AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Spatio-temporal Trends and Source Apportionment of PM2.5 Organic Carbon Thermal Fractions (OCx) across the Los Angeles Basin
EHSAN SOLEIMANIAN, Amirhosein Mousavi, Sina Taghvaee, Mohammad Sowlat, Sina Hasheminassab, Andrea Polidori, Constantinos Sioutas, University of Southern California
Abstract Number: 17 Working Group: Carbonaceous Aerosol
Abstract The main objective of this study was to identify and quantify the sources of organic carbon (OC) and its thermal fractions (OCx) across the Los Angeles Basin in five sampling sites, including West Long Beach, Anaheim, central Los Angeles (CELA), Rubidoux, and Fontana from July 2012 to June 2013. Total OC and OC volatility fractions (OC2-OC4), measured by thermal optical analysis as part of the fourth Multiple Air Toxics Exposure Study (MATES IV), gaseous pollutants, and particulates source tracers were used as the input data to Positive Matrix Factorization (PMF) receptor model. Vehicular emissions, secondary organic aerosols (SOA), and biomass burning were identified as the three major sources of OC and OCx across the sampling locations with a corresponding average contribution of 56±9%, 42±7%, and 5±3% to total OC, respectively. In addition, traffic contributed as the major source to OC2 and OC3 at the upwind sites of West Long Beach and CELA with the corresponding contribution of 79% and 60% to OC2, and 64% and 53% to OC3, respectively. On the other hand, SOA was the dominant contributor to OC4, especially in the downwind receptor sites with the corresponding contributions of 56% and 66% in Fontana and Rubidoux, respectively. Vehicular emissions and biomass burning were more significant during winter phase mainly due to the atmosphere stability and lower mixing height, while SOA contribution to total OC increased during warm phase as a result of higher photochemical activities. Results from this study provided insights regarding the sources and spatio-temporal variations of OC and OCx concentrations in PM2.5 across the Los Angeles Basin which can be used as an indicator of the extent of human exposure to primary and secondary aerosols.