Study on the Hygroscopic Water Property of Soil by Stable Hydrogen and Oxygen Isotopes

In this paper,indoor test is designed to simulate water evaporation process.The water having the known isotopic composition is added to the dried soil sample until the soil water is saturated,then the soil water is evaporated using the oven dry,finally the soil water moisture is equal or less than the hygroscopic water content.The hygroscopic water is collected by the vacuum pumping combined with the heating,then δ18O and δD of the collected water are determined.The results show that the hygroscopic water has an obvious enrichment of the hydrogen and oxygen isotopes and there are isotope exchange between the hygroscopic water and the film water.It is conclude that the hygroscopic water is not solid or irremovable,but the water molecule in the layer can have isotope exchange with others in the outer layers.