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  • From: Mark <mpludwig@facstaff.wisc.edu>
  • To: permaculture@lists.ibiblio.org
  • Subject: [permaculture] Heavy metal issues
  • Date: Thu, 19 Sep 2002 10:04:14 -0500

At 09:33 AM 9/19/02 -0400, you wrote:
Good day:)

In a message dated 9/18/02 4:35:09 AM, georg@websuxxess.com writes:

<< mushrooms are known to store heavy metals, so if these

are present in the water hyazint growing medium, they will end up on the

consumers plate? >>

Glad you brought this up Georg. I've always wondered about how utilization of
plants that are known to store heavy metals affects compost, food grown from
that compose etc.

Persons who advocate such use often offer little scientific proof. The best
hope is that in the process of breaking these things down somehow the heavy
metals are either converted to a harmless form or are somehow used up.

As you can see I don't have a clue about the actual process:) Frank

This is certainly an interesting topic, I'll try to dredge up my soil pollution class from 10 years ago...

On the topic of plants accumulating heavy metals, they are definitely still present in the plant, the key questions become what form they are in (how bio available they are) and what to do to dispose of the metals. I would guess that in most cases the bio availability is going to be quite high in plants, thats certainly the case with other minerals. As to what to do with them, as un-PC as it sounds the landfill may be the best bet for Pb, Hg, Cd and other metals which have no value for man, beast or plant. Zn, Cu, Cr and other metals that are of value as trace mineral could be safely spread around from areas of over concentration to areas where they could have value.
Another interesting fact is that many of these minerals bind fairly tightly to soils or may be microbially converted to less available forms over time. It may make sense in some situations to simply cover polluted soils with a membrane for a few months/years in order to limit leaching and allow these conversions to take place rather than extracting the metals and moving the problem elsewhere.


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Mark P. Ludwig
Poultry Research Lab
University of Wisconsin -Madison
608-262-1730 WK
608-846-7125 HM





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