Secondary Organic Aerosol Formation from Biomass Burning Emissions

Secondary organic aerosols (SOA) arise when volatile and semi-volatile organic compounds emitted by biomass burning undergo atmospheric transformation. Wildfire and agricultural residue combustion liberate a complex mixture of volatile organic compounds (VOCs), including phenolics, methoxyphenols and small aromatics. In the gas phase these precursors react with hydroxyl and nitrate radicals and ozone to form functionalised oxidation products. Aqueous-phase processing in cloud and aerosol water further converts these oxygenated intermediates into nitro- and oligomeric species. The interplay between temperature, relative humidity and nitrogen oxides dictates the yields of light-absorbing “brown carbon” components such as nitrophenols and nitrocatechols. These secondary products contribute significantly to fine particle mass, alter the particles’ optical properties, affect regional radiative forcing and represent a pathway for long-range transport of biomass-derived organic matter. Understanding the multiphase chemistry that links primary emissions to SOA is critical for accurate climate modelling and for the development of mitigation strategies to reduce health and ecological impacts.

Research from Nature Portfolio

One foundational investigation explored the aqueous-phase nitration of guaiacol-containing biomass burning aerosol under simulated environmental conditions. It demonstrated that, after initial consumption of the phenolic precursor, electrophilic nitration by reactive nitrogen species yields nitrophenolic products with enhanced toxicity. The study revised the understanding of atmospheric aqueous-phase chemistry by highlighting organonitrogen pathways that form light-absorbing brown carbon in remote biotopes downwind of urban sources. The findings underscored that multiphase processes can dominate secondary organic aerosol formation even in low-pollution environments.

Secondary Organic Aerosol Formation from Biomass Burning Emissions publication trend

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

Technical terms

Secondary Organic Aerosol (SOA): Particulate matter formed in the atmosphere by chemical transformation of gaseous organic precursors.

Brown Carbon (BrC): Fraction of organic aerosol that absorbs light in the near-UV and visible range, influencing radiative forcing.

Biomass Burning (BB): Combustion of plant matter, including wildfires and agricultural residues, that releases organic and inorganic pollutants.

Volatile Organic Compounds (VOCs): Organic chemicals that readily evaporate into the atmosphere, serving as SOA precursors.

Gas–Particle Partitioning: Distribution of semi-volatile compounds between the gas phase and particulate phase based on temperature and composition.

Box-Model Simulations: Simplified chemical models that track the transformation of pollutants within an air parcel over time.

References

1. Does toxicity of aromatic pollutants increase under remote atmospheric conditions?. Scientific Reports (2015).
2. Ambient nitro-aromatic compounds – biomass burning versus secondary formation in rural China. Atmospheric Chemistry and Physics (2021).
3. Guaiacol Nitration in a Simulated Atmospheric Aerosol with an Emphasis on Atmospheric Nitrophenol Formation Mechanisms. ACS Earth and Space Chemistry (2021).
4. Aqueous-Phase Brown Carbon Formation from Aromatic Precursors under Sunlight Conditions. Atmosphere (2020).