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STABLE ISOTOPES IN ECOLOGICAL STUDIES: EXPANDING THE SCOPE OF MIXING MODELS
Citation:
PHILLIPS, D. L. STABLE ISOTOPES IN ECOLOGICAL STUDIES: EXPANDING THE SCOPE OF MIXING MODELS. Presented at Presentation at University of Arkansas, Fayetteville, AR, September 21, 2006.
Description:
Stable isotopes are increasingly being used as tracers in ecological studies. One common application uses isotopic ratios to quantify the proportional contributions of multiple sources to a mixture. Examples include pollution sources for air or water bodies, food sources for animals, water sources for plants, and biogeochemical inputs to soils. Simple mixing models based on mass balance equations have been used for this purpose for several decades. One limiting factor in the application of such mixing models has always been that when n isotopic tracers are employed, they can only determine the contributions of n+1 sources. In this presentation, a method is outlined in which quantitative bounds on source contributions can be determined for >n+1 sources, even though unique solutions are not possible. Further developments which expand the scope of mixing model applications are described, including several approaches for combining sources, and using additional non-isotopic constraints. Both of these methods can result in more well-defined and interpretable results for source contributions to a mixture.