10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Over a Decade-long Trend of Concentrations of Ultrafine Particle and Carbonaceous Aerosols at a Traffic Intersection
YUJI FUJITANI, Katsuyuki Takahashi, Akihiro Fushimi, Shuichi Hasegawa, Yoshinori Kondo, Kiyoshi Tanabe, Shinji Kobayashi, National Institute for Environmental Studies
Abstract Number: 316 Working Group: Carbonaceous Aerosol
Abstract This study showed long-term monitoring data (2004-2017) of particle number concentrations (PNCs: particle size 10-480 nm), size-resolved particulate matter (PM) mass and carbon component, and atmospheric pollutants at the traffic intersection in a metropolitan area in Japan. Comparison was made between atmospheric concentrations of these pollutants at the traffic intersection and the tailpipe PM mass emissions from diesel trucks that passing through the traffic intersection, which is estimated from traffic volumes as a function of emission regulation year and gross weight of trucks obtained by license plate numbers research and giving emission factor of each category.
Decay rate of concentrations of elemental carbon in PM0.1 and in PM2.5 from 2005 to 2016 were excellently match with reduction rate of PM tailpipe emissions, which indicates tailpipe emission of diesel trucks was dominant source of atmospheric PM and the reduction in atmospheric concentrations directly reflected cleaner of traffic exhausts. From the traffic information, not only reduction of traffic volume during the period but also replacing vehicles that comply with tighter regulation were forward to reduce emissions, which also resulted in better correlations between atmospheric concentrations and tailpipe PM mass emission rather than traffic volume. On the other hand, slower decrease trend of exhaust related PNC than decrease trend of tailpipe PM mass emissions were found.
The positive matrix factorization (PMF) analysis using year-to-year data of PNCs and EC showed the largest contribution factor to EC in PM2.5 (about 50% in entire period average) attributed to tailpipe emission from the trucks of emission regulation of 1997-99 because emissions of this regulation vehicles also contribute about 50% to total tailpipe PM mass emission. As for PN particle smaller than 100 nm in entire period of winter, factors that attributed to emissions from 1988-94 regulation vehicles contribute about 50%. The result of PMF analysis, diurnal trend of pollutants, and comparison between summer and winter seasons suggested that high PN in winter morning is due to nucleation of semi-volatile gases mainly emitted from 1988-94 regulation vehicles concurrently in a cold temperature, low wind speed, and low height mixing layer. The implement policy of emission regulation in terms of PM mass did not effective to reduce atmospheric PN as much as PM mass otherwise removing semi-volatile gases which are co-pollutants of PM.