Trees and lawns beat the heat

by Lisa Potter, University of Utah

The fish eye images of the sky above a park (right) and a residential area (left) around Lone Peak park in the Salt Lake Valley in Utah, United States, have different canopy coverage--the park has more open sky than in the residential areas. The canopies influence the different ground surface temperatures. Credit: Carolina Gomez-Navarro

In cities, humans replace the natural ground cover with roofs, pavement and other artificial materials that are impervious to water. These surfaces significantly change how the land absorbs and releases energy and cause the urban heat island effect, a phenomenon where developed areas get hotter than nearby rural areas. As climate change pushes many cities towards dangerous temperatures, planners are scrambling to mitigate excessive heat.


One strategy is to replace artificial surfaces with vegetation cover. In water-limited regions such as Utah, a state with one of the lowest annual rainfall rates in the United States, municipalities have to balance the benefit of cooler temperatures with using precious water for irrigation.

A new University of Utah study will make those decisions easier for the semi-arid Salt Lake Valley, the largest metropolitan area in Utah located in the northern part of the state. The researchers used 60 sensors to analyze the microclimate in five locations throughout the valley. They found that neighborhoods dominated by impervious surfaces were warmer and drier than the urban parks—up to 2 degrees warmer in both the daytime and nighttime.

"It's intuitive—we've all stood in a parking lot on a hot summer day, and you feel the heat from the ground. And when you're standing on a lawn, it's cooler," said lead author Carolina Gomez-Navarro, postdoctoral researcher at the U. "But we need to back up intuition with data to determine the best strategy for our semi-arid cities."

Gomez-Navarro and the team measured the temperature and humidity inside five parks and in their adjacent residential areas from June through August in 2016. They also analyzed how the surrounding landscape impacted air temperature. Surprisingly, they found that lawns reduced daytime and nighttime temperatures even more than trees did. While trees provide shade, lawns and turfgrass act like a swamp cooler—water moves through the plant, evaporating from tiny holes in the leaves and cooling the air.

Thermal image showing the surface temperature variation at a Sugar House park site. Credit: Carolina Gomez-Navarro

Much of the heat that builds up during the day dissipates at night. The more open the land, the better heat can escape into the atmosphere. An area with many trees acts like a greenhouse, trapping heat close to the ground. The study concluded that a mixture of dispersed trees and grass is the most effective way to cool temperatures in the Salt Lake Valley.

"Understanding how ground cover impacts temperature is crucial for city planners to weigh the benefits and costs of its landscape design," said Gomez-Navarro. "This land used to be a valley of bushes and bare soil. Any vegetation we add is going to need lots of irrigation and modify the landscape in many ways."


The paper was published on October 13, 2020 in the journal Agricultural and Forest Meteorology.

Is the grass always greener?

Gomez-Navarro focused on five parks and the adjacent neighborhoods throughout the Salt Lake Valley: Hunter (northwest), Lone Peak (southeast), Midvale City (south central), Southridge (northwest) and Sugar House (northeast). Each location had 12 sensors that measured temperature and humidity: six within the park and six in the residential areas. Gomez-Navarro analyzed ground cover in a 10-meter diameter around each sensor using satellite images to estimate the percentage of the roofs, pavement, trees or turfgrass. She found that the more turfgrass in a given area, the lower the temperature.

Locations of the park and residential areas included in the study. Credit: Navarro et al (2021) Agricultural and Forest Meteorology

She analyzed canopy cover by taking photos of the sky above each sensor with a fish eye lens. She used software that calculated the area that trees obstructed the sky. She found that the more open the landscape, the hotter the daytime temperature. The more canopy cover, the more shade reduced temperature.

The authors expected there to be temperature and humidity differences between the parks and neighborhoods. They were surprised, however, that turfgrass had nearly the same impact on air temperature as trees. It seems counterintuitive because of the difference between air temperature and perceived temperature. Perceived temperature is how humans feel the environment. Wind, air temperature, humidity and solar radiation all factor into how comfortable we are.

"We didn't measure human comfort in this study, but we know that the amount of solar radiation on our skin has a big impact on the perceived temperature," said Gomez-Navarro. "Even if the air temperature is the same, we feel much cooler under the shade of a tree because it blocks some of the radiation."

Smart city planning

Next, Gomez-Navarro will study how different landscapes directly affect how humans feel comfortable in their environment, and how plant cover type affect soil water loss.

"It's going to keep getting hotter and parks can be a refuge from the heat. But exactly how many degrees can they cool the air? And what should we plant to maximize this cooling?" said co-author Diane Pataki, professor of biology at the U. "It's getting easier and cheaper to measure temperature all over parks and neighborhoods, and we're going to need this information to make good decisions about future park designs."


Explore further A cooler home is right in your own back yard
More information: Carolina Gómez-Navarro et al, Effects of vegetation on the spatial and temporal variation of microclimate in the urbanized Salt Lake Valley, Agricultural and Forest Meteorology (2020). DOI: 10.1016/j.agrformet.2020.108211
Journal information: Agricultural and Forest Meteorology


Provided by University of Utah

Turning plastic waste into hydrogen gas and carbon nanotubes

by Bob Yirka , Phys.org

Credit: Unsplash/CC0 Public Domain

A team of researchers from the U.K., China, and Saudi Arabia has developed a process for converting plastic waste into hydrogen gas and carbon nanotubes. In their paper published in the journal Nature Catalysis, the group describes their process and how well it worked when tested.

Over the past several decades, plastics have been found to be a major form of pollution—in addition to the billions of tons of plastic in landfills around the world, large amounts of it has made its way into the environment, where weather and other factors break it down—the resulting microplastics have been found in lakes, rivers and streams and all of the world's oceans, harming plants and wildlife. One of the major factors driving plastic pollution is the lack of a way to recycle it. Instead, it is simply discarded. In this new effort, the researchers have found a way to recycle ordinary consumer plastics into a useable energy source and a useable carbon nanotube source.

The process involved pulverizing the plastic samples—this was done using microwaves with aluminum oxide and iron oxide serving as catalysts. Microwaves allowed for heating the catalysts without heating the plastics—instead, the plastics were heated incidentally by the catalysts. This approach prevented unwanted side reactions, which made the process more efficient.

The researchers report that the conversion process lasted just 30 to 90 seconds, and resulted in recovery of 97% of the hydrogen in the plastic. In addition, the carbon nanotubes produced were of sufficient quality for use in other applications. They note that there are currently other large-scale applications that involve the use of microwaves in commercial venues, suggesting that such use for recycling plastics might be possible. They acknowledge that they have not yet tested their approach to recycling plastics at a larger scale. They suggest the magnitude of the disaster that lies in the world's future if plastic pollution is not brought under control will drive efforts like theirs to succeed.


Explore further

A new kind of plastic that is able to maintain its original qualities when recycled
More information: Xiangyu Jie et al. Microwave-initiated catalytic deconstruction of plastic waste into hydrogen and high-value carbons, Nature Catalysis (2020).

DOI: 10.1038/s41929-020-00518-5
Journal information: Nature Catalysis



© 2020 Science X Network

Plastic bags could be 'eco-friendlier' than paper and cotton bags in cities like Singapore

by Nanyang Technological University

The team carried out a life cycle analysis of five types of bags to evaluate the environmental impacts associated with their production, distribution, transportation, waste collection, treatment, and end-of-life disposal. Credit: Nanyang Technological University

Scientists from Nanyang Technological University, Singapore (NTU Singapore) have modeled the cradle-to-grave environmental impact of using different types of shopping bags and report that in cities like Singapore, single-use plastic bags (made from high-density polyethylene plastic) have a lower environmental footprint than single-use paper and multi-use cotton bags.


Reusable plastic bags made from polypropylene non-woven plastic were the most eco-friendly option, followed by single-use plastic bags.

The model revealed that cotton and kraft paper bags have relatively bigger environmental footprints due to their greater contribution to global warming and eco-toxicity potential in their production.

However, the NTU team stressed that their model applied specifically to Singapore and might be applicable in cities such as Tokyo, Hong Kong, and Dubai. Reusable and single-use plastic bags would be a comparatively better environmental option only in these cities, due to the model's focus on densely populated metropolitan areas that have waste management structures with similar end-of-life incineration facilities.

The findings were published in the scientific Journal of Cleaner Production in August 2020.

Assistant Professor Grzegorz Lisak, Director of Residues & Resource Reclamation Centre at the Nanyang Environment and Water Institute (NEWRI), who led the research, said: "Our main message is that re-usable plastic bags are the best option, provided that they are re-used many times—over 50 times to be precise. However, one surprising conclusion is that, in our model, in a single-use case, plastic bags, if treated properly afterwards, are less environmentally detrimental than the other types of bags in this study."

"It is essential to evaluate the implications case by case for dealing with plastic waste. In a well-structured closed metropolitan waste management system with incineration treatment, using plastic bags may be the best option that is currently available, provided that there is no significant leakage of waste into the environment."

To reach their conclusions, the team carried out a life cycle analysis of five types of bags to evaluate the environmental impacts associated with their production, distribution, transportation, waste collection, treatment, and end-of-life disposal.

The research team found that the global warming potential of a single-use kraft paper bag was the highest, over 80 times that of reusable plastic bags. Single-use plastic and reusable cotton bags (reused 50 times) were calculated to have over ten times the global warming potential of reusable plastic bags (reused 50 times).

To offset the emission equivalent to equal that of the creation of one single-use plastic bag, a reusable plastic bag would need to be reused four times.

The team also observed that the relative negative environmental impacts of cotton and kraft paper bags in the model are due to their production processes that consume immense amounts of water and natural resources. Hence, improving the production methods, optimizing resource usage, and following sustainable practices could in future favor the usage of bags made from cotton and paper.

Relevance to cities and their waste reduction goals

In the case of Singapore, the team recommends the usage of reusable plastic bags to the greatest extent possible to reduce consumption of single-use plastic bags. Reprocessing single-use plastic bags would be a good policy goal to cut down on their environmental impact.

Asst Prof Lisak said that based on 2018 statistics in Singapore, reducing the single-use plastic grocery bag consumption by half could prevent over 10 million kg-CO2 equivalent emissions in a year.


Explore further

How banning plastic bags could help New York mitigate climate change
More information: Ashiq Ahamed et al. Life cycle assessment of plastic grocery bags and their alternatives in cities with confined waste management structure: A Singapore case study, Journal of Cleaner Production (2020). 

DOI: 10.1016/j.jclepro.2020.123956
Journal information: Journal of Cleaner Production
Provided by Nanyang Technological University

Study confirms plastics threat to south pacific seabirds

by Canterbury Museum, Canterbury Museum

Northern Royal Albatross nesting on Big Sister, north of Rekohu (Chatham Island)

Plastic gathered from remote corners of the South Pacific Ocean, including nesting areas of New Zealand albatrosses, has confirmed the global threat of plastic pollution to seabirds.


Published on 12 October in the journal Aquatic Conservation: Marine and Freshwater Ecosystems, the study looks for patterns in the plastics seabirds from around the South Pacific ingest.

It uses data gathered by Canterbury Museum Senior Curator Natural History Dr Paul Scofield and Wellington ornithologist Christopher Robertson in the late 1990s and 2000s.

"Plastic pollution is a major threat to seabird species, not just here in New Zealand but around the world," says Dr Scofield. "Knowing more about how seabirds interact with plastic might help us solve this problem in the future. At the moment, it's only getting worse."

Christopher Robertson, co-author of the study says, "One of the interesting takeaways from this study is that it shows you just how far plastic can travel in the ocean. Some of the areas where we collected the plastic are very remote. To me, that shows that this is a global issue; it's not something a single country can solve on its own."

"The samples provided by our colleagues from New Zealand allowed us to assess the patterns of seabird-plastic interactions on a larger scale, across the entire South Pacific Ocean," says the study's lead author, Valeria Hidalgo-Ruz from the Chilean Millenium Nucleus Centre of Ecology and Sustainable Management of Oceanic Islands.

Great Frigate Bird tangled in plastic, Desventuradas Islands, Chile. Credit: Diego Miranda

"The results confirm that even seabirds in one of the most remote areas of the world, the Rapa Nui (Easter Island) ecoregion, are strongly affected by this global problem, highlighting the need for urgent solutions."

In the late 1990s and 2000s, fieldworkers gathered thousands of pieces of plastic from albatross nesting sites on the Chatham Islands, Campbell Island and Taiaroa Head in Otago. The birds swallowed most of the plastic while foraging at sea and then regurgitated it at the nesting sites as they tried to feed their chicks.

Between 2003 and 2004, the team also examined plastic from the stomachs of Sooty Shearwaters killed by fishing operations around the Chatham Rise and the southeast coast of the South Island.


The study compared these plastics with similar samples from other locations around the Pacific including coastal Chile and Rapa Nui. The researchers examined the types of plastic found along with their shape, colour and density.

Plastics in a Great Frigate Bird nest on the Desventuradas Islands, Chile. Credit: Diego Miranda
Plastics collected from albatross nesting sites on Big Sister in 2017. Credit: Mike Bell
Plastics in a Great Frigate Bird nest on the Desventuradas Islands, Chile. Credit: Diego Miranda

Plastics collected from albatross nesting sites on Big Sister in 2017. Credit: Mike Bell

Albatrosses are more likely to eat brightly-coloured plastic, in particular red, green and blue. The birds probably mistake these objects for prey. The study suggests the brightly-coloured fishing gear of commercial fishing operations around the Chatham Islands and in Chile could be the source of some of the plastic found at those nesting sites.

Plastics found in the stomachs of diving seabirds like the Sooty Shearwater were dominated by hard, white/grey and round plastic items. The researchers believe most of these objects are ingested accidentally when the birds eat fish or other prey that have consumed plastic.

The ingestion of marine plastics is a major issue for seabird conservation and will affect most seabird species by 2050, according to estimates.


Explore further   Seabird nests are full of discarded plastic debris
More information: Valeria Hidalgo‐Ruz et al. Factors (type, colour, density, and shape) determining the removal of marine plastic debris by seabirds from the South Pacific Ocean: Is there a pattern?, Aquatic Conservation: Marine and Freshwater Ecosystems (2020). DOI: 10.1002/aqc.3453
Provided by Canterbury Museum

Why microplastics found in Nigeria's freshwaters raise a red flag

by Emmanuel O. Akindele, The Conversation

Credit: Unsplash/CC0 Public Domain

Freshwater ecosystems are a priority for environmental scientists because they affect the health of animals and plants on land too—as well as people. They provide food, water, transport and flood control. Freshwater ecosystems also keep nutrients moving among organisms and support diverse forms of life.


Freshwater systems make a big difference to the quality of life in any human society. But they are under great pressure. Freshwater biodiversity is declining faster than terrestrial biodiversity.

Among the three major types of habitats—terrestrial, freshwater and marine – freshwater accounts for less than 1% of the earth's surface. Yet these habitats support more species per unit area and account for about 6% of the world's biodiversity.

One of the biggest stresses on freshwater ecosystems is the presence of plastics. Some microplastics—tiny pieces of plastic that have broken down from bigger pieces—get into water from various sources. Some are introduced from industrial sources like cosmetics, toothpaste and shaving cream. Another major source is dumping of plastic waste like bags and bottles.

In Nigeria, an important source is the plastic sachets that contain drinking water. Over 60 million of these are consumed in a day.

Ultimately all these types of plastic waste find their way to the aquatic environment. There they stay in the water column, settle on river beds or are ingested by aquatic animals.


My research group set out to assess the load and chemical nature of microplastics in two important rivers and Gulf of Guinea tributaries in Nigeria. We looked for the presence of microplastics in aquatic insects since they often dominate aquatic animal life. Most also spend their adult stage in the terrestrial environment, once they emerge from their larvae. We found that microplastics were present in large quantities in the insect larvae. The insects are part of a food chain and could transfer the harmful effects of microplastics throughout the chain.

This further reinforces the urgent need for Nigeria to go ahead with measures to reduce the use of plastic bags and single-use plastics.

The research findings

We used three of the rivers' aquatic insect species as bio-indicators and found that all three had ingested microplastics from the two rivers. The ingested microplastics include styrene-ethylene-butylene-styrene, acrylonitrile butadiene styrene, chlorinated polyethylene, polypropylene, and polyester. The quantity of microplastics ingested by the insects was fairly high, especially in the Chironomus sp. which is a riverbed dweller recorded in the Ogun River.

The diversity of plastic polymers recorded in these insects suggests a wide range of applications of plastics in Nigeria.

The three insect species spend their larval stages in the water and later migrate to land in the adult phase. The concern is that the insect larvae could serve as a link for microplastics' transfer to higher trophic levels in the aquatic environment. Also, the adults serve in the same capacity in the terrestrial environment. A trophic level is the group of organisms within an ecosystem which occupy the same level in a food chain.

Dragonfly larvae in the water are eaten by fish, salamanders, turtles, birds and beetles. Adult dragonflies on land are also eaten by birds and other insects.

Other research elsewhere has shown the link between microplastics and human health.

Through feeding, the transfer of microplastics in the environment could go as far as people – who caused the plastic pollution in the first place.

Evidence suggests that microplastics reduce the physiological fitness of animals. This comes through decreased food consumption, weight loss, decreased growth rate, energy depletion and susceptibility to other harmful substances. Human health could similarly be at risk on account of microplastic ingestion.

Microplastics can be retained for a longer time at the higher trophic levels where humans belong, thereby predisposing humans to serious health hazards.

Case for a plastic bags ban

A ban on plastic bags would curb the plastic pollution in Nigeria. There are alternatives to the use of plastic bags, for instance, bags made from banana stalks, coconut, palm leaf, cassava flour and chicken feathers. Unlike plastic bags, which could persist in the environments for over a century, bags made from these organic materials decompose readily in a manner that does not pose a health risk to the environment.

For a long while, the call to mitigate plastic pollution was not heeded in Nigeria. Recently, the House of Representatives passed a bill banning plastic bags. But this is yet to be implemented as the president has not assented to it.

A study in the European Union indicates that a ban on single-use plastics could reduce marine plastic pollution by about 5.5%.

It is about time Nigeria treated plastic pollution as a national emergency, considering its implications for human health and the ecological integrity of aquatic ecosystems. An approach that puts people at the centre of the issue has been suggested as one way to convince local communities to preserve the integrity of the environment.

Perhaps this approach could help restore plastic-laden aquatic ecosystems and preserve the pristine ones.


Explore further Opening plastic bags and bottles may generate microplastics
Provided by The Conversation

Changes in South Africa's rainfall seasons could affect farming and water resources

by Sarah Roffe and Jennifer Fitchett, The Conversation

Brewing thunderstorm in the dessert area of the Karoo in South Africa. Credit: Shutterstock

Most of South Africa's seasonal rainfall occurs during the warmer summer months, from October to March. As a result, October is an important period for farmers to begin planning when to sow crops (such as maize, wheat and sunflowers) for the growing season. October is also an important period for the tourism industry to think about water supplies for the upcoming summer holiday season.


The timing of summer rainfall, and all rainfall across South Africa, is determined by large-scale climate systems. Climate change is gradually changing the location of these systems and their moisture corridors, which bring rainfall to each region. The southward shift in the westerly winds (one of these large-scale climate systems) and their mid-latitude cyclones is one of the reasons Cape Town suffered such a severe water shortage between 2015 and 2017.

Research shows that the record low rainfall amounts were caused by recent expansion of the Hadley cell, the circulation of air from the tropics to subtropics. This expansion has changed the timing of summer rainfall and caused intensification of high-pressure systems (causing dry conditions), and a southward shift of the westerly wind belt (providing moisture for winter cold front rainfall).

South Africa has distinct spatial zones of rainfall seasonality. These are termed the summer-, winter- and year-round rainfall zones. Eastern and central regions get their rainfall during the summer months. That's when the southwestern Cape and west coast regions are dry due to strong high-pressure conditions. In winter, the high-pressure systems shift north, sitting across the interior of the country and causing dry conditions there. The southern coast and a strip of land between the summer and winter rainfall zones form the year-round rainfall zone.

Most research in South Africa has focused on how large-scale climate system changes are influencing rainfall totals. Little research has considered consequent changes in rainfall seasonality—the timing of rainfall, including when the wet season begins and ends. These changes are important to consider, because rainfall seasonality changes across South Africa may have detrimental impacts on crop yields and surface water supplies. This prompted our research, recently published in the International Journal of Climatology.


We used rainfall and temperature records between 1987 and 2016 from 46 weather stations across South Africa to calculate annual rainfall seasonality characteristics using two methods. These quantify the strength of seasonality, and the wet-season start- and end-dates, length, total rainfall amount, number of rain days and rainfall intensity. We then explored how these characteristics changed during 1987-2016. We chose this recent 30-year period because that's when climate change impacts have begun to show.

The hope is that this information can inform effective adaptation in sectors and activities dependent on rainfall seasonality characteristics. This is because, if sustained, the trends we calculated present a concerning outlook for continued crop production and water resource management.

What we found

As rainfall varies considerably over the years and decades, we didn't expect to find any conclusive evidence of rainfall seasonality changes over this relatively short period. But we did find that the trends across the different rainfall zones demonstrate patterns which can be linked to changes recorded for large-scale climate systems.

Our calculations reveal that the wet season started later and produced less rainfall across the interior summer rainfall zone and adjacent interior year-round rainfall zone. This is linked to Hadley cell expansion, which is associated with the tropical rain belt taking moisture south later. For the eastern coastal locations, the summer wet season started earlier, but also produced less rainfall. This can similarly be linked to Hadley cell expansion, but more strongly to changes in the high-pressure systems transporting moisture from the Indian Ocean.

The strongest trend signal for winter rainfall locations, and adjacent interior year-round rainfall locations, reflects reduced wet-season totals. This is consistent with a poleward shift of the westerlies, linking to less rainfall associated with cold fronts.

The most consistent trend for the southern coast year-round locations was for a longer dry season with increased wet-season rainfall. These trends are complicated to interpret, but can be linked to changes in the westerlies and high-pressure systems.

Why it matters

The trends we calculated are concerning, especially those of wet-season drying. Should these continue, activities that depend on rainfall could experience severe impacts. We've already seen this during the Cape Town "day zero" drought—and events like this are expected to occur more frequently in the decades to come.

Agriculture, for instance, relies on the wet-season timing, its length and total rainfall to dictate when to sow crops, and to select appropriate crops which will mature before the wet season ends. Later wet-season start dates and less rainfall will require additional planning and farmers will need to select crops that can be sown later and will fully mature with less rainfall.

Water resource managers also rely on rainfall seasonality characteristics to adequately manage use of water supplies. With many trends reflecting less wet-season rainfall, this would similarly require additional planning and monitoring to make sure water supplies do not run dry.

Going forward

Our research identified many consistent trends which can already inform management strategies for rainfall dependent activities. But there's a need to explore similar trends for longer periods, across more areas of the country. It's important to develop future scenarios considering rainfall seasonality changes and the mechanisms that drive trends. Among others, farmers, water managers and climatologists will need to closely monitor rainfall seasonality characteristics during coming years.


Explore further  Climate change projected to increase seasonal East African rainfall
Provided by The Conversation

As smoke from forest fires ages in the atmosphere its toxicity increases

by University of Kentucky

NOAA/NASA's Suomi NPP satellite captured this true-color image of the United States on Sep. 15, 2020 showing the fires in the West, the smoke from those fires drifting over the country, and several hurricanes converging with Sally making landfall. Credit: NOAA/NASA

Natural occurring wildfires create large smoke plumes that are transported several hundred miles away in the atmosphere exposing many people to pollutants that affect public health.

Every year, thousands of hectares of land are engulfed by forest fires across the globe. Just during the first three quarters of 2020, more than 2.6 million hectares in the Western United Sates have been consumed by fires. As the biomass in trees, bushes, grass, and peat are burned, large quantities of smoke, soot, and other pollutants are emitted to the atmosphere. The smoke can then rise several kilometers in altitude and spread across large continental regions, polluting the air of distant areas. For example, many residents in the states of California, Washington and Oregon have recently experienced the poor air quality of hazy smoke.

Chemistry professor Marcelo Guzman at the University of Kentucky leads a National Science Foundation research project, which is studying how emissions from biomass burning, including wildfires, change with time in the atmosphere to create new chemicals that impact the health of societies and the climate of Earth. Guzman, together with graduate student Sohel Rana, carefully studied in the laboratory the heterogeneous atmospheric chemistry of methoxyphenols, which are among the most abundant molecules emitted during biomass burning. The team highlighted that when methoxyphenols react at interfaces, i.e. such as on the surface of cloud and fog waters as well as aerosol particles from pollution, electron and proton transfer processes are favored to quickly convert aromatic molecules into highly water-soluble products.

'When you look at the mechanisms that these methoxyphenols undergo when exposed to background ozone gas and hydroxyl free radicals during atmospheric transport, you can start explaining the common observation of multifunctional carboxylic acids as abundant species in a lot of particles in the air we breathe. The report identifies unique reaction channels that can be used to distinguish the contribution of atmospheric processing of biomass burning emissions over other possible sources of multifunctional carboxylic acids,' said Prof. Guzman. 'The work is not only fundamentally interesting but identifies specific signatures for the daytime transformation of methoxyphenols emitted from forest fires as they age in the atmosphere.'


To do this, the researchers have used a special instrument in the laboratory that replicates the fast reaction between the methoxyphenols markers of biomass burning and ozone gas at the interface of air with micrometer size water droplets. They then vary the concentrations and acidity in the experiments to see how the interfacial chemistry changes for different conditions occurring in the environment.

'We are trying to understand the dominant transformations of the methoxyphenols from smoke in the atmosphere, determine their lifetime, and establish how they chemically evolve at interfaces,' said Prof. Guzman. 'We want to contribute new understanding of their impacts on human health and climate. Are the aged molecules more toxic? How do the structural changes of the molecules contribute to create particles that interact with sunlight affecting climate?'

A key finding of the work is that material released from forest fires can become more water soluble and likely toxic over the two weeks that smoke can be transported in the atmosphere. While in the air the methoxyphenols in smoke react with ozone and hydroxyl radicals to become oxidized and highly reactive. A person breathing in these reactive compounds can suffer oxidative damage of cells, especially in the respiratory track and lungs. In addition, these reactive compounds can make some people more prone to other health problems.

Prof. Guzman also states that characterizing the chemical processing of pollution from wildfires and domestic wood-burning can help to determine if the so-called brown carbon in soot emitted from fires contributes to absorb more heat from the sun or not. 'While the many small molecules in brown carbon can be quickly photobleached, the larger molecules are far more resistant, possibly contributing to warm up the atmosphere,' he said.


Explore further  'Four times more toxic': How wildfire smoke ages over time
More information: Find out more about this research: "Oxidation of Phenolic Aldehydes by Ozone and Hydroxyl Radicals at the Air–Water Interface" by Md. Sohel Rana and Marcelo I. Guzman, Journal of Physical Chemistry A, 2020, DOI: 10.1021/acs.jpca.0c05944.
Journal information: Journal of Physical Chemistry A


Provided by University of Kentucky

New technologies to achieve net-zero

emissions by 2050 and pre-industrial

 CO2 levels by 2150

October 14, 2020 by Mark E. Capron, Jim R. Stewart, and Antoine De Ramon N'yeurt

Diagram of processes involved in restoring the world’s climate to pre-industrial levels while supporting UN Sustainable Development Goals. Credit: OceanForesters

As humanity struggles to limit ever-rising temperatures, it also seeks to address growing poverty, disease and hunger across the world. Our team has designed an approach to address both issues in a way that is practical, economical, and effective, relying on three newly demonstrated technologies.

The world faces multiple crises affecting basic human needs for food, shelter and health, while at the same time maintaining aspirations for education and meaningful work. Crises affecting food and shelter, such as droughts, floods, groundwater depletion, diminished glaciers/snowpack and sea-level rise are exacerbated by increasing greenhouse gas concentrations. Health issues such as pandemics and increasing ranges of disease-transmitting organisms are also intensified by climate change.

Human needs and climate crises require finding interconnected opportunities addressing these interrelated challenges. Indeed, Pope Francis has issued a call to "...bring the whole human family together to seek a sustainable and integral development…" The 2015 Paris Agreement recommends "rapid reductions" of greenhouse gases be achieved "on the basis of equity, and in the context of sustainable development and efforts to eradicate poverty."

Our team found interconnected opportunities with two approaches addressing human and climate issues. The two approaches update our 2012 proposal to grow more seaweed to simultaneously solve the problems of feeding the world, fueling the world and reversing climate change. We discovered these approaches during our work on the U.S. Department of Energy Advanced Research Projects Agency-Energy (ARPA-E) MARINER Program. The program's goal was to reduce the cost of growing macroalgae for biofuel.

Figure 1 shows how wastes, biomass, and fossil fuels are employed by the three newly demonstrated technologies: (1) building floating flexible fishing reef ecosystems with nutrient recycling achieving many Sustainable Development Goals, such as producing a half-billion tonnes of seafood per year; (2) Allam-Fetvedt Cycle (Allam Cycle) power plants efficiently producing both electricity and sequestration-ready CO2; and (3) advances in hydrothermal liquefaction transforming any type of biomass into high quality biocrude oil.

During our MARINER work, we found that growing shellfish and fish close to seaweed improves the growth and potential yield of all three. In fact, farming annual mono-crops, or even dual-crops, in the ocean is sub-optimal. The best seaweed productivity is a perennial crop as part of a complete ecosystem that is managed as forests are managed. Perhaps as many as 30 species of fish, shellfish, crustaceans and others can be harvested, leaving the 100 ecosystem-supporting species. It's best to harvest a little macroalgae every week or so (as opposed to one to three harvests per year).

The permanent artificial reefs can be placed at any seafloor depth while floating at the ideal depth for the seaweed species. With ideal depth for sunlight and nutrient recycling, each reef can be even more productive than are natural reefs. This Total Ecosystem Aquaculture is a proposed program for the U.N. Decade of Ocean Sciences for Sustainable Development (2021-2030).

Co-author Antoine de Ramon N'Yeurt, a senior marine biologist at the University of the South Pacific in Fiji, has investigated marine ecosystems across many tropical islands of the Pacific and Indian Oceans. He says, "I have looked at the productivity and biodiversity of natural coral reefs and I realize that artificial seaweed reefs could be even more productive and thriving ecosystems. A scientifically designed mixture of seaweed and shellfish would uptake excess nutrients while attracting sustainable eco-communities of fish, crustaceans, sea cucumbers and their myriad associated microbial communities. This system could restore fishing jobs and natural habitat, helping island and coastal nations throughout the world not only to feed themselves, but export food to help feed humanity."

Allam cycle electrical plants make electricity with zero emissions whether burning coal or biofuels, allowing no gases to escape. The result could be the ending of dangerous pollution from power plants, yielding great health benefits while capturing all the carbon dioxide for sequestration. And if they burn trash, plastic, crop residues or other dry biofuels, the process is carbon negative, resulting in high net carbon removal. The company 8 Rivers currently has a working plant in Texas demonstrating that the technology is ready for commercialization.

Then we looked at the World Bank analysis of the 2 billion tons of waste generated by humanity every year. We saw that only a small fraction is recycled; most is either dumped in landfills, which emit climate-harming methane, or dumped in trash heaps that often catch fire, emitting dangerous air pollution. Too much waste, especially plastic, finds its way into the ocean, harming turtles, fish and birds. The economics of hydrothermal liquefaction (see page 13 in our paper and pages 22-27 in our Supplemental Material) have improved to support commercial-scale conversion of organic wastes, mixed with some plastics, into high quality biocrude oil. The biocrude oil can replace bunker fuel or be refined to make biodiesel and bio-gasoline at prices comparable to fossil fuels by applying the waste disposal fees to the production costs. By the time waste is fully used, the process economics should support using purpose-grown macroalgae.

Our analysis found that the world could achieve net-zero emissions by 2050, even with substantial fossil fuel use. In fact, a tax on fossil fuels could be used to pay for removing the trillions of tonnes of previously emitted CO2. The International Panel on Climate Change (IPCC) 1.5 degrees C report projects nearly 3 trillion excess tonnes of CO2 in the atmosphere and oceans (see the right side of Figure 2) if net zero emissions are achieved by 2050.

We put all this analysis into an Excel spreadsheet with 24 interlinked tabs that estimate the amount of waste and biomass of many kinds available globally. Combined with the three technologies and the estimated demand for energy, we were able to calculate how to remove all of the excess CO2. Removing excess CO2 will bring global air and water temperatures and ocean pH back to pre-industrial levels. Climates and ocean currents will more slowly stabilize and eventually return to pre-industrial conditions. Many species extinctions will be avoided.

Our spreadsheet (Supplemental Material in the zip document) allows countries and communities to choose a suitable balance using variations of low bio-electricity and high biofuels (for current vehicles) or high bio-electricity and low biofuels (to supply electric vehicles). The spreadsheet is designed so anyone can plug in estimates for their region and see the outcomes in terms of quantities, costs, and carbon sequestration amounts.

Figure 2: Our paper’s calculations superimposed on the IPCC 1.5ºC projections. Both our low and high bio-electricity alternatives show much more carbon removal than the IPCC each year in order to return CO2 levels to pre-industrial levels of about 300 ppm. Credit: OceanForesters calculations superimposed on Figures SPM 3a and SPM 1c from IPCC, 2018: Summary for Policymakers. In: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]

Figure 2 graphs possible emissions from both our approaches. Allam Cycle plants are only economical with dry fuels, such as trash, plastic, and crop residues. Some islands do not have sufficient quantities of dry biomass, but have access to Total Ecosystem Aquaculture reefs that could grow abundant seaweed biofuel that could make oil in hydrothermal liquefaction plants.

ARPA-E required us to have a path to market for our macroalgae-grow-harvest technology. That requirement inspired us to phase the three technologies for a path to full scale. We suggest roughly this order:

1. Grow up to 500 million tonnes/yr of seafood worth about $1 trillion/yr on permanent flexible floating reefs. While growing seafood, refine equipment for growing macroalgae for biofuel.
2. Produce 20 million barrels/day of biofuel from solid waste worth $0.3-0.7 trillion/yr. While processing trash, refine the process to use purpose-grown macroalgae economically.
3. Scale to produce more biocrude oil from macroalgae than current fossil oil.
4. Scale up to sequestration of 28 to 38 billion tonnes/yr of CO2, which could restore pre-industrial CO2 levels by 2140-2170. At full scale, our carbon dioxide removal costs are projected at $26 per tonne of CO2. That is less than one-third of cost estimates for bioenergy with carbon capture and sequestration with pre-2019 technology or the projected cost of direct air-capture removal.

The climate window of opportunity is rapidly closing. Action is needed now. Starting on our path to scale appears immediately economically viable, even without a carbon fee/tax.

We look forward to ongoing dialogues with scientists, engineers, political decisionmakers and communities to "bring the whole human family together" with "sustainable and integral development." The more perspectives, the better. For action opportunities involving the ocean, please participate in the U.N. Decade of Ocean Sciences for Sustainable Development (2021-2030).

This story is part of Science X Dialog, where researchers can report findings from their published research articles. Visit this page for information about ScienceX Dialog and how to participate.

More information: Mark E. Capron et al. Restoring Pre-Industrial CO2 Levels While Achieving Sustainable Development Goals, Energies (2020). DOI: 10.3390/en13184972

Mark E. Capron, M.S. in structural/ocean engineering from UC Berkeley, is a licensed professional engineer and founder of OceanForesters, a California technology company. Mark was a U.S. Navy diving officer and marine engineer and then a water resources engineer envisioning, gaining public support, finding funding, designing, building, and operating multi-million-dollar projects. As president, Mark leads OceanForesters guiding 40 scientists, engineers, and business people to design flexible floating reefs and associated technologies to feed and fuel the world, and reverse climate change.

Jim R. Stewart, Ph.D. in Physics from Yale University, is a scientist, environmentalist, manager, and editor with emphasis on energy and sustainability issues. His experience includes technology startups; founding climate and energy issue organizations; research and teaching; and directing social justice groups.

Antoine de Ramon N'Yeurt, Ph.D. in marine botany from the University of the South Pacific, is a senior marine biologist at the University of the South Pacific in Fiji. He is an internationally recognized expert on the study of seaweed of the Pacific Islands and author of numerous publications and books on taxonomy and issues of biofuels, algal blooms, ocean acidification and its effects on coral reefs, as well as food security through sustainable fertilizers from marine biomass.

A framework to increase the safety of robots operating in crowded environments

by Ingrid Fadelli , Tech Xplore

With the help of deep-learning and model-based control, the researchers’ risk-sensitive robot achieves safe and efficient navigation in real-world dynamic environments. Credit: Nishimura et al.

Humans are innately able to adapt their behavior and actions according to the movements of other humans in their surroundings. For instance, human drivers may suddenly stop, slow down, steer or start their car based on the actions of other drivers, pedestrians or cyclists, as they have a sense of which maneuvers are risky in specific scenarios.


However, developing robots and autonomous vehicles that can similarly predict human movements and assess the risk of performing different actions in a given scenario has so far proved highly challenging. This has resulted in a number of accidents, including the tragic death of a pedestrian who was struck by a self-driving Uber vehicle in March 2018.

Researchers at Stanford University and Toyota Research Institute (TRI) have recently developed a framework that could prevent these accidents in the future, increasing the safety of autonomous vehicles and other robotic systems operating in crowded environments. This framework, presented in a paper pre-published on arXiv, combines two tools, a machine learning algorithm and a technique to achieve risk-sensitive control.

"The main goal of our work is to enable self-driving cars and other robots to operate safely among humans (i.e., human drivers, pedestrians, bicyclists, etc.), by being mindful of what these humans intend to do in the future," Haruki Nishimura and Boris Ivanovic, lead authors of the paper, told TechXplore via email.

Nishimura, Ivanovic and their colleagues developed a machine-learning model and trained it to predict the future actions of humans in a robot's surroundings. Using this model, they then created an algorithm that can estimate the risk of collision associated with each of the robot's potential maneuvers at a given time. This algorithm can automatically select the optimal maneuver for the robot, which should minimize the risk of colliding with other humans or cars, while also allowing the robot to move towards completing its mission or goal.

"Existing methods for allowing autonomous cars and other robots to navigate among humans generally suffer from two important oversimplifications," the researchers told TechXplore via email. "Firstly, they make simplistic assumptions about what the humans will do in the future; secondly, they do not consider a trade-off between collision risk and progress for the robot. In contrast, our method uses a rich, stochastic model of human motion that is learned from data of real human motion."

For safe human-robot interactions, robots (e.g., autonomous cars) need to first reason about the possibility of multiple outcomes of an interaction (denoted by the colored shaded arrows), and understand how their actions influence the actions of others (e.g., surrounding pedestrians). Such reasoning then has to be incorporated into the robot’s planning and control modules in order for it to successfully navigate dynamic environments alongside humans. Credit: Nishimura et al.

The stochastic model that the researchers' framework is based on does not offer a single prediction of future human movements, but rather a distribution of predictions. Moreover, the way in which the team used this model differs significantly from the way in which previously developed robot navigation techniques integrated stochastic models.

"We consider the full distribution of possible future human motions," Nishimura and Ivanovic explained. "We then choose our robot's next action to achieve both a low risk of collisions (i.e., the robot collides with none or very few of the many predicted motions of the humans), while still driving the robot in the direction in which it intends to move. This is called risk-sensitive optimal control, and it essentially allows us to determine a robot's next action in real-time. The computation it requires happens in a fraction of a second and is continuously repeated as the robot's moves around in its environment."

To evaluate their framework, Nishimura, Ivanovic and their colleagues carried out both a simulation study and a real-world experiment. In the simulation study, they compared their framework's performance with that of three commonly used collision avoidance algorithms in a task where a robot had to determine the best actions to safely navigate environments containing up to 50 moving humans. In the real-world experiment, on the other hand, they used their framework to guide the actions of a holonomic robot called Ouijabot within an indoor environment that was populated by five moving human subjects.

The results of both of these tests were highly promising, with the researchers' framework calculating optimal trajectories that minimized the risk of the robot colliding with humans in its surroundings. Remarkably, the framework also outperformed all the collision avoidance algorithms it was compared to.

"Our overarching goal is to make autonomous cars and other robots safer for humans," the researchers said. "To ensure the safe operation of robots around humans, we need to teach them to predict human motion from experience and endow them with a sensitivity to risk, so that they avoid risky behaviors that may lead to collisions. This is precisely what our algorithm does."

In the future, this navigation framework could increase the safety of robots and self-driving vehicles, allowing them to predict the actions of humans or vehicles in their surroundings and promptly respond to these actions to prevent collisions. Before it can be implemented on a large scale, however, the framework will need to be trained on large databases containing videos of humans moving in crowded environments similar to the one in which robots will be operating. To simplify this training process, Nishimura, Ivanovic and their colleagues plan to develop a method that allows robots to gather this training data online as they are operating.

"We would also like for robots to be able to identify a model that fits the specific behavior of the humans in its immediate environment," Nishimura and Ivanovic said. "It would be very useful, for example, if the robot could categorize an erratic driver or a drunk driver at any given moment, and avoid moving too close to that driver to mitigate the risk of collision. Human drivers do this naturally, but it is devilishly difficult to codify this in an algorithm that a robot can use."

A framework for indoor robot navigation among humans
More information: Risk-sensitive sequential action control with multi-modal human trajectory forecasting for safe crowd-robot interaction. arXiv:2009.05702 [cs.RO]. arxiv.org/abs/2009.05702

© 2020 Science X Network

Using math to study paintings to learn more about the evolution of art history

by Bob Yirka , Tech Xplore

Credit: Pixabay/CC0 Public Domain

A team of researchers affiliated with a host of institutions in Korea and one in Estonia has found a way to use math to study paintings to learn more about the evolution of art history in the western world. In their paper published in Proceedings of the National Academy of Sciences, the group describes how they scanned thousands of paintings and then used mathematical algorithms to find commonalities between them over time.


Beauty, as the saying goes, is in the eye of the beholder—and so it is also with art. Two people looking at the same painting can walk away with vastly different impressions. But art also serves, the researchers contend, as a barometer for visualizing the emotional tone of a given society. This suggests that the study of art history can serve as a channel of sorts—illuminating societal trends over time. The researchers further note that to date, most studies of art history have been qualitatively based, which has led to interpretive results. To overcome such bias, the researchers with this new effort looked to mathematics to see if it might be useful in uncovering features of paintings that have been overlooked by human scholars.

The work involved digitally scanning 14,912 paintings—all of which (except for two) were painted by Western artists. The data for each of the paintings was then sent through a mathematical algorithm that drew partitions on the digital images based on contrasting colors. The researchers ran the algorithm on each painting multiple times, each time creating more partitions. As an example, the first run of the algorithm might have simply created two partitions on a painting—everything on land, and everything in the sky. The second might have split the land into buildings in one partition and farmland in another.

The researchers then ran other algorithms designed to look for patterns between the paintings. Doing so allowed them to see trends such as painting styles that predominated during certain eras. It also allowed them to see long-term trends, such as the placement of the horizon. The researchers found that over the past several hundred years, painters have been placing it increasingly higher. In the 17th century, the separation between Earth and sky dominated landscapes—those done in more modern times, in sharp contrast, have the horizon very near the top of the canvas.


Explore further

Composing creativity: Children benefit from new painting materials
More information: Byunghwee Lee et al. Dissecting landscape art history with information theory, Proceedings of the National Academy of Sciences (2020).

DOI: 10.1073/pnas.2011927117
Journal information: Proceedings of the National Academy of Sciences



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