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Data Analysis Methods and Models for Stable Isotopes:

Stable isotope analysis is being increasingly utilized in ecological studies to trace the movement of chemicals through the environment.  One common type of application is to use stable isotopes to quantify the proportion of different sources contributing to a mixture.  Examples include determining the contributions of various pollution sources to air or water bodies, food sources to animal diets, soil horizons to plant water uptake, inputs to soil organic carbon, etc.  Mathematical mixing models are used to quantify these source proportions.  Recent research at EPA’s Western Ecology Division has produced several new developments that extend the capabilities of these mixing models.  Descriptions of these methods, as well as software for free downloading, are available at the links below:

 IsoError: Confidence interval calculation for source partitioning using stable isotopes (Excel™)

 IsoConc: Concentration-dependent stable isotope mixing model (Excel™)

 IsoSource: Stable isotope mixing model for an excess number of sources (Visual Basic™)
      Version 1.3.1 now available (8-8-2006).

 Publications: Publications describing these methods and related research at the Western Ecology Division.

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