Organic Aerosol Dynamics and Emission Factors

Organic aerosols constitute a complex mixture of carbonaceous particles in the atmosphere, arising from direct emissions (primary organic aerosol, POA) and in-situ chemical transformation of gaseous precursors (secondary organic aerosol, SOA). The partitioning between gas and particle phases depends on volatility distributions and ambient conditions, while multiphase chemical ageing alters composition, hygroscopicity and optical properties. Emission factors quantify the mass of organic aerosol produced per unit activity—such as per kilogram of fuel combusted or per vehicle-kilometre travelled—and underpin both regional air-quality models and policy interventions. Recent advances have integrated semivolatile and intermediate-volatility organics into global and regional chemical transport models, revealing that these compounds can account for a substantial fraction of observed SOA and modify diurnal cycles, source apportionment and long-range transport. Understanding organic aerosol dynamics is pivotal for assessing climate forcing, human health impacts and the efficacy of emission control strategies across urban and rural environments worldwide.

Research from Nature Portfolio

Observational and modelling work across China has documented a marked nationwide decline in organic aerosol concentrations between 2013 and 2020, driven primarily by reductions in residential fuel burning. Declines in primary OA surpassed those of SOA, while meteorological variability and changes in precursor emissions (for example NOx and SO2) have modulated SOA formation. The study underscores the importance of cross-sector clean energy adoption and highlights that trade-offs in pollutant controls can lead to unexpected effects on SOA yields. A state-of-the-art regional model incorporating experimentally constrained parameters for OA ageing and intermediate-volatility emissions demonstrates that accounting for multigenerational oxidation and IVOCs can increase total OA in Eastern China by about 40%, with SOA enhanced by an order of magnitude. This inclusion significantly improves agreement with ambient measurements and implies that IVOCs may constitute over half of regional SOA loadings, prompting a reevaluation of fine-particle control policies.

Organic Aerosol Dynamics and Emission Factors publication trend

The graph below shows the total number of articles in organic aerosol dynamics and emission factors across all publications each year (not limited to Nature Index journals).

Technical terms

Primary organic aerosol (POA): Organic material emitted directly into the atmosphere from sources such as combustion.

Secondary organic aerosol (SOA): Particulate matter formed in the atmosphere via chemical oxidation of volatile organic compounds.

Intermediate-volatility organic compound (IVOC): Organic species with boiling points intermediate between volatile and semi-volatile compounds, serving as SOA precursors.

Emission factor: Mass of pollutant emitted per unit activity, such as grams of organic aerosol per kilogram of fuel burned.

Oxidation flow reactor: Experimental system that accelerates atmospheric oxidation to simulate aerosol ageing processes under controlled conditions.

References

1. Widespread 2013-2020 decreases and reduction challenges of organic aerosol in China. Nature Communications (2024).
2. Quantifying the effect of organic aerosol aging and intermediate-volatility emissions on regional-scale aerosol pollution in China. Scientific Reports (2016).
3. Modeling organic aerosols in a megacity: potential contribution of semi-volatile and intermediate volatility primary organic compounds to secondary organic aerosol formation. Atmospheric Chemistry and Physics (2010).
4. Marked impacts of transient conditions on potential secondary organic aerosol production during rapid oxidation of gasoline exhausts. npj Climate and Atmospheric Science (2023).
5. Secondary organic aerosol formation exceeds primary particulate matter emissions for light-duty gasoline vehicles. Atmospheric Chemistry and Physics (2014).
6. Secondary organic aerosol formation from photooxidation of naphthalene and alkylnaphthalenes: implications for oxidation of intermediate volatility organic compounds (IVOCs). Atmospheric Chemistry and Physics (2009).