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In estuaries, volatiles radionucleides (14C, 3H, 131I) 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 14CO2released 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.

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-1of 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 14C excess supplied by liquid releases of the nuclear plant. Carbon dioxide partial pressure, 14C activities were measured in air and sea water in the Bay of Seine and around the COGEMA-La Hague nuclear reprocessing plant during three cruises in 2000 and 2002. Results show clearly that sea is a source of CO2and 14C to the atmosphere. Higher 14C concentrations in air and water related to the La Hague liquid wastes are clearly recorded. The aim of this paper is to show results of these oceanographic campaigns. Flux between seawater and atmosphere are calculated in the North-West Cotentin and in Bay of Seine.

Les variations passées du carbone-14 atmosphérique peuvent être reconstruites sur les derniers 50 000 ans par l'étude des différences entre âges carbone-14 et âges calendaires. Liées en premier lieu à la modulation géomagnétique du taux de production du 14C par le rayonnement cosmique et aux variations d'origine climatique du stock de 14C océanique, ces variations ont atteint un facteur 2 au début du paléolithique supérieur. Des variations de même amplitude ont été provoquées par les essais nucléaires militaires des années 50 et 60. La contribution cumulée de l'industrie nucléaire depuis ses débuts jusqu'à nos jours est de l'ordre d'un centième des quantités relâchées dans l'environnement par les retombées des explosions nucléaires atmosphériques. Représentant annuellement 14 % du taux de production naturel de 14C, cette contribution au rapport isotopique 14C/12C est actuellement contrebalancée par l'effet de dilution du 14C par les émissions de CO2fossile (effet Suess).

The explosive activity of Réunion volcanoes since approximately 260 ka is investigated through detailed sedimentologic, isotopic, and geochemical analyses of three deep-sea marine cores. Twenty-four eruptions from Piton des Neiges and one from Piton de la Fournaise are identified. The marine stratigraphic record of ash layers is undisturbed, whereas corresponding tephra deposits on land may have disappeared or have been disturbed through erosion and volcano-tectonic processes. Consequently, the new data presented herein may be regarded as a reference sequence of the main explosive events of Réunion. In addition, the chronology based on ¹⁸O stratigraphy offers continuous time constraints with respect to other isotopic methods used for dating lavas. Explosive events were more frequent during the period 180-150 ka. The comparison of major element composition and chronologic data between known explosive deposits on land and marine ash layers allows us to propose correlations between marine and land data. However, most of the marine ash layers do not yet have a recognized subaerial counterpart. For the main explosive events known on land, we propose the following succession: Sainte Suzanne formations, 257-240 ka; Dalle Soudée Formation, 218 ka; Salazie formations, two groups at 165-168 ka and 80-102 ka; Saint Gilles formations, 175 ka; Saint Louis formations, 158-161 ka; and Saint Pierre formations, 165-166 ka.

Geochemical evidence shows that the silicic component of the widespread Ash Zone 1 in the North Atlantic is derived from a major ignimbrite-forming eruption which occurred at the Katla caldera in southern Iceland during the transition from glacial to interglacial conditions in Younger Dryas time. Both trace and major element evidence of the rhyolitic products excludes the Öræfajökull volcano as a source. The high-Ti basaltic component in the marine ash zone can also be attributed to contemporaneous eruption in the Katla volcanic complex. Dispersal of tephra from this event is primarily attributed to the generation of co-ignimbrite ash columns in the atmosphere, with ash fallout on both sea ice and on the ocean floor north and east of Iceland. Owing to the changing ocean circulation characteristics of the glacial regime, including suppression of the Irminger Current and a stronger North Atlantic Current, tephra was rafted on sea ice south into the central North Atlantic and deposited as dispersed Ash Zone 1. Sediments south of Iceland also show evidence of the formation of ash turbidites, generated either by the entrance of pyroclastic flows into the sea, or during discharge of jökulhlaups or glacier bursts from this subglacial eruption.

A 37 m long piston core (KC-01B) was collected from the Calabrian Ridge in the Ionian Sea. Astronomical calibration of sapropels and sapropelic signals—based on rock-magnetic and geochemical properties—yields a very accurate time-frame for the last 1.1 Myr, with the exception of the interval (650–850 ka) straddling the Brunhes/Matuyama boundary. We used the oxygen isotope data as an additional constraint on our age model. We arrive at an age of 812 ka for the Brunhes/Matuyama boundary, which indicates that its position is determined by delayed acquisition of NRM by some 40 kyr. The age of the top of Jaramillo subchron (100 ± 3 ka) is slightly older than that of Shackleton, Berger & Peltier (1990); that of its bottom (1072 ± 5 ka) concurs with their estimate. In the Brunhes Chron, four short reversal excursions (CR0-3) were found and dated (CR0 261 ± 3 ka, CR1 318 ± 3 ka, CR2 515 ± 3 ka, CR3 573 ± 3 ka). In all cases, a highcoercivity reversed component is overlapped to a varying degree with a low-coercivity normal component. Three of the reversal excursions (CR1-3) occur in zones where diagenetic processes were shown to be minimal. The fourth (CR0), in which a very large coercivity overlap occurs, is not well expressed and is found in a zone where some dissolution of magnetic minerals has occurred. The existing literature on reversal excursions is reviewed, and some of the older records with an oxygen isotope or sapropel record have been redated. CR0 could correspond to one of the Fram Strait excursions (Nowaczyk et al. 1994). CR3 corresponds to the Emperor, which is shown to be equivalent to the Big Lost reversal excursion. For CR1 and CR2 we propose the names Calabrian Ridge 1 and Calabrian Ridge 2, since correlation with existing reversal excursions is uncertain. The Blake was not detected because extensive diagenesis has occurred in the corresponding interval. All reversal excursions observed in KC-01B correspond to periods of minimal (relative) palaeointensity in the independently dated record of Valet & Meynadier (1993). This seems to imply that reversal excursions are more likely to occur in periods with a relatively large non-dipole field contribution

The title alkaloid (Xa) is synthesized accompanied of its epimer, (±)‐3‐epiprosafrinine (Xb), according to the scheme.

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