Invariably, roots showed the highest lead concentrations, followed by
successively lower accumulations in stems, leaves, and the typically
edible portions. Root concentrations varied widely, even within a given
species. For instance, her team reports that one sample of soil with a
lead concentration of 1,600 parts per million (ppm) produced no
measurable lead anywhere in a grape plant. In another case, the roots
of grapes grown in soil with 944 ppm lead showed lead contamination of
480 micrograms per gram (?g/g)-though there was no measurable
accumulation higher in the plant.
Mike Elvin
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