Continuous spectra of the aerosol absorption coefficient by an integrating-sphere spectral system

Elena Montilla, Sandra Mogo, Victoria Cachorro and Angel de Frutos


An integrating sphere spectral system has been developed that allows the measurement
of continuous spectra of light absorption coefficients, saðlÞ of atmospheric aerosols. This
system is based on the filter attenuation method covering the spectral wavelength
range 320–800 nm with a variable spectral resolution. The sample filters had to be
diluted in chloroform previous to the light attenuation measurements and hence the
system cannot measure continuously but only on the basis of daily sampling.
The system was calibrated using known amounts of absorbing and non-absorbing
industrial substances at relevant atmospheric absorption levels. The resulting values of
saðlÞ were compared with those delivered by a commercial photometer (particle soot
absorption photometer) in the laboratory and also with field measurements, with a
maximum discrepancy of 12.5% for atmospherically relevant values. The measurement
uncertainty of the integrating sphere system is about 10% maximum. The importance of
obtaining continuous spectral data is the possibility to determine the A˚ ngstro¨m
absorption exponent, aa, in different spectral ranges, including the UV. This exponent
can then be used to help in obtaining the aerosol composition information.

DOI:, 2011.

Categories: Publications