AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Characterization of On-road Vehicle Emissions in a Roadway Tunnel in Hong Kong
XIAOLIANG WANG, Judith Chow, John Watson, L.W. Antony Chen, Kin‐Fai Ho, Shun-Cheng Lee, Desert Research Institute
Abstract Number: 578 Working Group: Urban Aerosols
Abstract Traffic emissions were measured in the Shing Mun tunnel (SMT) in Hong Kong during winter 2015. Fleet-average emission factors (EFs) were calculated and compared to the 2003–2004 measurements in SMT to assess emission changes over time. The EF differences between the 2003–2004 and 2015 measurements were not statistically significant for carbon monoxide (CO), ammonia (NH3), and nitrogen dioxide (NO2). Sulfur dioxide (SO2) and PM2.5 measured in 2015 were only ~20% of those in 2003–2004. In contrast, nitrogen oxide (NO) and nitrogen oxides (NOx) measured in 2015 increased by ~20%. While the total measured volatile organic compounds (VOCs) were ~50% lower, the marker species for liquefied petroleum gas (LPG; e.g., n-butane and isobutene) increased in 2015, likely due to the increased LPG fleet. The EMFAC-HK mobile source emission model estimates and SMT measurements differed <40% for the 2015 data with EMFAC-HK being lower, while EMFAC-HK estimates were ~2 and ~5 times higher for CO and NO, respectively, in 2003. Polycyclic aromatic hydrocarbons (PAHs) were predominantly in gas phase, with gaseous PAH concentrations being ~15 time higher than those of particulate PAHs. Over 85% of the two- and three-ring PAHs were in the gaseous phase, while over 75% of the four- to six-ring PAHs were in particulate phase. Elemental and organic carbon were the major constituents of PM2.5 collected in the tunnels. Source apportionment of the tunnel PM2.5 using Positive Matrix Factorization (PMF) suggests the dominance of diesel engine exhausts, accounting for 48±16% PM2.5 mass concentration on average, followed by secondary sulfate and nitrate (27±9%), gasoline engine exhausts (20±6%), and road dust (5±4%).