Profiling Particles of Sahara Dust Settled on the Ground by a Simplified Dynamic Light Scattering Procedure and Sedimentation.

Abstract

Dust particles exist in the form of mineral aerosols and play a significant role in climate change patterns, while also having the potential to affect human health. The size of these particles is crucial, as it determines the atmosphere's albedo. In the past few years, a Saharan dust cloud has moved and arrived above Romania during spring, followed by rain containing the dust particles, which are deposited on various objects. We collected these particles in an aqueous suspension and employed natural sedimentation to separate them by density. We then conducted a dynamic light scattering (DLS) experiment to analyze their size. Our DLS setup was straightforward, and the time series analysis involved evaluating the frequency spectrum of the scattered light intensity-also known as the power spectrum-filtering it, and fitting the expected Lorentzian line to it to determine the parameters and the average diameter of the suspended particles. We found that the dust particles had a continuous distribution, with the biggest particles having a diameter around 1100 nm. The results obtained from the combination of sedimentation and DLS are consistent with reports on the size of Saharan dust particles in other regions of Europe.