Observational evidence for pollution‐influenced selective uptake contributing to biogenic secondary organic aerosols in the southeastern U.S.

During the 2013 Southern Oxidant and Aerosol Study, aerosol mass spectrometer measurements of submicron mass and single particles were taken at Look Rock, Tennessee. Their concentrations increased during multiday stagnation events characterized by low wind, little rain, and increased daytime isoprene emissions. Organic mass (OM) sources were apportioned as 42% “vehicle‐related” and 54% biogenic secondary organic aerosol (bSOA), with the latter including “sulfate‐related bSOA” that correlated to sulfate ( r = 0.72) and “nitrate‐related bSOA” that correlated to nitrate ( r = 0.65). Single‐particle mass spectra showed three composition types that corresponded to the mass‐based factors with spectra cosine similarity of 0.93 and time series correlations of r > 0.4. The vehicle‐related OM with m/z 44 was correlated to black carbon, “sulfate‐related bSOA” was on particles with high sulfate, and “nitrate‐related bSOA” was on all particles. The similarity of the m/z spectra (cosine similarity = 0.97) and the time series correlation ( r = 0.80) of the “sulfate‐related bSOA” to the sulfate‐containing single‐particle type provide evidence for particle composition contributing to selective uptake of isoprene oxidation products onto particles that contain sulfate from power plants. Key Points Aerosol organic concentrations were enhanced by multiday accumulation of isoprene‐related secondary particle mass Three types of single‐particle composition had mass fragments similar to three mass‐weighted aerosol mass spectrometer composition factors Isoprene‐related organic aerosol mass fragments were mostly found on sulfate‐containing particles, indicating selective uptake to particles