5th Conference on Atmospheric Chemistry: Gases, Aerosols, and Clouds


Characterization and Analysis of Ultrafine and Fine Particles at a Forest Site Near the Great Smoky Mountains National Park

Meng-Dawn Cheng, ORNL, Oak Ridge, TN; and R. L. Tanner




Meng-Dawn Cheng*1 and Roger L. Tanner2

1Oak Ridge National Laboratory, Environmental Sciences Division, Oak Ridge, TN 37831, USA

2Tennessee Valley Authority, Environmental Research Center, Muscle Shoals, AL 35662, USA

Abstract Continuous measurements were taken during a 22-day campaign held in the summer of 2000 at a forest site close to the Great Smoky Mountains National Park in eastern Tennessee. The campaign was focused on investigating the relationships between ultrafine/fine particles and gaseous species observed. A varimax-rotation factor analysis was performed to explore the relationship of the fine and the ultrafine particle number concentrations, the gaseous species (NOx, NOy, CO, SO2, and O3) concentration, the mean wind speed and the solar radiation. A 6-factor model was found to optimally resolve 79.7% of the variability embedded in the data. The model suggests that 31.4% of the data variability were caused by the ultrafine particles (the diameters smaller than or equal to 100 nm). However, it was difficult to label this factor without additional chemistry information of the particles. No gas species were identified on Factor 1 indicating the ultrafine particles observed in this study were not associated with primary source emissions. The decoupling of the ultrafine particles from the fine particles also implies that the former ones might have been produced and transported to the site by separate mechanisms from those of the fine particles. Factor 2 included the PM2.5 mass concentration and the number concentrations of particles in the diameter range of 101 to 400 nm. The loading pattern on Factor 2 led to the conclusion that this factor was contributed by regional transport. Factor 3 includes CO, NO2, reactive odd nitrogen (NOy), and SO2. These were contributed by primary source emissions. The mean wind speed and ozone were loaded in Factor 4 that was labeled as ozone transport. This factor could imply a decoupling of ozone transport from the regional transport of the fine particles (i.e., Factor 2). Solar radiation was singly included in the fifth factor indicating it is a unique factor. The quality of NO data was marginal and the variable was distilled singly by the factor-analysis model into Factor 6. A multiple regression analysis finds that PM2.5 mass concentration was best explained by CO, O3, and the number concentrations of the fine particles, particularly, in the diameter range between 101 and 400 nm. Two unique events, among several interesting ones, in which the number concentrations of 31-51 nm particles dramatically increased by a factor of 10 in 30 minutes. The peak reached 40,000 cm-3 from the level of 1,000 cm-3 lasting for a couple of hours during the campaign. Particles in the adjacent size ranges (below and above 31-51 nm size bin) exhibited in-phase increases during these events, but the changes were much less dramatic. The implications of such events in a forest area will be discussed.

*Corresponding Author. Tel. (865) 241-5918; fax: (865) 576-8646, Email address: chengmd@ornl.gov (M. D. Cheng).

The submitted manuscript has been authored by a contractor of the U.S. Government under contract DE-AC05-00OR22725. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.

extended abstract  Extended Abstract (388K)

Session 7, Aerosols
Thursday, 13 February 2003, 8:30 AM-2:15 PM

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