Light scattering from diatomaceous earth aerosol

- An IR extinction and visible light scattering study of diatomaceous earth aerosol is presented.
- Experimental results are compared with T-matrix theory simulations.
- The IR spectrum is used to infer the particle shape distribution.
- Model simulations are in good agreement with scattering data for diatomaceous earth.
- Errors may be due to a breakdown of the uniform spheroid assumption.

The light scattering and extinction properties of mineral aerosol are strongly affected by dust particle shape. In this work, scattering phase function and polarization profiles of diatomaceous earth aerosol are measured at a wavelength of 550 nm, and the results are compared to T-matrix theory based simulations using uniform spheroid models for the particle shape. The particle shape distribution is determined by spectral fitting of the experimental infrared (IR) extinction spectral line profile for diatomaceous earth dust. It is found that a particle shape model that peaks toward both extreme rod-like and disk-like shapes results in the best fits to the IR spectral data. This particle shape model is then used as a basis for modeling the visible light scattering properties. While the visible simulations show only modestly good agreement with the data, the fits are generally better than those obtained using more commonly invoked particle shape distributions.