Geochemical Fingerprinting - Application of Geochemical Tracers to Fluvial Sediment - page 15

Fig. 2.3 a Flow diagram showing typical sources and pathways of sediment movement within
upland areas (modified from USEPA 1999 ). b Classification of the potential sources of riverine
sediments commonly defined for geochemical fingerprinting studies
problem when the number of sources and their characteristics are known (Weltje
2012 ); it is typically solved using a statistically based inverse or unmixing model. In
essence, inverse modeling requires that the composition of the source materials be
known for a selected set of physical and/or chemical properties, and then defines the
mixing proportions from each source that best fits the observed composition of the
studied river sediment (Weltje 2012 ).
The application of inverse modeling to riverine sediments is complicated by the
fact that the composition of the alluvial sediment reflects a wide range of physical and
geochemical processes in addition to the simple mixing of particles from the source
areas (Johnnson 1993 ; Weltje and von Eynatten 2004 ). Of particular significance are
hydraulic sorting processes inwhich the original population of particles froma source