5 NATURAL ABUNDANCE OF THE STABLE ISOTOPES ... - Falw.vu

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Chapter 7-613 (HCO 3 ) (‰)-8RhineA-10-12Meuse-1412 0 2 4 6 8 10 12 12 2 4 6 8 10 12 24 2 4 6 8 10 12 361967 1968 1969-618 (H 2 O) (‰)B-7-8-9Meuse-10Rhine-110122436Fig.7.8A three-year observation of the isotopic composition of water from the N.W.Europeanrivers Rhine and Meuse (Mook, 1970):A. 13 values of the dissolved bicarbonate fraction, showing normal values during winterand relatively high values in summer, probably because of isotopic exchange of thesurface water bicarbonate with atmospheric CO 2 .B. 18 values, where the river Meuse is showing the average value and the seasonalvariations of 18 in the precipitation: high values in summer, low during winter; duringearly spring and summer the Rhine receives meltwater from the Swiss Alps withrelatively low 18 because of the high-altitude precipitation .102
Stable Isotopes of Hydrogen, Carbon and OxygenTable 7.3The stable isotopes of oxygen: practical data for the natural abundance, properties,analytical techniques and standards. Further details are given in Sect.7.2, and in Chapters10 and 11.MS=mass spectrometry16 O17 O18 Ostability stable stable stablenatural abundance 0.9976 0.00038 0.00205abundance rangein hydrological cycle15‰ 30‰reported as17 or 17 O18 or 18 Oin ‰ ‰instrument MS MSanalytical medium O 2 CO 2 or O 2usual standard deviation 0.05‰international standard . VSMOW for waterVPDB for carbonate etcwith absolute value VSMOW: 0.0020052VPDB: 0.00206727.2.2 OXYGEN ISOTOPE FRACTIONATIONSThe isotope effects to be discussed are within the system H 2 O (vapour) H 2 O (liquid) CaCO 3 . The equilibrium fractionation values have been determined by laboratoryexperiments. Fig.7.1 shows some actual isotope ratios. Fig.7.10 and Table 7.4 present asurvey of the temperature dependent equilibrium isotope effects.Equilibrium fractionations determined in the laboratory are also found in nature. The moststriking observation is that the carbonate shells of many molluscs appear to have been formedin isotopic equilibrium with seawater. The palaeotemperature scale as presented by Eq.7.18was presented by Epstein et al. (1953) (cf. Friedman & O'Neil, 1977). This relation is deducedfrom 18 O measurements on carbonate laid down by marine shell animals at knowntemperatures and water isotopic compositions. These data lost the original interpretation ofthe temperature dependence of the s/l by the later realisation that the major oceanicpalaeotemperature effect is the change in 18 of seawater –and, consequently of carbonateformed in this water- by the formation viz. melting of enormous ice caps on the poles duringor after ice ages.103
Page 1 and 2: 7 NATURAL ABUNDANCE OF THE STABLEIS
Page 3 and 4: Stable Isotopes of Hydrogen, Carbon
Page 5: Stable Isotopes of Hydrogen, Carbon
Page 8 and 9: Chapter 77.1.3 REPORTING 13 C VARIA
Page 10 and 11: Chapter 7oceanic air far removed fr
Page 12 and 13: Chapter 7Numerically this comes to
Page 16 and 17: Chapter 7for water18 VSMOW (‰)fo
Page 18 and 19: Chapter 7Table 7.4 Oxygen isotope f
Page 20 and 21: Chapter 7this procedure, the sample
Page 22 and 23: Chapter 7 3 : from 2 , 1 , and 1
Page 24 and 25: Chapter 718 VSMOWocean watertropic
Page 26 and 27: Chapter 7isotope depletion of preci
Page 28 and 29: Chapter 713 VPDB (‰)0lakeevapora
Page 30 and 31: Chapter 77.4.3 REPORTING 2 H VARIAT
Page 32 and 33: Chapter 7Henceforth all 2 values w
Page 34 and 35: Chapter 72 VSMOW (‰)+ 200meteori
Page 36: 124Chapter 7

5 NATURAL ABUNDANCE OF THE STABLE ISOTOPES ... - Falw.vu

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