EDM allowed the visualization of the 3D spatial dependence of elemental gradients. Statistical significance of the elemental distribution at each distance point was obtained from the data density plots in Figure , representing the concentration of each element versus particle depth. The particles were fairly spherical, according to assessments of FD⊥min/max, the quotient between the minimum diameter of the particle and the maximum orthogonal value. In general, the particles showed values spanning 0.66-0.75, with 1 representing the perfectly spherical limit. Two particles of different volumes (84±1 μm and 94±2 μm 3 ) were chosen in each gradient architecture for further analysis.