This study aimed to develop a measurement method for particulate matter emission from motorcycle engines, and to explore the feasibility of using opacity meter as a screening tool for emission test. A dynamometer was used to control a four-stroke motorcycle engine to generate stable exhaust aerosols. A sampling buffer chamber was built and used as an adaptor connecting to the tailpipe that provided a suitable location for aerosol sampling. A dilution system was made and mainly used to reduce the relative humidity of the motorcycle exhaust. The dilution ratio had to be high enough to eliminate the water vapor condensation on the particles. The diluter also helped bring the aerosol concentration down to the working range of the aerosol instruments. An electrical low pressure impactor (ELPI) was used to measure the aerosol number concentration and size distribution. A tapered element oscillating micro-balance (TEOM) was used to measure the aerosol mass concentration. Two opacity meters were used. The data from opacity meter together with ELPI, TEOM and filter samples were analyzed, to evaluate the feasibility of using opacity meter as a screening tool for motorcycle emission test. The results show that the ELPI appeared to be an ideal aerosol instrument for investigating the aerosol number concentration and size distribution of motorcycle exhaust, as the manufacturer claimed. However, the mass concentration converted from ELPI’s number concentration and size distribution did not match with the filter weighing data, because of the background noise of this instrument. Therefore, the ELPI only could be used to measure the number concentration and size distribution. The TEOM was suitable for mass concentration measurement, but the response time is over 20 minutes. The long response time prevented it from use as emission test. The opacity meter had a good correlation with the mass concentration measured using filter method, and therefore, was promising for use as a screening tool for motorcycle emission test.

Mobile sources, PM2.5、Particulate matter