Roadside nanoparticles corresponding to vehicle emissions during one signal cycle |
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| Authors: | Hiroaki Minoura Hideto Takekawa Shigeo Terada |
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| Institution: | 1. Toyota Central R&D Labs., Inc., Nagakute, Aichi, 480-1192, Japan;2. Petroleum Energy Center, 3-9, Toranomon 4-Chome, Minato-ku, Tokyo 105-0001, Japan;1. Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan;2. Faculty of Risk and Crisis Management, Chiba Institute of Science, 15-8 Shiomi-cho, Choshi, Chiba 288-0025, Japan;3. National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan;1. Guangdong Provincial Institute of Public Health, Guangdong Provincial Center for Disease Control and Prevention, Guangzhou 511430, China;2. Guangdong Provincial Center for Disease Control and Prevention, Guangzhou 511430, China;3. College for Public Health and Social Justice, Saint Louis University, Saint Louis, MO 63104, USA;1. Environmental Epidemiology Section, Center for Environmental Health Sciences, National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, Ibaraki 305-8506, Japan;2. Department of Obstetrics and Gynecology, Kyushu University Hospital, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan;3. Department of Obstetrics, Fukuoka Children''s Hospital, 5-1-1 Kashiiteriha, Higashi-ku, Fukuoka 813-0017, Japan;4. Graduate School of Engineering, Kyoto University, Katsura, Sakyo-ku, Kyoto 615-8530, Japan;5. Preventive Medicine and Public Health, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan;1. Beijing Anzhen Hospital, Capital Medical University, Beijing, China;2. Children''s Hospital of Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, China;3. Fuwai Hospital and National Center for Cardiovascular Diseases, Chinese Academy of Medical Science, Beijing, China;4. Shanghai Children''s Medical Center, National Children''s Medical Center, Shanghai Jiaotong University School of Medicine, Shanghai 200127, China |
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| Abstract: | The behavior of nanoparticles (NPs) in the roadside atmosphere has not been clarified because it involves unstable volatile components. It was thought that the number concentration (NC) and NP size distribution change due to variations in traffic conditions (e.g., traffic volume TV], velocity, acceleration, etc.) near the intersection, but the SMPS (Scanning Mobility Particle Sizer) lacks the temporal resolution required for rapid, transient measurements. Using a fast-response aerosol spectrometer capable of providing near-instantaneous particle NC measurements in real time, the behavior of NPs during one signal cycle became clear, and it was understood that the effect of condensation/evaporation processes is important, in addition to coagulation. As for the relation of the NC in proportion to the TV, this did not show a constant line but rather a hysteresis curve during the signal cycle, because the gas-particle equilibrium state at the roadside atmosphere was variable. Using two points of simultaneous measurement and on-board measurement, the behavior of NPs could be confirmed in response to the characteristics of automotive exhaust, which varied due to the on-road driving state, engine conditions, vehicle position, or traffic light timing, at the intersection. The on-board measurement of NP size distribution in the exhaust plume from a diesel vehicle was carried out as a reference for direct particle emissions, compared with the roadside NPs. The coagulation/deposition model simulation using the direct particle emissions underestimated the NCs compared with the observed values. The gas-particle equilibrium model could explain the underestimated portion caused by the condensation of ambient VOC (Volatile Organic Compounds) onto the particles. If this hypothesis is correct, the condensable VOC amount in the roadside atmosphere is suggested to be very large. |
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