Abstract. Oceans, seas, estuaries and rivers represent a vast sink for many substances of anthropic origin (metals, radionuclides, etc…). Depending on their chemical form, artificial radionuclides discharged into the sea by the nuclear industry can be carried onto land in marine aerosols, as well as by degassing seawater as is the case for tritium ( 3 H) or for radiocarbon ( 14 C). Three oceanographic cruises in the English Channel: TE-SEA, TRANSAT 1 and 2 have been performed on R.V. "Côtes de la Manche" to quantify the flux of 3 H in gaseous form, from the sea into the atmosphere, following particular discharge into the sea from the COGEMA spent fuel reprocessing plant at La Hague (North West France). During cruises, the maximum concentration measured in the air was 10.6 Bq.L -1 , which is distinctly higher than the background of 1 Bq.L -1 thus demonstrating the transfer of 3 H between water and atmosphere. The mean flux of 3 H between the water and the atmosphere, calculated during these cruises was 2.4 10 7 Bq.km -2 .d -1 . For the Seine Bay area (4400 km 2 ) this flux represents 39 TBq.yr -1 and hence less than 0.3 % of 3 H discharged into the ocean from the COGEMA spent fuel reprocessing plant at La Hague.

Abstract. In estuaries, volatiles radionucleides ( 14 C, 3 H, 131 I) originating from anthropogenic liquid waste release from nuclear reactor or hospitals are potentially transferable to the atmosphere. Due to the high biologic activity, the degradation of organic matter produce carbon dioxide fluxes to the atmosphere allowing transfer of 14 CO 2 released by nuclear industry. Similarly tritium is transfered to the atmosphere trough evaporation process. We present here, results obtained during FLORE-1 cruise in February 2003, a winter period when biological activity is supposed to be low. The first results of iodine 131 distribution and estimations of radiocarbon and tritium fluxes are presented.

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Abstract. COGEMA La Hague nuclear reprocessing plant is located in the North West of Cotentin peninsula near Cherbourg (France). This nuclear plant releases radioelements in atmosphere and in the English Channel. About 8.5 TBq.year -1 of radiocarbon are released as the liquid wastes through a pipe a few kilometres off sea shore, West of the reprocessing plant. Recent studies in the peninsula show anomalous higher radiocarbon contents in vegetation near the coast that have suggested a supplementary marine contribution through the degassing of the

Abstract. The aim of the study was to measure the carbon 14 activity at natural level in air samples using classical methods of radiochemistry and beta counting. Three different methods have been tested in order to minimise the detection limit. In the three methods, the first step consists in trapping the atmospheric carbon 14 into NaOH (1N) using a bubbling chamber. The atmospheric carbon dioxide reacts with NaOH to form Na 2 CO 3 . In the first method the Na 2 CO 3 solution is mixed with a liquid scintillate and is directly analysed by liquid scintillation counting (LSC). The detection limit is approximately 0.3 Bq.m -3 of air samples. The second method consists in evaporating the carbonate solution and then counting the solid residue with a proportional gas circulation counter. The detection limit obtained is equivalent to the first method (0.36 Bq.m -3 of air samples). In the third method, Na 2 CO 3 is precipitated into CaCO 3 in presence of CaCl 2 . CaCO 3 is then analysed by LSC. This method appears to be the most appropriate, the detection limit is 0.04 Bq.m -3 of air samples.