Developing the Pennsylvania State University Measurement of Ozone Production Sensor: MOPSv2.0

Open Access
Baier, Bianca Chae
Graduate Program:
Master of Science
Document Type:
Master Thesis
Date of Defense:
February 13, 2014
Committee Members:
  • William Henry Brune, Thesis Advisor
  • ozone
  • chemistry
  • instrument development
  • instrumentation
  • atmospheric chemistry
  • meteorology
  • air quality
Ambient ozone is a well-known pollutant found in or nearby urban areas that can have adverse health effects on humans and the environment. Air chemistry modeling is used to locate ozone sources, to test ozone mitigation strategies, and to forecast high episodes of ambient ozone. However, it is proving difficult to accurately depict ozone production, P(O3), due to model uncertainties and inconsistencies between modeled and measured species. Testing of model output and chemical mechanisms can be achieved with the direct comparison to measured P(O3). The Penn State MOPSv2.0 provides a more qualitative P(O3) measurement than the MOPSv1.0. Developments to the MOPS improve upon the MOPSv1.0 component limitations, the measurement technique, and the flow through the chambers. Air flow through the chambers is critical; interactions between air sampled at the output of the chambers and chamber walls can add or remove unwanted chemicals from the air. Thus, a great deal of the chamber and flow development aims to reduce the sampling of air that has interacted with the chamber walls. A new design to the MOPS includes the addition of a heating grid, which increases stability in the chambers. The air flow within the chambers has been developed to be much like a sheath flow regime, which aims to deter air sampled at the outlet of the chambers from interacting with the chamber walls. The MOPSv2.0 is now fully automated and includes a highly-efficient NO2-to-O3 converter unit that improves upon the MOPSv1.0 converter unit. In addition, photochemical box model characterization of this new version of the MOPS is much more comprehensive than the MOPSv1.0. Two MOPSv2.0s, MOPS1 and MOPS2, have been designed, built and deployed to Houston, TX during the ``Deriving Information on Surface conditions from COlumn and VErtically resolved observations Relevant to Air Quality" (DISCOVER-AQ) field campaign. The MOPSv2.0s retrieved continuous ozone production rate measurements at two locations: Houston, TX, and Smith Point, TX. Measurements of P(O3) in both locations provide insight into local ozone source locations and ozone production sensitivity regimes, and provide the first calculations of ozone advection rates. MOPSv2.0 measurements of P(O3) while they were running at the same location provide validation for the use of the MOPSv2.0s in a network setting and insight into possible sources of error in the MOPS measurement. The results presented in this thesis demonstrate the potential for the MOPSv2.0 measurement to determine where air quality model output and chemical mechanisms succeed and fail, to aid in the design of air quality standards for mitigating ozone pollution and to provide a direct P(O3) measurement for assimilation into air quality simulation models.