Carbonaceous Aerosol at Urban and Rural Sites in the United States

Abstract

This paper presents the results of over 1300 measurements of organic and elemental carbon in aerosol samples from both urban and rural sites across the United States. These samples were filter segments obtained from the National Air Surveillance Networks for the year 1975. Urban annual averages of organic carbon ranged from 2.7 to 13.4 μgC/m³ and rural averages ranged from 1.2 to 3.4 μgC/m³. Organic carbon accounted for an average of 8 percent of the total aerosol mass at both urban and rural sites. Urban annual averages of elemental carbon ranged from 0.9 to 7.7 μgC/m³ and rural averages ranged from 0.3 to 2.2 μgC/m³. Elemental carbon accounted for an average of 5 percent of the urban aerosol mass concentration and 4 percent of the rural mass concentration. Cities with total carbon concentrations of more than 15 μgC/m³ were Burbank (California), Dallas, New York, and Phoenix. Combustion was indicated as the principal source of organic aerosol.