Decadal changes in emissions of volatile organic compounds (VOCs) from on-road vehicles with intensified automobile pollution control: Case study in a busy urban tunnel in south China

摘要

AbstractIn the efforts at controlling automobile emissions, it is important to know in what extent air pollutants from on-road vehicles could be truly reduced. In 2014 we conducted tests in a heavily trafficked tunnel in south China to characterize emissions of volatile organic compounds (VOC) from on-road vehicle fleet and compared our results with those obtained in the same tunnel in 2004. Alkanes, aromatics, and alkenes had average emission factors (EFs) of 338, 63, and 42 mg km−1in 2014 against that of 194, 129, and 160 mg km−1in 2004, respectively. In 2014, LPG-related propane, n-butane and i-butane were the top three non-methane hydrocarbons (NMHCs) with EFs of 184 ± 21, 53 ± 6 and 31 ± 3 mg km−1; the gasoline evaporation marker i-pentane had an average EF of 17 ± 3 mg km−1; ethylene and propene were the top two alkenes with average EFs of 16 ± 1 and 9.7 ± 0.9 mg km−1, respectively; isoprene had no direct emission from vehicles; toluene showed the highest EF of 11 ± 2 mg km−1among the aromatics; and acetylene had an average EF of 7 ± 1 mg km−1. While EFs of total NMHCs decreased only 9% from 493 ± 120 mg km−1in 2004 to 449 ± 40 mg km−1in 2014, their total ozone formation potential (OFP) decreased by 57% from 2.50 × 103 mg km−1in 2004 to 1.10 × 103 mg km−1in 2014, and their total secondary organic aerosol formation potential (SOAFP) decreased by 50% from 50 mg km−1in 2004 to 25 mg km−1in 2014. The large drop in ozone and SOA formation potentials could be explained by reduced emissions of reactive alkenes and aromatics, due largely to fuel transition from gasoline/diesel to LPG for taxis/buses and upgraded vehicle emission standards.Graphical abstractDecadal changes of EFs (mg km−1), OFPs, and SOAFPs for VOCs from on-road vehicles as tested in the Zhujiang Tunnel in 2004 and in 2014.Display OmittedHighlights•Tunnel measurements for compositions and EFs of NMHCs from on-road vehicles.•Results from the same tunnel in 2014 and 2004 were compared.•NMHCs EF decreased ∼10% but O3and SOA formation potentials decreased ∼50%.•EFs for reactive aromatics and alkenes dropped from -90% to -5%.•LPG-related alkanes became dominant with their EFs largely increased.Tunnel tests in south China revealed that while emission factors of NMHCs from on-road vehicles decreased by only 9% between 2004–2014, ozone and SOA formation potentials decreased by over 50%.