RJLG experts are acknowledged for a paper published in the Journal of the Air & Waste Management Association. Authors include Gary S. Casuccio and Traci L. Lersch.
Abstract. The organic carbon (OC) and elemental carbon (EC) content of filter-based, 24-hr integrated PM10-2.5 was measured at two urban and two rural locations in the southeastern U. S. On average, total carbon (OC + EC) comprised roughly 30% of PM10-2.5 mass at these four sites. Carbonate carbon was measured on a subset of samples from three sites and was found to be undetectable at a rural site in central Alabama, < 31 2% of PM10-2.5 at an urban site in Georgia and < 10% of PM10-2.5 at an urban-industrial site in Alabama.
Manual scanning electron microscopy (SEM) and computer controlled SEM (CCSEM) along with energy dispersive X-ray spectroscopy (EDS) were used to identify individual carbonaceous particles in a selected subset of samples collected at one rural site and one urban-industrial site in Alabama. CCSEM results showed that biological material (e.g., fungal spores, pollen and vegetative detritus) accounted for 60-70% of the carbonaceous mass in PM10-2.5 samples with concentrations in the range of 2-16 μg/m338. Samples with higher PM10-2.5 concentrations (25-42 μg/m339 ) at the urban-industrial site were found by manual SEM to have significant amounts of unidentified carbonaceous material, likely originating from local industrial activities. Both filter-based organic and elemental carbon concentrations and SEM identified biological material tended to have higher concentrations during warmer months. Upper limits for organic mass to organic carbon ratios (OM/OC) are estimated for PM10-2.5 samples at 2.1 for urban sites and 2.6-2.7 for rural sites.
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