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  • From: fbanks <fbanks@theriver.com>
  • To: "Permaculture the Earth Forum" <permaculture@envirolink.org>
  • Subject: Re: Lead bioremediation in gardens
  • Date: Mon, 12 Apr 1999 12:53:49 -0700

Hello ~
 
I'm not a certified permaculturalist or anything fancy....   I  happened to read an article just last night that may help in this situation....   from  National Geographic, August 1993, "Bacteria:  Teaching Old Bugs New Tricks".... 
 
"Lethal cyanide poured daily from the Homestake Mine's gold processing plant into South Dakota's Whitewood Creek.  Mercury, arsenic, and sewage thickened the toxic flow....   A Homestake biochemist said "I thought bacteria could do it [clean up the cyanide].  I collected samples of water exposed to the poison.  They held cyanide-tolerant bacteria that actually feed on the poison's carbon and nitrogen.  We designed...  a series of tanks in which the cyanide effluent moves slowly past feeding bacteria.  It worked."
 
"....Groundwater Technology, Inc. of Norwood, Mass [are] specialists in treating polluted groundwater and soil.  They have used the technology of bioremediation to clean up hundreds of sites around the world...
 
".....[The author] sought out some sore spots...  a Superfund project on the lower Mississippi...  the soil [was] black with contaminants --- more than 200 toxic compounds....  [A biochemist with Louisiana St. University] identified bacteria that were already eating the pollutants and encouraged them to reproduce.  [They were] applied to a contaminated test site.  In nine months they cleaned it up.
 
"....Aviation fuel had been leaking from [a Traverse City, Michigan Coast Guard] station's underground tanks, maybe for decades.  Its invisible plume had moved a mile with the groundwater [contaminating wells].  Traverse Group, Inc, a bioremediation firm, drilled interdiction wells to pump out the fuel at the station boundary.  The effect on the plume was astonishing.   With the  spread of the spill halted, the indigenous soil microbes quickly did their work, and the plume collapsed on itself.  After 18 months no trace of it was found beyond the station."  [End of excerpt]
 
Why not try a cheaper easier solution to your lead-infested parking lot soil first, before buying expensive topsoil.....    Till or plow deeply, adding copious amounts of compost and rough, rotting organic matter like moldy hay or straw....    Water the soil thoroughly and keep it moist for several weeks.....  then have it retested and see if the lead levels are dropping...   It seems to me that since the soil had been sealed off from the air by the asphalt pavement, helpful bacteria had no opportunity to flourish....   Perhaps all they need is some air (deep rototilling and coarse organic additions), micronutrients (compost and water), and some innoculation (compost and moldy hay).....   and the dormant, lead-eating bacteria will clean up this site FOR you...??
 
Why not be a "test case" for this method, since you already have an investment in one official lead test....  Your results could be very helpful for others encountering the same problem.....  If it doesn't work, you can always resort to  the more expensive methods (imported soil, raised beds, etc.)  I'm betting  your soil cleans itself up....
 
Could I be mistaken?  I'm no biochemist, either...   But it sounds reasonable, even with heavy metals....  Bioremediation works on industrial sewage full of heavy metals.....  Harwich, Mass. has a sewage treatment facility that turns the town's residential and industrial sewage into clean water, using only biological processes....
 
Thanks for listening...
Mrs. Joy Banks in AZ
 
 
 
-----Original Message-----
From: Rachel Freifelder <rachel@devnull.net>
To: permaculture@envirolink.org <permaculture@envirolink.org>
Date: Friday, April 09, 1999 12:33 PM
Subject: Lead bioremediation in gardens

>
>
>I'm helping to start a garden on a site that was a parking lot.  After
>depaving, we got the soil tested for lead and it came back with 700 ppm.
>Some extension services say this is "safe to garden" as long as you wash
>everything with soap and don't grow roots or greens - in other words almost
>no cool-season vegetables.
>
>We're going to do more detailed spot testing to see if it's only in certain
>areas, and if it's just one spot we'll probably dig that out and fill it
>with city compost.  In the meantime I am trying to find out what we can do,
>particularly what crops are safe to eat, and what we can grow that would
>accumulate/concentrate the stuff that we could then harvest and landfill
>(or smelt!).  I heard of one person who grew a particular variety of corn
>on a lead-contaminated site, then smelted the corn to obtain a lead ingot
>(it was an art project).  The extension services all say corn, like other
>fruit/seed crops, is safe, but maybe the lead accumulates in the stalk and
>husks.  I would love to find out what variety of corn this is.
>
>  If you have any advice, contacts, books, etc, to suggest, I would be grateful.
>
>Thank you,
>Rachel Freifelder
>Mariposa Grove Community Garden
>828 59th St
>Oakland, CA 94609
>510-655-2936
>rachel@devnull.net
>
>


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