Determining Water Isotope Compositions for the IAEA WICO and North West Villages, South Africa

Abstract

Deuterium (2H) and oxygen 18 (18O) stable isotopes in water are the key indicators of hydrological and ecological patterns and processes. The water isotopes δ2H and δ18O have been employed widely as tracers in hydrological and ecological research, as they are integrated into geological and biological systems in a predictable manner. The aim of this study was to determine the water isotope composition of the International Atomic Energy Agency’s (IAEA) Water Isotope Inter-laboratory Comparison (WICO) samples and to determine the Local Meteoric Water Line for North West Province (NWP) villages in South Africa. The IAEA WICO 2020 samples were obtained from the IAEA, Vienna, and borehole water samples from selected villages in the North West province of South Africa were randomly collected to investigate the relationship between the stable isotopes (18O and 2H) and the climate in underground water aquifers. A cavity ring-down spectroscopy analyzer with laser-current-tuned cavity resonance, Picarro L2140-i, was used to measure triple water–isotope ratios with high precision. The IAEA WICO results obtained for the d-excess were in a satisfactory range and the margins of error were close to those required by the IAEA. The δ2H values ranged between −33.00‰ and −8.00‰, while the δ18O values ranged between −5.50‰ and −2.00‰. The results of this work have shown that our water science and management lab is capable of undertaking inter-laboratory comparisons for the IAEA.