Secondary Organic Aerosol Formation from Isoprene Oxidation

Isoprene, a ubiquitous biogenic volatile organic compound emitted predominantly by vegetation, undergoes atmospheric oxidation to yield a complex mixture of products that partition into the particle phase as secondary organic aerosol (SOA). Gas-phase reactions initiated by hydroxyl radicals or ozone generate intermediates such as isoprene epoxydiols (IEPOX) and methacryloyl peroxynitrate, whose subsequent reactive uptake on acidified or aqueous aerosol surfaces drives SOA growth. The relative importance of low- and high-NOₓ oxidation pathways governs the speciation of precursors and the overall yield. Environmental factors—most notably aerosol acidity, water content, inorganic seed composition and ambient oxidant levels—modulate the kinetics of multiphase partitioning and secondary chemistry. Isoprene-derived SOA influences climate through cloud interactions and radiative forcing, and poses air quality and health implications via fine particulate matter exposure. Advances in mechanistic understanding and modelling are vital to predict its global distribution and response to changing emissions.

Research from Nature Portfolio

Recent studies have demonstrated that urban emissions of nitrogen oxides can amplify biogenic SOA formation in otherwise pristine regions. High-resolution transport modelling over the Amazon reveals that city-sourced NOₓ increases IEPOX-driven SOA by up to several hundred per cent, mediated by enhanced oxidation of forest-emitted organics and acid-catalysed uptake. In parallel, novel causal-analysis frameworks employing information-transfer metrics and the Koopman operator have been applied to regional model outputs to disentangle the driving roles of chemical and meteorological variables in IEPOX-SOA formation. This approach provides the first rigorous identification of cause–effect relations beyond correlation, offering a powerful tool to uncover previously hidden processes in atmospheric aerosol chemistry.

Secondary Organic Aerosol Formation from Isoprene Oxidation publication trend

The graph below shows the total number of articles in secondary organic aerosol formation from isoprene oxidation across all publications each year (not limited to Nature Index journals).

Technical terms

Secondary Organic Aerosol (SOA): Particulate matter formed from the atmospheric oxidation of volatile organic compounds and subsequent gas-to-particle partitioning.

Isoprene Epoxydiols (IEPOX): Water-soluble oxidation products of isoprene that undergo acid-catalysed uptake to form SOA.

Reactive Uptake: Process by which gaseous oxidation products are absorbed onto or react within aerosol particles.

Aerosol Acidity: Measure of acidity (pH) in particle liquid water, influencing reaction rates of uptake and oligomerisation.

Low-NOₓ Conditions: Atmospheric regime where peroxy radicals preferentially react with hydroperoxy radicals, yielding IEPOX and related precursors.

High-NOₓ Conditions: Regime where peroxy radicals predominantly react with NO, altering precursor speciation towards aldehydes and organonitrates.

References

1. Combustion-related isoprene contributes substantially to the formation of wintertime secondary organic aerosols. National Science Review (2025).
2. Physics informed deep neural network embedded in a chemical transport model for the Amazon rainforest. npj Climate and Atmospheric Science (2023).
3. Diurnal Variations in High Time-Resolved Molecular Distributions and Formation Mechanisms of Biogenic Secondary Organic Aerosols at Mt. Huang, East China. Molecules (2023).
4. Application of advanced causal analyses to identify processes governing secondary organic aerosols. Scientific Reports (2024).
5. Urban pollution greatly enhances formation of natural aerosols over the Amazon rainforest. Nature Communications (2019).