.7 million deaths per year around the world, a large portion of which are heart-related. Pollution from fine particulates, tiny fragments measured at less than 2.5 micrograms that can be inhaled and are invisible to the naked eye, has most often been pinpointed as the culprit. But gaseous pollutants such as ozone have also been implicated in health effects of air pollution. Past studies found a link between exposure to ozone and mortality, but these links have been primarily respiratory.

Malik said he was surprised the new study found no association between rising particulate matter levels and cardiac arrest, whereas the link between ozone and cardiac arrest occurred at unexpectedly low levels of exposure—levels below federal standards.

The Environmental Protection Agency considers ground-level ozone to be harmful to human health at levels of 70 parts per billion. In this study, researchers found a higher risk of cardiac arrest at levels as low as 36.9 parts per billion—about half the EPA’s standard. For every 12 parts per billion increase in ozone, the study found, the risk of going into cardiac arrest rose 1.1%.

Malik said fine particulate matter levels may not have been high enough in his study to show any association.

The fine particulate air pollution found in smoke and haze created by forest fires, automobile emissions, power plants and other industries has been strongly linked to a higher risk of death from heart disease in numerous studies, with evidence suggesting it may be a causal risk factor for heart disease.

Two scientific statements from the AHA, one in 2004 and an update in 2010, detailed “mounting evidence” of the damage to heart health caused by exposure to fine particulate matter.

Dr. Sanjay Rajagopalan, chief of cardiovascular medicine at University Hospitals’ Harrington Heart and Vascular Institute in Cleveland, co-authored the 2010 AHA report on air pollution and heart disease. He called the new findings interesting because “prior studies have not shown a link between ozone and cardiovascular mortality.”

“It provides additional evidence to suggest that health effects continue below the current regulatory levels for ozone and (fine particulate matter). … Thus, this study provides additional support to reduce fossil fuel emissions and to switch to clean energy sources,” said Rajagopalan, also director of the Cardiovascular Research Institute at Case Western University’s School of Medicine. He was not part of the new study.

“What’s good for the climate is good for health,” he said. “This puts attention on the importance of regulation. Controlling emissions should be a priority because of the number of lives it can save.”

Rajagopalan also co-authored an AHA scientific statement published in November that addresses ways people can reduce their health risks from exposure to air pollution caused by fine particulate matter, whether at home or visiting areas that may be heavily polluted.

The statement provides information on portable air cleaners, personal air-purifying respirators, automobile air filters and behavioral strategies, such as avoiding exposure to areas with high levels of pollution, staying indoors and closing windows.

Rajagopalan said some populations may be more vulnerable to ozone levels than others and future research should explore this.

References: Ali Malik et al. Abstract 119: Association of Acute Exposure to Ambient Air Particulate Matter and Ozone with Risk of Out-of-hospital Cardiac Arrest, Circulation (2020). DOI: 10.1161/circ.142.suppl_4.119

Provided by American Heart Association

Clean Air Act Saved 1.5 Billion Birds (Nature)

Improved air quality, reduced ozone pollution may have averted bird deaths.

U.S. pollution regulations meant to protect humans from dirty air are also saving birds. So concludes a new continentwide study published today in The Proceedings of the National Academy of Sciences. Study authors found that improved air quality under a federal program to reduce ozone pollution may have averted the loss of 1.5 billion birds during the past 40 years. That’s nearly 20 percent of birdlife in the United States today. The study was conducted by scientists at Cornell University and the University of Oregon.

Great Blue Heron in front of an oil refinery. ©Gerrit Vyn

“Our research shows that the benefits of environmental regulation have likely been underestimated,” says Ivan Rudik, a lead author and Ruth and William Morgan Assistant Professor at Cornell’s Dyson School of Applied Economics and Management. “Reducing pollution has positive impacts in unexpected places and provides an additional policy lever for conservation efforts.”

Ozone is a gas that occurs in nature and is also produced by human activities, including by power plants and cars. It can be good or bad. A layer of ozone in the upper atmosphere protects the Earth from the harmful ultraviolet rays of the sun. But ground-level ozone is hazardous and is the main pollutant in smog.

To examine the relationship between bird abundance and air pollution, the researchers used models that combined bird observations from the Cornell Lab of Ornithology’s eBird program with ground-level pollution data and existing regulations. They tracked monthly changes in bird abundance, air quality, and regulation status for 3,214 U.S. counties over a span of 15 years. The team focused on the NOx (nitrogen oxide) Budget Trading Program, which was implemented by the U.S. Environmental Protection Agency to protect human health by limiting summertime emissions of ozone precursors from large industrial sources.

Blackburnian Warbler. ©Ian Davies

Study results suggest that ozone pollution is most detrimental to the small migratory birds (such as sparrows, warblers, and finches) that make up 86 percent of all North American landbird species. Ozone pollution directly harms birds by damaging their respiratory system, and indirectly affects birds by harming their food sources.

“Not only can ozone cause direct physical damage to birds, but it also can compromise plant health and reduce numbers of the insects that birds consume,” explains study author Amanda Rodewald, Garvin Professor at the Cornell Department of Natural Resources and the Environment and Director of the Center for Avian Population Studies at the Cornell Lab of Ornithology. “Not surprisingly, birds that cannot access high-quality habitat or food resources are less likely to survive or reproduce successfully. The good news here is that environmental policies intended to protect human health return important benefits for birds too.”

Last year, a separate study by the Cornell Lab of Ornithology showed that North American bird populations have declined by nearly 3 billion birds since 1970 (Rosenberg et. al. Science, 2019). This new study shows that without the regulations and ozone-reduction efforts of the Clean Air Act, the loss of birdlife may have been 1.5 billion birds more.

“This is the first large-scale evidence that ozone is associated with declines in bird abundance in the United States and that regulations intended to save human lives also bring significant conservation benefits to birds,” says Catherine Kling, Tisch University Professor at the Cornell Dyson School of Applied Economics and Management and Faculty Director at Cornell’s Atkinson Center for Sustainability. “This work contributes to our ever increasing understanding of the connectedness of environmental health and human health.”

References: Yuanning Liang, Ivan Rudik, Eric Zou, Alison Johnston, Amanda D. Rodewald, Catherine L. Kling. Conservation Co-Benefits from Air Pollution Regulation: Evidence from Birds. The Proceedings of the National Academy of Sciences, November 2020. https://www.pnas.org/content/early/2020/11/23/2013568117

There Are Microplastics Near the Top of Mount Everest Too (Earth Science)

Researchers analyzing snow and stream samples from the National Geographic and Rolex Perpetual Planet Everest Expedition have found evidence of microplastic pollution on Mount Everest. While the highest concentrations of microplastics were around Base Camp where hikers and trekkers spend the most time, the team also found microplastics as high up as 8,440 meters above sea level, just below the summit. The findings appear November 20 in the journal One Earth.

This image shows a view of the National Geographic and Rolex Perpetual Planet Everest Expedition climbers’ tents, made from waterproof acrylic material, at Camp IV/South Col. In the background, climbers make their way to the summit wearing plastic-based waterproof outdoor gear. http://www.NatGeo.com/Everest. ©Mariusz Potocki/National Geographic

“Mount Everest has been described as ‘the world’s highest junkyard,'” says first author Imogen Napper (@Imogennapper), a National Geographic Explorer and scientist based at the University of Plymouth who is described by her colleagues as a “plastic detective.” “Microplastics haven’t been studied on the mountain before, but they’re generally just as persistent and typically more difficult to remove than larger items of debris.”

Microplastics–tiny particles of plastic that come from the slow breakdown of larger litter–pose a huge ecological threat because they are easily consumed by animals and are so small that they are difficult to clean up. Microplastics are common in the ocean, but are not as carefully studied on land, especially remote mountaintops.

This image shows a selection of microfibers found in snow samples from Mt. Everest Balcony (8,440 m), collected during the National Geographic and Rolex Perpetual Planet Everest Expedition, which are consistent with fibers from outdoor clothing. http://www.NatGeo.com/Everest ©Imogen Napper/National Geographic.

“I didn’t know what to expect in terms of results, but it really surprised me to find microplastics in every single snow sample I analyzed. Mount Everest is somewhere I have always considered remote and pristine. To know we are polluting near the top of the tallest mountain is a real eye-opener.”

While some members of the research team climbed the mountain collecting samples during the Everest expedition in the spring of 2019, much of the work was done in a lab many miles away, where Napper and her team analyzed the samples. “The closest I got to Mount Everest was in my lab at University of Plymouth in the UK,” Napper jokes. She wanted to determine not only whether there was plastic on the mountain, but what type of plastic was there. This is an important step in figuring out where the pollution originated.

“The samples showed significant quantities of polyester, acrylic, nylon, and polypropylene fibers,” says Napper. “Those materials are increasingly being used to make the high-performance outdoor clothing climbers use as well as tents and climbing ropes, so we highly suspect that these types of items are the major source of pollution rather than things like food and drink containers.”

While this study clearly demonstrated the presence of microplastics on Mount Everest, the best way to clean this pollution remains to be seen.

“Currently, environmental efforts tend to focus on reducing, reusing, and recycling larger items of waste. This is important, but we also need to start focusing on deeper technological solutions that focus on microplastics, like changing fabric design and incorporating natural fibers instead of plastic when possible,” she says.

The researchers also hope that their work will help clarify the extent to which plastic pollution jeopardizes all environments, not just the ocean.

“These are the highest microplastics discovered so far,” says Napper. “While it sounds exciting, it means that microplastics have been discovered from the depths of the ocean all the way to the highest mountain on Earth. With microplastics so ubiquitous in our environment, it’s time to focus on informing appropriate environmental solutions. We need to protect and care for our planet.”

References: Bede F.R. Davies, Imogen E. Napper, Heather Clifford, et al., “Reaching New Heights in Plastic Pollution—Preliminary Findings of Microplastics on Mount Everest”, one Earth, VOLUME 3, ISSUE 5, P621-630, NOVEMBER 20, 2020. https://www.cell.com/one-earth/fulltext/S2590-3322(20)30550-9?utm_source=EA https://doi.org/10.1016/j.oneear.2020.10.020

Provided by Cell Press

Reducing Aerosol Pollution Without Cutting Carbon Dioxide could make the Planet Hotter (Earth Science)

Solving one environmental problem could create another.

Humans must reduce carbon dioxide and aerosol pollution simultaneously to avoid weakening the ocean’s ability to keep the planet cool, new research shows.

A system of currents known as the Atlantic Meridional Overturning Circulation carries warm water into the North Atlantic. It could be disturbed if CO2 and aerosols are not simultaneously cut. ©R. Curry, Woods Hole Oceanographic Institution/Science/USGCRP

Aerosol pollution refers to particles in the air emitted by vehicles and factories that burn fossil fuels. This pollution contributes to asthma, bronchitis, and long-term irritation of the respiratory tract, which can lead to cancer.

“The conundrum,” explained UC Riverside climate scientist and study co-author Robert Allen, “is that aerosols cause poor air quality and lead to premature deaths. However, these particles have a net cooling impact on the climate, so when you cut them that leads to a net warming effect.”

Much research has examined aerosol impacts on air quality and land surface temperatures. Less explored is the way aerosols might impact the oceans, which is the focus of a UC Riverside study now published in the journal Science Advances.

The research team created detailed computer models to determine the impact on oceans under two different scenarios — one in which there is only a reduction in aerosols, and another scenario in which greenhouse gases like carbon dioxide and methane are also reduced.

“The first scenario leads to the surprising result that fewer aerosols in the atmosphere could shift the region where most of the ocean is taking up heat, from the Southern Ocean toward the North Atlantic,” Allen said.

In particular, the Atlantic meridional overturning circulation, or AMOC, would be disturbed as aerosols are removed from the atmosphere, the study found. The AMOC pulls warm water further north and pushes colder water south, ensuring the climate on land areas at higher latitudes, such as Europe, are relatively mild.

Roughly half the carbon dioxide humans put into the atmosphere — mostly through fossil fuel combustion and deforestation — stays there, and the remaining half is taken up by land and vegetation, as well as the ocean.

One of the ways the ocean takes up our carbon dioxide emissions is through AMOC circulation.

“A projected decline in manmade aerosols potentially induces a weakening of the AMOC, which plays an important role in ocean heat uptake and storage in the North Atlantic,” said Wei Liu, an assistant professor of climate change and sustainability at UCR.

In addition, the researchers said a rise in sea level would occur if the North Atlantic Ocean were to get warmer.

This current study focused on ocean heat uptake and circulation via the AMOC. However, Allen explained the study did not attempt to rigorously identify the mechanisms by which aerosol reductions weaken the AMOC. Those mechanisms will be the focus of future studies.

Ultimately, the researchers conclude that even without a more in-depth explanation of the weakening mechanisms, it is necessary to reduce greenhouse gases and aerosols in tandem.

The Intergovernmental Panel on Climate Change recommends making every attempt to prevent the planet from reaching 1.5 degrees Celsius above pre-industrial levels in order to mitigate the worst effects of global warming.

Humans have already increased carbon dioxide levels by almost 50% since the 1850s, and it continues to increase worldwide. Stabilizing carbon dioxide at current levels would require zero net emissions before the year 2070, which is ambitious, but critical.

“Assuming complete removal, aerosols at most will cause warming of about 1 K,” said Allen. “However, aerosol-induced warming, as well as the associated ocean circulation changes, can be moderated by rigorous cuts in greenhouse gases including methane and carbon dioxide.”

References: Xiaofan MA, Wei Liu, Robert J. Allen, Gang Huang and Xichen Li, “Dependence of regional ocean heat uptake on anthropogenic warming scenarios”, Science Advances 06 Nov 2020: Vol. 6, no. 45, eabc0303 DOI: 10.1126/sciadv.abc0303 link: https://advances.sciencemag.org/content/6/45/eabc0303

Provided by University of CaliforniaRiverside

Plastic Pollution Is Everywhere. Study Reveals How it Travels (Material Science)

Plastic pollution is ubiquitous today, with microplastic particles from disposable goods found in natural environments throughout the globe, including Antarctica. But how those particles move through and accumulate in the environment is poorly understood. Now a Princeton University study has revealed the mechanism by which microplastics, like Styrofoam, and particulate pollutants are carried long distances through soil and other porous media, with implications for preventing the spread and accumulation of contaminants in food and water sources.

©Princeton University

The study, published in Science Advances on November 13, reveals that microplastic particles get stuck when traveling through porous materials such as soil and sediment but later break free and often continue to move substantially further. Identifying this stop-and-restart process and the conditions that control it is new, said Sujit Datta, assistant professor of chemical and biological engineering and associated faculty of the Andlinger Center for Energy and the Environment, the High Meadows Environmental Institute and the Princeton Institute for the Science and Technology of Materials. Previously, researchers thought that when microparticles got stuck, they generally stayed there, which limited understanding of particle spread.

Datta led the research team, which found that the microparticles are pushed free when the rate of fluid flowing through the media remains high enough. The Princeton researchers showed that the process of deposition, or the formation of clogs, and erosion, their breakup, is cyclical; clogs form and then are broken up by fluid pressure over time and distance, moving particles further through the pore space until clogs reform.

“Not only did we find these cool dynamics of particles getting stuck, clogged, building up deposits and then getting pushed through, but that process enables particles to get spread out over much larger distances than we would have thought otherwise,” said Datta.

The team included Navid Bizmark, a postdoctoral research associate in the Princeton Institute for the Science and Technology of Materials, graduate student Joanna Schneider, and Rodney Priestley, professor of chemical and biological engineering and vice dean for innovation.

They tested two types of particles, “sticky” and “nonsticky,” which correspond with actual types of microplastics found in the environment. Surprisingly, they found that there was no difference in the process itself; that is, both still clogged and unclogged themselves at high enough fluid pressures. The only difference was where the clusters formed. The “nonsticky” particles tended to get stuck only at narrow passageways, whereas the sticky ones seemed to be able to get trapped at any surface of the solid medium they encountered. As a result of these dynamics, it is now clear that even “sticky” particles can spread out over large areas and throughout hundreds of pores.

In the paper, the researchers describe pumping fluorescent polystyrene microparticles and fluid through a transparent porous media developed in Datta’s lab, and then watching the microparticles move under a microscope. Polystyrene is the plastic microparticle that makes up Styrofoam, which is often littered into soils and waterways through shipping materials and fast food containers. The porous media they created closely mimics the structure of naturally-occurring media, including soils, sediments, and groundwater aquifers.

Research has shown how plastics, depicted here as green particles, travel long distances in soil and other substances through a process of repeatedly getting stuck and then released. Credit: Princeton University/Datta Lab

Typically porous media are opaque, so one cannot see what microparticles are doing or how they flow. Researchers usually measure what goes in and out of the media, and try to infer the processes going on inside. By making transparent porous media, the researchers overcame that limitation.

“Datta and colleagues opened the black box,” said Philippe Coussot, a professor at Ecole des Ponts Paris Tech and an expert in rheology who is unaffiliated with the study.

“We figured out tricks to make the media transparent. Then, by using fluorescent microparticles, we can watch their dynamics in real time using a microscope,” said Datta. “The nice thing is that we can actually see what individual particles are doing under different experimental conditions.”

The study, which Coussot described as a “remarkable experimental approach,” showed that although the Styrofoam microparticles did get stuck at points, they ultimately were pushed free, and moved throughout the entire length of the media during the experiment.

The ultimate goal is to use these particle observations to improve parameters for larger scale models to predict the amount and location of contamination. The models would be based on varying types of porous media and varying particle sizes and chemistries, and help to more accurately predict contamination under various irrigation, rainfall, or ambient flow conditions. The research can help inform mathematical models to better understand the likelihood of a particle moving over a certain distance and reaching a vulnerable destination, such as a nearby farmland, river or aquifer. The researchers also studied how the deposition of microplastic particles impacts the permeability of the medium, including how easily water for irrigation can flow through soil when microparticles are present.

Datta said this experiment is the tip of the iceberg in terms of particles and applications that researchers can now study. “Now that we found something so surprising in a system so simple, we’re excited to see what the implications are for more complex systems,” said Datta.

He said, for example, this principle could yield insight into how clays, minerals, grains, quartz, viruses, microbes and other particles move in media with complex surface chemistries.

The knowledge will also help the researchers understand how to deploy engineered nanoparticles to remediate contaminated groundwater aquifers, perhaps leaked from a manufacturing plant, farm, or urban wastewater stream.

Beyond environmental remediation, the findings are applicable to processes across a spectrum of industries, from drug delivery to filtration mechanisms, effectively any media in which particles flow and accumulate, Datta said.

References: Navid Bizmark, Joanna Schneider et al., “Multiscale dynamics of colloidal deposition and erosion in porous media”, Science Advances 13 Nov 2020: Vol. 6, no. 46, DOI: 10.1126/sciadv.abc2530 link: https://advances.sciencemag.org/content/6/46/eabc2530

Provided by Princeton University