Measurements of OC and EC in coarse particulate matter in the southeastern United States.
The organic carbon (OC) and elemental carbon (EC) content of filter-based, 24-hr integrated particulate matter with aerodynamic diameters between 2.5 and 10 microm (PM10-2.5) was measured at two urban and two rural locations in the southeastern United States. On average, total carbon (OC + EC) comprised approximately 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, less than 2% of PM10-2.5 at an urban site in Georgia, and less than 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 microg/m3. Samples with higher PM10-2.5 concentrations (25-42 microg/m3) 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 OC and EC concentrations and SEM-identified biological material tended to have higher concentrations during warmer months. Upper limits for organic mass (OM) to OC ratios (OM/OC) are estimated for PM10-2.5 samples at 2.1 for urban sites and 2.6-2.7 for rural sites.
Edgerton
Eric S
ES
Atmospheric Research & Analysis, Inc., Cary, NC 27513, USA. ericedge@gte.net
Casuccio
Gary S
GS
Saylor
Rick D
RD
Lersch
Traci L
TL
Hartsell
Benjamin E
BE
Jansen
John J
JJ
Hansen
D Alan
DA
D000397:Air Pollution / Q000032:analysis*; D002244:Carbon / Q000032:analysis* / Q000737:chemistry; D004784:Environmental Monitoring; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis* / Q000737:chemistry; D011058:Pollen / Q000648:ultrastructure; D015144:Southeastern United States
D052638:Particulate Matter; D002244:Carbon