Chemical and Molecular Characterization of Atmospheric Aerosols

A comprehensive understanding of atmospheric aerosols hinges on detailed chemical and molecular analysis of their organic and inorganic constituents. Techniques such as high-resolution mass spectrometry, ultrahigh-performance liquid chromatography and spectroscopic refractive index measurements have revealed the complexity of particle composition, from low-volatility oxygenated organics to light-absorbing brown carbon. Molecular formula assignment and van Krevelen mapping provide insights into oxidation state, heteroatom content and the sources of secondary organic aerosol formed through gas-phase oxidation, aqueous-phase processing and biomass burning. Characterisation at this level informs climate models by quantifying hygroscopic growth, light absorption and cloud-nucleating potential. Advances in parameterisations of volatility and in-situ instrumentation now bridge laboratory and field observations, enabling quantification of mass concentrations, reaction pathways and temporal dynamics. This molecular perspective is critical to evaluating regional air quality, assessing health impacts and guiding mitigation strategies worldwide.

Research from Nature Portfolio

Recent studies have elucidated the optical and hygroscopic properties of wildfire-derived brown carbon. Measurements of solid-state brown carbon particles from a Pacific Northwest wildfire revealed that water uptake at high relative humidity doubles light absorption at visible wavelengths, while organic coatings can further amplify absorption. Variations in refractive index were shown to cause substantial shifts in regional absorption aerosol optical depth, emphasising the need to include water–organic interactions in radiative forcing estimates. Another investigation characterised the ultracomplex mixture of organic aerosols emitted by smouldering Arctic and boreal peat burns. Ultrahigh-resolution mass spectrometry uncovered thousands of aromatic and aliphatic compounds containing oxygen, sulfur and nitrogen. Comparisons between Arctic and boreal peat emissions highlighted systematic differences in organosulfur and organonitrogen content, revealing how geographic and fuel variations drive aerosol molecular diversity and reactivity.

Chemical and Molecular Characterization of Atmospheric Aerosols publication trend

The graph below shows the total number of articles in chemical and molecular characterization of atmospheric aerosols across all publications each year (not limited to Nature Index journals).

Technical terms

Brown carbon (BrC): Light-absorbing organic aerosol components that influence radiative forcing.

Hygroscopicity: The ability of particles to take up water vapour, affecting growth and optical properties.

Refractive index: A measure of how light propagates through aerosol particles, determining scattering and absorption.

Electrospray ionisation mass spectrometry: A soft-ionisation technique for assigning molecular formulas to complex organic mixtures.

Molecular corridors: Empirical relationships linking molar mass and volatility for organic compounds in aerosols.

Volatility: Tendency of a compound to partition between gas and particle phases, often expressed as saturation mass concentration.

References

1. Enhanced light absorption for solid-state brown carbon from wildfires due to organic and water coatings. Nature Communications (2024).
2. The complex composition of organic aerosols emitted during burning varies between Arctic and boreal peat. Communications Earth & Environment (2024).
3. Molecular corridors and parameterizations of volatility in the chemical evolution of organic aerosols. Atmospheric Chemistry and Physics (2016).
4. An extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) for online measurement of atmospheric aerosol particles. Atmospheric Measurement Techniques (2019).