Article

Origins and trend of radionuclides within the lower Rhône River over the last decades

¹ IRSN, PRP-ENV, Laboratoire d’Études Radioécologiques en milieu Continental et Marin, SESURE/LERCM, BP 3, 13115 Saint Paul Lez Durance, France.
² IRSN, PRP-ENV, Laboratoire de Surveillance et d’Expertise Environnementale par Échantillonnage, SESURE/LS3E, 31 rue de l’Écluse, BP 35, 78116 Le Vésinet, France.

^* frederique.eyrolle-boyer@irsn.fr

Received: 8 April 2013
Accepted: 5 August 2014

Abstract

Geological and climatic diversity leads to significant spatial variability of naturally occurring radioactivity levels, whether in soils, sediments or natural waters. The activity level of Rhône sediments is estimated at 1450 Bq/kg, between the levels observed in the Loire (1925 Bq/kg) and Seine (730 Bq/kg). The largest amounts of radioactive effluent from nuclear facilities concern tritium, for which activity levels are currently 1000 times higher than the sum of artificial gamma emitters discharged. The proportions of naturally occurring ¹⁴C and ³H in the lower reaches of the River Rhône are estimated at 50 to 70% and <5%, respectively, with the remaining amount coming from nuclear facilities. Long-term records from River Rhône monitoring show that the level of radioactive contamination from artificial sources declined sharply starting in the early 90s, with the level divided by 10 to 100 depending on the element. Radioactivity of natural origin remained unchanged as expected.