Determining Sources of Soil Erosion using Compound Specific Isotope Analysis: Application in a Rural Australian Catchment

摘要

Compound Specific Isotope Analysis (CSIA) was used to assesslability of the delta carbon-13 (5~(13)Cs) signature of fatty acid compounds to discriminate erosion sources in the Logan-Albert catchment, a rural river catchment on the Australian east coast. Thestudy augmented a previous sediment tracing study using fallout radionuclides and major/minor element geochemistry. Soil samples (presenting important erosion sources within the catchment were collected and the 6~(13)Cs values of bulk carbon and various fatty acids determined. It is found that surface soil from forest, pasture and cultivated land uses are well discriminated using CSIA. Furthermore, sib-surface soil sources associated with channel bank erosion and exposed subsoils (gullies and hillslope scalds) occurring specificallythe mid-western Logan catchment could also be discriminated. Sediment samples deposited during a high flow event in January 008 were also collected and analysed, and the IsoSource mixing model was used to determine erosion sources contributing sedi-nt. The results were compared with results obtained using other Hliment tracers. For the lower Logan River, the CSIA tracing resultsconsistent with fallout radionuclide and element geochemistry tracing, with channel bank erosion being confirmed as the majoriment source. Moreover CSIA has quantified the significanttribution of exposed subsoils originating on hillslopes and drain-e lines from the mid-western region of the Logan catchment. In le Albert River catchment about 40 percent of sediment comes omforest land use, although more than half of this may come from