Comparison of Daytime and Nighttime Concentration Profiles and Size Distributions of Ultrafine Particles near a Major Highway

Details

• Personal Author:
  Hinds WC ; Kuhn T ; Mayo P ; Zhu Y
• Description:
  Previously we have conducted systematic measurements of the concentration and size distribution of ultrafine particles in the vicinity of major highways during daytime in Los Angeles. The present study compares these with similar measurements made at night. Particle number concentration was measured by a condensation particle counter (CPC) and size distributions in the size range from 7 to 300 nm were measured by a scanning mobility particle sizer (SMPS). Measurements were taken at 30, 60, 90, 150, and 300 m upwind and downwind from the center of the I-405 freeway. Average traffic flow at night was about 25% of that observed during the day. Particle number concentration measured at 30 m downwind from the freeway was 80% of previous daytime measurements. This discrepancy between changes in traffic counts and particle number concentrations is apparently due to the decreased temperature, increased relative humidity, and lower wind speed at night. Particle size distributions do not change as dramatically as they did during the daytime. Particle number concentration decays exponentially downwind from the freeway similarly to what was observed during the day, but at a slower rate. No particle number concentration gradient has been observed for the upwind side of the freeway. No PM2.5 and very weak PM10 concentration gradients were observed downwind of the freeway at night. Ultrafine particle number concentration measured at 300 m downwind from the freeway was still distinguishably higher than upwind background concentration at night. These data may be used to help estimate exposure to ultrafine particles in the vicinity of major highways for epidemiology studies. [Description provided by NIOSH]
• Subjects:
  Air Pollution Humidity Occupational Health Particulate Matter Safety Temperature Transportation
• Keywords:
  Air Pollution Automotive Emissions Particle Aerodynamics Particle Size Particulates Temperature Effects Ultrafine Particles
• ISSN:
  0013-936X
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  California ; OSHA Region 9
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  40
• Issue:
  8
• NIOSHTIC Number:
  nn:20058395
• Citation:
  Environ Sci Technol 2006 Apr; 40(8):2531-2536
• Contact Point Address:
  Yifang Zhu, Department of Environmental Health Sciences, University of California Los Angeles, 650 Charles E. Young Drive South, Los Angeles, California 90095
• Email:
  Yifang@ucla.edu
• Federal Fiscal Year:
  2006
• Performing Organization:
  University of California Los Angeles
• Peer Reviewed:
  True
• Start Date:
  20050701
• Source Full Name:
  Environmental Science and Technology
• End Date:
  20270630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:b0cab8a5eb5339d7219f468e86755fa7f155c1620dfb3a3f88fe7564e67e0c36ec7ba17d664fb183a74aa2278a29e4c178c9da32c57778fb7dad420e0188a230
• Download URL:
  https://stacks.cdc.gov/view/cdc/221502/cdc_221502_DS1.pdf
• File Type:
  [PDF - 221.16 KB ]