The top of the atmosphere reflectivity of the planet, depends in part, on the optical properties of aerosol in the atmosphere. Frequently atmospheric chemists use chemical proxies for aerosol and here we describe a series of experiment using optical trapping with material extracted from atmospheric filter samples. The experiments demonstrating to a first approximation that organic matter may for core-shell morphologies, have refractive indexes that vary with location and that thin films on aerosol have chemical removal rates comparable to mechanical removal rates from the atmosphere. Basic radiative transfer modelling also demonstrates that thin organic films on atmospheric aerosol may have appreciable effects on planetary reflectivity. We will also show some early data that near-field scattering effects between pairs of aerosol particles predicted by theory (T-matrix) may not agree with experiment.

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