You know....they use bacteria to help clean up oils spills, haz mat spills, etc. Problem is, I have no idea which bacteria they use. I've also heard things about "rockdust" as a fertilizer for soil like you're talking about. It's too bad you can't just set it on fire. Fire damage in the wild is supposed to help new growth. I'm totally talking out of my a^* on that 'cause I know nothing about it except that forestry divisions will sometimes do this on purpose for that reason. So one would assume that it would have the same effect at home in a controlled environment. If nothing else, I'm sure you could get slapped with all kinds of fines for attempting it anyway, so that's probably moot. Since the tree roots are right there, I would go for the Rockdust. It's supposed to supply all kinds of 'trace' elements, promoting bacterial growth, that in turn breaks down the chemical spill in soil. I think they tried this at Chernyoble (sp?). Hope this helps.