Near-Roadway Mobile-Source Air Toxics (MSATs) Exposures Along

U.S. 95 in Las Vegas, NevadaPrepared by:

Paul T. Roberts, Michael C. McCarthy, and Steve G. BrownSonoma Technology, Inc.

Petaluma, California

Draft for EPA Webinar PresentationApril 30, 2009

Portions previously presented at:CRC Mobile Source Air Toxics Workshop

Phoenix, ArizonaDecember 2, 2008

906034.14-3615

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Outline of this Talk

Background on US95 Settlement Agreement

Introduction to US95 MSAT Study Ambient Black Carbon Concentrations Contribution of US95 to BC Concentrations BC Filtration Efficiencies Ambient Gas-phase MSAT Concentrations Mitigation Lessons & Summary

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US95 Settlement Agreement

A Court Settlement Agreement was reached between Sierra Club and NDOT/FHWA regarding urban freeway expansion where three schools are adjacent to roadway

Both mitigation and monitoring were required to reduce and assess student exposure. • 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)

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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

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Monitoring Sites at Schools

Hancock Elementary School

Adcock Elementary School

Western HighSchool

Fyfe ElementarySchool

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Fyfe Elementary School Monitoring Sites

Legend:   Air Inlet   Classroom    Ambient

Ambient is 20 meters from sound wall (SW); Air inlet is 76 meters from SW.

South, downwind, 110-250 degrees

North, upwind, 290-70 degrees

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Typical Time-Series of Black Caron Concentration at Fyfe In Winter

• BC, CO, NO, OC, EC profiles are similar.• Wind speed, wind direction, source strength have a major

influence on concentrations.

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BC Concentrations Upwind and Downwind Influence of Wind Speed (1 of 2)

When winds blow from south to north, observations show a significant difference across the freeway, suggesting freeway influence of BC could be at least 50% of the observed concentrations at these sites. Notch: median, 95% CI

Box: interquartile range

Whisker: 1.5*IQR

Points: beyond 1.5*IQRA significant difference is present if notches do not overlap

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

Wind speed

0

2

4

6

8

Am

bien

t B

C μ

g/m

3

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At low wind speeds, concentrations upwind/downwind are similar. Only at higher wind speeds are differences evident.

Same plot as previous slide

Same plot as previous slide but with the opposite wind direction

Adcock downwind

Fyfe upwind

Adcock upwind

Fyfe downwind

BC Concentrations Upwind and Downwind Influence of Wind Speed (2 of 2)

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

Wind speed

0

2

4

6

8

Am

bien

t B

C μ

g/m

3

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

Wind speed

0

2

4

6

8

Am

bien

t B

C μ

g/m

3

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Diurnal BC Concentrations; Fyfe

Effective filter efficiency: original system about 61%; improved system about 78%

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Diurnal BC Concentrations

Effective filter efficiency: original system about 74%; improved system about 97%

Effective filter efficiency: original system about 61%; improved system about 78%

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Average Black Carbon Exposure

0-1 1-2 2-3 >=3Wind Speed (m/s)

0

1

2

3A

nn

ua

l Ave

r ag

e B

C (

ug

/m3)

WesternHancockFyfeAdcock

SITENEW

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Winter 0900-1100 Distributions

Hancock Ambi

Adcock Air I

Adcock Ambie

Fyfe Ambient

Fyfe Air I

nl

Western Ambi

Western Air

SITE_CONCAT

0.010

0.100

1.000

10.000

RE

SU

LT_

PP

B

TolueneFormaldehydeBenzeneAcroleinAcetaldehyde1,3-Butadien

PARAMETER

Samples on 14 days

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Winter 0900-1100 Distributions

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Winter 0900-1100 Distributions

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Winter 0900-1100 Distributions

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Winter 0900-1100 Distributions

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Example BC Time-Series Showing Low BC Concentrations in Fyfe Classroom, except when door

left open by the teacher (after HVAC changes)

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Example BC Time-Series Showing Classroom Being Filled with Rush-hour Pollution by HVAC

(Before HVAC Changes)

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Summary of Filtration Characteristics

Modest BC removal with existing HVAC systems in old and new buildings.

Significant BC removal with modified HVAC filtration systems.

Indoor gas-phase MSAT concentrations are often higher than outdoors, including formaldehyde and acetaldehyde (even in older buildings).

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Mitigation Lessons Learned

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.

Diurnal pattern of pollution is an important consideration for exposure and mitigation (for both classroom and outdoors).

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Summary of Near-Roadway MSAT Characteristics (in an Urban Area)

• Fresh pollutants go up and down together.• Morning and overnight concentrations

dominate outdoor and indoor exposure.• Freeway contributes significant black

carbon at all wind speeds.• Low wind speeds often allow high black

carbon concentrations on both sides of roadway (with sound wall).

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Summary of Near-Roadway MSAT Exposure Characteristics

• Diurnal pattern of pollution is an important consideration for exposure and mitigation (for both classroom and outdoors).

• Exposures lower for elementary school students (09-15) than for high school students (07-13), (than for residents 20-08).

• Gaseous MSAT concentration distribution (09-11, 13-15) similar to National distribution, except for formaldehyde and acetaldehyde.

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Acknowledgments

This work was funded by the Nevada Department of Transportation (NDOT); John Terry was the NDOT Project Manager. Joanne Spaulding & Jane Feldman (Sierra Club), Pat Mohn (NDOT, now NDEP), and Rich Baldauf (EPA) contributed to the design of this study. Joey Landreneau and David Vaughn (STI) performed the monitoring and sampling.