Marine particles are a main vector by which the biological carbon pump transfers carbon from the atmosphere to the deep ocean. Particle dynamics processes such as aggregation, disaggregation, sinking, and remineralization govern the behaviour of particles in the ocean, and thus the strength and efficiency of the biological pump. These processes are notoriously difficult to measure directly, so we turn to chemical tracers to help us understand them. The GEOTRACES program is an international program to improve the understanding of biogeochemical cycles by studying the large-scale distribution of trace elements and their isotopes in the ocean. In this talk, I will give an overview of what we have found about the distribution and composition of size-fractionated particles during several U.S. GEOTRACES cruises. I will then give examples for how we can use a simple conceptual model to understand the distribution of particulate trace elements and their isotopes, and conversely, how different classes of particulate chemical tracers can help us understand the rates of key particle dynamics processes.