Isotopic exchange effects in the evaporation of water: 1. Low-temperature experimental results

Abstract

The deuterium and oxygen 18 concentrations of water evaporating into air of nonzero humidity do not follow the simple batch distillation equation but increase asymptotically to a stationary isotopic state as the mass of water decreases to zero. This effect is due to a rapid molecular exchange between liquid and vapor, which predominates over the simple separation effect of removal of vapor. In diy air the batch distillation law is obeyed, and the isotopic enrichment continually increases; however, the separation factor is larger than the equilibrium isotopic vapor pressure ratio when the evaporation rate is comparable to natural rates. The HDO and H2O18 enrichments in our experiments show a linear correlation with a slope of about 5.5, as found in the evaporation of natural water bodies. The mechanism of the molecular exchange will be described in following papers.

Improved methodologies for continuous-flow analysis of stable water isotopes in ice cores

“…9). The discrete samples (3 cm cuts) were measured using a uranium reduction technique for δD (Vaughn et al, 1998) and a CO 2 -H 2 O equilibration method for δ 18 O (Epstein, 1953;Craig et al, 1963). We find that the amplitude of the δ signal between the IRMS and CRDS-CFA techniques is nearly identical, albeit with an occasional offset in δD of 3-4 ‰ and δ 18 O of 0.4-0.5 ‰.…”

“…Typically, water samples are analyzed discretely using 3-5 cm intervals of ice. Isotopic ratios of oxygen are usually obtained using a CO 2 -H 2 O equilibration method (Epstein et al, 1953;Craig et al, 1963). For hydrogen isotopes, a variety of methods have been used, including H 2 -H 2 O equilibration using a platinum catalyst and reduction of water with uranium, zinc, or chromium (Bigelseisen et al, 1952;Bond, 1968;Coleman et al, 1982;Coplen et al, 1991;Vaughn et al, 1998;Huber and Leuenberger, 2003).…”

Final report on the Groundwater Isotope Project in the Brentwood Region of East Contra Costa County, California

“…Evaporating surface water that originates as rain or snow shifts to the right of the GMWL as evaporation progresses (Craig et al, 1963). Agricultural irrigation water is predominantly imported to the Brentwood region from a San Joaquin River source that originates as Sierra Nevada precipitation.…”

Geochemical and Isotopic Evaluation of Groundwater Movement in Corrective Action Unit 97: Yucca Flat/Climax Mine, Nevada Test Site, Nevada, Rev. No.: 0

“…The spring data plot along an evaporation line with a characteristic slope of ~3.5, which reflects a kinetic isotope exchange process with water vapor in the air (Craig et al, 1963). A regression line through the spring data intersects the LMWL at approximately -97.7 permil δD and -13.3 permil δ 18 O (the intersection with the GMWL gives slightly lower values).…”