Atmos. Chem. Phys. Discuss., 7, 8159-8192, 2007
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
The role of iron and black carbon in aerosol light absorption
Y. Derimian1,4, A. Karnieli1, Y. J. Kaufman2, M. O. Andreae3, T. W. Andreae3, O. Dubovik4, W. Maenhaut5, and I. Koren6
1Major part of this study was done while worked at: Jacob Blaustein Institute for Desert Research, Ben Gurion University of the Negev, Israel
2NASA Goddard Space Flight Center, NASA Goddard SFC, USA
3Max Planck Institute for Chemistry, Mainz, Germany
4Laboratoire de Optique Atmosphérique, Université de Lille 1/CNRS, Villeneuve d'Ascq, France
5Ghent University (UGent), Department of Analytical Chemistry, Institute for Nuclear Sciences, Gent, Belgium
6Department of Environmental Sciences, Weizmann Institute, Rehovot 76100, Israel

Abstract. Iron is a major component of atmospheric aerosols, influencing the light absorption ability of mineral dust, and an important micronutrient that affects oceanic biogeochemistry. The regional distribution of the iron concentration in dust is important for climate studies; however, this is difficult to obtain since it requires in-situ aerosol sampling or simulation of complex natural processes. Simultaneous studies of aerosol chemical composition and radiometric measurements of aerosol optical properties, which were performed in the Negev desert of Israel continuously for about eight years, suggest a potential for deriving a relationship between chemical composition and light absorption properties, in particular the spectral single-scattering albedo.

The two main data sets of the present study were obtained by a sun/sky radiometer and a stacked filter unit sampler that collects particles in coarse and fine size fractions. Analysis of chemical and optical data showed the presence of mixed dust and pollution aerosol in the study area, although their sources appear to be different. Spectral SSA showed an evident response to increased concentrations of iron, black carbon equivalent matter, and their mixing state. An empirical relationship that relates the spectral SSA, the percentage of iron in total particulate mass, and the pollution components was derived. Results calculated using this relationship were compared with measurements from dust episodes in several locations around the globe. The comparison reveals that dust over the eastern Mediterranean and Saudi Arabia contains less iron than that over Asia and the Sahara desert.

Citation: Derimian, Y., Karnieli, A., Kaufman, Y. J., Andreae, M. O., Andreae, T. W., Dubovik, O., Maenhaut, W., and Koren, I.: The role of iron and black carbon in aerosol light absorption, Atmos. Chem. Phys. Discuss., 7, 8159-8192, doi:10.5194/acpd-7-8159-2007, 2007.
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