Contributions of isotopic biogeochemistry to the knowledge of denitrification in underground waters

Whereas nitrate contents have been noticed in some hydrogeological contexts with a lower level than expected, this study, based on field observations on three different sites, aimed at determining the origin and causes of such decreases of concentrations. After a description of the chemical and biological denitrification as just a step in the nitrogen cycle, and the report of a bibliographical review on methods of identification of denitrification (hydro-geochemical method, method based on an over-saturation in dissolved molecular nitrogen, and isotopic method), it reports the application of isotopic tracing of the nitrate ion to the characterisation of denitrification in the three experimental sites