Airborne Gas and Particle Concentrations During the 2006 Rocky Mountain Airborne Nitrogen and Sulfur (RoMANS) Study

Florian M. Schwandner, Suresh Raja, Katherine B. Beem, Amy P. Sullivan, Taehyoung Lee
Gavin R. McMeeking, Christian M. Carrico, Courtney A. Gorin
Dept. of Atmospheric Science, Colorado State University, Fort Collins, Colorado

Derek E. Day
National Park Service/CIRA, Colorado State University, Fort Collins, Colorado

Jeffrey L. Collett, Jr., Sonia M. Kreidenweis
Dept. of Atmospheric Science, Colorado State University, Fort Collins, Colorado

Jenny Hand and William C. Malm
National Park Service/CIRA, Colorado State University, Fort Collins, Colorado

In the Rocky Mountain Airborne Nitrogen and Sulfur (RoMANS) study, airborne gas and fine particle concentrations were measured during spring (March - April) and summer (July - August) 2006. Sampling operations encompassed sites in Northern Colorado, centered in and around Rocky Mountain National Park (RMNP), spanning from Dinosaur National Monument in the West to Grant (NE) in the East. 24-hour integrated samples of gaseous ammonia, nitric acid and sulfur dioxide were acquired in tandem with fine particle (PM 2.5) concentrations of ammonium, nitrate, and sulfate. Results show substantially higher concentrations of ammonia at sites east of RMNP during both seasons. Gaseous ammonia concentrations exceeded concentrations of fine particle ammonium, and concentrations of both sulfur dioxide and nitric acid, at these eastern sites in both spring and summer. N(-III) tended to be more evenly split between gases and particles at higher elevation sites. N(V) tended to be fairly evenly split between gases and fine particles in the spring measurement period. Nitric acid concentrations generally exceeded fine particle nitrate concentrations during summer. During the hotter summer months, average gaseous nitrogen concentrations in northeastern Colorado were almost double the concentrations during the spring campaign. Sulfur dioxide concentrations were slightly higher in spring throughout the eastern and RMNP sites, while sulfate showed the opposite trend. Both 24 hr and higher time resolution measurements suggest that the highest concentrations of nitrogen species in RMNP are experienced during periods of transport from the east.