Characteristics and consequences of soot in the atmosphere

Abstract

Soot, as defined in this paper, consists of the primary carbonaceous particulate emissions from combustion sources. In the simplest terms, it can be divided into an organic carbon fraction that consists of a large number of organic compounds, and an elemental carbon fraction that has a graphite-like structure with many structural defects. It is because of these defects that elemental carbon absorbs light, reduces visibility, and serves as a catalyst for certain chemical reactions in the atmosphere. Presently, two of the most important sources of soot are diesel engines and woodburning, but virtually every process that burns carbonaceous fuel emits soot. As a result of the ubiquitous emission sources, measurable concentrations of soot occur in remote as well as urban areas. As expected, urban and suburban areas experience the highest concentrations. However, significant amounts of soot are found in remote areas such as the Arctic because of the long residence time of the soot particles in the atmosphere. In addition, the soot appears to be present in some areas in sufficient amounts to be a significant contributor to visibility reduction.