FW: Plant uptake of lead

J* V*

This is from a soil scientist who works in remediation.

"The greatest risk from lead is normally associated with ingesting
contaminated soil or dust particles. Most plants under normal conditions do
not take up significant concentrations of lead. However, as with most
metals,
solubility and plant availability increases as conditions become more
acidic.
If a soil has a low pH (less than 5.5) you may see significant accumulations
in the plant material. The roots tend to have the highest concentrations
because the lead that is absorbed tends to react with phosphate and
carbonates in the root and precipitate where they remain. Roots also may
have
higher measured soil concentrations due to contaminated soil particles
adhering on the root. It has been my experience that if you apply adequate
lime (to increase the soil pH to greater than 6.5) and high levels of
phosphate fertilizers you can severely restrict the amount of lead taken up
by most plants. Generally under these conditions the above ground plant
parts
should not pose a significant risk, as long as they are washed thourougly to
remove contaminated dust and soil residue.

Ingestion of root crops (carrots, potatoes, beets, etc.) must be done with
caution because of the difficulty in removing soil particles from the
surface
of the vegetable. Often times the best method is to construct a raised bed
or
provide a surface mulch as a barrier between the contaminated soil and the
crop.

In the absence of extremely high soil lead concentrations (greater than 1000
mg/kg) or acid soil conditions the lead concentrations in most vegetable
crops will remain below 50 ppm. However there are isolated cirmcumstance
when
a particular plant will accumulate significantly higer concentrations of
soil
lead.

I would expect the grain content to be fairly low under normal conditions."

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