Something I have discovered along the sides of our home that has been there for years I realize is that old blackish sooty buildup which can make a home seem like it has a floating dark mass of something around it which won't go away was actually there! I took to doing something about it by working with that soil and adding mulch and turning it for about 6 months or so often adding more mulch and grass and leaves also until it had a neutralizing effect on the stuff that was so dark. There are spores or fungus that grow there and it is allways is seemingly dark until I got the notion to do something about it. With this treatment that I used I was able to restore the soil to a better condition and slowly it made me feel better too! When I worked it I did this alot and then added some new soil and a box garden also to the area and it was more pleasant to look at and even be around and it does not look dark and sooty anymore.

Best of luck on this one!

Marc