Use of Water Isotopes in Hydrological Processes

Effects of season and slope orientation on stable isotopes of different water bodies in the subalpine shrub zone of the eastern Qilian Mountains in China

The subalpine shrub zone of the Qilian Mountains is an important water-retaining area, and it is crucial to clarify the processes of its hydrological cycle. Therefore, based on the stable isotope values of different water bodies in the subalpine shrub zone of the eastern Qilian Mountains from May to October 2019, the characteristics of δD and δ18O of different water bodies and their hydraulic relationships with each other were studied. The results showed that the stable isotope values of precipitation exhibited the largest fluctuations, while they were the most stable for groundwater. Plant transpiration was stronger than the evaporation of other water bodies. The stable isotope of precipitation was enriched in high temperature and low humidity environments. Isotopic values of plant and soil water were higher and more stable on the semi-sunny slope than on the semi-shady slope. According to the stable isotopes, there was a strong hydraulic relationship between the different water bodies in the study area, and precipitation was the ultimate source of all of them. Precipitation replenished soil water through infiltration. Part of the soil water was absorbed by plants, while the rest continued to infiltrate to replenish groundwater. Groundwater and precipitation replenished the river water.

An Integrated Approach to Characterising Sulphur Karst Springs: A Case Study of the Žvepovnik Spring in NE Slovenia

We present an integrated approach to characterizing the Žvepovnik sulphur spring, comprising detailed basic geological (mapping), geochemical (physico-chemical, elementary), isotopic (δ2H, δ18O, δ13CDIC, δ34S and 3H), and microbiological analyses. We used a multi-parameter approach to determine the origin of the water (meteoric or deeper infiltration), the origin of the carbon and sulphur, and water retention times. Our special research interest is the origin of the sulphur, as sulphur springs are rare and insufficiently investigated. Our results show that the Žvepovnik spring occurs along the fault near the contact between the dolomite aquifer and overlying shales and volcanoclastic beds. The spring water is the result of the mixing of (1) deeper waters in contact with gypsum and anhydrite and (2) shallow waters originating from precipitation and flowing through the surface carbonate aquifer. The results of δ2H and δ18O confirm local modern precipitation as the main source of the spring. δ13CDIC originates from the degradation of organic matter and the dissolution of carbonates. We therefore propose four possible sources of sulphur: (1) the most probable is the dissolution of gypsum/anhydrite; (2) barite may be a minor source of sulphur; (3) the microbial dissimilatory sulfate reduction; and (4) the oxidation of pyrite as the least probable option.

Review on Applications of 17O in Hydrological Cycle

The triple oxygen isotopes (16O, 17O, and 18O) are very useful in hydrological and climatological studies because of their sensitivity to environmental conditions. This review presents an overview of the published literature on the potential applications of 17O in hydrological studies. Dual-inlet isotope ratio mass spectrometry and laser absorption spectroscopy have been used to measure 17O, which provides information on atmospheric conditions at the moisture source and isotopic fractionations during transport and deposition processes. The variations of δ17O from the developed global meteoric water line, with a slope of 0.528, indicate the importance of regional or local effects on the 17O distribution. In polar regions, factors such as the supersaturation effect, intrusion of stratospheric vapor, post-depositional processes (local moisture recycling through sublimation), regional circulation patterns, sea ice concentration and local meteorological conditions determine the distribution of 17O-excess. Numerous studies have used these isotopes to detect the changes in the moisture source, mixing of different water vapor, evaporative loss in dry regions, re-evaporation of rain drops during warm precipitation and convective storms in low and mid-latitude waters. Owing to the large variation of the spatial scale of hydrological processes with their extent (i.e., whether the processes are local or regional), more studies based on isotopic composition of surface and subsurface water, convective precipitation, and water vapor, are required. In particular, in situ measurements are important for accurate simulations of atmospheric hydrological cycles by isotope-enabled general circulation models.

Application of Stable Isotopes and Tritium in Hydrology

The availability and quality of freshwater currently represent one of the great issues for mankind [...]