Mass specific optical absorption coefficients of mineral dust components measured by a multi wavelength photoacoustic spectrometer

Reviewers' comments: This manuscript describes the use of a four-wavelength (266 nm, 355 nm, 532 nm, 1064 nm) photoacoustic spectrometer to measure the absorption of various mineral dust (MD) components in aerosol form. The measured absorption values are combined with aerosol size distribution and mass measurements to derive mass specific absorption coefficients (MAC’s) for all seven components. These values could be of utility to others wishing to estimate absorption by mineral dust aerosols or, as the authors suggest, for comparing to bulk measurements. Comparisons to absorption redicted by Mie theory and based on previous (bulk) measurements of indices of refraction demonstrate general agreement between the two approaches but also indicate some discrepancy which may, or may not, be attributed to deficiencies in the methods used to make the bulk measurements.