AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Seasonal and Regional Differences in the Chemical Composition of Ambient Aerosol from Fresno and Fontana, California
CHIA-LI CHEN, Lynn Russell, Jun Liu, Derek Price, Raghu Betha, Kevin Sanchez, Sijie Chen, Jackie First, Alex K. Y. Lee, Xiaolu Zhang, Christopher Cappa, Scripps Institution of Oceanography
Abstract Number: 362 Working Group: Urban Aerosols
Abstract Aerosol emissions from residential, agricultural, and wildfire burning activities are highly seasonal, episodic, and have adverse impacts on climate. This study (1) identified and characterized the chemical composition of PM$_1 and PM$_(2.5) and (2) quantified the organic components from burning emissions and from atmospheric formation of secondary organic aerosol at two California locations, Fresno (December 2014) and Fontana (July 2015). Ambient aerosol was characterized by a suite of advanced instrumentation, including a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), a single-particle soot photometer (SP2), a scanning electrical mobility spectrometer (SEMS), an aerodynamic particle sizer (APS), an optical particle sizer (OPS), and Fourier Transform infrared spectroscopy (FTIR). Four aerosol components were identified with Positive Matrix Factorization (PMF) analysis in both Fresno and Fontana. The Fresno factors include a hydrocarbon-like organic aerosol (HOA), a biomass burning organic aerosol (BBOA), an oxygenated organic aerosol (OOA), and a fog-OOA component. The fog-OOA factor correlates with ammonium, nitrate and sulfate well (R$^2 > 0.77). Black carbon (BC), CO, and potassium (K) have higher correlation with the BBOA factor, indicating carbonaceous aerosols formed from residential or agricultural biomass burning activities. The Fontana factors include a less oxidized semi-volatile OOA (SVOOA), a highly oxidized low volatility OOA (LVOOA), a cooking emission OA (COA), and HOA. The LVOOA component dominates OA mass (66%) and correlates well with O$_3 formation, temperature and wind speed, suggesting aged aerosol formation from photochemical reaction regionally in Fontana. Bimodal particle size distributions were observed in the afternoon hours from Fontana measurements while most particles exhibit single mode size distributions in Fresno, indicating more nucleation and photochemical aging reactions occurred during the summer in Fontana compared to winter in Fresno. FTIR results from both Fresno and Fontana show that alkane groups were the major contributors to the total PM$_1 and PM$_(2.5) organic mass, followed by alcohol, carboxylic acid, and amine groups.