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A look at measurements taken near Seabrook, Texas during the September 27, 2002 Ozone Event

What I'll try to show you. The role of meteorology in this eventWhy the event was not that unusualWhy the data indicate that several groups of plumes crossed the Seabrook site during a short periodSome confirming organic compound dataSome other ozone measurements for the area. Recommended Web Addresses Houston Galveston Air Quality Science Evaluation http://home.tnrcc.state.tx.us/air/aqp/airquality_techcom.html Air Pollution Events http://www.tnrcc.state.tx.us/updated/air/monops/airpo29957

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A look at measurements taken near Seabrook, Texas during the September 27, 2002 Ozone Event

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    1. A look at measurements taken near Seabrook, Texas during the September 27, 2002 Ozone Event Presented by Ken Rozacky SEACAP meeting January 8, 2003

    2. What Ill try to show you The role of meteorology in this event Why the event was not that unusual Why the data indicate that several groups of plumes crossed the Seabrook site during a short period Some confirming organic compound data Some other ozone measurements for the area

    3. Recommended Web Addresses Houston Galveston Air Quality Science Evaluation http://home.tnrcc.state.tx.us/air/aqp/airquality_techcom.html Air Pollution Events http://www.tnrcc.state.tx.us/updated/air/monops/airpollevents/2003/sigevents_2003.html

    12. On September 27, 2002 the wind direction follows the clockwise rotation pattern, moving slowly from Westerly to Northerly during the morning hours 0500-1200 CDT; Wind speeds are light ( 2 to 5 mph); Sun up was about 0700 CDT with maximum solar radiation occurring near 1300 CDT The mixing height during the period was generally less than 1000 feet over land and probably somewhat lower approaching the shoreline and over the water. **This pattern repeats on September 28 and 29

    13. More on the September 27, 2002 Ozone Event compiled by Ken Rozacky as of 2/01/03

    14. New Information since 1/8/03 5 minute data from an industry sponsored Dual Cell FTIR operated for Shell just North of the TCEQ Deer Park monitoring site C035 5 minute data for NO, NO2, NOX, NOY, O3, CO, from TCEQ Deer Park monitoring site C035 1 hour PAMS AutoGC data from TCEQ Deer Park monitoring site C035

    15. New information since 1/08/03 Continued 5 minute data for NO, NO2, NOX, O3, CO, SO2 from TCEQ Clinton Drive monitoring site C055 1 hour PAMS AutoGC data from TCEQ Clinton Drive monitoring site C055 Additional plume plots for the overnight hours preceding the ozone event matched against NOX hourly measurements taken at area monitoring sites

    16. What the Data Now Seem to Indicate Significant build up of nitric oxide (NO) overnight (> 200 ppb) over city center. Very little nitrogen dioxide (NO2). Indicative of mobile sources as the dominate contributors. That air mass moved only a short distance Easterly. Near stagnation of the air mass over the mid-Ship Channel during the early morning hours. 0500 0800 CDT - VOC emissions local to Deer Park (C035) seem to be process feed stock type compounds (ethane, propane, n-butane, isobutane, isopentane) 0900 0940 CDT - VOC emissions local to Derr Park (C035) change to mainly ethylene and isobutane as the feed stock type compound levels drop off. Faster than normal ozone formation after sunup.

    17. Back Trajectory Estimates The hour listed is the begin time of a parcel of air arriving at the site. Each interval of advection is one hour based on local meteorological data. Trajectories end with the puff that originated at 0000 CDT 9/27/02 Measured ozone values are displayed next to the wind direction indicator for each TCEQ site ** Prepared by Bryan Lambeth, TCEQ senior meteorologist

    21. Plume Plots The hour listed is the begin time of a puff from a given NOX source. Each interval of advection is one hour based on local meteorological data. Trajectories end with the puff that occurred at 0000 CDT 9/27/02 Measured NOX values are displayed next to the wind direction indicator for each TCEQ site Prepared by Bryan Lambeth, TCEQ senior meteorologist

    30. After sunrise, increased ozone formation occurs. In the following Plume Plots, the measured ozone values are displayed next to the wind direction indicator for each TCEQ site.

    36. The General Synopsis Between 0000-0600 CDT air parcels moved less than 5 miles West to East Following sunrise at 0700 CDT, the wind speed increased and moved the air parcels to the South Air arriving at the Seabrook site between 0900 and 1200 CDT probably originated in the Ship Channel Industrial area Each air parcel accumulated local emissions as it traversed, then converged with other plumes along the Bay Breeze line The merged plumes arrived in Seabrook after 3 -5 hours of transport time from the emission sources. The merged plumes arrived in Texas City about an hour after passing the Seabrook site.

    37.

    39. Clinton Drive C055 (West Ship Channel) WS was low 1 to 3 mph 0000 - 0830 CDT WD was generally W - NW NOX (mostly as NO) built up over city center, peak ~ 400 ppb NO2 stayed ~ 30 ppb and moved slowly East during the overnight hours. CO built up at the same time, peak 2.5 ppm 0700 CDT sun up 0840 CDT - WS increases to 4 5 mph 0840 1025 CDT - NOX values fall dramatically, ~ 20 ppb local O3 production was probably scrubbed to NO2 until NO levels dropped due to ventilation and excess O3 existed. AutoGC - Alkane and olefin concentrations during the period were generally < 5 ppbv

    42. Deer Park C035 + Shell FTIR (Mid Ship Channel) WS was 0.5 to 1.5 mph 0530 0900 CDT WD - W at C035, S at Shell FTIR * not unusual for a low WS condition 0400 0800 CDT - NOX (mostly as NO) built up, peak ~ 240 ppb NO2 stayed ~ 20 ppb CO, CH4, CO2 built up at the same time, CO at site C035 tracks CO at the Shell FTIR closely except the period of 0800 0900 CDT when the CO at the Shell site is approximately 20% lower. 0700 CDT - sun up 0825 CDT - C035 CO peak 2.2 ppm confirm within 20 minutes of the Shell FTIR peak: CO 1.9 ppm, CH4 6 ppm, CO2 630 ppm at 0845

    44. Site C035 CO and NOX CO tracks NOX very closely The CO peak and NOX peak are coincident. The CO:NOX ratio is consistently 10:1

    46. Deer Park C035 + Shell FTIR (Mid Ship Channel) continued 0500 0800 CDT PAMS AutoGC Alkane concentrations rise to 30 to 100 ppbv (n-butane, isopentane, ethane, propane, isobutane) Olefins (ethylene and propylene) are low 6 10 ppbv but rising above normal background levels. 0600 0800 CDT Elevated ethylene and propylene (20- 30 ppb) observed at the Shell FTIR site before their sudden rise at C035 0900 - 0940 CDT a surge of over 100 ppbv ethylene and isobutane and a 5 ppbv propylene increase at C035. The other C2-C5 alkane levels fall back to levels below 10 ppbv 0845 0930 CDT Acetaldehyde (30 40 ppb) appears at the Shell FTIR following the drop of ethylene and propylene below the FTIR detection limit

    48. 0800 0900 CDT - Rapid conversion of NO to NO2 0900 - 0940 CDT PAMS AutoGC sample results Alkanes, except isobutane, have decreased significantly (about 60%) but Olefins, and isobutane, have increased Ethylene -10 ppbv to 168 ppbv Isobutane 30 ppb to 101 ppbv Propylene -10 ppbv to 15 pbbv Shell Dual Cell FTIR results confirm increase in Ethylene and Propylene 30 40 ppbv range during period although peak concentrations differ. 0845 - 0900 CDT - WS increased to 4 5 mph 0900 - 0920 CDT - Excess O3 increases to 40 ppbv 1000 1040 CDT PAMS AutoGC levels < 10 ppbv. Seabrook C045 + FTIR (Southeast of Ship Channel)

    51. Summary : C055, Clinton Drive site 0000-0830 CDT - increasing NO and CO with no significant VOC ozone precursor content. Ozone formation pattern after sunup appears normal. Slow, steady rise starting at 1000 CDT with peak between 1400 1600 CDT.

    52. Summary : C035, Deer Park site and the nearby Shell FTIR site 0000-0500 CDT - increasing NO and CO with no significant VOC ozone precursor content. 0500-0900 CDT - several hours of elevated C2 C5 alkanes at 30 100 ppbv and ethylene and propylene near 10 ppb. 0900-0940 CDT - a surge of over 100 ppbv ethylene and isobutane with a 5 ppbv (30%) propylene increase. The other C2-C5 alkanes fall back below 10 ppbv 0800-0900 CDT - Rapid rise of NO2 followed by rapid rise in O3 as NO2 leveled may indicate scavenging of initial ozone production by local NO Without NO scavenging the ozone peak might have been over 100 ppb at 0800-0900 CDT , which is not typical.

    53. Summary : C045, Seabrook site 0500-0830 CDT - increasing NO and CO with no significant VOC ozone precursor content. 0830-0930 CDT - Elevated ozone and VOC methanol, hexanes, 2-hexene, epichlorhydrin, isobutane, ethylene, propylene, and related ozone formation products, formaldehyde and acetaldehyde 0930-1100 CDT - hexanes fall off, propylene and formaldehyde rise Ozone peak occurs between 1000 1100 CDT , which is not typical.

    54. What the Data Now Seem to Indicate Significant build up of nitric oxide (NO) overnight (> 200 ppb) over city center. Very little nitrogen dioxide (NO2). Indicative of mobile sources as the dominate contributors. That air mass moved only a short distance Easterly. Near stagnation of the air mass over the mid-Ship Channel during the early morning hours. 0500 0800 CDT - VOC emissions local to Deer Park (C035) seem to be process feed stock type compounds (ethane, propane, n-butane, isobutane, isopentane) 0900 0940 CDT - VOC emissions local to Derr Park (C035) change to mainly ethylene and isobutane as the feed stock type compound levels drop off. Faster than normal ozone formation after sunup.

    55. Possible scenario : Pyrolysis furnace outage Hydrocarbon feedstock is diverted from the process to keep reaction ovens from coking up. Downstream customer for the ethylene product loses feed and has to suspend and restart operations. Coincident isobutane and ethylene may be indicative of a flare emission from either the supplier or the customer process. **** This is pure speculation, there have still been no unscheduled emission reports filed for this date with the local TCEQ office.

    56. The value of the Dual Cell FTIR data

    58. The data from TCEQ C045 alone might lead one to believe that this ozone formation event was due to NOX sources alone Which is not the whole story.

    59. Other available hourly ozone measurements in the Houston area for 9/27/02

    63. Regional mid-day background ozone for the day was estimated to be 65 ppb. Ozone production due to the 9/27/02 emission event added another 65 ppb to it.

    66. Summary The clockwise wind direction rotation pattern and the Bay Breeze convergence contributed to the elevated measurements at the Seabrook site. This wind pattern occurs on 37% of ozone exceedence days in Houston While there was little sunlight to stimulate photochemistry, there is evidence that significant photochemical reactivity occurred. There were no reports of unexpected emissions on 9/27/02

    67. Data collected during the TexAQS 2000 Study suggest a reasonable correlation of finding elevated ozone when elevated levels of formaldehyde and nitric acid are observed.

    70. Although nitric acid is not currently a target compound for the Seabrook FTIR, URS reviewed the 9/27/2002 data for the presence of nitric acid. It was determined that the FTIR spectra did not indicate that nitric acid was measured above the estimated FTIR detection limit of 10 ppbv.

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