Tritium in precipitation on 5 sites in North-West France during the 2017–2019 period
Résumé
Between October 2017 and May 2019, measurements of tritium in rainwater were carried out at several sites in
north-west France. Tritium is an important tracer for hydroclimatic studies and this work provided up-to-date
data that we compared with Global Network for Isotopes in Precipitation (GNIP) measurements. Of the
various sites studied, some could potentially be affected by atmospheric gaseous emissions from the nuclear
industries in the region (reprocessing plant, nuclear power plant). On our reference site, the activities measured
in rainwater are often below the decision threshold (<0.15 Bq.L- 1). Two other sites with little impact from
nuclear industries have mean activities of less than 0.7 Bq.L- 1. At the two Cherbourg sites closer to the nuclear
industries, the activities in rainwater are slightly higher on average, though still close to 1 Bq.L- 1, but the activities
are more variable when the rainfall accompanies an air mass from the Orano La Hague nuclear site. Using
existing GNIP data and a simple model to simulate predicted data up to 2019, it is shown that all our measured
data are comparable with the predicted activities for GNIP stations with a marine influence, in the case of the
reference site and the sites with little impact from nuclear industries, and for GNIP stations with a continental
influence, in the case of the other sites. Seasonal variation in activities was detected, with greater activities in the
spring-summer period corresponding to the well known ‘spring leak’ phenomenon. This study also reveals significant
differences between the activities measured on the western side of France (influenced by the Atlantic
Ocean) and those measured in a continental zone. The mean levels of tritium in rainwater in France, excluding
any nuclear influence, can be estimated on average at less than 0.3 Bq.L- 1 in the western marine zone, and at
around 1 Bq.L- 1 in the continental zones.
Domaines
Sciences de l'environnementOrigine | Fichiers produits par l'(les) auteur(s) |
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