AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Mass Spectral Observations of Submicron Aerosol Particles and Production of Secondary Organic Aerosol at an Anthropogenically Influenced Site during the Wet Season of GoAmazon2014
SUZANE SIMOES DE SA, Brett Palm, Pedro Campuzano-Jost, Douglas Day, Weiwei Hu, Matt Newburn, Joel Brito, Paulo Artaxo, Rodrigo A. F. Souza, Antonio O. Manzi, Jose-Luis Jimenez, Lizabeth Alexander, Scot Martin, Harvard University
Abstract Number: 486 Working Group: Aerosol Chemistry
Abstract As part of GoAmazon2014, a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed to characterize the composition, size, and spectral markers present in submicron atmospheric aerosol particles at a site downwind of Manaus, Brazil, in the central Amazon basin. The focus was on the influence of biogenic-anthropogenic interactions on the measured aerosol particles, especially as related to the formation of secondary organic aerosol (SOA). Through a combination of meteorology, emissions, and chemistry, the research site was affected by biogenic emissions from the tropical rainforest that were periodically mixed with urban outflow from the Manaus metropolitan area. Preliminary results from 1 February to 31 March 2014 show that for the wet season, the PM$_1 mass concentration varied from 0.4 to 3.0 micro-g/m$^3 (5 to 95 percentile). The composition was dominated by organic species (80%), and sulfate (13%). Most of the nitrate is estimated to be organic nitrates. The mass-diameter distribution of the particle population had a dominant mode between 300 and 400 nm (vacuum aerodynamic diameter, d$_(va)). At times, a smaller mode at d$_(va) between 100 and 150 nm was also present. Highly oxidized organic material was frequently observed, characterized by a dominant peak at m/z 44 that was on average 18% of the total organic mass spectrum. There was a diel trend in the elemental oxygen-to-carbon (O:C) ratio, starting from a typical value of 0.6 in the morning, peaking at 0.7 in the afternoon, and returning to 0.6 at night. The analysis of the results aims at delineating the anthropogenic impact on the measurements. Multivariate statistical analysis by positive-matrix factorization (PMF) is applied to the time series of high-resolution organic particle mass spectra. The factors and their loadings provide information on the relative and time-varying contributions of different sources and processes affecting the organic component of the aerosol particle phase.