Glyoxal molecules interacting with water droplets and iron particles, influencing air quality.

Can Kitchen Chemistry Save Our Skies? The Unexpected Role of Glyoxal in Air Pollution

Elliot Brynn in Climate & Environment August 2025 • 4 min read.

"New research reveals how a common compound, glyoxal, impacts the catalytic oxidation of sulfur dioxide, potentially altering air quality."

Air pollution is a complex challenge with impacts that span from our immediate health to global climate patterns. Among the many compounds contributing to this issue, sulfur dioxide (SO2) plays a significant role. In the atmosphere, SO2 transforms into sulfate, a key component of particulate matter that affects air quality, cloud formation, and even the acidity of rain.

The oxidation of sulfur dioxide in the aqueous phase—think cloud droplets and aerosols—is a critical area of study for environmental scientists. This process is often sped up, or catalyzed, by transition metals like iron, which are commonly found in atmospheric particles. However, the presence of organic compounds can further complicate this already intricate scenario.

Now, new research is shedding light on how one particular organic compound, glyoxal, influences this catalytic oxidation. Glyoxal, a simple dicarbonyl compound, is prevalent in the atmosphere, arising from both natural and human-caused sources. Understanding its role could be a game-changer in our fight against air pollution.

The Science Behind Glyoxal's Impact on Sulfur Dioxide Oxidation

Glyoxal molecules interacting with water droplets and iron particles, influencing air quality.

A recent study published in ACS Earth and Space Chemistry delves into the interactions between glyoxal and sulfur dioxide in acidic, aqueous environments. The researchers, led by Vicki H. Grassian, focused on how glyoxal affects the catalytic oxidation of S(IV)—sulfur dioxide in its dissolved form—when catalyzed by iron ions and iron oxide particles.

The team's findings reveal a nuanced picture. In the presence of glyoxal, the rate of S(IV) oxidation catalyzed by aqueous iron ions actually decreases. This inhibition is attributed to two primary mechanisms:

Trapping of Sulfate Radicals: Glyoxal appears to react with sulfate radicals (SO4-), key intermediates in the oxidation process, effectively reducing their concentration.
Formation of Glyoxal-S(IV) Adducts: Glyoxal combines with S(IV) to form adducts, which are less reactive and slow down the overall oxidation process.

Interestingly, even though the oxidation process slows down, the sulfur is still completely converted to sulfate over time. This suggests that glyoxal doesn't halt the reaction entirely but rather modifies its pace. Furthermore, the inhibitory effects of glyoxal are more pronounced when the reaction is catalyzed by dissolved iron ions compared to solid iron oxide particles, indicating that the form of the catalyst and the reaction mechanism play crucial roles.

Why This Matters: Implications for Our Atmosphere

These findings have significant implications for our understanding of atmospheric chemistry and air quality. Glyoxal, as a ubiquitous organic compound, can influence the rate at which sulfur dioxide is converted to sulfate, a major component of atmospheric aerosols. This, in turn, affects cloud formation, precipitation patterns, and the overall radiative balance of the Earth.

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This article is based on research published under:

DOI-LINK: 10.1021/acsearthspacechem.8b00168, Alternate LINK

Title: Influence Of Glyoxal On The Catalytic Oxidation Of S(Iv) In Acidic Aqueous Media

Subject: Space and Planetary Science

Journal: ACS Earth and Space Chemistry

Publisher: American Chemical Society (ACS)

Authors: Ellen M. Coddens, Liubin Huang, Cynthia Wong, Vicki H. Grassian

Published: 2018-12-04

Everything You Need To Know

What is glyoxal and how does it affect air quality and climate?

Glyoxal is a simple dicarbonyl compound found in the atmosphere from both natural sources and human activities. It influences the rate at which sulfur dioxide is converted to sulfate, which is a significant component of atmospheric aerosols. This conversion impacts cloud formation, precipitation patterns, and the Earth's radiative balance, thereby affecting overall air quality and climate.

Why is the catalytic oxidation of sulfur dioxide so important in the context of air pollution?

The catalytic oxidation of sulfur dioxide (SO2) is crucial because it transforms SO2 into sulfate, a key component of particulate matter. These sulfate particles affect air quality, contribute to cloud formation, and influence the acidity of rain. Understanding this process is essential for predicting and mitigating the impacts of air pollution on both human health and the environment.

What are the specific mechanisms by which glyoxal influences the oxidation of sulfur dioxide?

Glyoxal slows down the oxidation of S(IV) (dissolved sulfur dioxide) through two main mechanisms. First, it traps sulfate radicals (SO4-), which are essential intermediates in the oxidation process, reducing their concentration. Second, it forms glyoxal-S(IV) adducts, which are less reactive, thus decreasing the rate of sulfur dioxide conversion to sulfate. Even with these mechanisms, the sulfur is ultimately converted to sulfate, suggesting glyoxal primarily alters the reaction's pace rather than halting it completely.

How does the form of the catalyst, such as aqueous iron ions versus solid iron oxide particles, affect glyoxal's influence on sulfur dioxide oxidation?

The study found that glyoxal inhibits S(IV) oxidation catalyzed by aqueous iron ions more effectively than when catalyzed by solid iron oxide particles. This difference indicates that the form of the catalyst, whether dissolved iron ions or solid iron oxide particles, significantly influences the reaction mechanism and, consequently, the extent of glyoxal's inhibitory effect. This distinction is crucial for accurately modeling atmospheric processes involving sulfur dioxide oxidation.

What aspects of glyoxal's role in air pollution are not fully understood and require further investigation?

While the research highlights the interactions between glyoxal and sulfur dioxide, it does not extensively cover the synergistic effects of other organic compounds present in the atmosphere. Future studies could explore how glyoxal interacts with other volatile organic compounds (VOCs) and nitrogen oxides (NOx) to further refine our understanding of air pollution dynamics. Additionally, more research is needed to quantify the specific impact of glyoxal on cloud microphysics and precipitation efficiency under various atmospheric conditions.