June 1981

Document Type


Degree Name



Dept. of Environmental Science


Oregon Graduate Center


This study interpreted ambient aerosol carbon data obtained during a one-year data base study conducted by the Oregon Department of Environmental Quality in Medford, Oregon. Twenty-four hour total and fine aerosol samples were taken at an urban site (Medford Justice Building), an industrial site (White City), and a background site (Dodge Road). Organic and elemental carbon analyses were done on these samples with an automated analysis system developed at the Oregon Graduate Center. These data demonstrate the importance of carbon as a component of both total (aerosol collected with a high volume sampler) and fine (less than 2 µm) aerosol. At the Justice Building and White City sites ambient carbon concentrations of total carbon ranged from a low value of 10 µg/m3 in the summer to high values of about 100 µg/m3 during the winter. Fine carbon aerosol comprised about half of these values. As a fraction of aerosol mass carbon composition ranges from 15 to 50% for total aerosol and 25 to 60% for fine aerosol at these sites. A series of models were developed to characterize fine aerosol carbon in terms of meteorological dispersion and two general carbon sources: carbon not associated with space heating and carbon resulting from space heating emissions. Meteorological dispersion was characterized by two independent methods. One was a box model in which the dispersion parameter was the inverse product of wind speed and mixing height. The other used the ambient lead concentration as a measure of dispersion. Both methods produced similar results. Space heating demand was characterized by heating degree day values. For the urban site this modeling procedure explained 89% of the variance in the fine carbon concentration. It also showed that in winter the ratio of space heating derived carbon to non-space heating carbon ranged from 4 to 6. For data from White City and Dodge Road these models accounted for 56% of the fine carbon variance. At both these sites the ratio of space heating aerosol carbon to non-space heating aerosol carbon ranged from 1 to 1.5.





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