Wildfire in a wood stove: on the trail of the nitrogen oxide mystery

Paul Scherrer Institute

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

image: 

Markus Ammann and Fengxia Bao have elucidated how brown carbon produced by wildfires accelerates the conversion of nitrate to nitrogen oxides in the atmosphere. 

view more 

Credit: Paul Scherrer Institute PSI/Markus Fischer

In laboratory experiments, researchers at the Paul Scherrer Institute PSI have discovered how brown carbon from wildfires promotes the formation of harmful nitrogen oxides in the atmosphere. This could improve prediction of the effects wildfires have on air quality and climate. The results have now been published in the journal Science Advances.

Wildfires bring to mind a blazing sea of flames. But what happens to the smoke? Anyone observing a wildfire from a safe distance notices mainly the enormous clouds that tower above the fire. These rise several kilometres and then embark on journeys that can extend across continents and oceans. Pollutants from wildfires in Canada can still be detected, for example, at the Jungfraujoch in the Swiss Alps.

These pollutants – which include particulate matter, carbon dioxide, and nitrogen oxides – have diverse and well-documented effects on air quality and climate. Among other things, they lead to respiratory illnesses and accelerate climate change through the greenhouse effect. Now researchers led by Markus Ammann at the PSI Center for Energy and Environmental Sciences have investigated the formation of these pollutants in more detail, and they found an explanation for why elevated nitrogen oxide concentrations are still present even at great distances from wildfires.

The path of nitrogen oxides

Nitrogen oxides (NOx) – compounds consisting of one nitrogen atom and one or two oxygen atoms – are produced during combustion processes. Wildfires and lightning are natural sources. However, due to the burning of fossil fuels, current nitrogen oxide levels in urban areas are many times higher than in pre-industrial times.

In the lower atmosphere, nitrogen oxides are responsible for the formation of ozone, a greenhouse gas and irritant. Furthermore, nitrogen oxides oxidise to nitric acid (HNO3) in the atmosphere. This dissolves as nitrate in tiny aerosol particles, which act as nuclei for cloud droplets. Rain carries the nitrate back to earth, where it is deposited in the soil.

This continuous conversion of nitrogen oxides to nitrate should ultimately result in a much lower amount of nitrogen oxides in the atmosphere than is actually present.

There is also a known reverse pathway in the atmosphere: triggered by sunlight, nitrate can be converted back into nitrogen oxide. This process is called photolysis. “However, this process is far too slow to account for the observed amounts of nitrogen oxide,” Ammann says.

One hypothesis in aerosol chemistry was, therefore, that in addition to this known, slow photolysis, there must be another, faster photolysis process – and that other substances released during wildfires could play a role in this.

Simulated wildfire in a wood-burning stove

Wildfires differ from other sources of nitrogen oxide in that they also produce a large amount of particulate matter from organic compounds, including some soot. The cause of this is incomplete combustion of wood and other biomass. This organic particulate matter is responsible for the greyish-white colour of the smoke. Some of the organic compounds absorb light in the visible spectrum. These are collectively referred to as brown carbon.

To investigate the influence of brown carbon on photolysis, researchers at PSI conducted a laboratory experiment: in a wood-burning stove, they first simulated a wildfire by reducing the air supply to produce more smoke – and thus more brown carbon. This was collected using filters, then dissolved in water, and finally placed in a temperature-stabilised glass tube.

The researchers then exposed nitrate to the light of various UV lamps that simulated sunlight under different conditions – once without the added brown carbon and once with it. In each case, they measured the concentration of nitrogen oxides produced.

Nitrogen oxides were always produced with light containing a particularly high-energy ultraviolet component, that is, hard UV light. The photolysis of nitrate under hard UV light is known. However, the amount of nitrogen oxide was significantly higher in the samples that also contained brown carbon.

“When we then used lamps without a hard UV component, we could only detect nitrogen oxides in the presence of brown carbon,” says Fengxia Bao, a researcher in Markus Ammann’s group and first author of the study.

Since direct photolysis with the remaining soft UV light is not possible, the researchers concluded that the path to nitrogen oxide in this case is indirect: the organic substances in the brown carbon absorb the soft UV light. This causes them to enter an excited state and donate an electron to the nitrate. That’s how the nitrate is converted into nitrogen oxide. In this way, nitrogen oxide production is accelerated tenfold compared to the known process with hard UV light.

A powerful effect

“This is a clear, powerful result,” Ammann says. “We were able to demonstrate experimentally what up to now had only been vaguely suspected. Our study will enable better predictions about the effects of wildfires on air quality and climate.”

Further research will be needed to clarify additional pathways for the formation of nitrogen oxides, Ammann continues: “Our result can explain a larger proportion of the nitrogen oxides present in the atmosphere – but not yet all of them.”

In the future, he would like to make his research, which was funded by the ETH Board’s ReCLEAN project, even more realistic. For example, the simulation chamber at PSI could use all of the burned material, not just the components filtered out and dissolved in water.

Text: Oliver Morsch

 

About PSI

The Paul Scherrer Institute PSI is the largest research institute for natural and engineering sciences in Switzerland. It is the central location of Switzerland’s large research facilities, available to both the scientific community and industry. Its research spans future technologies, energy and climate, health innovation and fundamentals of nature. The annual budget is CHF 450 million. PSI employs 2300 people; around a quarter of these are postdoctoral researchers, PhD students or apprentices. PSI is part of the ETH Domain, which also includes ETH Zurich and ETH Lausanne, as well as the other federal research institutes Empa, Eawag and WSL. 

---

Journal

Science Advances

DOI

10.1126/sciadv.aeg9077

Article Title

Brown carbon in biomass burning aerosol enhances HONO production

Article Publication Date

11-Nov-2026

The wood stove at PSI that the researchers use to simulate a wildfire. 

Credit

Paul Scherrer Institute PSI/Markus Fischer

 

Ebola resource equips healthcare workers, policymakers and researchers with evidence-based interventions

Curated collection provides free access to the latest medical and social science research

Taylor & Francis Group

LinkedInWeChat
WhatsAppEmail

Leading knowledge publisher Taylor & Francis has announced a new collection of key books and journal articles, supporting the global response to the current Ebola outbreak. Curated by expert editors, the featured content is free for everyone to access, making trusted research available to all frontline workers, researchers and policymakers.

Drawing on the breadth of the Taylor & Francis publishing program across disciplines, the collection features not only critical medical and health research but also humanities and social science contributions, essential for addressing the societal, ethical, and policy impacts of the disease.

Across seven sections, the resource brings together articles and book chapters covering transmission and diagnosis; vaccine strategy; treatment; health communication; and international relations. Context for the latest outbreak is provided by resources examining the origins and history of the disease.

Leon Heward-Mills, Managing Director Academic and Chief Content Officer at Taylor & Francis, said: “Publishers play a key role in putting the latest peer-reviewed research into the hands of those who can apply it on the ground and that’s especially critical during health crises. The new Ebola resource features some of the most important contributions from experts across diverse disciplines, offering valuable knowledge to those tackling this devastating disease.”

The Ebola resource is available on the Taylor & Francis website.

 

Brain-inspired memristors open new pathways to energy-efficient artificial intelligence

Shanghai Jiao Tong University Journal Center

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

image: 

• Task-oriented perspective on neuromorphic memristors for artificial intelligence computing.
• From material systems and device structures to applications, flexibility, and system integration.
• A critical roadmap toward scalable, manufacturable, and practical neuromorphic hardware.

view more 

Credit: Jianhui Wang, Qingxin Chen, Jinhao Zhang, Jialin Meng*, Tianyu Wang*.

As artificial intelligence continues to advance, conventional computing architectures face growing challenges in energy consumption, data-transfer latency, and hardware scalability. The separation of memory and processing units in traditional von Neumann systems creates a significant bottleneck, particularly for data-intensive AI applications. Neuromorphic computing, inspired by the parallel and energy-efficient information processing of the human brain, offers a promising alternative. In a comprehensive review, researchers from Shandong University, Fudan University, and collaborating institutions examine the development of neuromorphic memristors, highlighting how materials, device architectures, and system integration can be tailored to meet the demands of next-generation artificial intelligence.

Why Neuromorphic Memristors Matter

Biological neurons and synapses process information through electrical signals and dynamically adjustable connections. Neuromorphic memristors mimic these functions by regulating and retaining electrical conductance states, enabling artificial synaptic plasticity and neuron-like behavior. Their compact structures, nonvolatile memory characteristics, and potential for dense integration make them attractive for in-memory computing, where data storage and processing can occur within the same hardware. By reducing data movement between separate memory and processing units, these devices offer opportunities to improve computational efficiency and reduce power consumption.

Innovative Design and Mechanism

The review systematically examines representative memristor platforms, including oxide-based materials, ferroelectric systems, polymers, and two-dimensional materials. It also explores different device architectures and switching mechanisms, such as conductive filament formation, ionic migration, polarization modulation, phase transitions, and charge storage. Importantly, the authors emphasize that device optimization should be guided by the intended computational task rather than conventional switching performance alone. Different platforms offer distinct advantages: ferroelectric oxides provide opportunities for CMOS-compatible integration, polymer systems support flexible electronics, and layered materials enable ion-controlled neuromorphic functions. Reconfigurable devices capable of switching between volatile and nonvolatile operating modes further expand the range of possible computing applications.

Outstanding Performance

Recent demonstrations highlighted in the review illustrate the practical potential of these technologies. A multifunctional memristive synapse achieves approximately two orders of magnitude lower energy consumption than a GPU-based computing solution. Memristor arrays have also enabled epilepsy-related neural signal analysis with 93.46% accuracy and nearly 400-fold higher power efficiency than state-of-the-art CMOS systems. Other examples include artificial neurons operating at voltages as low as 80 mV, flexible three-dimensional memristor arrays, and wearable textile networks capable of combining sensing and neuromorphic processing. Together, these advances demonstrate the potential of memristors for efficient, adaptive, and mechanically flexible intelligent hardware.

Applications and Future Outlook

The review connects neuromorphic memristor technologies with a broad range of AI applications, including medical signal recognition, image reconstruction, artificial vision, intelligent sensing, and gesture-based human–machine interaction. Nevertheless, challenges remain in manufacturing reproducibility, device variability, standardized performance evaluation, scalable fabrication, and system-level integration. The authors highlight the need to coordinate materials engineering, CMOS-compatible architectures, peripheral circuits, and software–hardware co-design. Ultimately, integrating sensing, memory, computing, and interaction into compact hardware platforms could bring energy-efficient neuromorphic intelligence closer to practical applications in wearable electronics, edge AI, and intelligent human–machine interfaces.

---

Journal

Nano-Micro Letters

DOI

10.1007/s40820-026-02322-5

Method of Research

News article

Article Title

Analysis and Applications of Neuromorphic Memristors in Artificial Intelligence Computing

 

Matter–antimatter asymmetry still provides no evidence of new physics

The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

image: 

Proton–proton collisions at the LHC produce, among other particles, mesons containing beauty and strange quarks and antiquarks. Differences between matter and antimatter were investigated in their decays into secondary particles.

view more 

Credit: Source: IFJ PAN

 

The Universe's dominance by ordinary matter is compelling evidence that matter and antimatter are not perfect reflections of each other. However, known differences do not explain the scale of this imbalance, leaving open the possibility that unknown physics is responsible. A new analysis of meson decays, conducted by the LHCb collaboration, has narrowed the scope of the search for such a scenario while paving the way for more precise measurements in the future.

 

 

Over the past decade, scientists working at the Large Hadron Collider have focused their efforts on searching for differences between particles of matter and antimatter produced in proton-proton collisions. The latest and exceptionally thorough analysis of data collected between 2016 and 2018 as part of the LHCb experiment was carried out by a team of physicists from the universities of Warwick, Manchester and Oxford in the UK, TU Dortmund University in Germany, and the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow.

 

The motivation behind this research lies in what is arguably the most astonishing feature of our world: the fact that it... simply exists. Why is this so surprising? Because, in its present form, it should not exist – at least according to our current understanding of physics. Cosmological models suggest that, shortly after the Big Bang, equal amounts of matter and antimatter must have been produced in the Universe. Yet when a particle meets its antiparticle, both are converted into energy in a process known as annihilation. Meanwhile, our reality is clearly dominated by particles of matter that have escaped annihilation. The worlds of matter and antimatter particles therefore cannot have been – and still are not – perfectly symmetrical.

 

“In many physical processes, simultaneously replacing all particles with their antiparticles and inverting all spatial coordinates leaves the laws governing these phenomena unchanged. This principle is known as charge-parity symmetry, or CP symmetry. We have been searching for processes that violate this symmetry in the decays of particles produced in proton–proton collisions at the LHC, specifically in the decays of mesons containing beauty and strange quarks and antiquarks,” explains Dr. Agnieszka Dziurda (IFJ PAN), an expert in the physics of these decays.

 

The Standard Model, a theoretical framework developed in the 1970s, describes the elementary particles and their interactions. According to this model, matter is made up of elementary particles known as fermions. These include quarks (down, up, strange, charm, beauty and top) and leptons (electrons, muons, tau leptons and their associated neutrinos). In addition, every type of matter particle has a corresponding antiparticle.

 

Each proton–proton collision at the LHC produces a large number of massive, short-lived particles. In earlier studies of CP violation, physicists have observed asymmetries in certain decay processes involving particles and antiparticles. However, these phenomena alone cannot account for the present-day dominance of matter. Now, in a paper published in the renowned journal Physical Review Letters, researchers have presented an analysis of the decays of Bs0 mesons. These mesons decay into lighter particles, and the Standard Model allows scientists to calculate the expected frequency of a given decay process and compare these predictions with experimental data.

 

“Interestingly, we chose to investigate a process in which the Standard Model predicts no asymmetry at all. So why study it at all?” asks Dr. Dziurda. She explains: “Because if an asymmetry were nevertheless observed, it could be a signal that previously unknown physics was at work. We also know that current theoretical predictions for the probabilities of certain beauty-meson decay channels differ significantly from the values obtained experimentally. This discrepancy could, for example, stem from theoretical effects that have not yet been fully accounted for in our calculations. At this stage, however, we cannot rule out the possibility that it points to physics beyond the Standard Model.”

 

Beauty mesons were exceptionally well suited to the search for CP symmetry breaking for another reason. They possess a remarkable property: they oscillate extremely rapidly between states corresponding to matter (a strange quark paired with a beauty antiquark) and antimatter (a beauty quark paired with a strange antiquark). One of the earlier measurements by the LHCb experiment showed that these oscillations can occur several trillion times per second. Thanks to such fast oscillations, the analysis could be carried out without having to determine the initial state of each meson.

 

A particular challenge for researchers was to thoroughly understand and characterise detector asymmetries, that is, differences in the detection of particles and antiparticles arising from the detector itself. This is because positively and negatively charged particles curve in opposite directions as they travel through the detector's magnetic field. Because detection efficiencies vary across the detector, this can affect the numbers of recorded particles and antiparticles. Such effects can produce an apparent asymmetry in the data even when the process being studied occurs with equal probability for particles and antiparticles. To account for these effects, the researchers used extensive calibration samples and computer simulations, and regularly reversed the direction of the detector's magnetic field. Corrections for differences in particle and antiparticle detection efficiencies were also applied when determining the final asymmetry in beauty-meson decays.

 

“We had to make sure that any asymmetry observed in the data, however small, was not caused by the detector itself. This was a crucial aspect of the entire analysis because, given the precision of our measurement, detector-related effects could have been of the same magnitude as the asymmetry we were looking for,” says Dr. Dziurda.

 

The data from the LHCb experiment analysed in this study revealed a difference of approximately one to two cases per thousand decays. However, since the measurement uncertainty was larger than the observed effect, the result is consistent with the predictions of the Standard Model. Although the finding does not solve the mystery of the missing antimatter or rule out the existence of new physics, it narrows down the range of possibilities in which new phenomena might be hiding. In the decays studied, any unknown process that would cause an asymmetry greater than about 2% would almost certainly have been detected.

 

Future research, using the larger datasets already collected with the upgraded LHCb detector, will allow scientists to investigate even more subtle effects in the discussed meson decays. Should a new source of CP violation be hidden therein, the analysis presented here provides physicists with a clearer understanding of where – and precisely how – the search should be conducted.

 

The Polish contribution to the research was funded by a grant awarded by the Polish Ministry of Science and Higher Education.

 

 

The Henryk Niewodniczański Institute of Nuclear Physics (IFJ PAN) is currently one of the largest research institutes of the Polish Academy of Sciences. A wide range of research carried out at IFJ PAN covers basic and applied studies, from particle physics and astrophysics, through hadron physics, high-, medium-, and low-energy nuclear physics, condensed matter physics (including materials engineering), to various applications of nuclear physics in interdisciplinary research, covering medical physics, dosimetry, radiation and environmental biology, environmental protection, and other related disciplines. The average yearly publication output of IFJ PAN includes over 600 scientific papers in high-impact international journals. Each year the Institute hosts about 20 international and national scientific conferences. One of the most important establishments of the Institute is the Bronowice Cyclotron Centre (CCB), which is an infrastructure unique in Central Europe, serving as a clinical and research centre in the field of medical and nuclear physics. In addition, IFJ PAN runs four accredited research and measurement laboratories. IFJ PAN is a member of the Marian Smoluchowski Kraków Research Consortium: “Matter-Energy-Future”, which in 2012-2017 enjoyed the status of the Leading National Research Centre (KNOW) in physics. In 2017, the European Commission granted the Institute the HR Excellence in Research award. As a result of the categorization of the Ministry of Education and Science, the Institute has been classified into the A+ category (the highest scientific category in Poland) in the field of physical sciences.

 

SCIENTIFIC PUBLICATIONS:

 

“First Measurement of the Decay-Time-Integrated CP Asymmetry in Bs0→Ds–π+ Decays”

LHCb Collaboration

Physical Review Letters 2026, 137, 081802

DOI: 10.1103/ljtv-y278

 

 

LINKS:

 

http://www.ifj.edu.pl/

The website of the Institute of Nuclear Physics, Polish Academy of Sciences.

 

http://press.ifj.edu.pl/

Press releases of the Institute of Nuclear Physics, Polish Academy of Sciences.

 

 

IMAGES:

 

IFJ261112b_fot01s.jpg                                  

HR: http://press.ifj.edu.pl/news/2026/11/12/IFJ261112b_fot01.jpg

Proton–proton collisions at the LHC produce, among other particles, mesons containing beauty and strange quarks and antiquarks. Differences between matter and antimatter were investigated in their decays into secondary particles. (Source: IFJ PAN)

 

---

Journal

Physical Review Letters

DOI

10.1103/ljtv-y278

Article Title

First Measurement of the Decay-Time-Integrated CP Asymmetry in Bs0→Ds–π+ Decays

Environmental steroid hormones in aquatic ecosystems: biogeochemical processes, mixture risks, and sustainable management

A new review maps how steroid hormones move, transform and persist in water — and why removing parent compounds alone may not remove the risk

Innovation Press

Facebook

XLinkedInWeChatBlueskyMessageWhatsAppEmail

image: 

Steroid hormones enter and persist in waters via wastewater, manure runoff, and airborne particles.

Conjugated forms and transformation products can be missed, while mixtures can amplify pollution risks.

These pollutants can disrupt reproduction in aquatic life and may pose broader risks to human health.

Monitoring, source control, and nature-based treatment provide a sustainable path forward.

view more 

Credit: Yang H., Feng Q., Tang Y., et al. (2026). Environmental steroid hormones in aquatic systems: Biogeochemical dynamics, mixture risks, and sustainable mitigation. The Innovation Water 1:100015. https://doi.org/10.59717/j.tiw.2026.100015

Every day, wastewater treatment plants, livestock farms and manure-fertilized fields release steroid hormones into rivers, lakes and coastal seas. The amounts are tiny — often measured in nanograms per liter — but for fish and other aquatic species, tiny is enough. Decades of research have linked these compounds to shifted sex ratios, impaired reproduction and population decline in fish. A new review in The Innovation Water argues that the usual way of tracking them — measuring a handful of parent compounds before and after treatment — understates both exposure and risk.

The review, led by Hang Yang and Yi Zhang of the Institute of Hydrobiology, Chinese Academy of Sciences, with Lei Wang of Shenzhen Polytechnic University, walks through the full life cycle of environmental steroid hormones: where they come from, where they go, what they do, and what can be done about them.

One central finding concerns what standard monitoring misses. Steroid hormones rarely travel as free, parent compounds alone. Conjugated forms excreted in urine can be deconjugated by microbes in the environment, regenerating active hormones; transformation products can retain or even gain biological activity. In some secondary wastewater effluents, the review notes, conjugated and halogenated estrogens together can account for 60–70% of the total molar load of steroid estrogens — fractions invisible to targeted assays focused on parent compounds.

Real waters also carry mixtures: natural hormones, synthetic analogues, transformation products and other co-contaminants such as microplastics and antibiotics. Mixture effects may be additive, synergistic or antagonistic, yet risk assessment frequently evaluates compounds one at a time. Evidence of harm is strongest for aquatic life — vitellogenin induction, skewed sex ratios, reduced fecundity — while direct epidemiological evidence linking environmental exposure to human health outcomes remains limited, a boundary the authors state explicitly.

On the treatment side, the review's message is equally cautious. Conventional processes lower parent-compound concentrations but vary with compound, process conditions and season. Sorption and membrane separation may simply relocate pollutants to sludge or concentrate streams; advanced oxidation can destroy parent structures without achieving full mineralization, leaving active transformation products. The authors argue that removal rates for parent compounds should not be compared across technologies without context, and that treatment should be judged by whether transformation products, residual endocrine activity and overall toxicity decline together.

Their proposed path forward is organized under a One Health framework: expand monitoring to wastewater, manure, agricultural runoff, receiving waters, sediments and indicator organisms; bring mixture effects into risk assessment; control sources from pharmaceutical use and disposal to livestock operations; and combine engineered treatment with nature-based solutions such as constructed wetlands and microalgae systems. Whether any of it works, the review concludes, should be verified by measurable, simultaneous declines in exposure, residual endocrine activity and toxicity — not by parent-compound removal rates alone.

###

Yang H., Feng Q., Tang Y., et al. (2026). Environmental steroid hormones in aquatic systems: Biogeochemical dynamics, mixture risks, and sustainable mitigation. The Innovation Water 1:100015. https://doi.org/10.59717/j.tiw.2026.100015

---

DOI

10.59717/j.tiw.2026.100015

Method of Research

Systematic review

Subject of Research

Not applicable

Article Title

Environmental steroid hormones in aquatic systems: Biogeochemical dynamics, mixture risks, and sustainable mitigation