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

soil was not allowed to equilibrate following the addition of Pb and prior to the addition of the
test organisms. This may have resulted in an increased bioavailability and overestimated Pb
toxicity relative to actual environmental conditions (Davies et al., 2003). See the discussion in
Section AX7.1.2 on the effects of aging on Pb sorption processes.
Lock and Janssen (2002) and Bongers et al. (2004) found that Pb-nitrate was more toxic
than Pb-chloride to survival and reproduction of the springtail Folsomia candida. However,
percolation (removal of the chloride or nitrate counterion) caused a significant decrease in Pb-
nitrate toxicity such that there was no difference in toxicity once the counterion was removed
(Bongers et al., 2004). No change in toxicity was observed for Pb-chloride once the chloride
was removed from the soil. Bongers et al. (2004) suggested that the nitrate ion was more toxic
than the chloride ion to springtails.
Uptake of Pb from soil into earthworms was also modeled as part of Eco-SSL
development (U.S. Environmental Protection Agency, 2005a). The relationship derived between
Pb in the soil and Pb in an earthworm was taken from Sample et al. (1999) and is as follows:
Ln(Cworm) = 0.807 * Ln(Csoil) – 0.218
where Cworm is the concentration of Pb in the earthworm (dry weight) and Csoil is the
AX7-42
(AX7-2)
concentration of Pb in the soil. This equation recognizes that the ratio of Pb concentration in
worm to Pb concentration in soil is not constant.
Wildlife
Research has been conducted to determine what Pb concentrations in various organs
would be indicative of various levels of effects. For example, Franson (1996) compiled data to
determine what residue levels were consistent with three levels of effects in Falconiformes (e.g.,
falcons, hawks, eagles, kestrels, ospreys), Columbiformes (e.g., doves, pigeons), and Galliformes
(e.g., turkey, pheasant, partridge, quail, chickens). The three levels of effect were (1) subclinical,
which are physiological effects only, such as the inhibition of δ-aminolevulinic acid dehydratase
(ALAD; see Section AX7.1.3.3); (2) toxic, a threshold level marking the initiation of clinical
signs, such as anemia, lesions in tissues, weight loss, muscular incoordination, green diarrhea,
and anorexia; and (3) compatible with death, an approximate threshold value associated with