Radiogenic Isotopes - Application of Geochemical Tracers to Fluvial Sediment - page 106

specific time periods. It is also important to recognize that the use of dated cores
allowed an historical understanding of Pb use and provenance in the catchment to be
determined.
Bird et al. ( 2010a , b ) overcame the multiple source problem by using a two-tiered
approach to assess Pb provenance within the River Maritsa catchment of Bulgaria
and Turkey. A binary isotopic approach was used within smaller tributary basins
to assess the contributions of Pb from mining operations to the channel. However,
highly variable Pb isotopic values inhibited the use of this binary method within
lower catchment areas where sediment was derived from a wider range of geological
units. Thus, sediment/Pb provenance was determined for the lower catchment areas
using multi-element geochemical fingerprinting methods similar to that described in
Chap. 2 . Bird et al. ( 2010a , b ) also applied a similar approach to the lower Danube
Catchment in Eastern Europe. The fingerprinting approach has also been applied
directly to Pb isotopic data to assess Pb provenance where multiple Pb sources
exist (Miller et al. 2007 ). A rather different graphical approach to quantifying Pb
contributions has occasionally been used where three end-member sources can be
identified on the basis of Pb concentration and a Pb isotopic ratio (e.g., Lima et al.
2005 ; N'guessan et al. 2009 ). The approach is based on the graphical plotting of
linear mixing lines between the three end-member sources on the basis of sample
concentrations and their associated isotopic ratios forming a ternary diagram. Once
the ternary diagram has been created, the relative contributions of Pb from the three
delineated sources then can be estimated from the plot.
4.4 Summary and Management Implications
Sr andNd isotopic systems have been extensively used as tracers to address such prob-
lems as weathering rates and intensities, the potential factors influencing temporal
variations in seawater chemistry, and the source of particulates in dust and sedimen-
tary rocks. Their application to historic and contemporary riverine environments,
particularly at small spatial scales, is more restricted, as is their use to source con-
taminated particles. However, their proven potential to source sedimentary particles
and recent studies suggest that both Sr and Nd isotopes may be used to differentiate
between various types of anthropogenic pollutants indicates that their application
to riverine contaminant issues will prove effective. Moreover, their application to
contaminated rivers will be able to make use of an extensive body of literature on
the topic that has been generated for the analysis of other geological systems. Their
utilization will likely be driven by the inability of a single isotopic system (e.g., Pb)
to distinguish between the known contaminant sources. Thus, we suspect that Sr and
Nd isotopes will be of most value when used in combination with Pb isotopes and/or
other elemental tracers.
Of these three isotope systems discussed herein, Pb has been the most extensively
utilized as a tracer of anthropogenic contaminants. Recent studies have demonstrated
that Pb isotopes can be effectively applied to riverine sediments to determine the