Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732Fingerprinting is a field based measurement technique that unmixes eroded-soils to their sources in order to budget erosion within a watershed. This study focuses upon evaluating tracer variability across a watershed for biogeochemical tracers including nitrogen and carbon stable isotopes (15N, 13C) and the carbon to nitrogen atomic ratio (C/N). We collected 355 surface soils and analyzed them using isotope ratio mass spectrometry to statistically evaluate the significance of four spatially associated factors including: plot-location to account for tracer variability between field plots in a single land-use; slope-location to contrast floodplain versus upland tracers; profile-depth to evaluate sampling depth upon tracer variability; and soil-pit to account for tracer variability from sample replications at the same site. The Upper Palouse Watershed was chosen as the field study site due to well established agriculture and forest land-uses and consistent soil morphology within the land uses. Results of our statistical analysis showed that in the agriculture soil, plot-location, slope location, profile-depth, and soil-pit all significantly impacted the 15N and 13C signatures. In the forest soil, soil-pit dominated data variability with profile-depth and plot-location as significant to a lesser extent. C/N was less sensitive to the spatially associated factors as compared to the stable isotopes. This new knowledge of tracer variability is expected to be used in future fingerprinting studies
