Geochemical Fingerprinting - Application of Geochemical Tracers to Fluvial Sediment - page 40

flood events (Fig. 2.10 ). The construction of a drainage ditch through an upstream
wetland altered the hydrologic connectivity of the catchment, allowing sediment and
sediment-associated nutrients to be transported from the headwaters to the lower
basin, a process that also increased downstream sedimentation rates as determined
by dating a sediment core. From an applied perspective, the results of the study
showed that the positive benefits of controlling sediment/nutrient exports from the
catchment by means of upland based best management practices were partly negated
by modifying the axial drainage system.
The above discussion may suggest that geochemical fingerprinting to assess sed-
iment provenance is a straightforward process that can be utilized by a relatively
well-defined methodology. In reality, each catchment exhibits a unique set of char-
acteristics requiring investigators to modify the approach to fit the catchments hydro-
logic, geomorphic and climatic setting. Nonetheless, the rapidly increasing volume
of literature on the topic shows that fingerprinting can provide important insights
into the temporal and spatial changes in sediment provenance for specific grain size
fractions. Moreover, it is apparent that geochemical fingerprinting can be combined
with other forms of geomorphic, hydrologic, and geochemical tracing to more fully
address a wide range of sediment related problems within a watershed.
2.5 Use of Geochemical Fingerprinting as a Management Tool
There is little debate that sediment source identification is a fundamental require-
ment for the effective mitigation of diffuse sediment and sediment-born contaminant
inflows to rivers and other aquatic environments. However, the use of fingerprinting
techniques to decipher the source and dispersal of non-point source contaminants,
including sediment, at the catchment scale has yet to be extensively utilized by
land-use managers or regulatory agencies. In fact, Mukundan et al. ( 2012 ) found
that only one state in the U.S. (Minnesota) was using geochemical fingerprinting
as part of a defined management strategy, and, to the best of our knowledge, it
remains the only state as of 2014. Given the nature of recent legislation in many
developed countries, and the need for a sound understanding of the predominant
sources of sediment to rivers, it seems likely that geochemical fingerprinting will
more extensively be used in the future for management or regulatory purposes. Actu-
ally, the potential benefits and difficulties of transforming geochemical fingerprint-
ing from a research to a management tool is currently being explored. Mukundan
et al. ( 2012 ), for example, examined the use of geochemical fingerprinting for the
establishment of total maximum daily loads (TMDLs) in the U.S. TMDLs, which
states must define for impaired waters as part of a management strategy, repre-
sent the maximum amount of a given pollutant, in this case sediment, that the water
body may receive without violating water-quality standards. A key component of the
USEPA's organizational framework for establishing TMDLs is contaminant source
assessment; thus, it would seem that geochemical fingerprinting could (and perhaps
should) be incorporated into the framework for establishing TMDLs. The analysis by