As one straightforward example, their estimate of the (change in) Debye length ignores that their equations (2 and 3) are in terms of the square of the Debye length, so the purported change should be only sqrt as large.
As another example, it's not clear why the author focuses on aluminium in the upper atmosphere, or worries about small particles of aluminium shielding the earth's magnetic field from space. While a conductive shell can shield a changing magnetic field, it needs to have long-range conductive paths. A mesh has this property, but a mesh is not the same as a suspended dispersed powder, even if the individual powder particles are conductive on the nano-scale.