ABSTRACT
The simultaneous injection of a conservative tracer (Br−) and a reactive contaminant (NO3 −) has helped elucidate pollutant behaviour and transport mechanisms in a shaly aquifer in Brittany. Rapid nitrate removal by autotrophic denitrification due to the presence of pyrite in the solid phase has been demonstrated. Tracers are partly transported along larger fractures, and partly along interconnected “microfissures” where chemical conditions seem more favourable for denitrification.
