10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Impact of Emissions from Ports of Los Angeles and Long Beach on the Oxidative Potential of Ambient PM0.25 Measured across the Los Angeles County
AMIRHOSEIN MOUSAVI, Mohammad Sowlat, Farimah Shirmohammadi, Sina Hasheminassab, Andrea Polidori, Martin Shafer, James Schauer, Constantinos Sioutas, University of Southern California
Abstract Number: 967 Working Group: Source Apportionment
Abstract In the current study, we carried out weekly ambient PM0.25 sampling in three contrasting sites located at Los Angeles (USC), north Long Beach (NLB), and Port of Long Beach (PRT) to investigate the chemical composition and oxidative stress as well as sources that are contributing to PM0.25 in the locations. Measurements took place during June-July of 2017 to partially avoid the formation of secondary origin organic particles. To assess the impact of emissions from ports of Los Angeles and Long Beach on the oxidative stress of ambient PM0.25 in different sites, an in vitro cell-based alveolar macrophage (AM) assay was used to quantify the pertinent levels of oxidative potential. Additionally, detailed chemical analyses were also performed to evaluate the chemical components of PM0.25 collected at each site. To connect the oxidative potential of the ambient PM0.25 to the major sources impacting the three locations, two different approaches were used: (1) a molecular marker-based chemical mass balance (MM-CMB) analysis to apportion the sources that contribute to PM0.25; and (2) a principal component analysis combined with multiple linear regression (PCA-MLR) approach to link source factors and individual species to the measured oxidative potential of PM0.25. With respect to all the sites, results revealed that vehicular emissions are the dominant source (60%±4%) followed by road dust (10%±3%), and ship emissions (7%±2%). Further, relatively higher shares of secondary organic aerosol (SOA) were found at the receptor sites (33%±4% at NLB and 35%±3% at USC) as opposed to the PRT site (8%±1%). Moreover, oxidative potential induced by ambient PM0.25 was also primarily impacted by mobile sources among all sites (with an average contribution of 50%±5%), followed by ocean-going vessel (OGV) emissions near the port terminals (33%±2%) and secondary organic aerosol (SOA) in central Los Angeles (49%±2%). OGV emissions were more pronounced in the oxidative potential of PM0.25 at the port terminal area in comparison to the central Los Angeles which highlights the superlative importance of vessel emissions-originated PM0.25 in the vicinity of ports of Los Angeles and Long Beach. Our results indicate a 35%±3% decrease from 2007 to 2017 in PM0.25 concentrations due to the implementation of the Clean Air Action Plan (CAAP) by the San Pedro Bay Ports executives in 2006.