Using Source Fingerprinting Techniques to Investigate Sediment Sources during Snowmelt and Rainfall Erosion Events in a Small Catchment in the Black Soil Region of Northeast China

Concern for the offsite impact of eroded sediment and the need to develop effective catchment sediment management strategies has directed attention to the need for an improved understanding of the primary sediment sources within catchments and the potential of sediment source fingerprinting techniques to provide such information. The study reported here was undertaken in the black soil region of Northeast China, where soil erosion is seen as a serious threat to the sustainable use of soil resources and offsite impacts of eroded soil are also concerned. The study applies source fingerprinting techniques to the evaluation of sediment sources in a small (3.46 km(2)) agricultural catchment. Sediment sources from five snowmelt and five rainfall events of varying magnitude were contrasted. Three key potential sediment sources were identified within the study catchment: gullies, cultivated topsoil and uncultivated topsoil. Geochemical properties of the source materials (Ti, Ga, Br and Ba) were used as composite fingerprints capable of discriminating between the three potential sources. A mixing model, optimized using a genetic algorithm and coupled with a Monte Carlo procedure to quantify the uncertainty associated with the resulting estimates, was used for source apportionment. The results indicated mean source contributions for the set of 10 events for cultivated topsoil, uncultivated topsoil and the gullies of similar to 30%, similar to 10% and similar to 60%, respectively. In general, snowmelt and rainfall events were characterized by increased contributions from gully sources and cultivated topsoil, respectively. The study is seen as demonstrating the potential for using source tracing techniques to investigate sediment sources in environments where strong seasonal contrasts between snowmelt and rainfall events exist.