Scientists disclose how upper layer ozone intrusions boost surface ozone and aerosol pollution in China

Science China Press

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Schematic diagram of ULOI events and their impacts on surface O3 concentration and secondary aerosol (SA) formation, spatial distribution of ULOI probability in China from December 2020 to February 2021.

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Credit: ©Science China Press

The research team, led by Professors Yongchun Liu from Beijing University of Chemical Technology, along with Professor Jiannong Quan from the Chinese Meteorological Administration, and Professor Douglas R. Worsnop from the University of Helsinki, proposed a novel method for identifying upper-layer ozone intrusion (ULOIs) events by ranking observational ozone concentrations on the ground surface. The result shows that ULOI events substantially elevate surface ozone levels, intensify atmospheric oxidation capacity, and accelerate wintertime sulfate and secondary organic aerosol formation in the North China Plain.

Ozone is an important air pollutant on the ground, having adverse effects on human health and the ecosystem. Surface ozone usually shows obvious daily variation with a peak at noon, followed by a continuous decrease after sunset, due to photochemistry and evolution of mixing layer height.

However, anomalously nocturnal ozone enhancements are often observed, which cannot be explained by local photochemistry alone. This emphasizes the role of vertical transport or horizontal transport processes in the atmosphere, while it is a big challenge to identify such events and quantify their impacts on atmospheric chemistry based on ground surface observations.

In a new study, researchers proposed a simple but robust method to ULOI events based solely on surface ozone measurements before dawn. ULOI events can be identified by a threshold of ozone concentration, which is objectively determined according to a sudden increase in slope of the ozone concentration before dawn versus its ranking percentile. Unlike previous approaches that rely on isotopic analysis or complex chemical transport models, the new method ranks early-morning ozone concentrations to detect signatures of ozone transported downward from higher atmospheric layers, such as the residual layer, upper troposphere, or even the lower stratosphere.

Applying this method to nationwide observational data across China, the research team found that ULOI events are far more widespread than previously recognized. Depending on the region, these events occur during 22% to 74% of the analyzed periods, with particularly high frequencies in eastern and southern coastal areas. These regions are strongly influenced by meteorological systems such as sea–land breezes, low-level jets, and tropical cyclones, which promote vertical mixing and facilitate the downward transport of ozone-rich air.

The results show that ULOI events significantly elevate surface O3 concentrations. At night, O3 levels increase by approximately 13–43 ppbv, while daytime concentrations rise by 3–14 ppbv. These enhancements substantially strengthen atmospheric oxidation capacity and enhance the contribution of the O3 oxidation path to wintertime sulfate and secondary organic aerosol formation in the North China Plain.

This study highlights the critical role of interactions between different atmospheric layers in shaping surface air quality. It shows that physical processes have complicate influence on O3 pollution and secondary aerosol formation, underscoring the need to incorporate vertical transport and upper-layer influences into air pollution research and management strategies. As the observational network for air quality is developed worldwide, the results can be applied in other regions for evaluating the impacts of these events on surface air quality and the ecosystem.

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Journal

National Science Review

DOI

10.1093/nsr/nwaf593 

Method of Research

Observational study

 

From palm oil to designer enzymes: Frankfurt researchers reprogram yeast cells

Protein engineering enables sustainable production of industrially important fatty acids

Goethe University Frankfurt

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Schematic representation of biosynthesis in a cell (top) and in the laboratory (bottom). The designer enzyme shortens the chain length of the fatty acid.

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Credit: Felix Lehmann & Martin Grininger/Goethe University

FRANKFURT. Whether laundry detergents, mascara, or Christmas chocolate – many everyday products contain fatty acids from palm oil or coconut oil. However, the extraction of these raw materials is associated with massive environmental issues: rainforests are cleared, habitats for endangered species are destroyed, and traditional farmers lose their livelihoods. The team led by Prof. Martin Grininger at Goethe University in Frankfurt, Germany, has now developed a biotechnological approach that could enable a more environmentally friendly production method.

 

A Molecular Assembly Line with Precise Control
At the heart of this research is an enzyme called fatty acid synthase (FAS) – a type of molecular assembly line that builds fatty acids in all living organisms. “FAS is one of the most important enzymes in a cell's metabolism and has been fine-tuned by evolution over millions of years,” explains Grininger.

 

The enzyme typically produces palmitic acid, a 16-carbon fatty acid that serves as a building block for cell membranes and energy storage. Industry, however, primarily requires shorter variants with 6 to 14 carbon atoms, which today are sourced from plant oils produced on large-scale oil palm plantations linked to deforestation and biodiversity loss. The decisive advantage of the new, FAS-based method: “Fundamentally, our advantage lies in the very precise control of chain length. We can theoretically make any chain length, and we're demonstrating this with the example of C12 fatty acid, which otherwise can only be obtained from palm kernels or coconut,” says Grininger.

 

Understanding Through Modification
Grininger and his team have significantly contributed to understanding the molecular foundations of FAS over the past 20 years. They discovered that chain length is regulated by the interplay between two subunits: ketosynthase repeatedly elongates the chain by two carbon atoms while thioesterase cleaves off the finished chain as a fatty acid. “We then asked ourselves whether we could go beyond analysis and build FAS with new chain length regulation,” says Grininger. “True understanding begins when you can change or customize a phenomenon.”

 

Two Targeted Interventions Lead to Success

Grininger’s doctoral student Damian Ludig took up this idea. “We asked what would happen if we specifically intervened in the interaction between these two subunits,” Ludig explains. “Could we then control the chain length of the fatty acids that are produced?”

 

Ludig employed protein engineering methods where individual amino acids can be exchanged or entire protein regions modified. “Two changes to FAS through protein engineering ultimately led us to our goal,” says Ludig. “In the ketosynthase subunit, I first exchanged one amino acid which resulted in chains being extended only with low efficiency beyond a certain length. Additionally, I replaced the thioesterase subunit with a similar protein from bacteria that shows activity in cleaving short chains.” Depending on further adjustments, Ludig was able to produce short- and medium-length fatty acids.

 

From Frankfurt to Dalian
Collaboration with Prof. Yongjin Zhou’s research group at Dalian Institute of Chemical Physics, Chinese Academy of Sciences, ultimately achieved breakthrough results. Supported by the German Research Foundation (DFG) and the National Natural Science Foundation of China (NSFC), Zhou and his lab succeeded in developing yeast strains that produce fatty acids containing only 12 carbon atoms instead of 16. Various designer FAS from Grininger's lab were integrated into these yeasts for optimization.

Both laboratories have already filed patents for their technologies. “On the Chinese side, Unilever was involved in this project. Our development has thus far taken place without industrial participation. However, we are striving for a collaboration with an industry partner in order to bring the technology into application,” says Grininger.

 

Thinking Ahead: From Fatty Acids to Pharmaceuticals
In a second project, Felix Lehmann from Grininger's lab took the research even further by investigating how universally applicable FAS are for tailored biosyntheses: “This question is also driven by necessity – to continually develop chemical processes towards more sustainable green chemistry,” explains Grininger.

 

The specific question was: Can FAS be redirected to make not only fatty acids, but also entirely different compounds, such as styrylpyrones? These molecules are precursors to substances derived from kava plants that attract medical interest due to their potential anxiolytic properties. Here, too, Lehmann achieved success with relatively few modifications: “First we cut away part of FAS that we didn't need for our target products; then we altered ketosynthase so that cinnamic acid could be used as starting material,” he explains. The team even integrated another protein into the FAS structure so it became part of multi-enzyme complex.

 

“In this project we systematically examined how entire biosynthetic pathways can be constructed with FAS from readily available building blocks,” Grininger explains. While the results do not yet have immediate practical applications, they provide important guidance for the future design of novel synthases.

 

At the Intersection of Chemistry and Biology
“Our lab has made significant strides towards biocatalysis and biotechnological applications over recent years, driven by the contributions of many projects and collaborations. We will continue down this path”, Grininger summarizes. “Within the Cluster of Excellence SCALE, we will also use this enzyme to generate tailored biomembranes, whose analysis will help deepen our understanding of key organelles such as the endoplasmic reticulum and mitochondria.”

 

Whether technology can indeed alleviate palm oil issues now depends on successful scaling up alongside industry partners. The scientific foundation has certainly been laid and the lab still has many ideas to explore.

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Journal

Nature Chemical Biology

DOI

10.1038/s41589-025-02105-w 

Method of Research

Experimental study

Subject of Research

Cells

Article Publication Date

7-Jan-2026

 

SwRI evaluates fire risks associated with solar panel installations

Engineers test three common racking orientations, roof assemblies to identify fire mitigation

Southwest Research Institute

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SwRI conducted large-scale fire testing of photovoltaic panel systems for the Fire Protection Research Foundation, an affiliate of the National Fire Protection Association, and the Property Insurance Research Group. The research will help fire safety organizations update standards and fire mitigation strategies.

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Credit: Southwest Research Institute

SAN ANTONIO — January 12, 2026 — Southwest Research Institute (SwRI) conducted a series of large-scale tests to investigate factors that affect flame spread beneath photovoltaic (PV) panel installations on flat, commercial and industrial rooftops. The research will help fire safety organizations update standards and fire mitigation strategies.

The team fabricated test decks to replicate large roofing assemblies with mounted PV solar panels. Researchers exposed the leading edge of the deck to flame and crosswind to better understand fire hazards and evaluate mitigation strategies. The testing provided critical data for builders, insurance groups and first responders.

SwRI performed baseline tests with three different PV panel racking orientations to determine which exhibited the fastest flame spread. The team also tested two fire prevention techniques, uncovered walkways and vertical barriers, with the selected racking orientations. Finally, a comparison test was performed with a bare deck.

“SwRI’s large indoor fire testing facilities and custom pollution abatement system allowed us to safely conduct the largest-scale evaluations of PV panels to date with greater exposure control while protecting the environment,” said Alexandra Schluneker, principal engineer on the project. “Previous testing was either done on a smaller scale or performed outdoors.”

Sponsored by the National Fire Protection Association’s Fire Protection Research Foundation and its Property Insurance Research Group, the research will help the organizations update building codes and fire mitigation protocols specifically for commercial and industrial solar panel installations.

“Large-scale fire testing of PV panels to evaluate performance, flame spread and potential prevention and suppression strategies is not just a technical necessity — it is a cornerstone of advancing fire safety to ensure renewable energy solutions remain both sustainable and secure for the communities they power,” said Karen C. Carpenter, director of SwRI’s Fire Technology Department.

SwRI’s Schluneker co-presented preliminary findings from the tests at the 2025 NFPA conference in Las Vegas, Nevada, on June 18, 2025. A second round of fire testing will be performed in early 2026 to further investigate additional mitigation strategies.

For more information, visit https://www.swri.org/markets/chemistry-materials/fire/fire-research-engineering.

 

Important new source of oxidation in the atmosphere found

International team reports on new reaction pathway with implications for air quality and climate in Science Advances

Leibniz Institute for Tropospheric Research (TROPOS)

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Photoreactor at TROPOS for laboratory studies on processes in the atmospheric liquid phase – i.e. in water-containing particles. These studies were conducted using a similar system.

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Credit: Thomas Schäfer, TROPOS

Shantou/Turin/Leipzig. Hydroperoxides are strong oxidants that have a significant influence on chemical processes in the atmosphere. Now, an international research team involving the Leibniz Institute for Tropospheric Research (TROPOS) has shown that these substances also form from α‑keto acids such as pyruvic acid in clouds, rain and aerosol water when exposed to sunlight. These reactions could be responsible for 5 to 15 percent of the observed atmospheric hydrogen peroxide (H₂O₂) in the aqueous phase. This means that the photolysis of α-keto acids has now been identified as another important source of atmospheric oxidants, the researchers write in Science Advances, the open-access journal of the renowned scientific journal SCIENCE. Since these oxidation processes influence both the formation and degradation of particles and air pollutants, the newly discovered reaction pathway is of great importance for air quality and climate forecasts.

 

The key to this discovery are α-keto acids. These carboxylic acids  contain an additional so-called keto group with a carbon atom and a double-bonded oxygen atom. The α-keto acids get into the atmosphere through different reactions from a number of precursor gases such as isoprene, aromatics, or acetylene, which can be biogenic or anthropogenic – originating from both vegetation and industry. They are widespread and play a fundamental role in life on Earth, for example in biochemistry in amino acid metabolism in cells. However, their importance for the atmosphere and the global climate has been rather underestimated until now. Using three α-keto acids (glyoxylic acid, pyruvic acid and 2-ketobutyric acid), the researchers were able to demonstrate in laboratory experiments and model calculations that these substances, together with light, are involved in the formation of hydroperoxides, which in turn produce hydrogen peroxide. These processes take place in the atmospheric liquid phase – in other words, in water-containing particles.

 

The study involved researchers from the Chinese Academy of Sciences (Guangzhou), the Guangdong Technion - Israel Institute of Technology, the Weizmann Institute of Science, Fudan University (Shanghai), the University of Chinese Academy of Sciences (Beijing), Kunming University of Science and Technology, the University of Turin, Shandong University (Qingdao) and the Leibniz Institute for Tropospheric Research (TROPOS). Three experts in photochemical processes in atmospheric liquids played an important role in the collaboration: Sasho Gligorovski, who wrote his doctoral thesis at TROPOS in Leipzig 20 years ago, then conducted research in France, became a professor at the Guangzhou Institute of Geochemistry of the Chinese Academy of Sciences, and has been conducting research at the Chinese-Israeli joint venture Guangdong Technion - Israel Institute of Technology (GTIIT) since 2025. Davide Vione, who works as a professor at the University of Turin. And Prof. Hartmut Herrmann, who has been researching the tropospheric multiphase system at TROPOS and the University of Leipzig since 1998, as well as at Shandong University since 2018 and Fudan University in Shanghai since 2019.

 

The atmospheric chemistry department at TROPOS in Leipzig used the laboratory data from Shanghai and Turin in its liquid phase model CAPRAM (Chemical Aqueous Phase Radical Mechanism) to evaluate the atmospheric effects of the laboratory results and make projections. The CAPRAM model has been refined over many years of work to the point where it can map highly complex reaction chains, and such new findings have now be incorporated as new feedback channels.

 

"This work provides the first quantitative framework for the formation of hydroperoxides from α‑keto acids and clarifies the pH and concentration dependencies that are crucial for atmospheric models. Through international cooperation, we have succeeded in finding another piece of the puzzle in the highly complex field of multiphase atmospheric chemistry," explains Prof. Hartmut Herrmann from TROPOS and Shandong University Qingdao.

 

The study now published provides initial approaches, but also highlights gaps in knowledge: for example, there is a lack of systematic field measurements of the concentrations of α-keto acids in aerosols and cloud water in different environments, which are needed to incorporate these mechanisms into climate models. Such studies would help to better estimate the global budget of hydroperoxides in the atmosphere and their role in particle formation in the aqueous phase and sulfate production. Tilo Arnhold

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Journal

Science Advances

DOI

10.1126/sciadv.adx4527 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Evidence for Hydroperoxides Formation through Atmospheric Aqueous Photochemistry of α-Keto acids

Article Publication Date

9-Jan-2026