Stable hydrogen and oxygen isotope techniques for studying arid basin hydrology

A technique was developed to measure both H- and O-isotope compositions of 5 μl water samples to study concentrated lake brines and fluid inclusions in primary halite. The method involves high temperature distillation under vacuum and splitting of the extracted water into two aliquots. One aliquot was reacted with Zn to produce H₂ for H/D analysis whereas the other was converted to CO₂ for ¹⁸O/¹⁶O analysis by reaction with guanidine hydrochloride. The isotope data did not appear to require corrections for 'salt effects' as found for some methods. The technique has been used to obtain data for arid regions in the western USA and the Qaidam basin of western China. Such data are proving informative in the modelling of current and past hydrologic systems in these and similar environments.