Are thin films on night and day aqueous aerosol different?

The size, shape and refractive index of atmospheric aerosol controls the amount of sunlight scattered back to space and is a poorly characterized modern climate cooling mechanism. The size, shape and refractive index of atmospheric aerosol changes with atmospheric oxidation, by OH radical - photochemistry during the day, nitrate radical at night and ozone both day and night. Naturally occurring surfactant forms the shell or film on core-shell aerosol. The thickness and resistance to atmospheric oxidation of this film is critical to atmospheric science. We have collected nearly 24 months of night-time and day-time aerosol from an urban atmosphere and wish to measure the film thickness and reaction with OH radical at the air-water interface. A film thickness of >10Å and oxidation lifetime between 1 hour and 10 days require inclusion in atmospheric models and a difference in film thickness of 2 Å and a difference in oxidation lifetime of ~30% between day and night would be meaningful difference.