Abstract View
Quantitative Analysis on the Relationship between Aerosol Optical Properties and Chemical Composition in Urban Areas
PAULO ARTAXO, Djacinto Monteiro dos Santos, Bruno Backes Meller, Milena Ponczek, University of Sao Paulo
Abstract Number: 64
Working Group: Aerosol Chemistry
Abstract
The urban and regional climate is strongly affected by aerosol optical properties. Aerosol composition and size distribution influence the optical properties significantly. Studies have been focused on looking at aerosol source apportionment or the physical properties of particles. We intend with this study to look at the integration between aerosol composition and physicochemical properties. Measurements were performed at three urban areas: São Paulo, Manaus, and Rio Branco. São Paulo has an unusual fuel mixture. Manaus links biogenic VOCs and urban emissions leading to rapid aerosol formation, and Rio Branco is loaded with biomass-burning aerosols. The properties measured include submicron particle number size distributions (PNSD), using SMPS, Mass absorption efficiency (MAE) derived from equivalent black carbon, with Multi-Angle Absorption Photometer (MAPS) and AE33 Aethalometer, light scattering using TSI and Ecotech nephelometers. The aerosol non-refractory chemical composition was determined using a Quadrupole Aerosol Chemical Speciation Monitor (ACSM). Multiple linear regression models between PMF results from ACSM and size distribution plus optical properties reveal the association between mechanisms that control the aerosol size, optical properties, and submicron particles' composition.
For Rio Branco, the most efficient in terms of scattering was the BBOA (12.77 ± 0.63 m² g-1 at 532 nm), while the least efficient was the HOA (1.95 ± 0.56 m² g-1 at 532 nm). Regarding MAE, strong spectral dependence was detected both for black carbon and organics. For São Paulo, where 60% of PM1 mass loading was attributed to SOA and secondary inorganic aerosol, accumulation mode was mainly associated with highly oxidized OOA and traffic-related emissions. In contrast, Aitken mode shows strong contributions of sulfate and nitrate aerosols. Also, high AAE values (>2) and strong contribution of organics to the absorption coefficients were observed in São Paulo, especially under regional biomass burning influence.