Problems on the Horizon

Is there a way to create a soft edge horizon between a sky object and a floor object? I want to get a sort of foggy hazy blend between the two and can't seem to figure it out. The Fog/Environment object covers the whole sky.

I also want to create sort of a reverse BLACK horizon blur. I have an Abstract BG and floor with spot lights on my foreground . The floor goes to black but then there is a hard edge where floor meets sky. The Sky and Floor are Tiled so I can't really add the blur in the texture.

I have been playing with a tube light and negative values laid in the back... and I guess the other way to approach is to planes or half spheres and light it.

Any suggestions?

THANKS

TAK