The
natural lead concentration of dandelion (Taraxacum
officinale) leaves is estimated to be 0.2 μg/g (dry
weight), or 1–3 orders of magnitude below most contemporary
measurements of that value for dandelions and other plants. This estimate
is based on analyses of lead concentrations of dandelions grown in
a trace metal clean laboratory, with environmental lead concentrations
approximating natural levels. The protocols used in this study paralleled
those in our previous study that estimated the natural blood lead
level in humans (0.016 μg/dL), which is also 1–3 orders
of magnitude below most contemporary measurements. Analyses of the
isotopic ratios (206Pb/207Pb:208Pb/207Pb) of the lead in the plants grown in the laboratory and
greenhouse and those collected in the field, as well as the isotopic
ratios of the soils the plants were grown in in the laboratory, indicate
that anthropogenic lead makes up a substantial amount of labile lead
in today’s environments. Consequently, this estimate of the
natural lead level in dandelion leaves provides both a benchmark for
comparison of lead concentrations in contemporary plants and yet another
measure of persistent lead contamination in the biosphere.
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