Wednesday, May 14, 2025

Onion-like nanoparticles found in aircraft exhaust

Revealed by high-resolution transmission electron microscopy

National Institute for Environmental Studies

Fig. 1. Four types of aircraft exhaust particles and their typical number fractions at engine exit and 15 m downstream. — image:
(a) Turbostratic (soot) particles (diameter 67 nm). (b) Onion-like particles (diameter 17 nm). (c) Amorphous particles (diameter 26 nm). (d) Trace amorphous particles (diameter 17 nm). The four particle types were divided into single and agglomerated particles, and their fractions are shown.
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Credit: NIES/ZHAW/TMU

1. Background and purpose of the study

Aircraft emit nanoparticles (<50 nm Note 1 in diameter) into the atmosphere, from the ground to the upper troposphere. Studies in Europe, the U.S., and Japan have reported high concentrations of particles in and around airports Ref 1, and there is worldwide concern regarding the effects on human health. The atmospheric heating effects by contrails generated from aircraft exhaust particles are also known, and research is being conducted to assess their potential impacts on climate. Particle number emissions from turbofan jet engines, which are commonly used in civil aviation, are generally dominated by volatile particles (sulfate or organics) rather than non-volatile particles (mostly soot). However, the emission and formation mechanisms of the volatile particles are not well understood. Our research team investigated the physicochemical properties of aircraft exhaust nanoparticles (volatile and non-volatile) to obtain information on the emission and formation mechanisms of volatile particles.

2. Methods

We measured the morphology and internal (microphysical) structure of exhaust particles at the engine exit and 15 m downstream of commercial turbofan jet engines at a test facility in Zurich Airport, Switzerland. The morphology and internal structure of the particles were observed by high-resolution transmission electron microscopy (HRTEM) using bulk particulate samples collected on thin films.

3. Results and discussion

Four types of aircraft engine exhaust particles with different internal structures were observed (Fig. 1). Type (a) represented turbostratic particles with scattering-layered graphene-like structures Note 2 and were considered typical for soot (non-volatile particles). Type (b) consisted of onion-like particles with partial graphite-like structures, which are well-ordered graphene-like spherical multilayers. Type (c) particles were amorphous (non-crystalline), and type (d) were trace amorphous particles (images are thin and non-crystalline). Before this study, onion-like particles were not identified in the combustion exhaust or atmosphere. Although graphitic soot with the turbostratic structure emitted from aircraft has been studied for many years, three other types of particles were identified for the first time in this study.

The number fraction of turbostratic (soot) particles was high at the engine exit and lower than 1% at 15 m downstream (Fig. 1). Fifteen meters downstream, the remaining fraction was dominated by onion-like, amorphous, and trace amorphous particles. These three types of particles were mostly single (non-agglomerated, Note 3) spherical particles with diameters of 10–20 nm. Further analysis suggested that these three types of particles are volatile particles formed via nucleation and condensation downstream of the engine and mainly consist of organic compounds originating from the lubrication oil.

4. Outlook

These unique internal structures may affect the physicochemical properties of the particles, including volatility, surface reactivity, and solubility, and potentially affect the interaction of the particles with the human respiratory tract. Our research team found that aircraft emit onion-like, amorphous, and trace amorphous particles in addition to soot particles. However, there are many questions regarding the physicochemical characteristics, origin, and formation mechanism of onion-like particles, and whether they are similar in nature to soot or volatile organic particles, such as oil mist. The onion-like particles may have different dynamics in the atmosphere and in the body compared with other particles; therefore, further research is needed to understand their climate and health implications.

In the field of nanomaterials, onion-like particles are synthesized by applying high energy to soot, among other methods. The formation mechanism of onion-like particles from aircraft engines is scientifically interesting and has potential implications in materials and other fields.

5. Annotations

Note 1. nm: Nanometer. One nanometer is one-millionth of a millimeter (mm). Particle diameter (size) of 50 nm is about 1/1000th the size of cedar pollen (about 30 μm in diameter). One micrometer is 1/1000th of a millimeter.

Note 2. Graphene: A thin sheet of material with a crystalline structure of carbon atoms linked together in a hexagonal shape.

Note 3. Agglomeration: Adhesion and coalescence of particles to form large aggregates. Soot particles produced by incomplete combustion often form large agglomerates that are shaped like grape bunches.

Ref 1．Fushimi, A.; Saitoh, K.; Fujitani, Y.; Takegawa, N. Identification of jet lubrication oil as a major component of aircraft exhaust nanoparticles. Atmos. Chem. Phys. 2019, 19, 6389−6399.

https://doi.org/10.5194/acp-19-6389-2019 (Connect to an external site)

Journal

ACS ES&T Air

DOI

10.1021/acsestair.4c00309

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Unique Microphysical Structures of Ultrafine Particles Emitted from Turbofan Jet Engines

Echidna microbiome changes while mums nurse puggle

University of Adelaide

Echidna credit Ken Hurley — image:
Microbial communities in echidna pseudo-pouches undergo dramatic changes while the animal is lactating, says the University of Adelaide's Isabella Rose Wilson.
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Credit: Ken Hurley

Research from the University of Adelaide shows microbial communities in echidna pseudo-pouches undergo dramatic changes while the animal is lactating, which could help in creating an environment for their young, known as puggles, to thrive.

Echidnas are monotremes, which are the only mammals that lay eggs. The early developmental stage at which they hatch from their egg means that the puggles lack a functioning immune system.

“We know the reproductive microbiome is important to infant health, including for humans, but little is known about how it functions in egg-laying monotremes,” says the University of Adelaide’s Isabella Wilson, whose study was published in FEMS Microbiology Ecology.

“Instead of picking up vaginal microbiota during delivery like other mammals, echidnas are shielded by the eggshell and don’t come into direct contact with the cloaca.”

The first few weeks of life are critical for puggles, as they hatch at an early developmental stage. They continue to grow in the pseudo-pouch, which is created from the contraction of abdominal muscles and disappears when a female is not nursing.

“We investigated changes in the echidna pseudo-pouch microbiota during different stages of the reproductive cycle and found that during lactation pseudo-pouch microbial communities show significant differences in composition compared with samples taken outside of breeding season or during courtship and mating,” Wilson says.

“This suggests that the echidna pseudo-pouch environment changes during lactation to accommodate young that lack a functional adaptive immune system.”

The way puggles suckle may contribute to the shift in microbes.

“Another unique aspect of echidna biology is that they lack nipples. Instead of suckling like other species, the puggle rubs its beak against a part of the pseudo-pouch called the milk patch, causing milk to come out of the skin, sort of like a sweat or oil gland,” says Wilson.

“We think that compounds within the milk and from the skin probably contribute to the changes we see in the pseudo-pouch microbiota during lactation.”

Echidnas are commonly held in zoos in Australia and around the world. Previous work from the same research group showed big differences in the gut microbiome between echidnas in zoos and in the wild.

“We were surprised to find no major difference in the pseudo-pouch between zoo-managed and wild animals, which suggests to us that the milk, rather than external environmental factors like captivity, is what primarily shapes the bacterial landscape of the pseudo-pouch,” Wilson says.

“For conservation in the wild, and in breeding programs, we need to learn more about the bacteria found in echidna pseudo-pouches and better understand how these affect echidna health.”

An echidna puggle.

Credit

Peggy Rismiller and Michael McKelvey

The University of Adelaide and the University of South Australia are joining forces to become Australia’s new major university – Adelaide University. Building on the strengths, legacies and resources of two leading universities, Adelaide University will deliver globally relevant research at scale, innovative, industry-informed teaching and an outstanding student experience. Adelaide University will open its doors in January 2026. Find out more on the Adelaide University website.

DOI

10.1093/femsec/fiaf036

Unprecedented progress in tackling smoking during pregnancy threatened by NHS cuts, experts warn

University of East Anglia

Unprecedented progress in reducing the number of women smoking during pregnancy in England could be put at risk by NHS funding cuts, according to a UEA addiction expert.

A new BMJ article, co-authored by Prof Caitlin Notley from UEA’s Norwich Medical School, reveals that the proportion of women smoking during pregnancy in England has almost halved in the last decade.

Most of the decline happened in the last five years thanks to the introduction of dedicated stop smoking advisers in NHS maternity services since 2020.

But the team fear that the reduction could be threatened by cost-cutting exercises.

And they are calling for continued investment to give every child a smokefree start in life.

The article has been written by members of the Smoking in Pregnancy Challenge Group - a coalition of organisations committed to reducing rates of smoking in pregnancy.

It shows how the amount of women smoking during pregnancy dropped from 11.7 per cent in 2014/15 to 5.9 per cent as of Q3 2024/25.

Prof Notley, professor of Addiction Sciences at UEA, said: “The progress on reducing rates of smoking in pregnancy has accelerated in recent years, thanks to the focused efforts of all healthcare professionals involved in the pregnancy care pathway.

“However, there remain significant inequalities, as rates of smoking remain higher in deprived areas - suggesting that we need innovative targeted approaches for those who really struggle to quit.”

The authors say that cuts to integrated care boards (ICB) budgets and the loss of ringfenced funding for NHS tobacco treatment services could threaten the success.

Stop smoking support in some hospitals and mental health services has already been cut, according to the group, with further cuts expected.

The Smoking in Pregnancy Challenge Group is a partnership between the Royal College of Midwives, the Royal College of Obstetricians and Gynaecologists and the Royal College of Paediatrics and Child Health, the voluntary sector and academia.

Prof Linda Bauld, director of the SPECTRUM Research Consortium, co-chair of the Smoking in Pregnancy Challenge Group and co-author of the BMJ article said: “The evidence is clear that stop smoking support for pregnant women has played a vital role in reducing rates of maternal smoking and saving babies’ lives. Without continued investment in these services there is a real risk that this decline could stall, or even start to reverse, with tragic consequences for parents and families.”

Dr Clea Harmer, chief executive of Sands and co-chair of the Smoking in Pregnancy Challenge Group, said: “As the government sets its sights on a smokefree generation, now is not the time to be cutting investment in these services. Instead, they should be going further and faster to ensure every child has a smokefree start in life.”

John Waldron, policy and public affairs manager at Action on Smoking and Health and co-author of the BMJ article said: “The 2024 Labour manifesto committed to ensuring that all hospitals integrate smoking cessation support into routine care. The government must deliver on this commitment by protecting funding for these lifesaving services.”

‘NHS Cuts Could Spark Surge in Smoking During Pregnancy, Experts Warn’ is published in the British Medical Journal (BMJ).

ENDS