Boron Isotopes in the Mount Vulture Groundwaters (Southern Italy): Constraints for the Assessment of Natural and Anthropogenic Contaminant Sources

Abstract

The Mt. Vulture volcanic aquifer is an important reservoir of effervescent mineral water in southern Italy. This area is included in the Vulture Regional Park and is located on a popular tourist route for its high scenic and ecological value. Unfortunately, signs of anthropogenic impact have recently increased. Among minor elements, boron and its isotopes are considered useful environmental tracers since different anthropogenic and natural sources can be distinguished. In this study, B content and (δ11B) isotope composition were determined in the Mt. Vulture groundwaters. The groundwater chemistry is strongly influenced by input of CO2-rich volcanic gases, and two different hydrofacies are observed. The first water type (BAW) has bicarbonate alkaline and alkaline-earth composition and relatively low salinity, whereas the second one (HSW) has bicarbonate-sulphate alkaline composition and higher salinity. The HSW are enriched in boron and have low δ11B values (from –9.6‰ to –4.3‰) similar to those measured in the local magmas suggesting that B contents in these waters are influenced by prolonged interaction between local meteoric water and volcanic rocks. As to BAW, a wide variability in B concentrations (from 14 μg/l to 769 μg/l) and B isotope composition (from -16.1‰ to +23‰) has been observed. A possible anthropogenic input is thought to be responsible for such variability. The water samples with high B concentrations and negative δ11B values (−12.2‰ to −16.1‰) are probably influenced by agricultural activities; for water samples characterized by positive δ11B values (from +5.8‰ to +7.9‰) and low B contents, a slight contamination by sewage effluents cannot be excluded. These conclusions are also supported by B/Cl molar ratios (7.8E−3 to 1.6E−2) different from those of the HSW group (1.1E−2 to 7.0E−2). This study highlights that also in the Mt. Vulture volcanic area B isotopes coupled to the B/Cl ratio can be a useful tool for the assessment of natural and anthropogenic contaminant sources.

Hydrology and water quality of a dune-and-swale wetland adjacent to the Grand Calumet River, Indiana, 2019–22

“…Boron is commonly found in coal combustion residue leachate (Naylor and others, 2012), in construction and demolition debris (Xu and others, 2020), and may be leaching from the coal fly ash and other materials that were used to build the access road. Other sources of boron are from manufacturing of glass, ceramics, fertilizers, and detergents (Paternoster, 2019), which may be in this heavily industrialized part of Gary. As a conservative geochemical element, boron transports readily through surface water and groundwater without substantial interaction with biota, evaporation, volatilization, oxidationreduction reactions, mineral precipitation, or dissolution (Buszka and others, 2007).…”

HydroQuakes, central Apennines, Italy: Towards a hydrogeochemical monitoring network for seismic precursors and the hydro-seismo-sensitivity of boron

“…It should be also noted that the least square fittings are statistically significant (Fig. 11a and b), and the regression extrapolation points towards high B concentration/ 11 B-depleted water samples interacting with silicates (Battistel, 2014;Paternoster, 2019).…”

Application of using a boron tracer to evaluate groundwater contamination in the Quaternary limestone aquifer in the southern region of Okinawa Island, Japan

“…Borate's high solubility makes its boron isotopic composition a potential tracer when mixed with other contaminants in the natural environment (Palmer and Swihart 1996). Boron chemistry has been used to investigate groundwater contamination in many areas, including water-rock interaction and anthropogenic contamination (Barth 1998;Komor 1997;Paternoster 2019). Quantitative analysis of boron concentration is widely used for investigating anthropogenic contamination (Bundschuh et al 1993).…”

“…Several studies have successfully utilized boron as a tracer to assess both natural and anthropogenic contamination sources, including volcanic sources, sewage, fertilizer, and seawater (e.g., Bassett et al 1995;Paternoster 2019;Xiao et al 2001). These studies have proposed possible endmembers to illustrate the variation in boron isotopic composition and have verified the range of different contaminant sources (e.g., Vengosh et al 1998).…”