Sulfates as pollution particulates: catalytic formation on carbon (soot) particles.

Experimental evidence (obtained by electron spectroscopy for chemical analysis) is presented which shows that finely divided carbon (soot) particles may play a major role in the catalytic oxidation of sulfur dioxide to sulfate in polluted atmospheres. The results obtained with sulfates produced in the laboratory by the oxidation of sulfur dioxide on graphite particles and combustion-produced soot particles are compared with the properties and behavior of ambient sulfates. The proposed sulfur dioxide oxidation mechanism is qualitatively consistent with field observations.