Characteristics of isotopic evolution of liquid water during evaporation: Experimental validation using the Rayleigh fractionation and Craig-Gordon models; [물 안정동위원소의 증발 거동 특성: 레일리 분별 모델과 크레이그-고든(Craig-Gordon) 모델을 활용한 실험적 검증]

Abstract

Stable water isotopes (δ18O, δ2H) are key tracers that sensitively respond to phase change processes such as evaporation and condensation, and are widely used to interpret hydrological cylce and climate change. In particular, quantitatively constraining the enrichment trend of stable water isotopes during evaporation provides crucial insights into hydrological processes and the reconstruction of past climate and environmental conditions. In this study, we conducted an open-system evaporation experiment using distilled water to investigate the evolution of isotopic change in relation to the residual water fractions, and analyzed the controlling factors influencing isotopic fractionation. Application of the Rayleigh model to the experimental results yielded effective fractionation factors (αeff) of 1.0171 for δ18O and 1.0792 for δ2H. To further distinguish between equilibrium (αeq) and kinetic (αk) fractionation factors during evaporation, the Craig-Gordon model was applied, resulting in αeq = 1.0113 and αk = 1.0180 for δ18O, and αeq = 1.0830 and αk = 1.0064 for δ2H. These results suggest that δ18O is more strongly influenced by humidity-dependent kinetic fractionation, while δ2H is predominantly controlled by temperature-dependent equilibrium fractionation. Overall, this study provides an experimental basis for quantitatively evaluating isotopic fractionation during evaporation, thereby improving the interpretation of relationships between evaporation intensity and climatic factors (e.g., temperature and relative humidity) and enhancing the precision of evaporation and humidity reconstructions in natural water bodies. © The Geological Society of Korea 2026.