Click to edit Master title style Click to edit Master subtitle style 1 Modeling of 1,3-Butadiene for Urban and Industrial Areas B. Rappenglück and B. Czader

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1

Modeling of 1,3-Butadiene

for Urban and Industrial Areas

B. Rappenglück and B. Czader

Department of Earth and Atmospheric SciencesUniversity of Houston



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Why 1,3-butadiene?• It is toxic and human carcinogen.

• It is designated as Hazardous Air Pollutant (HAP) by the Clean Air Act. Therefore, EPA is required to regulate its emissions.

• Its presence in the air accelerates ozone formation.Breathing ozone causes health effects as well as damages vegetation.

• Potential precursor of secondary organic aerosol (SOA) under high NOx levels (Sato et al., 2011)



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Why 1,3-butadiene?• It is toxic and human carcinogen.

• It is designated as Hazardous Air Pollutant (HAP) by the Clean Air Act. Therefore, EPA is required to regulate its emissions.

• Its presence in the air accelerates ozone formation.Breathing ozone causes health effects as well as damages vegetation.

• Potential precursor of secondary organic aerosol (SOA) under high NOx levels (Sato et al., 2011)

• High emissions and concentrations in the Houston metropolitan area:

City/StateObservation

countMean(ppbV)

Median(ppbV)

75th-percentile(ppbV)

90th-percentile(ppbV)

Port Neches, TX 61 1.02 0.51 1.40 2.66

Houston, TX 7218 1.30 0.18 0.68 2.10

Phoenix, AZ 26 0.19 0.14 0.34 0.46

New York, NY 12 0.14 0.13 0.25 0.30

Calexico, CA 31 0.20 0.11 0.21 0.39

Los Angeles, CA 25 0.13 0.10 0.18 0.23

Wilmington, NC 48 0.52 0.05 0.05 0.58

Seattle, WA 25 0.06 0.04 0.08 0.12

Year 2006

source: EPA AirData, available at http://www.epa.gov/airdata



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Measured data

Collected by an automated gas chromatograph (Auto_GC) by Texas Commission on Environmental Quality (TCEQ) and Houston Regional Monitoring (HRM); Reported in 1-h intervals

Aug. 25 – Sep. 30, 2006HRM3LynchburgMilby ParkTexas CityMustangDanciger

Aug. 25 – Aug. 31, 2006ChannelviewWallisvilleCesar Chavez

MethodologySimulated time period: August 25 – September 30, 2006

Simulation: CMAQv4.6 with an extended SAPRC99 mechanism 1,3-butadiene explicitly represented

Emission Inventory:Texas Point Source Inventory 2006 (TPSI2006)TCEQ’s area, mobile, and biogenic emissionsNational Emission Inventory 2002 (NEI 2002)



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SundaySaturday

SundaySaturday

National Level (EPA, 1996):National Level (EPA, 1996):Incomplete combustion of gasoline and diesel fuels:Incomplete combustion of gasoline and diesel fuels: ~ 82% ~ 82% Residential wood combustion, agricultural burning, forest fires, biomass burning: Residential wood combustion, agricultural burning, forest fires, biomass burning: ~ ~ 16%16%Petroleum refining and manufacturing facilities (production of plastic goods): Petroleum refining and manufacturing facilities (production of plastic goods): ~ 2% ~ 2%

Emissions of 1,3-Butadiene



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SundaySaturday

SundaySaturday

SundaySaturday





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SundaySaturday

SundaySaturday

Average daily profile of 1,3- butadiene emissions in HGB counties

8/25/2006 - 9/30/2006

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

CST

kg

/hr





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9 monitors in the Houston - Galveston area08/25 - 09/30/2006

0

0.04

0.08

0.12

0.16

0.2

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

CST

pp

bv

median observed

median modeled

nitrate radical (NOnitrate radical (NO33))

ozone (Oozone (O33))

the average summertime the average summertime lifetime is ~ 4 h lifetime is ~ 4 h during photochemical episodes ~ 25 min during photochemical episodes ~ 25 min (Dollard et al. 2001).(Dollard et al. 2001).

1,3-butadiene + hydroxyl radical (OH) 1,3-butadiene + hydroxyl radical (OH) → → ozone (O3) ozone (O3)

→ → carbonyl compoundscarbonyl compounds1,3-butadiene + 1,3-butadiene + lifetime is ~11h (Olifetime is ~11h (O33))

lifetime is ~ 2.4 days (NOlifetime is ~ 2.4 days (NO33) )

(Dollard et al. 2001)(Dollard et al. 2001)

Removal of 1,3-butadiene

Dry and wet deposition of 1,3-butadiene is not a significant removal process.Dry and wet deposition of 1,3-butadiene is not a significant removal process.

1,3-Butadiene Mixing Ratios



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midnight

Nighttime mixing ratios are low, morning mixing ratios high due to mobile emissions

In the urban area

morning rush hours



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midnight

Nighttime mixing ratios are low, morning mixing ratios high due to mobile emissions

In the urban area

morning rush hours

In industrial areas Mixing ratios are higher in the industrial areas than in the urban area Mixing ratios high during night and morning hours




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Processes affecting 1,3-butadiene mixing ratios at the surface

Averaged over urban area Averaged over industrial area

Emissions higher during daytime, lower during nighttime

High emissions during both daytime and nighttime

— mixing ratios— horizontal transport— vertical transport— emissions— reactions



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Processes affecting 1,3-butadiene mixing ratios at the surface

— mixing ratios— horizontal transport— vertical transport— emissions— reactions

Emissions are much higher in the industrial area; therefore, mixing ratios also higher in the industrial area 1,3-butadiene removed from the surface mainly by the vertical transport (~90%) Removal by chemical reactions (~10%). Contribution likely be higher when whole mixing layer is considered.



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Loss of 1,3-butadiene by means of chemical reactions


Daytime: ~90% of 1,3-butadiene reacts with the OH radical, both in urban and industrial environment

— O(3P)— NO3— O3— OH



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Loss of 1,3-butadiene by means of chemical reactions


~56% of 1,3-butadiene reacts with the NO3 radical in the urban area where high NOx emissions occur ~ 13 % contribution from reaction with ozone

reaction with OH significant, even at night (~57%); ~33% contribution from reaction with NO3

~10% contribution from reaction with ozone

— O(3P)— NO3— O3— OH

Nighttime, urban area: Nighttime, industrial area:



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TCEQ special point source inventory TCEQ base case inventory

Locations of auto-GC CAMS sites and point sources for 1,3-butadiene in the Houston area



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0.0

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NNE

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ENE

E

ESE

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SSES

SSW

SW

WSW

W

WNW

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NNW

observed v > 0.2 m/s

simulated v> 0.2 m/s

HRM-309/16/06 - 09/30/06[ppbv]

1,3-Butadiene

0.0

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NNE

NE

ENE

E

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SSES

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HRM-308/25/06 - 09/15/06[ppbv]

1,3-Butadiene



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Reported emission event:9/14/06 4 pm – 9/15/06 6:30 am in Houstonestimated 375.5 lbs. of 1,3-butadiene released (Source: http://www11.tceq.state.tx.us/oce/eer/index.cfm)

Peak ambient 1,3-butadiene reached 1.6 ppm !!!

SE

0.00.20.40.60.81.0

N

NNE

NE

ENE

E

ESE

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SSES

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WSW

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WNW

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NNW



Milby Park08/25/06 - 09/30/06[ppbv]

1,3-Butadiene

Change in scale!



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ESE

E SE

SE

0.00.20.40.60.81.0

N

NNE

NE

ENE

E

ESE

SE

SSES

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Milby Park08/25/06 - 09/30/06[ppbv]

1,3-Butadiene

0.00.20.40.60.81.0

N

NNE

NE

ENE

E

ESE

SE

SSES

SSW

SW

WSW

W

WNW

NW

NNW



Milby Park08/25/06 - 09/30/06[ppbv]

1,3-Butadiene

Sep 14-15 data excluded

Change in scale!



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CST

HRM-308/25 - 09/30/2006 weekdays

observed mean

simulated mean

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Lynchburg Ferry08/25 - 09/30/2006

observed mean

simulated mean

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Milby Park08/25 - 09/30/2006 (09/15-15 excluded)

observed mean

simulated mean

High variability of measured mixing ratios.+ Variability caused by variable emissions from point sources that do not have specific daily or hourly patterns.

The model does not reflect high variability.+ Emission inventory does not reflect highly variable hourly emissions values.

Particular case: Milby Park siteHigh mixing ratios, both night and day!+ site very close to emission source+ fugitive emissions .

Highly polluted sites[daily mean 1,3-butadiene mixing ratio > 0.1 ppbv]



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Texas City08/25 - 09/30/2006

observed mean

simulated mean

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Mustang08/25 - 09/30/2006

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simulated mean

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bv

CST

Danciger08/25 - 09/30/2006

observed mean

simulated mean

Moderately polluted sites[daily mean 1,3 butadiene mixing ratio > 0.1 ppbv]

Low mixing ratios. Less variability in both, measured and modeled values.



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Conclusions

Point source emissions of 1,3-butadiene are much higher than mobile and area emissions in the HGB area;

Emissions of 1,3 – butadiene are higher during daytimes, but its concentrations are higher during the nighttime and early mornings.

Mixing ratios are highly variable due to the impact of variable emissions

CMAQ captures background concentrations of 1,3-butadiene well,but is not able to capture irregular emission events.

1,3-butadiene is removed from the surface through vertical transport (~90%) and reactions (~10%). The contribution likely higher when whole mixing layer considered.

During daytime reaction with OH radical is the most significant removal reaction

During nighttimes reactions with O3 and NO3 are significant, contributing to a new radical formation without consuming a radical.

Under-prediction of 1,3-butadiene may lead not only to ozone (and potentially SOA) under-prediction but also under-prediction of nighttime radicals.

Documents

Click to edit Master title style Click to edit Master subtitle style 1 Modeling of 1,3-Butadiene for Urban and Industrial Areas B. Rappenglück and B. Czader