A Review of the Publications on Carbon Isotopes in Groundwater and Rainwater

The terrestrial components of the hydrological cycle include rainwater, surface water, and groundwater. Carbon (C) isotopes allow hydrologists to pinpoint the age of groundwater, track its flow rate, and identify the sources and processes. This research summarizes previous investigations conducted on the isotopes of groundwater and precipitation. The Scopus database contains works from authors from fifty nations, who have conducted research integrating C isotopes in groundwater and precipitation. The review shows that there have been few C isotope investigations on carbon storage and sequestration, as well as on δ13C of precipitation in arid regions. An integrated e-DNA investigation on the process of C isotope fractionation in diverse environments, as well as research on 13C of precipitation in arid regions before and after dust storms, is required to elucidate the relative contributions of biogenic, geogenic, and anthropogenic sources. However, carbon isotope fingerprints that are unique to individual compounds, such as those of fugitive gases, need sophisticated analytical equipment in order to be investigated, limiting this type of study to nations with robust scientific infrastructures and well-trained manpower. The International Atomic Energy Agency (IAEA) has been instrumental in this effort by providing collaborative research and analytical support, resulting in the development of a network for isotope data generation.