From jim.mcnelly@granite.mn.org Thu Dec 29 22:35:46 EST 1994
Article: 4925 of alt.sustainable.agriculture
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Newsgroups: alt.sustainable.agriculture
Subject: Lead contamination
From: jim.mcnelly@granite.mn.org (Jim Mcnelly)
Message-ID: <36.1081.1470@granite.mn.org>
Date: Thu, 29 Dec 1994 02:51:00 +0600
Organization: Granite City Connection St. Cloud MN 612-654-8372
Lines: 73


C> my concerns are about lead contamination.  our soil has been tested
C> and lead levels range from 140 to 600 ppm.

C> Does anyone know the following?

C> 1. does lead naturally occur in soil and at what levels? 

I used to manage lead clean up projects in the 80's, and might take a 
stab at some of your questions. I have seen background lead levels 
range from 10 PPM up to 250 PPM, with 50 being fairly typical. Your 
levels are fairly high, and characteristic of soils near traffic ways 
in urban settings.

2. Can lead be removed by growing a cover crop and disposing of it rather
C> than composting it? 

Lead, as I understand it, is not uptaken by leaves, stems, or fruits, 
or for that matter, most plants. Its problem is associated with the 
soil itself, meaning that it attaches itself to roots, which are then 
ingested. It is also a problem with the "pica" phenomenon of children 
eating the soil, which another pathway of ingestion. Finally it is a 
concern for the soil worker, in the form of dirt on the skin, dust 
which is breathed, or dust on the skin. Lead is easily absorbed 
through the skin.

Composting does not "treat" lead or other metals. If anything, it 
might dilute the metal a bit. Composting is used for treating 
explosives, petrochemicals, oil, gasoline, diesel, and some herbicides 
and pesticides. But microbes are not alchemists. They can not convert 
base minerals into other minerals.

3. What methods can be used to remove lead from soils? 

The only two methods I am aware of are to dig up the soil and remove 
it or to put a new layer of soil on top of the old.

4. What is considered a safe level of lead in the soil? 

Well, the EPA hazardous level I worked with in the 80's was 5,000 PPM. 
In sewage sludge and compost, the levels are set around 250 PPM as a 
maximum. Added over the years, since lead does not break down into 
anything else, even a 250 PPM compost or sludge could bring the soil 
lead levels up to 250 PPM if it started at 50 PPM.

Personally, If I had soils over 300 PPM, I would avoid growing or 
eating root vegetables. Over 500 PPM, I would keep kids from playing 
in the soil and would be concerned with skin exposure.

5. I
C> understand that tomatoes, eggpplant etc. are better to grow in lead
C> contaminated soils than leafy greens because the leaves absorb ythe
C> lead.  Is this correct?

Not to my knowledge, although there might be new data showing lead 
uptake that I am not aware of. Leaf uptake is typically associated 
with cadmium.  Root vegetables are the concern. Much of the issue is 
related also to the pH of the soil. The more acid the soil, the more 
likely a metal can get absorbed, the more alkaline, the less likely 
metals will leach.

C> any help/ advice that you can offer me to help remediate this
C> problem would be very appreciatted.  I would like to rehabilitate
C> the soil as much as possible rather than just using raised beds.



 * RM 1.3 02460 * What profit to gain the world and lose your soil?

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   Granite City Connection (612) 654-8372 28.8K 3 Lines
   Email: jim.mcnelly@granite.mn.org (Jim Mcnelly)
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From hansm001@maroon.tc.umn.edu Thu Dec 29 22:37:03 EST 1994
Article: 4927 of alt.sustainable.agriculture
Newsgroups: alt.sustainable.agriculture
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From: "Thomas Hansmeyer" <hansm001@maroon.tc.umn.edu>
Subject: Re: Lead contamination
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>Does anyone know the following?
>
>1. does lead naturally occur in soil and at what levels?
>2. Can lead be removed by growing a cover crop and disposing of it
>rather than composting it?
>3. What methods can be used to remove lead from soils?
>4. What is considered a safe level of lead in the soil?
>5. I understand that tomatoes, eggpplant etc. are better to 
>grow in lead contaminated soils than leafy greens because the leaves
>absorb ythe lead.  Is this correct?
>

Something you should research is the pH ofyour soil.  I understand that 
lead will only become available to plants when the soil in more acidic.  I 
am not sure whether this applies to leafy vegetables.  As far as removeing 
the lead from the soil, a big problem.  You might be better off building 
beds with a soil compost mixture.  Getting back to the availability of lead 
to plants, a soil fertility text book would present the effect of pH on 
lead availabilty.  Contact me if you are not able to locate it.
-- 
              Thomas Hansmeyer
              USDA-ARS
              St. Paul MN
              hansm001@maroon.tc.umn.edu


From jim.mcnelly@granite.mn.org Sat Dec 31 11:03:35 EST 1994
Article: 4935 of alt.sustainable.agriculture
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Distribution: world
Newsgroups: alt.sustainable.agriculture
Subject: Lead contamination˙˙˙˙˙˙˙
From: jim.mcnelly@granite.mn.org (Jim Mcnelly)
Message-ID: <36.1092.1470@granite.mn.org>
References: <aquilla.1139121949E@sadye.emba.uvm.edu>
Date: Sat, 31 Dec 1994 02:10:00 +0600
Organization: Granite City Connection St. Cloud MN 612-654-8372
Lines: 57


A> In Article <36.1081.1470@granite.mn.org>,
A> jim.mcnelly@granite.mn.org (Jim Mcnelly) wrote: ...(deleted)... >
A> >Lead, as I understand it, is not uptaken by leaves, stems, or
A> fruits, >or for that matter, most plants. Its problem is associated
A> with the >soil itself, meaning that it attaches itself to roots,
A> which are then >ingested. It is also a problem with the "pica"
A> phenomenon of children

A> If this is the case, wouldn't washing remove most of the lead from
A> root crops? Tracy

Yes, Tracy,

Washing and scrubbing root vegetables will remove the soil, and hence 
the lead. From an EPA perspective, as I have read some of the 
background "statements of need and reasonableness" regarding the 
impacts of priority pollutants in the soil, the decision to set lead 
limits is based on the "Most Effected Individual" (MEI)

As such lead limits do not take into consideration soil pH, the crop 
raised, the likelihood of children eating the soil, or whether or not 
root crops are washed. They assume that all land application sites 
share risk to a greater or lesser degree. The MEI for cadmium, for 
example, would be a two pack a day cigarette smoker (#1 source of 
"natural" cadmium ingestion) who was a vegetarian who ate exclusively 
>from  his own garden, and then mostly leafy vegetables, who also 
applied cadmium laden sludge on his garden every year at three times 
the recommended rate for a period of thirty years. We are talking 
about extreme cases.

They do, however, provide for several standards and Parts Per million, 
levels depending on the proposed end use. But in the case of the 
person who was describing a community garden, the Class A standards 
for unrestricted use would apply.

It is not likely that a community garden would be able to keep 
children from playing in the soil or that the users of the garden 
would thoroughly wash their root vegetables, even if there were an 
educational campaign.

Given the fact that we know little of where our food is grown, it is a 
wise practice to thoroughly wash all fruits and vegetables before 
eating them.

Mr Compost~~~

Jim~ McNelly
jim.mcnelly@granite.mn.org


 * RM 1.3 02460 * Mammals eating dinosaur eggs.

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   Granite City Connection (612) 654-8372 28.8K 3 Lines
   Email: jim.mcnelly@granite.mn.org (Jim Mcnelly)
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