Articles | Volume 15, issue 2
Research article
20 Jan 2015
Research article |  | 20 Jan 2015

Investigating types and sources of organic aerosol in Rocky Mountain National Park using aerosol mass spectrometry

M. I. Schurman, T. Lee, Y. Sun, B. A. Schichtel, S. M. Kreidenweis, and J. L. Collett Jr.

Abstract. The environmental impacts of atmospheric particles are highlighted in remote areas where visibility and ecosystem health can be degraded by even relatively low particle concentrations. Submicron particle size, composition, and source apportionment were explored at Rocky Mountain National Park using a High-Resolution Time-of-Flight Aerosol Mass Spectrometer. This summer campaign found low average, but variable, particulate mass (PM) concentrations (max = 93.1 μg m−3, avg. = 5.13 ± 2.72 μg m−3) of which 75.2 ± 11.1% is organic. Low-volatility oxidized organic aerosol (LV-OOA, 39.3% of PM1 on average) identified using Positive Matrix Factorization appears to be mixed with ammonium sulfate (3.9% and 16.6% of mass, respectively), while semi-volatile OOA (27.6%) is correlated with ammonium nitrate (nitrate: 4.3%); concentrations of these mixtures are enhanced with upslope (SE) surface winds from the densely populated Front Range area, indicating the importance of transport. A local biomass burning organic aerosol (BBOA, 8.4%) source is suggested by mass spectral cellulose combustion markers (m/z 60 and 73) limited to brief, high-concentration, polydisperse events (suggesting fresh combustion), a diurnal maximum at 22:00 local standard time when campfires were set at adjacent summer camps, and association with surface winds consistent with local campfire locations. The particle characteristics determined here represent typical summertime conditions at the Rocky Mountain site based on comparison to ~10 years of meteorological, particle composition, and fire data.

Short summary
Atmospheric particles can contribute to environmental degradation. An aerosol mass spectrometer was used with positive matrix factorization to explore submicron particle sources in Rocky Mountain National Park, finding that ammonium (3.9%), nitrate (4.3%), sulfate (16.6%), and two types of oxidized organic aerosol (66.9% total) are transported on upslope winds from the urban Front Range, while local campfires contribute 8.4% of mass.
Final-revised paper