A Processor-Controlled Multisample Soot Photometer

The technique of the integrating plate method for the measurement of aerosol light absorption has been expanded significantly in a multisample soot photometer. The instrument consists of a double-beam, single detector, digital measurements, and control system. Transmission changes due to particle absorption on the order of 10 −4 can be detected with the new instrument, corresponding to a few nanograms of elemental carbon per sample. The photometer has been calibrated with known amounts of a well-characterized reference soot. The usefulness of the instrument is demonstrated with field results of three areas of application: aerosol light absorption at a Swedish remote area station, soot in cloud water, and light-absorbing particles in an Arctic ice core.