Correlation of secondary organic aerosol with odd oxygen in Mexico City

Photochemically processed urban emissions were characterized at a mountain top location, free from local sources, within the Mexico City Metropolitan Area. Analysis of the Mexico City emission plume demonstrates a strong correlation between secondary organic aerosol and odd oxygen (O3 + NO2). The measured oxygenated‐organic aerosol correlates with odd oxygen measurements with an apparent slope of (104–180) μg m−3 ppmv−1 (STP) and r2 > 0.9. The dependence of the observed proportionality on the gas‐phase hydrocarbon profile is discussed. The observationally‐based correlation between oxygenated organic aerosol mass and odd oxygen may provide insight into poorly understood secondary organic aerosol production mechanisms by leveraging knowledge of gas‐phase ozone production chemistry. These results suggest that global and regional models may be able to use the observed proportionality to estimate SOA as a co‐product of modeled O3 production until more complete models of SOA formation become available.