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Characteristics of Mobile-Source Air Toxics MSATs at Several Schools Next to U.S. 95 in Las Vegas, NV

2. Outline . Introduction to US95 MSAT StudyMonitoring sites at schoolsTypical characteristics of CO, NO/NOx, and black carbon (BC) at these sitesExamples of BC before and after HVAC modificationsGeneral characteristics of VOC and carbonyl concentrations (near, far, inside, outside)Preliminary summary of characteristicsMitigation lessons learned, so farUncertainties, existing gaps in knowledge.

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Characteristics of Mobile-Source Air Toxics MSATs at Several Schools Next to U.S. 95 in Las Vegas, NV

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    1. Characteristics of Mobile-Source Air Toxics (MSATs) at Several Schools Next to U.S. 95 in Las Vegas, NV Prepared by: Paul T. Roberts and Michael C. McCarthy Sonoma Technology, Inc. Petaluma, CA Presented at: A Workshop on Air Pollution Impacts of Secondary Roadways and Their Mitigation UC Davis, Davis, CA January 24, 2008

    2. 2 Outline Introduction to US95 MSAT Study Monitoring sites at schools Typical characteristics of CO, NO/NOx, and black carbon (BC) at these sites Examples of BC before and after HVAC modifications General characteristics of VOC and carbonyl concentrations (near, far, inside, outside) Preliminary summary of characteristics Mitigation lessons learned, so far Uncertainties, existing gaps in knowledge

    3. 3 US95 Settlement Agreement Court Settlement Agreement between Sierra Club and NDOT/FHWA regarding urban freeway expansion where three schools are adjacent to roadway Required components of settlement MSAT monitoring study at schools (this study) Filtration added to HVAC systems at schools Bus retrofit program Bus idling education FHWA gradient study (with EPA)

    4. 4 Introduction to US95 MSAT Study MSAT Study Objectives: Characterize outdoor and indoor concentrations at schools (student exposure) Determine US95 vehicle contributions (before and after new lanes opened) Determine MSAT removal efficiencies of new filtration systems Focus on priority MSATs: diesel particulate matter, benzene, 1,3-butadiene, acrolein, formaldehyde, and acetaldehyde

    5. 5 Monitoring Sites at Schools

    6. 6 Fyfe Elementary School Monitoring Sites

    7. 7 Western HS Monitoring Sites

    8. 8 Adcock Elementary School Monitoring Sites

    9. 9 Fyfe Trailer and Shelter Next to Classroom (before HVAC changes)

    10. 10 School Characteristics

    11. 11 Distances (meters) from Sites to Roadway

    12. 12 Typical Time-Series of Concentrations at Fyfe In Winter (BC, CO, NO, OC, EC profiles are similar)

    13. 13 Indoor & Air Inlet BC Concentrations at Fyfe Classroom Showing about 66% Removal (before HVAC changes)

    14. 14 Example BC Time-Series Showing Low BC Concentrations in Fyfe Classroom, except when door left open by the teacher (after HVAC changes)

    15. 15 Example BC Time-Series Showing Low BC Concentrations in Fyfe Classroom, except when door left open by the teacher (after HVAC changes)

    16. 16 Example BC Time-Series Showing Classroom Being Filled with Rush-hour Pollution by HVAC (Before HVAC Changes)

    17. 17 General Characteristics of VOC and Carbonyl Concentrations Compared concentrations at air inlets with those nearer the roadway (“ambient” or “play field”) Compared concentrations at air inlets with indoor classroom concentrations Summer only (so far; winter data being collected now) Pollutants were split into hydrocarbons and carbonyls Hydrocarbons: 1,3-butadiene, benzene, carbon tetrachloride, 2,2,4-trimethylpentane, m-&p-xylene, and toluene Carbonyls: acrolein, acetaldehyde, formaldehyde

    18. 18 Outdoor comparison of hydrocarbons

    19. 19 Outdoor comparison of carbonyls

    20. 20 Outdoor Carbonyls Concentrations at Western often much higher closer to the roadway.

    21. 21 Indoor/outdoor comparison of hydrocarbons

    22. 22 Indoor VOC concentrations at Adcock higher than outdoor for all species except CCl4.

    23. 23 Indoor/outdoor comparison of carbonyls

    24. 24 Preliminary Summary of Characteristics (1 of 2) Fresh pollutants go up and down together. Morning concentrations dominate indoor and outdoor exposure (summer); overnight and morning dominate in the winter. Expected pollutant gradients not always evident. Low wind speeds often allow high pollutant concentrations on both sides of roadway (with sound wall).

    25. 25 Preliminary Summary of Characteristics (2 of 2) Modest BC removal with existing HVAC system in older building. Significant BC removed with new HVAC with filtration (summer); not as good in winter. Indoor concentrations are often higher for formaldehyde and acetaldehyde, even in older buildings (before filtration added).

    26. 26 Mitigation Lessons Learned, So Far (1 of 2) Typical HVAC operation will fill classroom with polluted air early in the morning which can result in higher concentrations indoors in mid-to-late morning. Leaving classroom doors open to outdoor hall can defeat filtration system. Adding filtration system significantly reduces indoor concentrations (of BC; no data yet for VOC and carbonyls).

    27. 27 Mitigation Lessons Learned, So Far (2 of 2) Diurnal pattern of pollution is an important consideration for exposure and mitigation (for both classroom and outdoors).

    28. 28 Gaps To Be Addressed by US95 MSAT Study Compare MSAT concentrations with concentrations at background school. Compare MSAT concentrations before and after new lanes opened. Correlate MSAT concentrations with winds, traffic counts, congestion, etc. Complete analysis of filtration efficiencies for BC, VOCs, and carbonyls.

    29. 29 Uncertainties, Existing Gaps in Knowledge Better understanding of concentration gradients in controlled situations. Influence of sound walls, openings in sound walls, and other complications (grade, other obstructions, etc.). Better understanding in urban, non-freeway situations. Do carbonyl concentrations indoors really go away with building age?

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