Toward a Quantitative Assessment of the Influence of Regional Emission Sources on Ozone Production in the Colorado Front Range
Abstract:Photochemical ozone production results from the oxidation and reaction of volatile organic compounds (VOCs) with nitrogen oxides (NOx = NO2 + NO). As with many US urban regions, ozone levels observed in the Northern Front Range Metropolitan Region of Colorado are influenced by urban emissions of NOx and VOCs. Despite nationwide decreases in these urban emissions, the Front Range of Colorado is one of the few US locations where ozone is currently increasing. It has also recently gone out of compliance with national ambient air quality standards for ozone during summer months. High ozone in Colorado may result from a number of factors, including long-range transport from Asia, increased influence of biomass burning, population increases, or increased emissions from oil and gas activities. The Front Range is home to the Denver-Julesburg (D-J) Basin, which has recently been experiencing a rise in oil and natural gas (O&NG) activity associated with the increase in non-conventional drilling techniques. The VOC and NOx emissions from O&NG activity in close proximity to the urban area may uniquely influence ozone in this region.
This presentation will focus on using reactive nitrogen (NOx, NOy) and ozone measurements from a tall (300 m) tower to study the influence of local emissions on Front Range ozone. The tower is located between the D-J Basin and agricultural areas to the north and the Denver metro area to the south. In-situ reactive nitrogen and ozone measurements were collected using a custom Cavity Ring-Down instrument. Additional CH4, CO, and NH3 measurements from the tower serve as tracers for O&NG, urban, and agricultural emissions. Concurrently measured aircraft data is used to confirm the relationships between the tracer species. This presentation will discuss methods for determining the contributions of different emission sources to Front Range ozone, with a focus on differentiating the influence of urban and O&NG sources.