The Aethalometer® draws the sample air stream through a filter tape with a flow rate from 2 to 5 liters per minute. Aerosols are collected on two spots on the tape, and are illuminated by a multi-wavelength light source. Detectors measure the attenuation of light by the absorbing components of the aerosols, relative to a reference through an un-exposed portion of the tape.
The filter tape advances on a time schedule, or when a pre-set loading limit is reached. The instrument operates completely automatically from power-up, and provides continuous real-time data with no operator attention.
Sample collection and analysis is performed on two filter spots simultaneously at different flow rates. Mathematical combination of the data eliminates the “Filter Loading Effect” and provides continuously corrected data in real time with no discontinuities at filter advances.
The Aethalometer® analyzes the sample at 7 optical wavelengths from UV (370 nm) to IR (950 nm). Optical absorption by different aerosol components may have different variations across the spectrum: most notably, the differences between diesel exhaust and emissions from biomass burning. The 7-wavelength data allows for a separation of these components, providing a real-time speciation of the aerosol sources and a determination of their origins.
