Transuranics transfer in a Spanish marine ecosystem

Joumst of Radiryurytical and Nuclur Cfumistry, A,rticlq, Vol. 156,No. I (1992) 15l-163

TRANSURANICSTRANSFERIN A SPANISHMARINE ECOSYSTEM C. GASCO, E. IRANZO, L. ROMERO CI EMAT, Radiologic al Protection Instiute, Av. Complutense 22, Madrid (SPain) (Received June 3, 1991)

(Spein)' aa Duc to an accidental relcasc of ha¡suranics et Pdmrarcs, Almetie possiblc thc a¡ca of 2.3 k* was contaminatcd (1,2,3). With thc objecüvc of studying scdimcnts transfe¡ of the transrranic from land to s€s (4), e sampling nctwotk fo merinc of Concc¡tlstions Get8. Cape a¡d sea water was establishcd betwcen Cepe Palos and plutonium, amcricium and radiocesium wcre dctcnnincd in scdimc¡t corcs takc¡ from was the sea shclf su¡rounding Palomates. The depositional history of scdimcnts 2loPbmethod. An i¡creesc in transu¡anic elucidatcd us.ing thc unsupportcd of which conccntrations was obscrvcd off the southcrn coast of Palomarcs, thc sourccs are discr¡ssedin this PaPct.

INTRODUCTION The principal source of radionuclide fallout to the marine envitonment was atmospheric nuclear weapons testing which occurred mainly during the 1950s and 1960s (5,6,7). Other anthropogenic sources are discharges to sea produced by rcprocessing plants, effluents released from nuclear power plant accidents and radioactive waste disposal. Aarkrog (8), in a necentPaPer about global fallout in oceans,has compiled ¡adionuclides inventories in world-seas (9,10,1 l,l2). However, large-scale data on radionuclide distributions and factors governing water-sedimenr tmnsport in the western Mediter¡anean arca have not been obtained (13,14,15). The differences among the concent¡ations of radionuclides found throughout the Continental Shelves provides a basis for understanding the process involved in the scavenging of radiotruclidcs from seawater and the biogeochemical cycles that are operative. Particulate mattet is an impottánt factor in the removal of radionuclides-from the water column. This source of phytoplankton productivity is an input of inorganic particles from tertestrial runoff or winds neat the bottom resuspensionof sediment. Elsevia Seqtoia S. A.,I'atryw Ald¿núai Kldó, Budg

C.GASCO et al.:TRANSURANICS TRANSFER IN A SPANISH MARINE The terrigenous conttibution of the rives prcduces a high quantity of particulate matúer which is released to the sea and plays an important role in the'transport and settling of radionuclides dissolved in the seawater. In Januar¡ 1966, in the coastal village of Palomares, four thermonuclear weapons were dropped during a rcfueling operation between aB-52 bomber and a KC-135 tanker of the American Sttategic Ai¡ Force. Two of the weapons parachutes had opened, and they were found intact. The res of the weapons experienced non-nuclear explosion with some burning and release of the fossil fuel at impact. The studied area is a typical semidesert Mediterranean zone, with sparse yearly precipitation. The Almanzota, a seasonal river, crosses the zone and certain areas of the dry river bed were polluted. There was a flood in this area in 1973 and some of the contamination from the flooded may have been t¡ansferred to the sea. This ecosystem provides a unique natuml laboratory and facilitates the experimental study of transuranic transfer f¡om land to sea and also some others factors affecting the radionuclide dist¡ibutions along the Meditenanean coastal zone. The purposes of this study arc, first to investigate the different pathways of transuranics in the marine ecosystem, and theit later evolution in an ocean environment, and second to differentiate the transuranic contributions that were a direct consequenceof the 1966 accident from those due to global fallout.

AREA DESCRIPTION

The thermic model of this arca confotms with the model described by Lacombe and Tchernia for the Southwest Mediter¡anean. T h e s a l i n i t y s h o w s t h e p r e s e n c eo f A t l a n t i c s e a w a t e ri n t h e a r e a d u e t o a n t i c y c l o n i c circulation. This water is driven into the Medite¡raneanSea via the Straits of Gibralter by wind strcss. This Atlantic influence is greaterin spring and autumn than in summer. The high values of salinity correspondto the entranceof Atlantic water mixed with Mediterraneanwater. The particle population is seasonallywell defined and is in the range of 0. | 7 -O.40mglL clependingon water depth and water column. The averagecomposition of marine sedimentsis SiO, (35%!6 o), CaO (23Vo!4 o), COz (2O%!4 o), and Al2O3 (87o!2 o). The mineral compouncls,shown by the associati