Boron isotope composition was used to identify boron sources in groundwater in the eastern part of central Italy, on the west side of the lower alluvial plane of the Pescara river, a few kilometres from the coastline. This area was characterized by two possible boron sources: human activity and a geogenic source.
We collected 10 water samples during two sampling surveys, in October 2015 and February 2016. We conducted chemical analyses to determine major ions, boron concentrations and boron isotope values. The results obtained highlight that the groundwater is characterized by high mineralization with electrical conductivity values that reach 8180 µS/cm. Sodium and chloride are the principal ions, reaching values that exceed 3000 mg/L. Boron values exceed the limit provide by Italian legislation for groundwater (1 mg/L) in many samples, reaching the maximum value of 9630 µg/L during February 2016. The isotope values allow the identification of different sources of boron such as landfill leachate, rock leaching and water–rock interaction with terrigenous–evaporitic sequence. This manuscript highlights that isotope analyses are a powerful tool for monitoring and environmental planning.