Hiding in plain sight – a less-explored secret of secondary organic aerosols

The amount of secondary organic aerosol (SOA) in the atmosphere may be significantly enhanced by a rapid, particle-phase oligomerization process, not presently accounted for in many models. Researchers at the Pacific Northwest National Laboratory performed a sensitivity analysis for SOA formation whilst varying parameters and processes including oligomerization, precursor compound emissions of differing volatility and source type. By adopting a quasi-Monte Carlo approach, fewer model runs are required to obtain useful information on which parameters and processes affected SOA loading the most. Incorporating the oligomerization process into the model yielded results closer to those obtained experimentally in the CARES 2010 campaign in California, and was the factor accounting for the greatest variance in SOA above even emissions factors. Neglecting or including oligomerization also changed the relative importance of different source types; including it, biogenic VOC emissions were the dominant precursor source while neglecting it suggested anthropogenic semi- and intermediate-volatility compounds dominated.

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