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tracer of Cu pollution (Hoefs
2009
). For example, within the sedimentary compo-
nents of aquatic environments, their use may be complicated by redox reactions that
alter the Cu isotopic ratios both during dispersal and after deposition. In addition,
Cu isotopic variations with natural materials are likely to overlap with those found
within anthropogenic Cu sources (Hoefs
2009
; Thapalia et al.
2010
).
In spite of the recognized difficulties of using Cu isotopes as an effective tracer
of Cu provenance, a few recent studies have shown that their use will depend on the
local environmental conditions and the nature of the Cu isotopic composition of the
background and anthropogenic sources. Thapalia et al. (
2010
), for example, found
that Cu isotopic values exhibited similar trends to those observed for Zn within the
Lake Ballinger core discussed above. More specifically, measurable shifts in
65
Cu
values correlated to the operational history of the smelter located upwind of the site
(Fig.
5.1
). In contrast to Zn isotopes, however,
ʴ
65
Cu values in sediments that pre-
dated smelting activity were lighter than those that were deposited during and follow-
ing smelting operations. Thapalia et al. (
2010
) also suggested that Cu isotopic data
may be effective for determining the source of Cu from urban sources, such as from
tires and automobile emissions (although perhaps not as effective as Zn isotopes).
Using a rather novel approach, El Azzi et al. (
2013
) demonstrated that Cu isotopes
may also be effective at determining the source and fate of Cu in riverine environ-
ments. Their study focused on a small Mediterranean catchment in southern France
(the Baillaury catchment) where Cu-based pesticides (referred to as the Bordeaux
mixture) were applied to vineyards to protect grapevines from fungus. Within the
catchment, they sampled actively cultivated soils and abandon soils, both of which
served as potential sources of anthropogenic Cu to the river. They also sampled
channel bed sediments, suspended particulate matter (SPM), and river water dur-
ing a flood event in February, 2009. They found that Cu enrichment factors were
generally greater than 2 and, based on Cu concentrations, that anthropogenic Cu
contributions ranged between 50% in the abandoned soils to more than 75% in the
cultivated soils, river bed sediments, and SPM. Isotopic analyses performed on the
bulk samples found that the local bedrock (
ʴ
+
0
.
07%), river bed sediment (
−
0
.
10
65
Cu values, but differed from the
to
+
0
.
06), and SPM (
+
0
.
09) exhibited similar
ʴ
water samples (
14). Based on these bulk
analyses, it appears that Cu isotopes could not be used as a tracer of anthropogenic
Cu. However, El Azzi et al. (
2013
) recognized that natural Cu is often derived from
rock forming minerals and where it is bound to silicate and oxide minerals is rela-
tively immobile. Cu associated with these minerals is usually found to be associated
with the residual fraction when a sequential extraction method is applied to the sedi-
ments. In contrast, anthropogenic Cu is mostly associated with various non-residual
phases and, therefore, is more mobile. Thus, they reasoned that the isotopic analyses
of sequentially extracted phases could be used to quantify the magnitude of nat-
ural and anthropogenic sources. In doing so, they found using sequential extraction
methods that the residual phase accounted for more than 60% of the Cu in soils
of the abandoned vineyard, but only about 30% in the cultivated soils, river bed
sediments, and SPM. Cu associated with the residual phase exhibited
+
0
.
31) and analyzed soils (
−
0
.
06 to
−
0
.
65
Cu values
similar to that of the bedrock, and could therefore be interpreted as coming from
ʴ
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