Recent measurements in Mexico City show a high correlation (r2 > 0.9 ) between CO and the light absorption coefficient of aerosols. This is not unexpected as both CO and soot, the principal component of absorbing particles, are the result of incomplete combustion. Since the absorption coefficient is linearly related to the mass mixing ratio of soot, CO can be used as a surrogate for soot concentrations once the physical basis that links these two atmospheric components is well understood. The amount of soot and CO produced by combustion is proportional to the type of fuel that is used and the amount of available oxygen; thus, it is likely that the soot-CO relationship varies from city to city. The ability to estimate soot concentration from CO measurements is highly promising, however, because of the ease of measuring CO compared to soot, the abundance of past CO measurements that could be analyzed with this relationship, and the potential for better monitoring of soot in the future.
The present study discusses the physics and chemistry that link CO and soot and describes an analysis approach that can provide a more accurate assessment of urban soot emissions than is available at this time
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