AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
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Source Apportionment Algorithm for an Urban Micro-environment Based on Sub-micrometer Particle Number Concentration, Equivalent Black Carbon and PM2.5 Mass Concentration Measurements
RICARDO MORALES BETANCOURT, Boris Galvis, Sivaraman Balachandran, Julian David Gomez Tibaquira, Universidad de los Andes
Abstract Number: 417 Working Group: Source Apportionment
Abstract A source apportionment method for fine aerosol particles at traffic impacted urban micro-environments is presented in this work. The proposed source apportionment algorithm is based on the assumption (from reported literature values) of the aerosol particle size distribution and elemental carbon content for the most prevalent sources in the micro-environments considered in the study. The contributing sources considered in this work include freshly emitted diesel exhaust particles, light duty gasoline vehicle exhaust emissions, and the contribution from urban background aerosol particles. The proposed method was applied to data collected during a 12–day measurement campaign performed in the city of Bogota during late July and early August of 2015. The exposure concentration to particulate matter to which commuters in different modes of transport (pedestrians, bicycle users, private vehicles, and several public transport alternatives) was measured. The measurements were performed with portable Diffusion Size Classifiers (DiSCmini) for sub-micrometer particle number concentration (Np), hand held Aethalometers (AethLabs, AE51) for mass concentration of equivalent black carbon (eBC), and laser scattering monitors for PM2.5 mass concentration (TSI DustTrack 8520). The mass concentration of equivalent black carbon reported by the AE51 monitors was used in combination with detailed Mie-Scattering calculations to quantify the impact of light-absorbing material on the laser scattering intensity and therefore, on the DustTrack instrument response. Additionally, a model of the DiSCmini instrument was developed to further constrain the size distribution of particles that would reproduce the reported signals by the DiSCmini instrument. The method presented here allowed us to use the limited information available from these portable instruments in the determination of the source contribution to the particle exposure of commuters in different transport micro-environments investigated.