On-road particulate matter (PM2.5) and gaseous emissions in the Shing Mun Tunnel, Hong Kong

Y. Cheng, Shuncheng Lee, K. F. Ho, P. K K Louie

Research output: Journal article publicationJournal articleAcademic researchpeer-review

56 Citations (Scopus)


Real-world emission factors of PM2.5(particle's aerodynamic diameter of less than 2.5 μm), NOx(the sum of NO2and NO), and CO from mixed vehicles in the Shing Mun Tunnel in Hong Kong have been determined. A total of 16 runs were made during varying times that encompassed different traffic fractions of diesel-fueled vehicles. During the study, a total of 27,310 vehicles traversed the tunnel, comprising approximately 50% diesel-fueled vehicles, 41% gasoline-fueled vehicles, and 9% LPG-vehicles. The PM2.5emission factors, derived from the DRI (Desert Research Institute, USA) particulate sampler, ranged from 0.066 to 0.190 g veh-1km-1. Result from a t-test showed no statistical significance for PM2.5difference in summer and winter. The PM2.5emission factors were found to correlate well with NOx(R2=0.65) and both had a positive relationship with the proportion of diesel-fueled vehicles. Two DustTrak air monitors were also used to monitor PM2.5masses in the tunnel. The mean emission factor derived from DustTrak, 0.150±0.045 g veh-1km-1, had reasonable agreement with the filter method, 0.131±0.037 g veh-1km-1, demonstrating that the DustTrak air monitor can be used in tunnel studies, but needs careful calibrations with the filter method. The emission factors for PM2.5mass and NOxwere obtained for on-road diesel-fueled vehicles based on the linear regression analysis and they were 0.257±0.031 and 1.931±0.309 g veh-1km-1, respectively.
Original languageEnglish
Pages (from-to)4235-4245
Number of pages11
JournalAtmospheric Environment
Issue number23
Publication statusPublished - 1 Jul 2006


  • CO
  • Emission factor
  • NO x
  • PM 2.5
  • Tunnel

ASJC Scopus subject areas

  • General Environmental Science
  • Atmospheric Science


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