Single scattering albedo of fine mineral dust aerosols controlled by iron concentration

Aerosol optical properties have been investigated at two wavelengths (405 nm in the violet and 870 nm in the near IR spectral region) for entrained PM_2.5 from 10 soil samples representing the Arabian Peninsula, the Sahara and Sahel regions and samples from Northeast Africa and South-Central Asia. Findings include that the SSA at both wavelengths is dominated by and linearly correlated with the iron content of the entrained PM_2.5 with much lower SSAs at 405 nm than at 870 nm. This result points towards the potential use of SSA remote sensing to measure aerosol iron content and vice versa, the measurements of iron content with simple filter sampling followed by XRF analysis yielding information about aerosol SSA as needed for aerosol radiative forcing calculations and modeling. However, these potential applications may be hindered by unknown and variable MD size distributions that affect SSA and by ambient MD often being mixed with other absorbing or non-absorbing aerosols such as combustion aerosols or sea spray, which would also modify ambient SSA.