Sediment Fingerprinting

There is increasing interest in tracing the key sources of sediment in river channels to support the targeting of mitigation actions that aim to reduce sediment delivery to surface waters.

Sediment fingerprinting technology relies upon identifying significant differences in the chemical properties of soil from different sediment sources. Catchment sediment fingerprints can differ owing to a range of natural and anthropogenic processes reflecting underlying geology, land use and contamination. Subsequently, the properties of channel sediments can be matched to those of the potential sources to identify the main areas contributing sediment (and contaminants) to the river channel.

Sediment fingerprinting studies are carried out using the source-pathway-receptor framework and study sites are initially assessed to determine the potential source components such as agricultural surface soils, road-derived or quarry material for example. Key pathways (e.g. drainage gullies; farm tracks; road surfaces) are identified and also the main receptor component of interest (e.g. river channel reach or lake waters). Samples of sediment are taken from each site using a pre-defined sampling strategy and the geochemical properties of the sediment then form the basis of fingerprinting approach.

Properties that can be used to discriminate sources are: (i) fallout radionuclides (137Cs, 7Be and 210Pbxs) which enable discrimination of surface, subsurface and cultivated sources, (ii) major and minor element geochemistry, which is related to geological substrate but also modified by soil formation processes and weathering and hence has potential to discriminate landuse, (iii) mineral magnetic properties, which are sensitive to soil formation processes and pollution, and (iv) contaminants from industrial or other anthropogenic activities e.g. heavy metals.

Among the leading experts in the field of Sediment Source Fingerprinting are Prof. Will Blake (Plymouth University) and Prof. Adrian Collins (Rothamsted Research) who have collaborated in a detailed source apportionment investigation of sediment sources in the River Taw.