Geochemical Fingerprinting






Heavy Metals

Stream Restoration

Sediment Generation and Transport





It is impractical to develop strategies for reducing sediment or contaminant loads in river systems if it is unclear where the contaminants originate and if they are continuing to enter the system, perhaps on a sporadic basis. Documenting sediment/contaminant sources, however, is not an easy task. Consider, for example, the influx of sediment-borne trace metals. In many situations these anthropogenic pollutants can be derived from multiple point and non-point sources that create complex and often overlapping geographical patterns in metal values. Moreover, at low contaminant loadings, the concentration of metals from anthropogenic sources may be masked by those found naturally in rocks, sediment, and soils, making it extremely difficult to use spatial patterns in metal concentrations to determine their primary source.

The difficulties of identifying contaminant sources have led to the development of various physical and geochemical tracers and tracer methods. In general, a tracer represents some unique characteristic of the source material (contaminated or otherwise) that allows it to be distinguished from other sediment in the basin. Tracers are now widely accepted as an important tool for identifying contaminant sources and for distinguishing the relative contributions of sediment and sediment-borne contaminants to river systems. Currently, my colleagues and I are involved in a number of research projects that (1) use multivariate geochemical fingerprinting methods to identify non-point sources of sediment and sediment-associated contaminants, and (2) apply isotopic methods to track specific substances, particularly lead, from both point and non-point sources through riverine environments. The importance of both of these techniques for site assessments is likely to grow because with ever more stringent controls on contaminant releases to river systems, a more forensic approach will be required to assess the complexities of the contaminant source-to-sink relationships (see, for example, Macklin et al., 2006).