Sediment Fingerprinting to Determine the Source of Suspended Sediment in a Southern Piedmont Stream.

Fingerprinting suspended sediment was used to determine the source of high stream sediment concentrations in a typical southern Piedmont watershed. 21 potential tracers were tested for the ability to discriminate between sources, conservative behavior, and lack of redundancy. Four of the 21 were selected: ¹³⁷Cs, d¹⁵N, U, and Cr. Tracer concentrations were determined in potential sediment sources (forests, pastures, row crop fields, stream banks, and unpaved roads/construction sites) and suspended sediment samples collected from the stream and analyzed using two methods: mixing models and end-member analysis. Results indicated that about 60% of the sediment originated from eroding stream banks, 23-30% from upland subsurface sources such as construction sites and unpaved roads and about 10-15% from pastures. This is the first study that has found a way to distinguish bank sediment from construction/unpaved road sources. Investment of resources in improving water quality should consider the contribution of bank erosion and unpaved roads/construction sites to water quality impairment.