The dependence on wavelength of 13C isotope effects in photolysis of aqueous solutions of ferrie oxalate

1976 ◽  
Vol 54 (16) ◽  
pp. 2577-2580 ◽  
Author(s):  
Robert H. Betts ◽  
Wayne D. Buchannon
Keyword(s):  
Carbon Dioxide ◽  
Aqueous Solutions ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Isotopic Fractionation ◽  
Isotopic Discrimination ◽  
Carbon Isotopic ◽  
13C Isotope ◽  
Photochemical Activation ◽  
Carbon Isotopic Fractionation

The formation of carbon dioxide by photolysis of aqueous solutions of ferric oxalate is accompanied by carbon isotopic fractionation. 12C appears preferentially in the evolved CO2, but the isotope effect depends markedly on the wavelength of the light used. Fractionation is essentially zero (k12/k13 = 1.001) at 366 nm, and increases with wavelength, reaching 1.050 at 520 nm. It is proposed that this variation of isotopic discrimination arises from the differing properties of the excited levels formed by photochemical activation.

An applied mineralogical investigation of concrete degradation in a major concrete road bridge

1990 ◽  
Vol 54 (377) ◽  
pp. 637-644 ◽  
Author(s):  
G. Macleod ◽  
A. J. Hall ◽  
A. E. Fallick
Keyword(s):  
Carbon Dioxide ◽  
Cement Paste ◽  
Atmospheric Carbon Dioxide ◽  
Meteoric Water ◽  
Isotope Analysis ◽  
Isotopic Fractionation ◽  
Physical Growth ◽  
Carbon Isotopic ◽  
Mineralogical Investigation ◽  
Atmospheric Carbon

AbstractA core of concrete taken from a major road bridge in the Strathclyde Region, Scotland, has been subjected to an applied mineralogical investigation, which involved stable isotope analysis, petrography, X-ray diffraction and scanning electron microscopy.The structure is actively undergoing severe degradation due to mineral growth which is related to chemical reactions between the concrete and pore fluid. The physical growth of minerals causes disfigurement and structural weakening.Pyrite and pyrrhotine hosted by dolerite aggregate appear to have been oxidized, providing sulphate for the deposition of ettringite and minor gypsum, in spheroidal cavities within the cement paste. The rainwater which passes through the structure mobilising sulphate from original gypsum in the paste and oxidizing the iron sulphides is also involved in the further leaching of elements from the cement paste and in the deposition of calcite. The isotopic values of calcites forming a crust on the concrete and a stalactite under the bridge are similar with δ13C= −19‰ PDB and δ18‰= +16‰ SMOW. We suggest that atmospheric carbon dioxide was the carbon source. The carbon isotopic fractionation of −12‰ from atmospheric carbon dioxide of δ13C= −7‰, (O'Neil and Barnes, 1971) can best be explained as due to a kinetic fractionation related to the hyper-basicity of the pore water. The equilibrium formation temperature of about 45°C calculated from the oxygen isotope values and assuming a δ18O value of meteoric water of −8‰ SMOW, is considered unreasonable. The exceptionally low δ18O values are attributed mainly to reaction kinetics and the calcite inheriting its oxygen, two-thirds from atmospheric carbon dioxide and one third from the meteoric formation water (O'Neil and Barnes, 1971). A δ18O value of atmospheric carbon dioxide of +41‰ SMOW and a δ18O value of meteoric water of −8‰ SMOW, lead to a calculated δ18O value for the calcites of +10‰ SMOW. The calcites analysed have a value of +16‰ and this may be due to partial re-equilibration towards a calculated value of +21‰ for calcite in equilibrium with the meteoric water at 20°C.

Carbon isotopic fractionation associated with lipid biosynthesis by a cyanobacterium: Relevance for interpretation of biomarker records

1997 ◽  
Vol 61 (24) ◽  
pp. 5379-5389 ◽  
Author(s):  
Susumu Sakata ◽  
John M. Hayes ◽  
Andrew R. McTaggart ◽  
Ronald A. Evans ◽  
Kristen J. Leckrone ◽  
...  
Keyword(s):  
Isotopic Fractionation ◽  
Lipid Biosynthesis ◽  
Carbon Isotopic ◽  
Carbon Isotopic Fractionation
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