1. 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 Department of Earth and Atmospheric Sciences University of Houston

2. Click to edit Master title style Click to edit Master subtitle style 2 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 NO x levels (Sato et al., 2011)

3. Click to edit Master title style Click to edit Master subtitle style 3 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 NO x levels (Sato et al., 2011) High emissions and concentrations in the Houston metropolitan area: City/State Observation count Mean (ppbV) Median (ppbV) 75th-percentile (ppbV) 90th-percentile (ppbV) Port Neches, TX 61 1.02 0.511.402.66 Houston, TX 7218 1.30 0.180.682.10 Phoenix, AZ 26 0.19 0.140.340.46 New York, NY 12 0.14 0.130.250.30 Calexico, CA 31 0.20 0.110.210.39 Los Angeles, CA 25 0.13 0.100.180.23 Wilmington, NC 48 0.52 0.05 0.58 Seattle, WA 25 0.06 0.040.080.12 Year 2006 source: EPA AirData, available at http://www.epa.gov/airdata

4. Click to edit Master title style Click to edit Master subtitle style 4 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, 2006 HRM3 Lynchburg Milby Park Texas City Mustang Danciger Aug. 25 – Aug. 31, 2006 Channelview Wallisville Cesar Chavez Methodology Simulated 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 emissions  National Emission Inventory 2002 (NEI 2002 )

5. Click to edit Master title style Click to edit Master subtitle style 5 SundaySaturday SundaySaturday National Level (EPA, 1996): Incomplete combustion of gasoline and diesel fuels: ~ 82% Residential wood combustion, agricultural burning, forest fires, biomass burning: ~ 16% Petroleum refining and manufacturing facilities (production of plastic goods): ~ 2% Emissions of 1,3-Butadiene

6. Click to edit Master title style Click to edit Master subtitle style 6 SundaySaturday SundaySaturday SundaySaturday National Level (EPA, 1996): Incomplete combustion of gasoline and diesel fuels: ~ 82% Residential wood combustion, agricultural burning, forest fires, biomass burning: ~ 16% Petroleum refining and manufacturing facilities (production of plastic goods): ~ 2% Emissions of 1,3-Butadiene

7. Click to edit Master title style Click to edit Master subtitle style 7 SundaySaturday SundaySaturday National Level (EPA, 1996): Incomplete combustion of gasoline and diesel fuels: ~ 82% Residential wood combustion, agricultural burning, forest fires, biomass burning: ~ 16% Petroleum refining and manufacturing facilities (production of plastic goods): ~ 2% Emissions of 1,3-Butadiene

8. Click to edit Master title style Click to edit Master subtitle style 8 nitrate radical (NO 3 ) ozone (O 3 ) the average summertime lifetime is ~ 4 h during photochemical episodes ~ 25 min (Dollard et al. 2001). 1,3-butadiene + hydroxyl radical (OH) → ozone (O3) → carbonyl compounds 1,3-butadiene + lifetime is ~11h (O 3 ) lifetime is ~ 2.4 days (NO 3 ) (Dollard et al. 2001) Removal of 1,3-butadiene Dry and wet deposition of 1,3-butadiene is not a significant removal process. 1,3-Butadiene Mixing Ratios

9. Click to edit Master title style Click to edit Master subtitle style 9 1,3-Butadiene Mixing Ratios midnight  Nighttime mixing ratios are low, morning mixing ratios high due to mobile emissions In the urban area morning rush hours

10. Click to edit Master title style Click to edit Master subtitle style 10 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 1,3-Butadiene Mixing Ratios

11. Click to edit Master title style Click to edit Master subtitle style 11 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

12. Click to edit Master title style Click to edit Master subtitle style 12 Averaged over urban area Averaged over industrial area 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.

13. Click to edit Master title style Click to edit Master subtitle style 13 Loss of 1,3-butadiene by means of chemical reactions Averaged over urban areaAveraged over industrial area  Daytime: ~90% of 1,3-butadiene reacts with the OH radical, both in urban and industrial environment — O(3P) — NO3 — O3 — OH

14. Click to edit Master title style Click to edit Master subtitle style 14 Loss of 1,3-butadiene by means of chemical reactions Averaged over urban areaAveraged over industrial area  ~56% of 1,3-butadiene reacts with the NO 3 radical in the urban area where high NO x emissions occur  ~ 13 % contribution from reaction with ozone  reaction with OH significant, even at night (~57%);  ~33% contribution from reaction with NO 3  ~10% contribution from reaction with ozone — O(3P) — NO3 — O3 — OH  Nighttime, urban area:  Nighttime, industrial area:

15. Click to edit Master title style Click to edit Master subtitle style 15 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

16. Click to edit Master title style Click to edit Master subtitle style 16

17. Click to edit Master title style Click to edit Master subtitle style 17 Reported emission event: 9/14/06 4 pm – 9/15/06 6:30 am in Houston estimated 375.5 lbs. of 1,3-butadiene released (Source: http://www11.tceq.state.tx.us/oce/eer/index.cfm)http://www11.tceq.state.tx.us/oce/eer/index.cfm Peak ambient 1,3-butadiene reached 1.6 ppm !!! SE Change in scale!

18. Click to edit Master title style Click to edit Master subtitle style 18 ESE E SE Sep 14-15 data excluded Change in scale!

19. Click to edit Master title style Click to edit Master subtitle style 19  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 site High 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]

20. Click to edit Master title style Click to edit Master subtitle style 20 Moderately polluted sites [daily mean 1,3 butadiene mixing ratio > 0.1 ppbv ]  Low mixing ratios.  Less variability in both, measured and modeled values.

21. Click to edit Master title style Click to edit Master subtitle style 21 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 O 3 and NO 3 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.