Light absorption by black sand dust

Light absorption by fine and coarse aerosols derived from Hawaiian black sand was determined by light transmission. The real part of the refractive index of this material was measured directly, and the imaginary part was estimated. The measured light absorption coefficients (B(ap)) were adjusted for multiple scattering artifacts by use of absorption-to-extinction ratios estimated with Mie theory. The best agreement between calculated and measured fine and coarse B(ap) was achieved with a value of 0.014 for the imaginary part of the refractive index. The corresponding absorption efficiencies for the fine and coarse black sand aerosols were 0.22 and 0.09 m(2)/g, respectively.