| The findings of this study revealed that some urban areas such Jefferson Street, Atlanta, GA (JST) exceeded the routinely used ratio of OM/OC and there is not one single value of the conversion factor that can be applied to both urban and rural areas. The grand overall average ratio from the extraction experiment was of 2.14 +/- 0.17 for JST, which, remarkably agrees with the grand average ratio calculated from the second approach. The grand overall average ratio was 2.16 +/- 0.43 using the mass balance between the PM 2.5 and the speciated components for JST. The concentration-weighted average ratio (Cz) for Atlanta, GA was 1.55 +/- 0.07, which is the lowest possible value due to the limited number of the quantified compounds.; The findings from the sequential extraction of the filter samples from five IMPROVE national parks sites showed an overall grand average ratio of 1.92 +/- 0.40, and the ratio ranged from 1.58 at Indian Gardens, AZ (INGA) in the Grand Canyon to 2.58 at Mount Rainier (MORA). Using the second approach to calculate the OM/OC for the five national parks sites showed an overall grand average ratio of 1.88 +/- 0.35. The overall OM/OC ratio for about 49 sites in United States based on 38,829 samples was 2.02 +/- 0.32.; The combined results suggest that the commonly accepted value of 1.4 for the OM/OC ratio is too low and inapplicable to aerosols in either urban or rural areas impacted by different emission sources. A ratio of 2.0 is more likely appropriate. (Abstract shortened by UMI.)... |
