Erosion source discrimination in a rural Australian catchment using compound-specific isotope analysis (CSIA)

摘要

Compound-specific isotope analysis (CSIA) has been used to assess the ability of d13C signatures of fatty acid compounds tondiscriminate erosion sources in a rural Australian catchment. The study focussed on a high flow event (10-year recurrenceninterval) which occurred in the Logan–Albert catchment in January 2008, and augmented a previous sediment tracing studynusing fallout radionuclides and major/minor element geochemistry. It is found that surface soil from forest, pasture and cultivatednland uses are well discriminated using CSIA. Furthermore, sub-surface soil sources associated with channel bank erosion andnexposed subsoils (gullies and hillslope scalds) occurring specifically in the mid-western Logan catchment could also bendiscriminated. Selected fatty acid and bulk carbon d13C data were used in the IsoSource mixing model to determine erosionnsources contributing sediment. The results were compared with results obtained using other sediment tracers. For the lowernLogan River, the CSIA tracing results are consistent with fallout radionuclide and element geochemistry tracing, with channelnbank erosion being confirmed as the major sediment source. Moreover, CSIA has quantified the significant contribution ofnexposed subsoils originating on hillslopes and drainage lines from the mid-western region of the Logan catchment. In the AlbertnRiver catchment, about 40% of sediment comes from forest land use, although more than half of this may come from sub-surfacensources. These results have demonstrated that CSIA has the potential to significantly enhance the ability of sediment tracingnstudies to determine the extent that different land uses and erosion processes are contributing eroded soil to rivers, allowing annassessment of soil erosion and transport model predictions. Copyright © 2012 John Wiley & Sons, Ltd.