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

aquatic plants and insects and on the concentration of metals in the waters of these aquatic
systems (Albers and Camardese, 1993a,b).
Three geochemical factors that influence metal bioaccumulation in aquatic organisms
include speciation, particulate metal form, and metal form in the tissues of prey items (Luoma
and Rainbow, 2005). Lead is typically present in acidic aquatic environments as PbSO4, PbCl4,
ionic Pb, cationic forms of Pb-hydroxide, and ordinary hydroxide Pb(OH)2. In alkaline waters,
common species of Pb include anionic forms of Pb-carbonate (Pb(CO3)) and Pb(OH)2. Labile
forms of Pb (e.g., Pb 2+ , PbOH + , PbCO3) are a significant portion of the Pb inputs to aquatic
systems from atmospheric washout. Particulate-bound forms are more often linked to urban
runoff and mining effluents (Eisler, 2000). Little research has been done to link the complex
concepts of chemical speciation and bioavailability in natural systems (Vink, 2002). The
relationship between the geochemistry of the underlying sediment and the impact of temporal
changes (e.g., seasonal temperatures) to metal speciation are particularly not well studied (Vink,
2002; Hassler et al., 2004).
Generally speaking, aquatic organisms exhibit three Pb accumulation strategies:
(1) accumulation of significant Pb concentrations with a low rate of loss, (2) excretion of Pb
roughly in balance with availability of metal in the environment, and (3) weak net accumulation
due to very low metal uptake rate and no significant excretion (Rainbow, 1996). Species that
accumulate nonessential metals such as Pb and that have low rates of loss must partition it
internally in such a way that it is sparingly available metabolically. Otherwise, it may cause
adverse toxicological effects (Rainbow, 1996). Aquatic organisms that exhibit this type of
physiological response have been recommended for use both as environmental indicators of
heavy metal pollution (Borgmann et al., 1993; Castro et al., 1996; Carter and Porter, 1997) and,
in the case of macrophytes, as phytoremediators, because they accumulate heavy metals rapidly
from surface water and sediment (Gavrilenko and Zolotukhina, 1989; Simòes Gonçalves et al.,
1991; Carter and Porter, 1997).
Uptake experiments with aquatic plants and invertebrates (e.g., macrophytes,
chironomids, crayfish) have shown steady increases in Pb uptake with increasing Pb
concentration in solution (Knowlton et al., 1983; Timmermans et al., 1992). In crayfish, the
process of molting can cause a reduction in body Pb concentrations, as Pb incorporated into the
crayfish shell is eliminated (Knowlton et al., 1983). Vázquez et al. (1999) reported on the uptake
AX7-148