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

Stable Isotopes of Hydrogen, Carbon and OxygenThe average 2 value of the secondary standard SLAP on the VSMOW scale (Sect.7.2.3)consequently is 428.2 ± 0.1‰. Based on these data the 2 value has been defined as:2 SLAP / VSMOW = 428.0‰ (7.33)No significant difference in 2 has been detected between the original SMOW standard andVSMOW (IAEA, 1978).Table 7.6Hydrogen isotope fractionation in the equilibrium system liquid water (l), water vapour(v), and ice (i); y / x represents the fractionation of compound y relative to compound xand is approximately equal to 2 (y) 2 (x). Values for intermediate temperatures may beobtained by linear interpolation; T = t (C) + 273.15 K.t2 v/l 1 )18 v/l2 v/l / 18 v/l 2 )C(‰)(‰)0 101.0 11.55 8.75 94.8 11.07 8.5 510 89.0 10.60 8.415 83.5 10.15 8.2 520 78.4 9.71 8.125 73.5 9.29 7.930 68.9 8.89 7.7 535 64.6 8.49 7.640 60.6 8.11 7.41 ) Majoube, 1971 :ln 2 = 24 844/T 2 + 76.248/T 0.052612 (7.31a)1/T adjustment : 2 v/l = 85 626/T + 213.4‰ (7.31b)Values at higher temperatures can be obtained from Horita and Wesolowski(1994)2 ) The ratios between the fractionations for 18 O and 2 H at the liquidvapour equilibrium areobtained from Majoube (1971).Majoube, 1971 : 2 i/l = + 19.3‰ (at 0C) (7.32)Reference and intercomparison water samples are available from the IAEA (Table 11.3). The2 H contents of hydrogen-containing samples are determined by completely converting them tohydrogen gas. Therefore, fundamental problems of isotope fractionation during samplepreparation, as with 18 O, do not occur; however, the analyses are more troublesome (Sect.10).119