Biogeochemistry of Isotopically-distinct Sources of Lead in a Former WWII Aerial Gunnery Range
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Date
2014-01-08
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Abstract
Isotopic composition and concentrations of Pb are used to identify sources of
anthropogenic and natural Pb and to assess Pb bioavailability in soils and native plants at
a former military installation that served as a WWII era aerial gunnery range. Surficial
soil and plant samples are obtained both in target practice areas where copious amounts
of bullets persist and areas unaffected by target practice that are devoid of bullets. A
selective sequential extraction procedure is used to determine the distribution of Pb
amongst different soil components: soil carbonates and ion-exchangeable minerals,
organics, oxide and hydroxide minerals, and leachate of residual silicate clays. Plants
samples are obtained by sampling multiple species within 1 m square area for each soil
sample location. Isotopic compositions of samples directly reflect the presence or
absence of bullets in the sample area.
Anthropogenic Pb in sample locations with abundant bullets display a wide range
of ^(206)Pb/^(207)Pb values (1.140–1.234), but relatively less variation in ^(206)Pb/^(208)Pb values
(0.473–0.488), which is hypothesized to be reflective of ore-mixing in the manufacture
of bullets. Plant samples exhibit a distinction between anthropogenic and natural Pb
similar to soil samples, but consistently display lighter ^(206)Pb/^(207)Pb values than soil
samples, which is inferred to be representative of the influence of regional atmospheric
deposition of contaminant Pb.
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Keywords
Pb isotopic compositions, Pb, legacy Pb, contaminants, legacy military contamination, Pb bioavailability