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Über dieses Buch

This book takes an in-depth look at the theory and methods inherent in the tracing of riverine sediments. Examined tracers include multi-elemental concentration data, fallout radionuclides (e.g., 210Pb, 137Cs, 7Be), radiogenic isotopes (particularly those of Pb, Sr, and Nd), and novel (“non-traditional”) stable isotopes (e.g., Cd, Cu, Hg, and Zn), the latter of which owe their application to recent advances in analytical chemistry. The intended goal is not to replace more ‘traditional’ analyses of the riverine sediment system, but to show how tracer/fingerprinting studies can be used to gain insights into system functions that would not otherwise be possible. The text, then, provides researchers and catchment managers with a summary of the strengths and limitations of the examined techniques in terms of their temporal and spatial resolution, data requirements, and the uncertainties in the generated results.

The use of environmental tracers has increased significantly during the past decade because it has become clear that documentation of sediment and sediment-associated contaminant provenance and dispersal is essential to mitigate their potentially harmful effects on aquatic ecosystems. Moreover, the use of monitoring programs to determine the source of sediments to a water body has proven to be a costly, labor intensive, long-term process with a spatial resolution that is limited by the number of monitoring sites that can be effectively maintained. Alternative approaches, including the identification and analysis of eroded upland areas and the use of distributed modeling routines also have proven problematic. The application of tracers within riverine environments has evolved such that they focus on sediments from two general sources: upland areas and specific, localized, anthropogenic point sources. Of particular importance to the former is the development of geochemical fingerprinting methods that quantify sediment provenance (and to a much lesser degree, sediment-associated contaminants) at the catchment scale. These methods have largely developed independently of the use of tracers to document the source and dispersal pathways of contaminated particles from point-sources of anthropogenic pollution at the reach- to river corridor-scale. Future studies are likely to begin merging the strengths of both approaches while relying on multiple tracer types to address management and regulatory issues, particularly within the context of the rapidly developing field of environmental forensics.

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract
Tuero Chico is a small village located along the Rio Pilcomayo of southern Bolivia.
Jerry R. Miller, Gail Mackin, Suzanne M. Orbock Miller

Chapter 2. Geochemical Fingerprinting

Abstract
Use of geochemical fingerprinting methods to determine sediment provenance has progressively increased since the late 1990s, and is now considered by many investigators as the method of choice to quantify sediment source contributions at the catchment scale. Application of geochemical fingerprinting largely rests on four factors: (1) the inability of other techniques (e.g., sediment load monitoring, photogrammetric methods, and mathematical modeling approaches) to effectively determine sediment provenance at the required spatial scales, (2) improvements in analytical methods that allow for the analysis of large numbers of samples for a wide range of elements, (3) the modification of the utilized statistical methods (e.g., inverse/unmixing models) to more effectively account for uncertainty in the modeled results, and (4) the ability to apply the methods to historic sedimentary deposits retrospectively to determine changes in sediment provenance at a site through time. In this chapter, we focus on the application of geochemical fingerprinting to contemporary river sediments as well as alluvial deposits that are less than about 150 years old. Our intent is not simply to summarize the voluminous and growing body of literature on the subject, but to document the strengths, weaknesses, and uncertainty inherent in the approach.
Jerry R. Miller, Gail Mackin, Suzanne M. Orbock Miller

Chapter 3. Fallout Radionuclides

Abstract
A number of short-lived radioactive isotopes of both natural and anthropogenic origins which are (or were) atmospherically deposited over the landscape have been extensively utilized as sediment tracers in riverine environments. The three most extensively utilized isotopes, which are often referred to as fallout radionuclides (or FRNs), include in decreasing order of application, \({{}^{137}\mathrm{Cs}},\,{{}^{210}\mathrm{Pb}_\mathrm{ex}}\), and \({{}^7\mathrm{Be}}\). Herein we examine the primary ways in which these three isotopes have been applied to gain insights into the riverine sediment system. More specifically, we explore the strengths and weaknesses of using FRNs in combination with mixing models to determine sediment provenance at the catchment scale, particularly with regards to determining whether the sediment was derived by means of sheet, rill, gully, or bank erosion. The nuclide inventory approach is also examined for its ability to characterize other components of the sediment system at much smaller spatial scales, including the redistribution of sediment on hillslopes and between landscape units. Our discussion concludes by examining the ability of \({{}^7\mathrm{Be}}\) to document dynamic processes operating along the channel bed by determining sediment residence times, scour and fill depths, particle filtration, and sediment travel distances.
Jerry R. Miller, Gail Mackin, Suzanne M. Orbock Miller

Chapter 4. Radiogenic Isotopes

Abstract
Radiogenic isotopes have been widely used to assess an extensive range of geological processes. In this chapter, we focus on the use of three radiogenic isotope systems (Sr, Nd, and Pb) to determine the source of sediment and sediment-associated contaminants in riverine environments. We begin by examining the past and continuing use of Sr and Nd isotopes to determine the provenance of sediment at large spatial scales before exploring their potential use to track anthropogenically contaminated sediment at much smaller (local to regional) spatial scales. We then turn our attention to the use of Pb isotopes as a tracer of Pb contaminated sediments in riverine environments. Given the many and increasing ways in which radiogenic isotopes can be applied to environmental, geomorphic, and hydrologic issues, the discussion is not meant to be exhaustive. Rather, it is intended to provide an overview of the sorts of methodological approaches that have been used to address the sediment/contaminant source problem in riverine environments, and the strengths and weaknesses inherent in the approach.
Jerry R. Miller, Gail Mackin, Suzanne M. Orbock Miller

Chapter 5. Stable ‘Non-Traditional’ Isotopes

Abstract
Recent advances in analytical capabilities, particularly the MC-ICP-MS, have allowed for a precise determination of a wide range of stable isotopes in geological and biological materials that could not be assessed prior to the 1990s. As a result, research into the use of these ‘non-traditional’ isotopes (or ‘non-CHONS’) as tracers of both elemental sources and biogeochemical processes has been increasing at an exponential rate. While their utilization as a tracer of contaminated sediments in the near surface environment is often complicated by multiple physical and biological fractionation processes, there is increasing evidence to suggest that they may be effectively used as tracers in aquatic environments. In this chapter, we examine the potential use of four stable metal isotopes (Zn, Cd, Cu, and Hg) that appear on the basis of the limited studies conducted to date to have the potential to track sediment-associated trace metals in rivers.
Jerry R. Miller, Gail Mackin, Suzanne M. Orbock Miller

Backmatter

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