You can’t blame it on the snow
Maria has completed her model calculations and has estimates of the role of snow in the recycling of reactive nitrogen in the Uintah Basin. I wanted to share her main conclusions with you here.
The figure below shows her calculated fluxes of reactive nitrogen from the snow (y-axis) in the Uintah basin during the field campaign in January – February 2014 (dates are on the x-axis). To calculate these fluxes, she used her observations of the optical properties of the snow, and the model is constrained by her observations of nitrate concentrations and isotopes in the snow during the field campaign.
The fluxes of reactive nitrogen were highest at the beginning half of the campaign because that is when the nitrate concentrations in the very surface layer of the snow were highest. Remember that it is the breakdown of nitrate in the snow by sunlight that is the source of reactive nitrogen from the snow to the atmosphere. Snow nitrate concentrations were highest at the beginning of the campaign because it hadn't snowed for over a month, and nitrate from that atmosphere was depositing to and accumulating on the surface of the snow during that time. You can see that the fluxes occur only during the daytime, because it requires sunlight. Fluxes decrease dramatically after the fresh snowfall event on January 31. The decrease occurred because the fresh snow diluted the nitrate concentrations in the surface of the snow.
We compare these calculated fluxes (on the order of 109 molecules/cm2/s at noon) with estimates of emissions of reactive nitrogen from oil and gas activities (on the order of 1012 molecules/cm2/s day and night). The comparison reveals that fluxes from the snow are several orders of magnitude lower than emissions from human activities in the Uintah basin. Although active recycling of reactive nitrogen is occurring in the snow during the entire field campaign, it is negligible compared to sources of reactive nitrogen derived from human activities. This means that recycling of reactive nitrogen in the snow can be safely ignored in air quality models designed to inform policy makers on the most effective strategy for reducing ground-level ozone concentrations in this region.
Maria will be defending her Ph.D. dissertation on Monday August 10 in Johnson Hall room 175 at 10:30am. It is open to the public, so if you are in town and available at that time, you are welcome to come by! She will talk about this project as well as her research in Greenland and Antarctica.
Thanks again for your support! I will continue to update you on the status of her publication.