We need to know the toxin.

The soil microbes will detox soil, too,...depending on the toxins.

I have read about soil remediation using sunflowers. You have to dispose of the plants afterward. It was an auto plant site where the soil was contaminated with lead. The area was planted with sunflower and the plants were harvested and removed. They had good results.

I think this should be done in many city sites to help detoxify the soil there. Of course, the sunflower plants then become the toxic things. Ironically, many birds and animals love sunflowers. They will eat the seeds and spread the toxins that way.

Sunflowers and mustard greens both have an ability to pull certain toxins (primarily heavy metals) from the soil and have been used in various phytoremediation projects, most notably in New Orleans, cleaning up after Katrina. According to the literature, the greens are not edible but the seeds of the sunflowers are - the toxins are apparently accumulated and stored in the roots and leafy growth but not in the seeds. Other plants that are known to have similar characteristics are spinach, corn, carrots, peas, Commelina communis (dayflower), brake fern and lamb's quarters - brake fern (Pteris vittata) has been widely used for this purpose.

Here is a link that might be useful: plants & soil remediation

Would be interested to see the actual results from now a 2 year old study.
No doubt new and exiting things can and are being discovered,
however, I was under the impression that contaminated soil was removed and burned as the contaminate leached so far down as to not be attainable by roots extending 3-6 foot down.
I was also only aware of Solarization as to the only means to eradicate certain soil bourne virus's and wilts.

If the contamination could not be reached by the roots, I'd be happy enough with that.

Whoops:
My bad.......meant that the roots extending through the whole zone would be affected.

Bump for Oregongirlie PNW...

Blutranes

If one is genuinely interested try: soil remediation method that uses sunflower

Here are a couple of URLs that might be informative.

Mycoremediation

http://www.fungi.com/mycotech/mycova.html

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Effective Microorganisms (EM)

http://www.emamerica.com/environment/bioremediation/index.php

Clickable links:

Mycoremediation

Effective Microorganisms (EM)