AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Light Scattering and Absorption of the Individual PM1 Chemical Components in the Central Amazonian Basin at ATTO Tower
SAMARA CARBONE, Luciana Rizzo, Joel Brito, Nga Lee Ng, Lu Xu, Jorge Saturno, Christopher Pöhlker, Bruna Holanda, Meinrat O Andreae, Henrique Barbosa, Paulo Artaxo, University of Sao Paulo
Abstract Number: 382 Working Group: Remote and Regional Atmospheric Aerosols
Abstract Measurements of PM1 chemical composition and optical properties were performed at the ATTO (Amazonian Tall Tower Observatory) station, in the Amazon forest, during the dry season of 2014 (August-December) and wet season of 2015 (February-May). The particle size distribution was measured with the Scanning Mobility Particle Sizer (SMPS, TSI, mobility diameter=10-370 nm) and chemical composition with the Aerosol Chemical Speciation Monitor (ACSM, Aerodyne Inc.). Determination of organics, sulfate, nitrate, ammonium and chloride jointly with optical properties (absorption and scattering) were accomplished. The Mie scattering code was used to estimate the mass scattering efficiency (MSE) and scattering coefficient values of each PM1 component, during the dry season. The following refractive index values were assumed 1.52+0i, 1.55+0i, 1.52+0i, 1.54+0i and 1.55+0.37i, for sulfate, nitrate, ammonium, chloride and eBC, respectively. In addition, the organics refractive index was calculated based on the effective refractive index retrieved iteratively, and varied from 1.55 to 1.65+0i. The MSE values obtained were 5.4, 4.6, 4.6, 5.0, and 4.8 m$2 g^$^(-1) for organics, sulfate, ammonium, nitrate and chloride, respectively. These results indicate that all PM1 components scatter the visible radiation (lambda=525 nm) very efficiently. However, because the organics represented, on average, 76% of the PM1 mass concentration, this component was responsible for 83% of the scattering coefficient in the dry season, followed by sulfate (8%). It was observed a good agreement between the scattering coefficient obtained by the Mie scattering code and Nephelometer measurements (slope=0.80, R2=0.84). This is the first time the MSE is calculated for each individual PM1 component in the atmosphere of the Amazon forest.