Examining Oxidation Photochemistry In Bakersfield, California and Comparison To Other Metropolitan Areas

Open Access
- Author:
- Thomas, Jordan Leigh
- Area of Honors:
- Meteorology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- William Henry Brune, Thesis Supervisor
Jenni Evans, Thesis Honors Advisor - Keywords:
- Meteorology
Photochemistry
Air Quality - Abstract:
- Poor air quality is a major problem that affects many metropolitan areas in the United States due to an increase in population and industrialization. Bakersfield, CA suffers from this problem. An extensive field campaign was conducted during the summer of 2010 to measure the reactive gases hydroxyl (OH) and hydroperoxyl (HO2) along with OH reactivity (the inverse of the OH lifetime). The goals of this field campaign were to better understand the underlying pollution problems and to provide a comparison with other metropolitan areas. The field campaign was composed of two distinct periods: a cool period (May 16 – May 30) and a warm period (June 21 – June 28). During the cool period, OH was measured to be ~0.5 x 107 molecules cm-3 and during the warm period around 0.75 x 107 molecules cm-3, values that are fairly typical for many urban areas. These measurements are substantially lower than the modeled output using the Regional Atmospheric Chemistry Mechanism 2 (RACM2), particularly for OH. The outputs OH concentrations around 1.5 x 107 molecules cm-3 during the cool period and ~2 x 107 molecules cm-3 during the warm period, values that are a little higher than those for many urban areas. HO2 was ~ 5-10 pptv during the cool period and above 15 pptv during the warm period, which is generally lower than other urban areas. Generally measured and modeled OH is in better agreement in urban areas, so that Bakersfield is an anomaly that we cannot currently explain. During the cool period OH reactivity was measured to be ~ 5 s-1 during the day, but rose to 15-25 s-1 at night. The measured OH reactivity remained lower than the modeled OH reactivity during the night, but rose to be above the modeled during the day. Throughout the warmer period, the OH reactivity was ~ 10 s-1 midday and 20-25 s1 at night. The measured OH reactivity remained higher than the modeled OH reactivity during the warmer period, indicating that some OH reactants were not measured. These results provide insight to the complicated oxidation photochemistry in Bakersfield, CA and highlight areas where research can be improved on in order to better understand the underlying mechanics behind air pollution problems.