Surface ozone pollution remains stubbornly persistent even as emissions of traditional precursors decline. New research reveals that oxygenated volatile organic compounds (OVOCs), long treated as secondary or minor players, in fact dominate the radical chemistry that drives ozone formation in background air. By comprehensively accounting for a wide range of OVOCs, the study shows that these compounds supply more than half of the radicals responsible for ozone production. Several overlooked OVOCs exert outsized influence despite their low concentrations, reshaping current understanding of atmospheric oxidation processes. The findings challenge conventional ozone control strategies and point to hidden chemical pathways that must be addressed to effectively mitigate regional ozone pollution.
Ground-level ozone is a major air pollutant that threatens human health, ecosystems, and climate stability. Despite aggressive reductions in nitrogen oxides and primary volatile organic compounds, ozone levels continue to exceed air quality standards in many regions. This paradox reflects the complex and nonlinear nature of atmospheric photochemistry, where reactive radicals control ozone formation. Oxygenated volatile organic compounds (OVOCs) are key intermediates in this process, acting as both sources and sinks of radicals. However, most previous studies have measured only a small subset of OVOCs, leaving major uncertainties in radical budgets. Based on these challenges, there is a critical need to systematically investigate how a broader spectrum of OVOCs drives radical cycling and ozone formation.
In a study published (DOI: 10.1016/j.ese.2026.100659) in January 2026 in Environmental Science and Ecotechnology , researchers from the Southern University of Science and Technology , The Hong Kong Polytechnic University , Hong Kong Baptist University , Beijing University of Chemical Technology , and the University of Helsinki investigated how oxygenated volatile organic compounds shape atmospheric chemistry in background air over southern China. Combining intensive field observations with photochemical box modeling, the team examined the role of OVOCs in radical cycling and ozone formation. Their results show that commonly used models relying on limited OVOC measurements substantially misrepresent radical budgets and ozone production under real atmospheric conditions.
The study combined high-resolution field measurements with a detailed photochemical box model to quantify the role of OVOCs in atmospheric radical chemistry. When models were constrained using only three commonly measured OVOCs, simulated hydroxyl radical levels were overestimated by up to 100 percent. By contrast, including measurements of 23 OVOCs brought simulations into close agreement with observations.
The analysis revealed that OVOC photolysis contributed approximately 49–61 percent of total radical production, making it the dominant radical source in background air. Surprisingly, several OVOCs present at relatively low concentrations accounted for a disproportionate share of radical generation. Errors in simulating these compounds caused cascading biases in radical budgets, altering ozone formation pathways.
The study further showed that traditional chemical mechanisms systematically overestimate some OVOCs while underestimating others, masking offsetting errors that appear acceptable when only limited measurements are used. These hidden inaccuracies significantly affect predictions of ozone production rates and sensitivity regimes. Overall, the findings demonstrate that a narrow observational focus can lead to misleading conclusions about the drivers of ozone pollution.
"This work shows that what we don't measure can matter more than what we do," said one of the study's senior authors. "OVOCs have often been treated as secondary products, but our results demonstrate that they are central to controlling radical chemistry and ozone formation. Without comprehensive OVOC observations, models may appear accurate while fundamentally misrepresenting atmospheric processes. Expanding OVOC measurements is therefore essential for designing effective air quality management strategies in regions struggling with persistent ozone pollution."
These findings have important implications for air pollution control and atmospheric modeling worldwide. Strategies focused solely on reducing traditional ozone precursors may fail if OVOC-driven radical chemistry is ignored. Incorporating comprehensive OVOC measurements can improve model accuracy, guide emission control priorities, and help policymakers identify more effective mitigation pathways. The study also highlights the need to update chemical mechanisms and expand monitoring networks to include reactive OVOC intermediates. Ultimately, recognizing the hidden role of OVOCs may be key to resolving the long-standing challenge of persistent surface ozone pollution in both developing and industrialized regions.
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References
DOI
Original Source URL
https://doi.org/10.1016/j.ese.2026.100659
Funding information
This research was funded by the Hong Kong Research Grants Council via Theme-Based Research Scheme (T24-504/17-N) and General Research Fund (HKBU 15219621), the National Natural Science Foundation of China (42325504), the National Key Research and Development Program of China (2023YFC3706205), and the Shenzhen Science and Technology Program (JCYJ20220818100611024).
About Environmental Science and Ecotechnology
Environmental Science and Ecotechnology (ISSN 2666-4984) is an international, peer-reviewed, and open-access journal published by Elsevier. The journal publishes significant views and research across the full spectrum of ecology and environmental sciences, such as climate change, sustainability, biodiversity conservation, environment & health, green catalysis/processing for pollution control, and AI-driven environmental engineering. The latest impact factor of ESE is 14.3, according to the Journal Citation Reports TM 2024.
Environmental Science and Ecotechnology
Not applicable
OVOCs drive radical cycling and ozone formation in background air
22-Jan-2026
The authors declare that they have no competing interests.