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- Kim, S. W., et al.
(author)
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Evaluations of NOx and highly reactive VOC emission inventories in Texas and their implications for ozone plume simulations during the Texas Air Quality Study 2006
- 2011
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:22, s. 11361-11386
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Journal article (peer-reviewed)abstract
- Satellite and aircraft observations made during the 2006 Texas Air Quality Study (TexAQS) detected strong urban, industrial and power plant plumes in Texas. We simulated these plumes using the Weather Research and Forecasting-Chemistry (WRF-Chem) model with input from the US EPA's 2005 National Emission Inventory (NEI-2005), in order to evaluate emissions of nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs) in the cities of Houston and Dallas-FortWorth. We compared the model results with satellite retrievals of tropospheric nitrogen dioxide (NO2) columns and airborne in-situ observations of several trace gases including NOx and a number of VOCs. The model and satellite NO2 columns agree well for regions with large power plants and for urban areas that are dominated by mobile sources, such as Dallas. How-ever, in Houston, where significant mobile, industrial, and inport marine vessel sources contribute to NOx emissions, the model NO2 columns are approximately 50 %-70 % higher than the satellite columns. Similar conclusions are drawn from comparisons of the model results with the TexAQS 2006 aircraft observations in Dallas and Houston. For Dallas plumes, the model-simulated NO2 showed good agreement with the aircraft observations. In contrast, the model-simulated NO2 is similar to 60 % higher than the aircraft observations in the Houston plumes. Further analysis indicates that the NEI-2005 NOx emissions over the Houston Ship Channel area are overestimated while the urban Houston NOx emissions are reasonably represented. The comparisons of model and aircraft observations confirm that highly reactive VOC emissions originating from industrial sources in Houston are underestimated in NEI-2005. The update of VOC emissions based on Solar Occultation Flux measurements during the field campaign leads to improved model simulations of ethylene, propylene, and formaldehyde. Reducing NOx emissions in the Houston Ship Channel and increasing highly reactive VOC emissions from the point sources in Houston improve the model's capability of simulating ozone (O-3) plumes observed by the NOAA WP-3D aircraft, although the deficiencies in the model O-3 simulations indicate that many challenges remain for a full understanding of the O-3 formation mechanisms in Houston.
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| 2. |
- De Gouw, J. A., et al.
(author)
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Airborne Measurements of Ethene from Industrial Sources Using Laser Photo-Acoustic Spectroscopy
- 2009
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In: Environmental Science & Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:7, s. 2437-2442
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Journal article (peer-reviewed)abstract
- A laser photoacoustic spectroscopy (LPAS) instrument was developed and used for aircraft measurements of ethene from industrial sources near Houston, Texas. The instrument provided 20 s measurements with a detection limit of less than 0.7 ppbv. Data from this instrument and from the GC-FID analysis of air samples collected in flight agreed within 15% on average. Ethene fluxes from the Mt. Belvieu chemical complex to the northeast of Houston were quantified during 10 different flights. The average flux was 520 +/- 140 kg h(-1) in agreement with independent results from solar occultation flux (SOF) measurements, and roughly an order of magnitude higher than regulatory emission inventories indicate. This study shows that ethene emissions are routinely at levels that qualify as emission upsets, which need to be reported to regional air quality managers.
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