Rocky Mountain National Park reduced nitrogen source apportionment

Abstract

Excess wet and dry deposition of nitrogen-containing compounds are a concern at a number of national parks. The Rocky Mountain Atmospheric Nitrogen and Sulfur Study Part II (RoMANS II) campaign was conducted from November 2008 to November 2009 to characterize the composition of reactive nitrogen and sulfur deposited in Rocky Mountain National Park (RMNP). RoMANS II identified reduced nitrogen as the major contributor to reactive nitrogen deposition in RMNP, making up over 50% of the total. Motivated by this finding, the particulate source apportionment technology within the Comprehensive Air Quality Model with extensions was used here to estimate source apportionment of reduced nitrogen concentrations at RMNP. Source apportionment results suggest that approximately 40% of reduced nitrogen deposition to RMNP comes from ammonia sources within Colorado. However, the model evaluation also suggests that this number could be underrepresenting ammonia sources in eastern Colorado due to the difficulty of capturing upslope airflow on the eastern side of the Continental Divide with meteorological models. Emissions from California, the western model boundary, and the Snake River Valley in Idaho, the next three most influential sources, contribute approximately 15%, 8%, and 7%, respectively, to total reduced nitrogen measured in RMNP. Within Colorado, about 61%, 26%, and 13% of the total Colorado contribution comes from sources to the east of the Continental Divide, sources to the west of the Continental Divide, and from the park itself.

Sources of nitrogen deposition in Federal Class I areas in the US

“…This is consistent with the spatial distributions of the emissions of NH 3 compared to those of NO x surrounding the park. The high sensitivity of reduced Nr to sources west of RM in California and Idaho agrees with other recent studies (Benedict et al, 2013b;Malm et al, 2013;Thompson et al, 2015).…”

“…Still, adequate model performance in other seasons and locations suggests a considerable contribution of dry deposition of NH 3 in some locations and seasons, consistent with Schwede and Lear (2014). A significant fraction of Nr deposition in the central mountain region (including Rocky Mountain National Park) is estimated to be in the form of reduced nitrogen, similar to several other recent studies (Benedict et al, 2013b;Malm et al, 2013;Thompson et al, 2015), although such estimates are sensitive to model uncertainties in NH 3 emissions and modeled NO − 3 . The spatial and sectoral distribution of annual Nr deposition sources are investigated using the adjoint of GEOSChem.…”

“…Steep initial rises for JT and SQ correspond to the influence of local urban centers (Los Angeles and San Francisco, respectively). Additional analysis was performed for RM, given the prevalence of studies on Nr deposition in this area (Benedict et al, 2013b;Malm et al, 2013;Thompson et al, 2015). Figure 7 shows the source distributions of oxidized and reduced Nr deposition.…”

Impacts of the Denver Cyclone on regional air quality and aerosol formation in the Colorado Front Range during FRAPPÉ 2014

“…To assess the extent of boundary layer mixing and dilution, potential temperature profiles measured by the Pennsylvania State University NATIVE integrated ozonesonde (A. M. Thompson et al, 2015), launched near Platteville (40 • 10 53 N, 104 • 43 36 W) during NASA DISCOVER-AQ, were examined. Except for 26 July when at 12:00 MST the boundary layer (BL) height was observed to be at 2200 m a.s.l., midday BL heights on other days were consistently at ∼ 3400-3600 m a.s.l.…”

“…Recent studies have shown O & G emissions of non-methane hydrocarbons (NMHC) such as short-chain alkanes (C 1 -C 4 ) and alkenes act as precursors to ozone (Pétron et al, 2012(Pétron et al, , 2014Edwards et al, 2013;Gilman et al, 2013;Karion et al, 2013), but the potential for these emissions to contribute to primary and secondary OA in the region has not been investigated. Additionally, agricultural practices and powerplant operations in the greater Colorado region contribute to visibility impairment and ecosystem degradation through formation of secondary nitrate and sulfate-containing compounds (Williams and Tonnessen, 2000;Nanus et al, 2003;Blett et al, 2004;Burns, 2004;Boy et al, 2008;Malm et al, 2013;Mast and Ely, 2013; T. M. Thompson et al, 2015).…”