permaculture

[Toby Hemenway <hemenway@jeffnet.org>]

Michele May wrote:

> Can you write more [about lead and trees]

I read somewhere (which puts this information in the class of hearsay about a hypothesis--yikes) that because leaded gasoline was used for so many years, significant quantities of lead were put into the air and soil. Long-lived plants and animals have picked up this lead and now hold it in their tissues (sorta like DDT and breast tissue). Tissue from trees that was laid down before 1900 contain less lead than more recent tissue. And very young trees from the recent, unleaded era also contain little lead. So the hypothesis is that the lead came from leaded gasoline. I don't remember the source of this information. But it would explain why leachate from wood chips contain almost as much lead as leachate from shredded tires.

Toby
_____________________________________________
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Gaia's Garden: A Guide to Home-Scale Permaculture, visit
http://www.chelseagreen.com/Garden/GaiasGarden.htm