Geochemical Fingerprinting - Application of Geochemical Tracers to Fluvial Sediment - page 20

Fig. 2.4 Illustration of the types of river sediments that are collected for the geochemical finger-
printing of contemporary and historical sediments. Each type of sample is associated with a specific
timeframe of analysis, ranging from instantaneous samples collected during a specific part of a
flood hydrograph ( red , filled circles ) to passive and channel bed sediments (periods of months to
a few years, horizontal rectangles ) to floodplain and reservoir sediments (representing periods of
years or decades, vertical rectangles )
consideration, andmay range fromrecent, instantaneous suspended sediment samples
collected during a specific portion of a flood hydrograph to river sediments deposited
within floodplains or riparian wetlands during an entire flood and that may be hun-
dreds or even thousands of years old.
Historically, suspended sediments were sampled to assess the contributions of
contemporary sediments to the channel from key sources during flood events (e.g.,
Collins et al. 1997a , 1998 , 2001 ; Peart and Walling 1986 ; Walling and Woodward
1992 , 1995 ). There has been a growing realization, however, that the fingerprinting
of instantaneously collected samples may not be the most time and cost effective
method of determining sediment provenance for an entire flood. At issue is the fact