First step - make sure you have your soil tested so that you can measure the results of your efforts.
Most problems of contamination can be addressed by adding humus. Recall that Soil has 5 main components: Air, Water, Organic material, Minerals and Micro-organisms. If you increase the organic matter air and water components then the concentration of any contaminants will be lessened. Micro-organisms also work to break down many contaminants such as petro-chemicals [PIJ June 1996] and bacteria feed on toxins produced by some algae such as blue green algae [ECOS spring 1995].
Bacteria is used in industry to digest and render less harmful organic contaminants such as diesel and arsenic. [ECOS Summer 1995-1996]
Bacteria and fungi also act to breakdown toxins such as residue pesticides [Peter Mayne 1995].
Recent reserach shows that compost can be effective in fighting parasitic diseases of plants. It can also be an efective fungicide capable of working on a commercial scale. [New Scientist Oct 96]
Smith and Krãmer from Dept of Plant Sciences Oxford University found that the plant Alyssum lesbiacum mops up nickel. Coghan [New Scientist Feb 1996] writes: "No-one knows why some plants accumulate metals instead of keeping them out, one theory is that the metals keep insect pests at bay by deterring them from feeding" Another useful plant is alpine penny-cress (Thlaspi caerulescens) a native plant of Britian, accumulates Zinc. Decontamination with plants is much more environmentally sensitive than current procedures which use acid to leach the metals, this kills micro-organisms and is highly costly.
What to do if your steps to rehabilitate the soil fail,