EVIDENCE OF NATURAL DENITRIFICATION MECHA NISM AT BEUXES (VIENNE, FRANCE)

The denitrification mechanism identified at Beuxes (Vienne, France) is caused by the confinement of the Oxfordian limestone aquifer beneath the clayey Cenomanian sediments. The measured increase of total iron a nd SO42-, and the decrease of NO3-, dissolved O-2 and Eh are consisten t with the petrographic observation of pyrite alteration. The denitrif ication is established through 300 m of confinement (from 100 to 0 mg/ l NO3-). The denitrification rate of 0.9 to 1.7 mg NO3-/l/day suggests the superimposition of the chemical and the microbial mechanisms (Thi obacillus denitrificans).