Research Projects

Project at a Glance

Project Status: complete

Title: Sampling and analysis of organic aerosol: carbonaceous species methods comparison study.

Principal Investigator / Author(s): Turpin, Barbara J

Contractor: Oregon Graduate Center, Department of environmental Science and Engineering

Contract Number: A5-149-32


Research Program Area: Atmospheric Processes


Abstract:

Field testing and implementation of a time-resolved in situ carbon analyzer, examination of organic aerosol sampling artifacts, and the investigation of organic aerosol speciation took place during the Carbonaceous Species Methods Comparison Study (CSMCS) in Glendora, California, during August, 1986. Uncertainties due to sample handling and loss of organic carbon during storage were eliminated in the in situ carbon analyzer by combining the sampling and analysis functions into a single instrument. Comparison of the diurnal profiles of organic carbon with those of elemental carbon, a tracer for primary combustion aerosol, and ozone, an indicator of photochemical activity, provided evidence for the secondary formation of organic aerosol in the atmosphere. From the study of organic sampling artifacts organic carbon concentrations on quartz fiber backup filters behind Teflon front filters (TQ) were found to be about 1.4 times greater than concentrations on quartz fiber backup filters behind quartz fiber front filters (QQ). Organic carbon concentrations on quartz fiber front filters showed a strong face velocity dependence which was virtually eliminated when apparent organic carbon concentrations from TQ backups are subtracted from QQ front filter concentrations. In an additional experiment samples were collected with different combinations of three unknowns: adsorbed organic vapor, volatilized organic particulate material, and organic aerosol. Both experiments indicated that adsorption is the dominant artifact in the collection of organic aerosol on quartz fiber filters. Saturation of adsorbed vapor was observed in a laboratory experiment but was not observed for the loadings obtained in the Carbonaceous Species Methods Comparison Study data. Samples were also analyzed by direct thermal desorption / gas chromatography / mass spectroscopy (TD / GC / MS). Carboxylic acid, polycyclic aromatic hydrocarbon, and alkane concentrations were examined for diurnal variations and differences in front and backup filters.


 

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