STI_LasVegasNearRoad_AAAROct08_PUBS by liwenting

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									Characteristics of Aerosol at Schools
Near U.S. 95 in Las Vegas, Nevada
       Steven G. Brown, Paul T. Roberts,
      David L. Vaughn, Michael C. McCarthy
            Sonoma Technology, Inc.
                  Petaluma, CA
        Taehyoung Lee, Jeffery L. Collett
           Colorado State University


         AAAR 27th Annual Conference
                Orlando, FL
              October 23, 2008


                                             STI-3355
    U.S.95 Settlement Agreement
A court settlement was reached between the Sierra Club
and the Nevada Department of Transportation and
Federal Highway Administration regarding urban freeway
expansion near three schools adjacent to a roadway.
Both mitigation and monitoring were required to reduce
and assess student exposure.
   Monitoring study at schools (this study)
   Filtration added to air systems at schools
   Bus retrofit program
   Bus idling education
   FHWA gradient study (with EPA)



                                                         2
 Introduction to U.S.95 MSAT Study
Routine network (May 2007-September 2008):
    AethalometerTM black carbon (BC)
    CO
    NO/NOx and pPAH (PAS2000)
    Meteorological parameters
Intensive Measurements (May/June 2007, January 2008)
  2-hr VOC and carbonyl samples
  1-hr Sunset OC and EC
  Aerodyne HR-ToF-AMS (January only)
Routine traffic data at two locations:
  5-minute traffic counts, by lane, with   OC: organic carbon

   vehicle-class bins and vehicle speeds    EC: elemental carbon
                                            HR-ToF-AMS: high-resolution
                                              time of flight aerosol mass
                                              spectrometer
                                                                            3
 Fyfe Elementary School Monitoring Sites

                                            North, upwind,
                                            290-70 degrees




                         South, downwind,
                         110-250 degrees




Ambient is 20 meters from sound wall (SW); Air inlet is 76 meters from SW.
             Legend:    Air Inlet   Classroom   Ambient

                                                                             5
 Fyfe Black Carbon, December – Early March
BC vs. wind speed,                                                               BC vs. wind speed
Winds from the north,                                                            Winds from the south,
upwind, N=12,063                                                                 downwind, N=6,225
            10                                                10
            9                                                 9
            8                                                 8
            7                                                 7




                                                   BC μg/m3
 BC μg/m3




            6                                                 6
            5                                                 5
            4                                                 4
            3                                                 3
                              Median 0.74 μg/m3                                  Median 1.27 μg/m3
            2                                                 2
            1                                                 1
            0                                                 0
             0   1   2   3 4 5 6 7 8        9 10               0   1   2   3 4 5 6 7 8        9 10
                         wind speed m/s                                    wind speed m/s
    High BC concentrations are seen at low wind speeds regardless
    of direction. Concentrations are higher at wind speeds > 2 m/s
    when winds are from the south and US 95.
                                                                                North=290-70 degrees
                                                                                South=110-250 degrees
                                                                                                         6
                Primary Aerosol Characteristics
           15
                                             BC correlates well with
                                               particulate PAH, OC, NO, and
                                               CO. A strong freeway signal is
                                               evident.
           10
BC μg/m3




                                             BC and other primary species
                                               show an expected diurnal
                                               pattern with peaks in the
           5                                   morning and overnight.
                                             In the morning when school is
                                               in session, exposure to pPAH,
                                               BC, etc. is relatively high.
           0
                           HOUR              Notch: median, 95% CI

                 Fyfe, winter, 5-min data    Box: interquartile range
                                             Whisker: 1.5*IQR
                                             Points: beyond 1.5*IQR             7
                OC/EC Variation
                                               25
   OC and EC generally
    correlate, though the                      20




                             Sunset OC ug/m3
    OC/EC ratio varies
    throughout the day.                        15

   The OC/EC ratio on
                                               10
    weekends is higher,                                            TIME
    typical with decreased                                           0500-0900
                                               5                     0900-2100
    diesel traffic on                                                2100-0500
    weekends.
                                               0
                                                0   2       4      6      8      10
                                                        Sunset EC ug/m3




                                                                                  8
                   BC Concentrations Upwind and Downwind
                        Influence of Wind Speed (1 of 2)
                   8
                                                        When winds blow from south to
                                                        north, observations show a
                                                        significant difference between
Ambient BC μg/m3




                   6
                                                        either side of the freeway,
                                                        suggesting freeway influence of
                   4                                    BC could be at least 50% of the
                                                        observed concentrations at
                   2
                                                        these sites.

                                                        Notch: median, 95% CI
                   0
                       0-1 m/s 1-2 m/s 2-3 m/s >3 m/s   Box: interquartile range
                                 Wind speed             Whisker: 1.5*IQR
                                                        Points: beyond 1.5*IQR
                                                        A significant difference is present if notches
                                                        do not overlap                                   9
      BC Concentrations Upwind and Downwind
           Influence of Wind Speed (2 of 2)
Adcock upwind                                                                                                              Adcock
            8                                                                         8
Fyfe downwind                                                                                                              downwind
                                                                                                                           Fyfe upwind
         Ambient BC μg/m3




                            6




                                                                   Ambient BC μg/m3
                                                                                      6


                            4                                                         4


                            2                                                         2


                            0                                                         0
                                  0-1 m/s 1-2 m/s 2-3 m/s >3 m/s                          0-1 m/s 1-2 m/s 2-3 m/s >3 m/s
                                            Wind speed                                              Wind speed

                                Same plot as previous slide                           Same plot as previous slide but
                                                                                      with the opposite direction
          At low windspeeds, concentrations upwind/downwind are
          similar. Only at higher wind speeds are differences evident.
                                                                                                                                         10
                           Comparison Among Measurements
                  Preliminary comparisons with initial data show good
                  correlation (>0.80) between Sunset OC with AMS OM and
                  Sunset EC with AethalometerTM BC
                                                                                             10
                  25                                                                                                                       1:1 line
                                                         1:1 line                            9

                                                                                             8
                  20                                                                                  y = 0.5314x + 0.0511
                                                                                                             2
                                                                                             7             R = 0.8588




                                                                           Sunset EC μg/m3
Sunset OC μg/m3




                                                                                             6
                  15
                                                                                             5

                  10                                                                         4

                                                                                             3

                   5                                                                         2
                                       y = 0.7076x + 2.4811
                                                                                             1
                                            R2 = 0.8172
                   0                                                                         0
                       0     5    10         15        20            25                           0   1    2    3    4    5    6   7   8        9     10
                                 AMS OM μg/m3                                                                         BC μg/m3
                                                                    OM=organic matter

                                                                                                                                                           11
                                                               Preliminary AMS data, BC and the ratio between the m/z=44(COO+) and
                                                               m/z=57(C4H9+) show higher OM concentrations in the morning and overnight
                                                               when the OOA/HOA ratio is low, and BC is high.

                                                                              High BC,
                                                        30                                                        Mostly
                                                                              pPAH, OM
                                                                                                                  secondary                                       Black
                                                                              that is
AMS Organic Matter (ug/m3), OOA/HOA ratio, BC (ug/m3)




                                                                                                                  with lower                                      Carbon
                                                                              mostly
                                                        25                                                        OM and BC
                                                                              primary                                                                             AMS OM
                                                                                                                                                                  OOA/HOA
                                                        20



                                                        15



                                                        10



                                                         5



                                                         0
                                                        1/5/2008   1/7/2008    1/9/2008   1/11/2008   1/13/2008   1/15/2008   1/17/2008   1/19/2008   1/21/2008   1/23/2008
                                                                                                                                                                              12
                   Summary
   A suite of measurements at schools near the
    U.S. 95 freeway in Las Vegas offers a number
    of opportunities to better understand
    conditions and exposure near freeways.
   Low wind speeds often contribute to high
    pollutant concentrations on both sides of the
    roadway (with sound wall).
   Measurements can be further compared once
    data are finalized to better understand the
    differences in techniques and the sources
    impacting the sites.
                                                    13
            Acknowledgments
This work is funded by the Nevada Department of
Transportation (NDOT); John Terry is the NDOT Project
Manager. Joanne Spaulding and Jane Feldman (Sierra
Club), Pat Mohn (NDOT), and Rich Baldauf (EPA)
contributed to the design of this study.




                                                        14

								
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