Health & Environmental Research Online (HERO)


Print Feedback Export to File
4254200 
Journal Article 
On the Delta O-17 budget of atmospheric O-2 
Young, ED; Yeung, LY; Kohl, IE 
2014 
Yes 
Geochimica et Cosmochimica Acta
ISSN: 0016-7037 
135 
102-125 
WOS:000335656900006 
We modeled the Delta O-17 of atmospheric O-2 using 27 ordinary differential equations comprising a box model composed of the stratosphere, troposphere, geosphere, hydrosphere and biosphere. Results show that 57% of the deficit in O-17 in O-2 relative to a reference water fractionation line is the result of kinetic isotope fractionation attending the Dole effect, 33% balances the positive Delta O-17 of O(D-1) in the stratosphere, and 10% is from evapotranspiration. The predicted Delta'O-17 O-2 relative to waters is -0.410 parts per thousand as measured at the delta O-18 of air. The value for Delta'O-17 O-2 varies at fixed delta O-18 with the concentration of atmospheric CO2, gross primary production, and net primary production as well as with reaction rates in the stratosphere. Our model prediction is consistent with our measurements of the oxygen isotopic composition of air O-2 compared with rocks if rocks define a fractionation line with an intercept in delta'O-17 - 10(3)ln(delta O-17/10(3) + 1) vs. delta'O-18 - 10(3)ln(delta O-18/10(3) + 1) space less than SMOW but more positive than some recent measurements imply. The predicted Delta O-17 is less negative than that obtained from recent measurements of O-2 directly against SMOW. Underestimation of Delta'O-17 O-2 can only be ameliorated if the integrated (bulk) Delta'O-17 for stratospheric CO2 is significantly greater than measurements currently allow. Our results underscore the need for high-precision comparisons of the O-17/O-16 and O-18/O-16 ratios of atmospheric O-2, VSMOW, and rocks. (C) 2014 Elsevier Ltd. All rights reserved.