Despite great efforts undertaken in the past decades to address the problem of high ozone concentrations, our understanding of the key precursors that control tropospheric ozone production remains incomplete and uncertain. Sensitivity of ozone production to nitrogen oxides (NOx) and volatile organic compounds (VOCs) represents a major uncertainty for oxidant photochemistry in urban areas and is expected to vary from location to location and from time of a day. Understanding of the non-linear relationship between ozone production and its precursors is critical for the development of an effective ozone control strategy.
The DISCOVER-AQ campaign in Houston in August/September 2013 provided rich data sets to examine and improve our understanding of atmospheric photochemical oxidation processes related to the formation of secondary air pollutants like ozone and particulate matter (PM). In this project, an analysis of ozone production and its sensitivity to NOx and VOCs will be performed. An observation-constrained box model based on Carbon Bond mechanism, Version 5 (CB05) will be used to study the photochemical processes along the NASA P-3B flight track, as well as at eight surface sites where the P-3B conducted spiral profiles. Ozone (O3) production rates will be calculated at different locations and at different times of day and its sensitivity to NOx and VOCs will be investigated. Spatially and temporally resolved ozone production and its sensitivity will also be investigated.
This project specifically addresses one of the AQRP priority research areas: Improving the understanding of ozone and particulate matter (PM) formation, and quantifying the characteristics of emissions in Texas through analysis of data collected during the DISCOVER-AQ campaign. The following tasks will be performed in this project:
(1) An investigation of spatial variations of ozone production and its sensitivity to NOx and VOCs in Houston during DISCOVER-AQ.
(2) An investigation of temporal variations of ozone production and its sensitivity to NOx and VOCs in Houston during DISCOVER-AQ.
(3) Investigate non-uniform emission reduction of O3 pollution in Houston using spatial and temporal variations of ozone production and its sensitivity to NOx and VOCs.
(4) Calculation of ozone production efficiency (OPE) at different locations using the ratio of ozone production rate to the NOx oxidation rate calculated in the box model.
These activities will strengthen our understanding of O3 production, which is essential to meet the primary and secondary National Ambient Air Quality Standards (NAAQS) for ozone.