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  • From: list@ginda.us
  • To: North American Fruit Explorers <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] Lead takes root in urban gardens
  • Date: Sat, 29 Nov 2003 17:03:13 -0500


On Nov 29, 2003, at 5:44 PM, Rick Valley wrote:



From: list@ginda.us

2) Lead from gasoline fumes is more prevalent than I would have
guessed. I nearly bought one house that bordered a semi-major road.
(Not a highway, but a town road with traffic most of the day.) There
was a striking gradient across the yard. The gradient isn't nearly as
steep as with paint - obviously, fumes travel farther than chips.
Right by the road the levels were about 500 ppm which is high enough
that I'd prefer not to grow edible leaves, and maybe not edible roots.
Edible fruits would probably be okay, though. 100 feet from the road
the levels were down to perhaps 100-200 ppm (I don't remember exactly,)

This is interesting because it contradicts findings cited in Lead in Seattle
Community Gardens, a paper from Center for Urban Hort. in Seattle from
around '86. They said that levels correlated with intensity and length of
human (read "civilized" human) occupation of a site, not distance from a
road. Probably sampling differences, also the gardens are all tilled.

I did a dozen samples at one house, and another dozen spread over several houses while house-hunting, so my experience might not be statistically valid. I do agree with the Community Gardens folk in part - the amount of lead in the soil right next to the house (a sample I took at every house) was very well correlated with the age of the house. The only outlier was the house with more than 6 inches of mulch - I didn't find any lead in my sample. I assume the lead was there, but below the level I dug to. Since I was primarily interested in child safety right next to the house, I figured I should measure the stuff the kids would play in. (I was more careful about mixing depths for samples I took in prospective garden spots.)

I have, more than once, scalped an entire yard, and re-contured to eliminate
lead. I think its a very quick way to procede, if you're re-doing a
landscape, because lead doesn't leach down, but stays in the surface zone.
I've never had a yard that couldn't spare some dirt, and it makes fine
landfill cap.

-Rick

Doesn't that remove all the top soil?

Ginda





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