Re ECF Project: 2012-01

Project Title: Investigation of primary PM and NO2 emissions from on-road vehicles and their impact on the roadside and ambient air quality in Hong Kong

Applicant: Dr. Zhi NING of City University of Hong Kong

Total Approved Grant: $499,000

Duration: 1/6/2013 to 31/5/2015

Project Status/Remarks: Completed

The project aims to:

  1. investigate the relationship between the primary NO2 fraction and fine particulates PM emission with different on-road vehicle fleets through direct emission characterization using plume chasing approach; and
  2. examine the contributions of primary emissions from on-road vehicles and secondary formation with involvement of ozone on the roadside and ambient air quality. The success of the project will provide knowledge of the factors controlling the concentrations of roadside pollutants for the future implementation of targeted and cost-effective vehicle emission control strategies.

Summary of the Findings/Outcomes:
The measurements revealed that high-emitters of different vehicle fleets make a disproportionally large contribution to overall traffic emissions in HK. Results indicated that not all the high-emitters are from the older Euro classes. High vehicle emitters for one pollutant may not be a high vehicle emitter for another pollutant(s). Multi-pollutant control strategy needs to be considered in the emission control policy which requires more comprehensive retrofitting technological solutions and matching I/M programme to ensure the proper maintenance of vehicle fleets. An increasing, though statistically insignificant, trend of NO2/NOx ratios with the introduction of newer Euro emission standards was found. The tunnel study provides a convenient drive-through approach for fast determination of tunnel and individual vehicle fleet emission factors. It can be used as a cost effective method to validate the emission inventory. The ambient measurement for the dispersion of primary ultrafine particles, PAH and black carbon showed complex processes involving secondary aerosol formation and gas-particle partitioning. The regional ozone episode has played an important role in the evolution of primary NO2 from roadside to ambient while there is less impact in the dispersion phase from vehicle tailpipe to the roadside.