Geochemical Fingerprinting - Application of Geochemical Tracers to Fluvial Sediment - page 11

methods have been aided in recent years by technological advances in surveying,
remote sensing, and photogrammetric techniques that have improved our ability to
document temporal and spatial patterns in erosion (Collins andWalling 2004 ). Collins
andWalling ( 2004 ) point out, however, that thesemethods fail to determine the degree
to which sediment sources are connected to the river and the inherent uncertainty in
routing sediment from the source to the channel. To overcome the problems inherent
in the direct measurement of sediment loads or upland erosion rates, distributed mod-
eling routines have been used, but these complex algorithms require the collection
and compilation of significant input and validation data, and often have difficulties
apportioning riverine sediments to individual sources (Collins and Walling 2004 ).
As a result, investigators have turned in recent years to the use of physical and geo-
chemical tracers, which can be applied relatively rapidly to gain insights into the
source of sediment and sediment-associated contaminants within a catchment.
The specifics of the fingerprinting approach vary widely, as do the parameters that
have been used as tracers to determine the source of sediments contained within a
river or its associated features (e.g., floodplain, reservoir, riparian wetland, etc.) (for
a review, see D'Haen et al. 2012 ). Table 2.1 , while far from exhaustive, shows the
most commonly utilized parameters with regards to riverine systems. The applica-
bility of these methods varies according to (1) the grain size fractions to which they
can be applied (i.e., gravel, sand, or silt and clay-sized material), and (2) the temporal
and spatial scale for which they can be used (D'Haen et al. 2012 ). To date, an over-
whelming majority of source ascription studies at the catchment scale have focused
on fine-grained sediments (

< ∼ µ

m in size) eroded from diffuse upland areas in
response to either natural or anthropogenic disturbances (e.g., wildfires, deforesta-
tion or timber harvests, agricultural practices, and urban/exurban development). The
focus on fine sediment, as noted in Chap. 1 , reflects both its direct impacts on river-
ine ecosystems (Wood and Armitage 1997 ; Armstrong et al. 2003 ; Syvitski et al.
2005 ;Boetal. 2007 ;Kempetal. 2011 ) and its chemically reactive nature, which
allows for a wide range of contaminants (e.g., nutrients, agricultural chemicals, and
trace metals and metalloids) to be carried from upland areas to the drainage network
(Horowitz 1991 ; Collins et al. 2005 ; Miller and Orbock Miller 2007 ). The movement
of nutrients from agricultural lands to rivers, reservoirs, and lakes, for example, is
often a significant issue in rural areas, and can lead to severe cases of eutrophica-
tion (Fig. 2.1 ). With regards to fine-grained sediments, geochemical tracers, fallout
radionuclides (FRNs), and mineral magnetic properties have been most extensively
utilized in provenance studies of both historical (50-10,000ybp) and contemporary
(

63

50ybp) sediments (D'Haen et al. 2012 ) (Fig. 2.2 ).
In this chapter, we focus on a specific methodological approach often referred to
as geochemical fingerprinting to determine the provenance of sediments suspended
within the water column or contained within alluvial deposits that are less than
about 150 years old. The catchment-scale approach involves two primary compo-
nents: (1) the identification of a set of sediment-associated geochemical parameters
(i.e., a fingerprint) that can be used to discriminate between the sediments of variously
defined sediment sources, and (2) the estimation of the relative proportion of sediment
from each of the individual sources that comprise suspended sediments (or other type

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