PMID- 16683588
OWN - NLM
STAT- MEDLINE
DCOM- 20060915
LR  - 20190715
IS  - 0013-936X (Print)
IS  - 0013-936X (Linking)
VI  - 40
IP  - 8
DP  - 2006 Apr 15
TI  - Comparison of daytime and nighttime concentration profiles and size distributions 
      of ultrafine particles near a major highway.
PG  - 2531-6
AB  - 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 1-405 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 thefreeway 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.
FAU - Zhu, Yifang
AU  - Zhu Y
AD  - Department of Environmental Health Sciences, University of California Los 
      Angeles, 650 Charles E. Young Drive South, Los Angeles, California 90095, USA. 
      Yifang@ucla.edu
FAU - Kuhn, Thomas
AU  - Kuhn T
FAU - Mayo, Paul
AU  - Mayo P
FAU - Hinds, William C
AU  - Hinds WC
LA  - eng
GR  - P30 ES07048-07/ES/NIEHS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, N.I.H., Extramural
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, Non-P.H.S.
PL  - United States
TA  - Environ Sci Technol
JT  - Environmental science & technology
JID - 0213155
RN  - 0 (Air Pollutants)
RN  - 0 (Dust)
RN  - 0 (Vehicle Emissions)
SB  - IM
MH  - Air Pollutants/*analysis
MH  - Dust/*analysis
MH  - Environmental Monitoring
MH  - Humidity
MH  - Los Angeles
MH  - Particle Size
MH  - Seasons
MH  - Temperature
MH  - Vehicle Emissions/*analysis
MH  - Wind
EDAT- 2006/05/11 09:00
MHDA- 2006/09/16 09:00
CRDT- 2006/05/11 09:00
PHST- 2006/05/11 09:00 [pubmed]
PHST- 2006/09/16 09:00 [medline]
PHST- 2006/05/11 09:00 [entrez]
AID - 10.1021/es0516514 [doi]
PST - ppublish
SO  - Environ Sci Technol. 2006 Apr 15;40(8):2531-6. doi: 10.1021/es0516514.