Re: [gardeners] toxic marsh
Dan Dixon (gardeners@globalgarden.com)
Fri, 29 Jun 2001 09:33:19 -0500
> From: "Annetta Green" <agreen@cfl.rr.com>
>
> what is the half life of DDT? How long can it sit in the ground and be a
> viable poison? The research, by state scientists, is showing that the toxic
> levels of the farm chemicals, most outlawed now, are what is/has been
> killing the birds. They found very high levels in the soil, water and
> birds. They have been trucking out the worst of the soil and are now trying
> to let it flood again. I think they are also hoping that the second
> flooding will dissipate even more of the chemicals to acceptable levels in
> the water.
The problem with DDT is that it is a "POP" chemical: it is subject to
"Persistently Overstated Paranoia." :)
Here is Extoxnet's DDT profile:
http://ace.ace.orst.edu/info/extoxnet/pips/ddt.htm
Half life varies depending on where it is located, between 2-15 years.
Breakdown chemicals (DDE and DDD) also persistent, however, so overall
persistence can potentially be very long. My enviro-geologist friend tells
me that the deeper DDT gets in the ground, the longer it lasts (don't know
about 50 yrs, though). DDT is relatively immobile in soil, though, so only
small amounts get carried down really deep. It was banned in the early 70s,
so it's pushing 30 years since it was last used in the US. Not much DDT left
in the environment in this country, I'd guess.
Toxicity to birds is slight to almost none. DDT isnt what's killing the
birds in FL marsh reclamation, at least not directly. They would pretty much
have to eat it raw out of the package to die from it. Contrary to popular
belief, the eggshell thinning research is not conclusive either, eg, many of
the raptor populations thought to be affected were in trouble before DDT was
used, no direct mechanism linked to DDT is known, etc.
Just curious: which Florida wetlands reclamation project are you discussing?
Dan Dixon