Project Results

Reactive nitrogen is a precursor to the formation of ground-level ozone, also known as photochemical smog.  Ozone frequently exceeds the EPA limit in the Uintah basin in winter when the ground is covered in snow, which can lead to the recycling of reactive nitrogen and enhanced ozone concentrations.  We found that this recycled source of reactive nitrogen in the Uintah basin is negligible compared to direct emissions from local fossil fuel burning.

About This Project

Ask the Scientists

What is the context of this research?

Ground-level ozone forms during chemical reactions in the atmosphere between volatile organic compounds (VOCs) and nitrogen oxides, both of which are emitted from natural gas fracking. Ozone formation also requires sunlight; thus, sunny, high-populated areas such as Los Angeles are best known for having unhealthy levels of ozone. So it was a surprise when extremely high levels of ground-level ozone were measured during the winter in remote locations of Wyoming, Utah, and Colorado. Normally pristine areas such as Rocky Mountain National Park are now exceeding federal ozone standards. These areas all have something in common - they are high-density areas of natural gas fracking. However, high ozone amounts in the Uintah Basin occur only when snow is on the ground. Might snow act as a catalyst for nitrogen oxide formation? The recycling of nitrogen oxides in the snow may limit the effectiveness of controls on emissions from the fracking industry. Understanding the importance of snow on the recycling of pollutants is one process that is critical to understand in order to design effective policies to reduce air pollution levels in these locations.

What is the significance of this project?

Breathing ground-level ozone has a number of negative health impacts that mainly impact our respiratory (lung) function. The Clean Air Act requires the EPA to set limits on ozone and five other pollutants. The current limit for ozone is set to 75 parts-per-billion (ppbv); however, ozone concentrations in the Uintah Basin frequently exceed the EPA limit and can reach as high as twice this value. These high ozone concentrations are unhealthy for everyone, and are especially dangerous for sensitive people such as children and the elderly. Designing policies that will result in the reduction of ozone concentrations down to healthier levels requires an understanding of where the ingredients for ozone formation, VOCs and nitrogen oxides, are coming from. There has been considerable effort during field campaigns in previous winters to understand the ozone problem, and much has been learned. However, important uncertainties remain, most notably in the role of snow on the recycling of nitrogen oxides.

What are the goals of the project?

We will collect nitrate aerosol from the atmosphere and the snow from Jan. 13 – Feb. 7 in Utah's Uintah Basin and measure its isotopic composition in our lab at the UW. Nitrate is a major sink for nitrogen oxides, and its isotopic composition reflects that of nitrogen oxides. The main natural source of nitrogen oxides in the Uintah Basin is from chemical reactions within the snow. The snow measurements will be used to quantify the flux of nitrogen oxides from the snow, while the atmospheric measurements will be used to quantify the amount of nitrogen oxides originating from the snow compared to from fracking. This project will be part of a larger field campaign with scientists from the U.S. and Canada, and will make a significant contribution to our understanding of the ozone problem in the Uintah basin. The information obtained during this field campaign is critical for designing effective strategies to improve local air quality.