Radiogenic Isotopes - Application of Geochemical Tracers to Fluvial Sediment - page 108

Fig. 4.11 a Lead concentrations measured in bone, liver and muscle within rainbow trout from
Richland Creek, western North Carolina; b Temporal changes in Pb concentrations in fish subject
to a seven-day dose of lead nitrate. Concentrations in bone and liver decrease as different rates;
c Pb isotopic ratios in fish from Richland Creek; d Temporal changes in 207 Pb/ 208 Pb ratios of
laboratory trout following exposure to a Pb source. No statistically significant change occurred in
bone, whereas a systematic change was observed in liver tissues. The latter change correlated with
rapid decreases in Pb concentrations (adapted from Miller et al. 2005 )
accumulated Pb within a few days, while nearly all of the Pb was excreted within a
few weeks. As the Pb was excreted, the isotopic signature of the liver and muscle
changed toward that of the 'clean' water (Fig. 4.11 ). Additional studies are needed to
determine if such phenomena affect other biota in other environments. Nonetheless,
the Richland Creek study suggests that the Pb isotopic analysis of trout may not
only provide insights into whether biota is exposed to a particular Pb source, but the
length of exposure. In the case of rainbow trout, for example, it seems possible that
the isotopic composition of fish bone can be used as an indicator of long-term Pb
exposure whereas the composition of the liver and muscle will provide insights into
their shorter-term exposure to Pb (Miller et al. 2005 ).