UC San Diego

Biogenic Secondary Organic Aerosols (bSOA) account for a large fraction of the global aerosols budget, and thus have a significant impact on climate and public health. Observations of bSOA in the southeastern U.S. included Fourier Transform Infrared Spectroscopy (FTIR) and Aerosol Mass Spectrometer (AMS) measurements of submicron mass at Look Rock (LRK), Tennessee, and Centreville (CTR), Alabama. At LRK, Organic mass (OM) sources were apportioned to three factors, including “sulfate-related bSOA” that correlated to sulfate (r=0.72). Single-particle mass spectra also 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 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 sulfate particles. NOx had nighttime-to-early-morning peaks 3~10 times higher at CTR than at LRK, but OM sources identified by FTIR had three very similar factors at both sites including Biogenic Organic Aerosols (BOA). The BOA spectrum from FTIR is similar (cosine similarity > 0.6) to that of lab-generated particle mass from isoprene and monoterpene with NOx. NOx was correlated with FTIR-BOA and AMS related biogenic factors for NOx concentrations higher than 1 ppb at both sites, producing 0.5 to 1 μg m-3 additional biogenic OM for each 1 ppb increase of NOx. Submicron organic mass (OM), particle number, and cloud condensation nuclei concentrations were measured at a costal Antarctica site and were found to be highest in summer. Natural sources that included marine sea spray and seabird emissions contributed 56 % of OM in austral summer but only 3 % in austral winter. Fourier transform infrared spectra showed the natural sources of organic aerosol were characterized by amide group absorption, which may be from seabird populations. Carboxylic acid group contributions from natural sources were correlated to incoming solar radiation, indicating both seasonal sources and likely secondary reactions.