To a point, "it's Florida" the way we look at it. We've been down to various parts of the state numerous times over the years with motorcycles and have noticed the "black dirt and dust" that seems to accumulate on them. More visible to us since the bikes have been black. Doesn't seem specific to TV though I'm sure it's more prevalent near the construction areas. It doesn't really seem to matter what part of the state we've been in, it's there. Also noticeable in the wash bucket when cleaning up the bike......or a car, for that matter.
I think it's from the sand.
Bill