Stable isotope ratios of light elements (like oxygen) undergo significant mass-dependent fractionation during phase changes such as evaporation, because the relative mass difference between light and heavy isotopes (e.g., 16O vs 18O) is large enough to measurably affect reaction/phase-change kinetics; heavier radiogenic isotope systems (Sr, Nd) show negligible mass-dependent fractionation.
During evaporation of seawater, lighter water molecules (containing 16O) evaporate preferentially over heavier molecules (containing 18O) due to their relative mass difference, causing significant fractionation...
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