Migratory particles in porous media experience mechanical and chemo-physical interactions with fluids, pore walls and other particles. The resulting forces (buoyant weight, drag, inertia, and electrical particle-particle and particle-wall) determine particle migration, adhesion and pore clogging. We investigate underlying pore-scale phenomena in convergent radial flow using microfluidic chips. Images reveal distinct clogging mechanics as a function of the particle mass density. The heavy glass particles collide with pore walls and the transient increase in the local volume fraction of particles enhances the probability of bridge formation and clogging at pore throats. On the other hand, quasi-buoyant latex particles follow streamlines closely, but can stick to nearby pore walls at pore constrictions as electrical attraction towards the wall overcomes the repulsive forces. A clogged pore increases the tortuosity of streamlines and promotes further clogging at nearby pores. Statistical data gathered through image analyses identify causal interactions between sequential clogging events.