title: Simultaneous measurements of on-road/in-vehicle nanoparticles and NOx while driving: Actual situations, passenger exposure and secondary formations.
abstract: Simultaneous measurements of on-road and in-vehicle NO and NO2 levels, particle number concentrations (PNCs), and particles size distributions were performed while driving using a test vehicle equipped with real-time sensors. The results obtained on regional roads showed that heavy-duty vehicles in traffic seem to have a major impact on on-road air quality. Measurements on highways that included a 10km tunnel and a 2km uphill section of road indicated that sub-50nm particles have different features from the other species because of their higher volatility. The other species showed quite high on-road concentrations in the tunnel. In-vehicle conditions were made similar to the on-road ones by setting the air conditioning (AC) mode to the fresh air mode. The in-vehicle NO2 concentration in the tunnel was over 0.50ppmV, which is almost five times higher than the 1-hour ambient air quality standard proposed by the World Health Organization (WHO). In sections other than the tunnel, the in-vehicle NO2 concentration was almost the same as the 1-hour WHO standard. Higher on-road NO2/NOx ratios than those of exhaust gases and different behavior of sub-50nm particles from other species suggested that NO2 and sub-50nm particles were mainly due to secondary products formed by atmospheric reactions.
authors.affiliation: National Traffic Safety and Environment Laboratory, 7-42-27 Jindaiji-higashimachi, Chofu, Tokyo 182-0012, Japan. Electronic address: h-yamada@ntsel.go.jp.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamada
authors.affiliation: Division for Environment, Health and Safety, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan.
authors.forename: Rumiko
authors.initials: R
authors.lastname: Hayashi
authors.affiliation: Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Tonokura
mesh_terms: D000397:Air Pollution / Q000032:analysis*; D001336:Automobiles; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D007564:Japan; D053758:Nanoparticles / Q000032:analysis*; D009589:Nitrogen Oxides / Q000032:analysis*; D010316:Particle Size; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D009589:Nitrogen Oxides; D001335:Vehicle Emissions
keywords: In-vehicle air quality; NO(x); On-road air quality; Particle number concentrations; Secondary formed pollutant