Application of boron and tritium isotopes for tracing landfill contamination in groundwater

Abstract

Groundwater beneath a municipal solid waste landfill area in central Italy has been studied. The study included two sampling events: in June and October 2014. The aim of this study was to determine the quality of groundwater and to test the use of boron and tritium isotopes as tracers of contamination due to the presence of the landfill. The results of chemical analyses indicate that the samples collected from boreholes located downgradient from the landfill are contaminated. The principal contaminants are Cl−, NH4+, Fe, As, Cr, B, Hg and Zn, which were detected at maximum levels during the June sampling event. The boron and tritium isotopic composition of the collected water samples was analysed to evaluate the source of contamination. The results indicated a δ11B value of 19.31‰ for uncontaminated groundwater, while δ11B values between 4.37 and 9.41‰ were reported for contaminated groundwater. The correlation between boron and chloride provided a basis for evaluating the plume direction. Tritium (3H) isotopes were analysed during the second sampling event (October). The results indicate that 3H values ranging between 2.7 and 3.6 TU were reported for uncontaminated waters; this groundwater has a short residence time in the aquifer. A 3H value of 34.5 TU was reported for one groundwater sample (Sample 7). This value is indicative of contamination by landfill leachate.