Hi
You can use that layer to make a mask.The depth layer is lightest close to the camera and darkest furthest away.
So for example
Make the depth layer visible
Go to channels click on RGB and then on the Selection icon to load the gray image as a selection
Add a hue and saturation layer which will have that selection as a mask
Switch off visibility of the depth layer
Invert the mask (click on it and Ctrl+I)
Now you could use the hue and sat layer to make distant objects bluer and less saturated just the way they are in nature
I hope that helps you
Dave