Introduction - Application of Geochemical Tracers to Fluvial Sediment - page 6

tracers have not only been used to determine sediment/contaminant provenance in
riverine systems, but they have now been applied to address a host of other issues
ranging from the redistribution of sediment on hillslopes, to the exchange rates and
residence times of sediment within the channel, to the rates of sediment movement
to the catchment mouth, to the biogeochemical cycling of contaminants within the
aquatic environment. Tracers have also been used to provide retrospective infor-
mation on geomorphic and geochemical processes and process rates over the past
several decades to centuries, data that cannot be obtained by traditional monitoring
programs. For example, geochemical tracersmay be incorporated into channel, flood-
plain, or terrace deposits where their analysis may be used to unraveled such things as
the timing and history of contaminant influx to rivers and/or the dispersal pathways
through which contaminants are distributed along the river (Miller 2013 ; Miller and
Orbock Miller 2007 ). In light of the above, tracers can be used to decipher potential
environmental impacts of sediment and sediment-associated contaminants on river
systems, and determine potentially responsible parties associated with these impacts.
The primary objectives of the following chapters are to (1) provide an in depth
discussion of the theory, methodology, and application of environmental tracer and
fingerprinting methods that have and are currently being used to address the source,
transport, and deposition of sediment and sediment-associated contaminants within
river systems, and (2) provide an analysis of the strengths and limitations of the exam-
ined techniques in terms of their temporal and spatial resolution, data requirements,
and inherent uncertainties in the generated results. We will focus on the use of natural
and anthropogenic geochemical tracers that currently exist within surficial geologi-
cal materials, rather than 'particle-tracking' techniques. It is important to recognize
that our intent is not to replace other forms of analyses of the sediment system, but
to show how tracer/fingerprinting studies can be used to gain insights into system
functions that would not otherwise be possible. In fact, significant attention is given
to ways in which fingerprinting and tracer technologies may be integrated with other
hydrological, geochemical, geomorphic, and stratigraphic techniques to address the
complexity inherent in the dispersal of sediment and sediment-contaminated materi-
als through riverine environments. Given that the use of tracers to address legislative
or legal issues will undoubtedly increase in the coming years, we will, where possi-
ble, address a number of topics that are critical to environmental forensics, including
whether the methods represent (1) valid and testable approaches that have gained
widespread acceptance through the peer review process, (2) generate results with
quantifiable errors or levels of uncertainty, and (3) can be easily understood by indi-
viduals who may not have a scientific background (e.g., as a judge or jury).
1.2 Book Format and Overview
We begin our discussion of environmental tracers in Chap. 2 with an overviewof what
is typically referred to as geochemical fingerprinting. The fingerprinting approach
is typically focused on sediment, rather than contaminants (although contaminants