I submitted CO2 samples for stable isotopic analyses that were produced
by reacting the CaCO3 in biohydroxyapatite with H3PO4 at 90C.  Results
for d13C and d18O values were returned relative to PDB.  If I wanted to
convert the d18O values to SMOW, would it be safe to use the equation
provided by Friedman and O'Neil (1977, pg KK4), where
dSMOW=1.03086*dPDB+30.86?  This equation is based on CO2 liberated in
H3PO4 from calcite at 25C.  Dr. Yang Wang provided a fractionation
factor for CO2 liberated from CaCO3 with H3PO4 at 25C of 1.01025, which
is the same as for calcite under similiar conditions.  Is there a more
applicable conversion equation?  Thanks in advance for any insights...
-Mark



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R. Mark Larson
Department of Rangeland Ecology and Watershed Management
University of Wyoming
Laramie, WY 82071-3354

Phone: (307) 766-5470
Fax: (307) 766-6403
Email: [log in to unmask]