Re ECF Project: 2009-26

Project Title: Improvement in roadside PM2.5 pollution after vehicle emission control measures in Hong Kong

Applicant: Dr. Linwei TIAN of The Chinese University of Hong Kong

Total Approved Grant: $249,280

Duration: 1/5/2010 to 31/3/2012

Project Status/Remarks: Completed

The project aims to evaluate the effectiveness of the staged vehicle emission control measures in improving the roadside PM2.5 pollution from 2001 to 2005, and from 2005 to 2009, respectively, by time-series analysis.

Summary of the Findings/Outcomes:
1) The change point of March 2004 (an abrupt decrease) of the roadside excess PM2.5 mass corresponded to 3 control measures: the diesel vehicle taxi and light bus switching to LPG ones, and the diesel oxidation catalyst (DOC) retrofit program for the heavy diesel vehicles.

2) The long term trend of PM2.5 roadside excess has been evaluated after adjustment of seasonality. During 1999-2009, the roadside excess PM2.5 (CL-TW) had been decreasing at a rate of 7.7% per year. However, this was accompanied by an increase of NO2 at a rate of 6.8% per year.

3) Consistent with the TEOM data, the filter-based PM2.5 speciation data for 2001, 2005, and 2009 also show that PM2.5 mass, organic carbon, and elementable carbon had been decreasing while nitrate in PM2.5 had an increasing trend.