Understanding and predicting the transfer of pollutants in soil, such as metal particles all the way to the now infamous microplastics, is a pressing environmental question. Transcribed to a scientific question, we deal with the movement of nm-μm particles, of various densities, inside an opaque porous matrix filled with water. In the bulk, depending on the particle size and mass, a combination of diffusion (stochastic motion) and sedimentation (directional motion) takes place and this balance is neatly represented by the so-called gravitational Peclet number. Under confinement (which entails also interactions with the matrix) the situation is of course much more complex. In this M2 project we want to investigate the particle motion at different gravitational Peclet numbers using dynamic light scattering (DLS), both in a bulk liquid and inside a well-known porous matrix filled with a liquid (e.g. controlled porous glasses). DLS measures the particle motion via a time-correlation function, g2(t). For purely diffusive monodisperse particles, the diffusion coefficient can easily be extracted by fitting g2(t) with an exponential. However, its shape becomes complex when two types of motion are superimposed and/or in the presence of confinement. This M2 project is a preparative study for a PhD position opening in autumn 2025 (funding already available!).