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  • From: "TradingPostPaul" <tradingpost@riseup.net>
  • To: livingontheland@lists.ibiblio.org
  • Subject: Re: [Livingontheland] Lead contamination
  • Date: Mon, 10 Jul 2006 21:54:16 -0600

This may help. Questions always welcome - someone may have an answer.

paul, tradingpost@riseup.net
---------------

Gardening on Lead- and Arsenic-Contaminated Soils
http://cru.cahe.wsu.edu/CEPublications/eb1884/eb1884.pdf

Soil acidity is reported in units of pH. A pH value of 7.0 is defined as
neutral. Values above 7
are termed alkaline, and values below 7 are acidic. The pH range found in
natural Washington
soils is about 4 to 9.
Plant lead concentrations typically decrease with increasing soil pH.
Plants tend to take up
the least amount of soil arsenic at neutral soil pH. Amend acidic soils
contaminated with lead
but not arsenic with agricultural lime (calcium carbonate or dolomite) to
pH 7 or greater. Lime
acid soils containing elevated arsenic concentrations but not lead to pH 7.
Maintain soils
containing both lead and arsenic at pH 7 to minimize plant uptake of both
elements. It is difficult
to reduce the pH of soils that contain free lime (also known as caliche),
which have a pH of 8 or
greater. Using an acidic fertilizer formulation such as one containing
nitrogen as ammonium or
urea will help reduce soil pH over time.
Increase soil organic matter by adding compost, manures, and other organic
soil amend-
ments. Normally, this will reduce plant uptake of soil lead and arsenic.
Part of this effect appears
to be simple dilution of soil lead and arsenic concentrations. Beyond some
maximal amount of
added organic material increases have no further beneficial effect. Test
all composts and other
organic amendments or choose those certified low in lead and arsenic. Avoid
preparing compost
using plant materials grown on lead- and arsenic-contaminated soils.
Use of phosphate-containing soil amendments such as triple superphosphate
sometimes can
reduce plant uptake of soil lead, by causing lead phosphate minerals of
very low solubility to
form. This approach does not work if soil lead already occurs as lead
phosphate minerals, as it
may on soils that have a history of phosphorus fertilizer application.
Adding phosphate amendments to high arsenic soils can increase plant uptake
of soil
arsenic. Apply phosphorus-containing fertilizers to high arsenic soils only
when plant growth is
restricted by lack of phosphorus. In this case the phosphorus-stimulated
increase in plant
biomass will dilute any extra absorbed arsenic and reduce plant arsenic
concentration.
Other proposed techniques for reducing soil lead and arsenic concentrations
and
phytoavailability are still in the testing stage. Specific recommendations
are not yet available.

SUMMARY
Lead and arsenic occur naturally in soils. Both elements are potentially
toxic if present at
high concentrations. Past human activities have increased the lead and
arsenic content of some
soils used for home gardens, sometimes to levels that create concern about
human health.
Geographical and historical factors give clues about the possibility of
soil contamination with
lead and arsenic. Soil testing can confirm higher than natural background
concentrations.
Ingestion is the principal route by which lead and arsenic enter the human
body. Human
health is best protected by minimizing total dietary intake of these
elements. People ingest lead
and arsenic in water, food, soil, and housedust. Because lead and arsenic
concentrations in soil
are much higher than in plants, home gardeners and their families are
likely to have greater
exposure to lead and arsenic in soil directly or in soil particles adhering
to the outside of plants
than to lead and arsenic actually within garden produce. The lead and
arsenic contents of plants
and most soils are not high enough to be acutely toxic to people; however,
they contribute to
overall lead and arsenic exposure. The amount of lead and arsenic ingested
increases with
increasing exposure to lead and arsenic in soil. Young children generally
have greater likelihood
of exposure to soil lead and arsenic than do older children and adults.
Children also are more
likely to be harmed by lower doses of lead and arsenic.

Home gardeners can reduce the potential hazard of gardening on lead- and
arsenic-
contaminated soils by combining appropriate land use, horticultural, and
personal hygiene
practices. These practices reduce the amount of lead and arsenic in or on
garden produce, and
minimize direct exposure of gardeners and their families to contaminated
soil.

*********** REPLY SEPARATOR ***********

On 7/10/2006 at 6:01 AM Malisa Hodges wrote:

>Hi,
> I enjoy reading the post. I tend to observe and stay in the background,
>but occasionally post. I am wanting to know what I can do about lead
>contamination in the soil where my dad's old shop sits. I will eventually
>tear it down. Are there plants, trees I can plant that would absorb the
>lead?
>
>
>Malisa Hodges
>Independent Associate
>http://www.prepaidlegal.com/hub/malisahodges
>_______________________________________________
>Livingontheland mailing list
>Livingontheland@lists.ibiblio.org
>http://lists.ibiblio.org/mailman/listinfo/livingontheland








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