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Fig. 5.4 a
Cd isotope data for various Earth materials and meteorites. The sampled meteorites are
limited to enstatite chondrites (of type EH), achondrites (eucrites and SNC meteorites from Mars),
and carbonaceous chondrites.
b
Cd Isotope data obtained on samples from Zn-Pb smelting/refining
plants and various types ofmaterial contaminated by smelter emissions. All samples reported relative
to the NIST 3108 Cd standard.
Circled data
represents results from unfractionated carbonaceous
chondrites that have not been overprinted by strong metamorphism (Wombacher et al.
2003
,
2008
).
Shown uncertainties are reported as shown in original publications, except for the average calculated
for 5 unpolluted river sediments (Gao et al.
2008
) (figure from Rehkämper et al.
2011
)
Like Zn, the observed differencewas interpreted to result fromevaporation processes.
In addition, they found that analyzed soil materials located up to 4.5km from the
refinery exhibited systematic spatial variations in
114
Cd values, with the lowest val-
ues occurring closest to the smelters. The observed variations were attributed to the
mixing of Cd in the furnace/exhaust dust within slag-derived materials. It appeared,
then, that Cd isotopes served as an effective tracer of anthropogenic Cd, at least over
a relatively short distance. The argument is supported by the finding of (1) Shiel et al.
(
2010
) who studied the Cd isotopic composition of materials associated with a Pb-Zn
smelter and refining plant, this one located in Canada, and (2) Shiel et al. (
2012
)who
were able to use a combination of Pb, Zn, and Cd isotopes to determine the extent of
anthropogenic Cd accumulation in marine bivalues off the coast of British Columbia
and the Eastern US.
With regards to riverine environments, we know of only one study using Cd
isotopes as a tracer of anthropogenic Cd; that of Gao et al. (
2008
) who worked on
the North River of southern China. The North River is highly contaminated, in part,
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