Daily Variation in Particle-Phase Source Tracers in an Urban Atmosphere |
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| Authors: | Rebecca J Sheesley James J Schauer Mark Meiritz Jeffrey T DeMinter Min-Suk Bae Jay R Turner |
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| Affiliation: | 1. Environmental Chemistry and Technology Program , University of Wisconsin , Madison, Wisconsin, USA;2. Environmental Chemistry and Technology Program , University of Wisconsin , Madison, Wisconsin, USA;3. Wisconsin State Laboratory of Hygiene , University of Wisconsin , Madison, Wisconsin, USA;4. Wisconsin State Laboratory of Hygiene , University of Wisconsin , Madison, Wisconsin, USA;5. Department of Energy, Environmental and Chemical Engineering , Washington University , St. Louis, Missouri, USA |
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| Abstract: | One full year of daily 24-hour fine particulate matter samples collected in East St. Louis, IL at the EPA funded St. Louis-Midwest Supersite were analyzed for organic carbon (OC), elemental carbon (EC) and non-polar organic tracers including polycyclic aromatic hydrocarbons (PAH(s)), hopanes, and alkanes. Two different analytical methods were used for analysis, solvent extraction gas chromatography/mass spectrometry (GCMS) and thermal desorption GCMS (TD-GCMS). The TD-GCMS method was equivalent to the solvent extraction GCMS method for key molecular markers. Select PAH(s) and alkanes were found to have extreme events within the annual study which had daily 24-hour concentrations that were 10 to 22 times higher than the annual average daily concentration. The OC and EC maxima were only 3 to 5 times higher than the annual average. To further assess the impact of point sources and to evaluate the compatibility of the two organic speciation methods, the six potential every sixth day annual averages were calculated and compared. The extreme concentration days were large enough, in the case of benzoa]pyrene, to make every sixth day analysis not representative of the true annual average even with events greater than the 99th percentile of the annual distribution removed. The final analysis calculated day of the week averages for select representative organic tracers and revealed that gasoline motor vehicle tracers and OC do not have a distinct day of the week trend. EC, believed to be largely impacted by diesel exhaust, had a midweek concentration peak. These trends cannot necessarily be extrapolated to other urban areas or other events. |
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