Here is a wikipedia link about land cleanup... http://en.wikipedia.org/wiki/Bioremediation

From the article: "Not all contaminants, however, are easily treated by bioremediation using microorganisms. For example, heavy metals ... Phytoremediation is useful in these circumstances, because natural plants or transgenic plants are able to bioaccumulate these toxins... [heavy metals in biomass] may be further concentrated by incineration or even recycled for industrial use."