Organic Aerosol Chemistry and Nitrogen Oxide Reactivity
Summary
Organic aerosol arises from both primary emissions and secondary chemical transformations of volatile organic compounds in the atmosphere. Biogenic and anthropogenic precursors undergo oxidation by hydroxyl radicals, ozone and nitrate radicals, yielding multifunctional products that partition into the particle phase. The presence of nitrogen oxides modulates these pathways by diverting peroxy radical reactions towards organic nitrates, altering aerosol yields, volatility and hygroscopic properties. Daytime photo-oxidation typically produces oxygenated organics with modest nitrate content, whereas nocturnal chemistry driven by the nitrate radical leads to high organic nitrate fractions that influence particle growth and lifetime. Organic nitrates act as temporary nitrogen reservoirs, affecting regional nitrogen budgets and linking air quality with ecosystem fertilisation. The balance between formation and hydrolysis of organic nitrates further governs secondary organic aerosol mass and composition. These processes impact climate by modifying particle radiative forcing and cloud activation, and they affect human health through fine particulate exposure. Recent advances in laboratory kinetics, field measurements and global modelling have revealed the spatial heterogeneity of aerosol–nitrogen interactions and underscored the need for improved representation of non-photochemical mechanisms in atmospheric models.
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Organic Aerosol Chemistry and Nitrogen Oxide Reactivity publication trend
The graph below shows the total number of articles in organic aerosol chemistry and nitrogen oxide reactivity across all publications each year (not limited to Nature Index journals).
Technical terms
Organic aerosol (OA): Particulate matter composed of carbon-based compounds, originating from direct emissions or secondary formation.
Secondary organic aerosol (SOA): Fine particles formed by atmospheric oxidation of volatile organic compounds followed by gas-to-particle partitioning.
Nitrogen oxides (NOx): Reactive gases, principally nitric oxide and nitrogen dioxide, that control oxidant levels and influence aerosol chemistry.
Nitrate radical (NO3): A nocturnal oxidant formed from NO2 and ozone, critical for night-time oxidation of biogenic and anthropogenic VOCs.
Organic nitrates (RONO2): Nitrogen-containing organic products of VOC oxidation that partition into particles and act as temporary nitrogen reservoirs.
Cloud condensation nuclei (CCN): Aerosol particles capable of activating into cloud droplets, with properties influenced by aerosol composition and hygroscopicity.
References
- Dissecting the contributions of organic nitrogen aerosols to global atmospheric nitrogen deposition and implications for ecosystems. National Science Review (2023).
- Observational evidence reveals the significance of nocturnal chemistry in seasonal secondary organic aerosol formation. npj Climate and Atmospheric Science (2024).
- Contrasting Influence of Nitrogen Oxides on the Cloud Condensation Nuclei Activity of Monoterpene‐Derived Secondary Organic Aerosol in Daytime and Nighttime Oxidation. Geophysical Research Letters (2023).
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