Relationships between visible extinction, absorption and mass concentration of carbonaceous smokes

A linear relation, independent of the size distribution, between visible and near-i.r. extinction coefficient σ_e(m^-1) and mass concentration M (gm^-3) of carbonaceous smokes is predicted. For a wavelength λ = 0.55μm the relation is σ_e/M = 9.5m²g^-1, assuming a particle density of 2gcm^-3. The relation is in good agreement with measurements on coal-fired stack plumes, oil smoke, soot and diesel exhaust that are available in the literature. A similar relationship between carbonaceous smoke visible and near-i.r. absorption coefficient σ_a, and mass concentration is also derived. The relations suggest that integrated mass concentration along a path within a carbonaceous smoke cloud can be inferred from measurement of the transmission from one end of the path to the other, and that the mass concentration at a particular location in the cloud can be determined from an in situ measurement of aerosol absorption at that location with a visible or near-i.r. laser spectrophone.