Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

thin films (DGT), and ICP techniques have also increased the abilities of researchers to quantify
Pb phases in solutions (Berbel et al., 2001; Scally et al., 2003). In addition to the development of
techniques for describing and quantifying Pb species in the soils and solutions, researchers have
used radiogenic Pb isotopes ( 206 Pb, 207 Pb, 208 Pb) to quantify the distribution, speciation, and
transport of anthropogenic Pb in soil profiles and in vegetation (Bindler et al., 1999; Erel et al.,
2001; Kaste et al., 2003; Klaminder et al., 2005).
Over the past several decades, workers have also developed time-series data for Pb in
precipitation, vegetation, organic horizons, mineral soils, and surface waters. Since
atmospherically delivered Pb often comprises a significant fraction of the “labile” Pb (i.e., Pb not
associated with primary minerals), these data have been useful for developing transport and
residence time models of Pb in different terrestrial reservoirs (Friedland et al., 1992; Miller and
Friedland, 1994; Johnson et al., 1995a; Wang and Benoit, 1997). Overall, a significant amount
of research has been published on the distribution, speciation, and behavior of anthropogenic Pb
in the terrestrial environment since 1986. However, certain specific details on the behavior of Pb
in the terrestrial environment and its potential effects on soil microorganisms remain elusive.
AX7.1.2.1 Speciation of Atmospherically-delivered Lead in Terrestrial Ecosystems
Lead in the Solid Phases
Lead can enter terrestrial ecosystems through natural rock weathering and by a variety of
anthropogenic pathways. These different source terms control the species of Pb that is
introduced into the terrestrial environment. While Pb is highly concentrated (percent level) in
certain hydrothermal sulfide deposits (e.g., PbS) that are disseminated throughout parts of the
upper crust, these occurrences are relatively rare. Therefore, the occurrence of Pb as a minor
constituent of rocks (ppm level), particularly granites, rhyolites, and argillaceous sedimentary
rocks is the more pertinent source term for the vast majority of terrestrial ecosystems. During
the hydrolysis and oxidation of Pb-containing minerals, divalent Pb is released to the soil
solution where it is rapidly fixed by organic matter and secondary mineral phases (Kabata-
Pendias and Pendias, 1992). The geochemical form of natural Pb in terrestrial ecosystems will
be strongly controlled by soil type (Emmanuel and Erel, 2002). In contrast, anthropogenically
introduced Pb has a variety of different geochemical forms, depending on the specific source.
While Pb in soils from battery reclamation areas can be in the form of PbSO4 or PbSiO3, Pb in
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