Tritium as a tool to assess leachate contamination: An example from Conversano landfill (Southern Italy)

This paper describes the geochemical and isotopic data processing combined with statistical analysis aimed to fine-tune the tritium background threshold limits to identify groundwater contamination due to leachate dispersion at a very high level of sensitivity. The selected case study refers to a landfill located in area subjected to marine intrusion and intense anthropic pressure due to agricultural activities. The investigated aquifer pertains to a karst system with a geological structure that potentially allows an easy spread of contamination. Twenty wells, with depth ranging from 179 to 462 m, and 4 leachate samples, were collected and analysed for main dissolved ions, some minor and trace species (NH4+, NO2- , Br- ) and isotope content (delta18O, delta2H and tritium). The adopted approach allowed defining the geochemical background of groundwater tritium content, and confirming that tritium content is an effective leachate tracer, both for the high contrast between groundwater and leachate, and for its conservative characteristics. These characteristics make tritium the leachate tracer par excellence, far preferable to any chemical or other isotopic parameters, whose variations may be influenced by chemical and physical processes other than leachate contamination.