Evolution of Air Quality Influences in Central Texas: 1980–2018

The period between 1980 and 2019 has seen significant change in the demographic and land-use environment in Central Texas, particularly along the Interstate 35 corridor and in the cities of Austin and San Antonio. These changes, along with policy changes, natural disasters, and changes in oil and gas production have all influenced the air quality in this heavily populated region. A suite of analysis techniques will be employed to investigate the cumulative effect of these influences on air quality in this region.

Observational surface monitor and meteorology data from the Texas Commission on Environmental Quality and the Environmental Protection Agency was obtained from an array of monitors in and around the Austin and San Antonio region. Some particular areas of interest for study include:

El Nino/Southern Oscillation – an effect has been identified on coastal data in the region, but this influence has not been evaluated inland. Since the primary driver of the phenomenon along the coast is largely the effect of clean marine air being transported inland, it is not clear whether this influence would reach Central Texas.

The Eagle Ford Shale – the Eagle Ford Shale is broad area of land in the central part of the state which was opened to oil and gas drilling in the early 2000s. There are currently ________ fracking wells on the play, which release a variety of VOCs as a part of normal operations. Given San Antonio’s location just north and west of the Eagle Ford Shale, it is important to understand the influence this activity has on air quality in the city.

Fire – Evergreen trees provide a significant source of natural volatile organic compounds. The city of Bastrop, Texas, southeast of Austin, is home to a large pine forest. Combined with NOx from vehicle traffic and other activities, these VOCs can play a role in the production of ground level ozone. Following a year of intense drought, Bastrop and the surrounding forest was struck by a severe wildfire which decimated many acres of pine forest. In the aftermath of that fire, the long term effect of this change in land cover will be evaluated.

Population growth and land use change – Evaluation of demographic data and comparison of the National Digital Vegetation Index parameter will be used in an attempt to correlate changes in population and urbanization to changes in air quality.

Initial comparison of 8-hour peak tropospheric ozone concentrations in Austin and San Antonio reveal a complex environment, with some stations exhibiting a long-term decrease in the last three decades, some exhibiting an increase, and some stations experiencing a change in long term trend. A variety of analysis techniques will be leveraged to investigate the roles of these various influences on the long term trend in tropospheric ozone concentrations in Central Texas.