Petroleum refinery emissions cause serious air quality

problems as they are respiratory irritants causing significant

health effects and suspected of elevating cancer risks in

certain populations. Nitrogen oxides and various VOCs

emitted by the petroleum refineries and associated chemical

facilities are precursors for ozone and particulate pollutants.

The Houston-Galveston Airshed (HGA) has become one of

the most severe ozone non-attainment regions in the U.S. for

both 1-hour ozone and the number of days above the

National Ambient Air Quality Standard. The HGA contains

about 50% of the nationís petrochemical capacity: 27.6

billion pounds of ethene (i.e., 52% of the nationís capacity)

and 10.9 billion pounds of polymer grade propene (63% of

the nationís capacity). These olefin emissions can affect

ozone concentrations significantly. A variety of

measurements made during the Texas Air Quality Study

(TexAQS2000), August 15-September 19, 2000, [112] have

detected massive and frequent spikes of ozone, which

appear to be associated with releases of reactive unsaturated

hydrocarbons (olefins) from the petrochemical industries.

Compared with typical ozone evolution patterns in other

U.S. cities, several monitoring sites in the area show distinct

rapid transient high ozone events (THOEs) [113].


Meteorology and air quality of the episode

In summer, a high-pressure system persists over the Gulf of

Mexico, leading to stagnant conditions in southeast Texas.

Under this weak synoptic scale forcing, a land-sea breeze

circulation becomes apparent and dominates the weather

pattern in the Houston-Galveston area. The TexAQS 2000

episode had numerous exceedences (daily maximum ozone

concentration greater than 125 ppb) in both Houston and

Beaumont. There were six exceedence days in the HGA

during the eight-day period, including a period of low ozone

in the middle. The episode included several days with

continued veering wind vectors causing flow reversal from

morning to afternoon hours. These high ozone

concentration events were frequently linked with a land-sea

breeze circulation in the HGA.


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