Boron and δ11B in hydrological studies: A comprehensive overview based on the IsoBorDat repository

Over the last decades, the use of boron stable isotopes has steadily increased in the Earth Science literature, including hydrological studies. This paper presents “IsoBorDat”, a global open-access database containing boron stable isotope ratios (expressed as permil δ 11 B) measured in various hydrologic reservoirs such as groundwaters, surface waters, and rainwaters. The repository includes B contamination-related samples that have been (i) characterized in their isotopic signature as raw material or (ii) identified as potential sources of pollution in hydrological systems. IsoBorDat provides information on B content and B isotope ratios, water type, analytical methods, sampling time, and location. Data are available in open, structured .ods format, adhering to the FAIR principles. The database is hosted by the National Research Council of Italy (CNR) and is openly accessible at https://isobordat.cnr.it . We also present a quantitative and qualitative explorative approach applied to the statistical distribution of boron concentrations and isotope compositions across the four water types (meteoric, river, lake, and groundwater) and diverse water contamination sources of IsoBorDat. The statistical analysis reveals general distribution patterns and highlights differences among reservoirs, offering insights into geochemical processes influencing boron behaviour. This work supports the integrated use of isotopic data to better understand natural and anthropogenic influences on hydrological systems. IsoBorDat will be integrated within the ISOTOPE VRE, a Virtual Research Environment dedicated to environmental isotopes. • IsoBorDat is a global open-access database of boron concentrations and δ 11 B in waters • The dataset covers meteoric, river, lake, groundwater and contaminated waters • B and δ 11 B distributions show non-linear and multimodal behaviour • IsoBorDat supports isotope-based interpretation of hydrological systems