Relative Contribution of Different Source Categories to Ozone Exceedances in the Houston-Galveston-Brazoria Area

Abstract

The goal of this study is to analyze the relative contribution of different emission source categories to ozone in the Houston-Galveston-Brazoria (HGB) area of Texas. Emission Processing System (EPS3) is used to prepare the emission files for five different source combination cases (Base case, Biogenic, Area + Biogenic, Mobile + Biogenic, Low-level Point + Biogenic). These emission files are used to perform photochemical modeling with Comprehensive Air Quality Model with Extensions (CAMx), and the results are analyzed with Visual Environment for Rich Data Interpretation (VERDI) tool. The daily maximum ozone concentrations and individual contributions of the source categories were analyzed over a 15-day study period between June 1-15, 2012, at three locations (University of Houston-Sugarland, Bayland Park and Conroe). Biogenic sources contributed an average of 49.7% ± 12.8%, 43.1% ± 12.0%, and 39.9% ± 9.28% at Sugarland, Bayland Park and Conroe sites respectively, indicating the significance of isoprene emissions from the vegetation in northeast Houston. On peak ozone days, contribution of Mobile + Biogenic source category averages about 80.1% ± 12.6%, 79.9% ± 6.50%, and 75.9% ± 10.9% at Sugarland, Bayland Park and Conroe sites respectively, indicating the dominance of mobile source NO X emissions and the necessity for regulatory focus on mobile source emissions control.

Anthropogenic Source Contributions to Ozone Formation in the Greater Houston Area

“…However, at Houston downtown, both the mobile sources and point sources contributed in a similar range. Kommalapati et al (2018) observed that the biogenic sources contributed an average of 43.1% ± 12.0% of all sources at Bayland park near Houston downtown to ozone formation and also noted that the contribution is 76.3% ± 7.20% from biogenic and mobile sources together [18]. According to Qi Ying, the largest anthropogenic sources of ozone formation are industrial sources followed by gasoline vehicles and solvent utilization in the HGB area [45].…”

“…In the HGB area, point, area, and mobile sources contributed 61%, 16%, and 23% respectively in 2014 and 67% of NO x emitted from mobile sources in the same year [17]. A photochemical modeling study shows that mobile sources have a dominant effect on ozone formation at Sugarland, Bayland, and Conroe areas in the Greater Houston region [18]. In the summer season, the HGB region experiences hot and humid conditions with intense solar radiation that can be conducive for O 3 formation as a high concentration of ozone mainly develops in sunny days with light wind speed, which allows more pollutants to form and accumulate [10].…”