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Homework Help: Isotope Tracers and Mixing

  1. Dec 5, 2015 #1
    1. The problem statement, all variables and given/known data
    Two water samples are mixed. Sample 1 has δ18O-H2O = -1(per mil), Sample 2 has δ18O-H2O = -20 (per mil), and the mixture has δ18O-H2O = -15 (per mil).

    What fraction of water came from sample 1 and what fraction came from sample 2?
    Assume that F = the fraction of the water that came from Sample 1
    Assume that 1-F = the fraction of the water that came from Sample 2

    2. Relevant equations
    QT=Q1+Q2 where QT is total percent, and Q1 and Q2 are the percent contributions to the mixture from samples 1 and 2, respectively.

    δ18OTQT = δ18O1Q118O2Q2

    3. The attempt at a solution
    I've uploaded my work...if I am using the write mixing equation for two endmembers, my problem really is then just isolating and solving for F. From there I can solve for F2

    Attached Files:

  2. jcsd
  3. Dec 11, 2015 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
  4. Dec 13, 2015 #3
    @Greg Bernhardt I've used the Isotopic Mixing Equation: δ18OTQT = δ18O1Q118O2Q2 in order to solve it. It can also be solved using a Two-component Mixing Model, according to the equations: F2 = (δ18Omix18O1) / (δ18O218O1) ; F1 = 1 - F2
    Using both equations, you find that the fraction of the sample coming from sample 1 is 0.26 (or 26%), and percent contribution from sample 2 is 0.74 (or 74%)
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